FM 3-34.214 (FM 5-250) EXPLOSIVES AND DEMOLITIONS (July 2007)

Chapter 2

Table 2-3. M21 Characteristics

Tabulated Data

Length

2.25 to 2.35 in

Aluminum-tube detonator

Diameter

0.230 to 0.241 in

Material

Various plastics

Shock tube

Length

500 ft

Diameter

0.09 in

Detonator

Lead azide, PETN

Filler

Shock tube

HMX and aluminum

Actuation method

Impulse from attached minitube

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonating, assemblies, nonelectric

UN serial number

0500

NSN

1375-01-494-6945

DODAC

Live: MN88

Inert: MN89

DOT container marking

NEW (per cap)

19 gr

Drawing

12999559

Specification

QAA-1430

8 units per fiberboard box; 5 boxes per wooden

Packaging

box (40)

Dimensions

44 by 16.38 by 17.38 in

Cube

5.25 cu ft

Packing box

NEW

0.28 lb

Gross weight of package

20 lb

References

TM 9-1375-213-34&P

TM 9-1375-213-12

DOD Consolidated Ammunition Supply Catalog

M13 NONELECTRIC BLASTING CAP WITH A 1,000-FOOT SHOCK

TUBE

2-78. The M13 is a low-strength blasting cap, factory-crimped to a 1,000-foot length of shock tube. A

special plastic connector is attached to the detonator to facilitate quick and easy attachment to the shock

tube of up to five shock tubes or five low-strength detonating cords or one strand of standard detonating

cord. The M13 is provided on a spool as shown in Figure 2-39.

2-40

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-39. M13 Shock Tube Component and Blasting Cap With a Splicing Kit

USE

2-79. The M13 is used as a transmission line in a firing system. It does not have enough output to initiate

military explosives reliably.

FUNCTIONS

2-80. The M13 functions by sending an initiating shock or a small detonation through the shock tube to the

blasting cap. This blasting cap then actuates five shock tubes, five low-strength detonating cords, or one

strand of high-strength detonating cord held by the plastic connector. The M13’s shock tube must be

initiated by another blasting cap or by the M81 fuse igniter. Table 2-4, page 2-42, shows the M13

characteristics.

11 July 2007

FM 3-34.214

2-41

Chapter 2

Table 2-4. M13 Characteristics

Tabulated Data

Length

2.7 in

Aluminum-tube detonator

Diameter

0.296 in

Material

Various plastics

Shock tube

Length

1,000 ft

Diameter

0.118 in

Detonator

Lead azide, PETN

Shock tube

HMX and aluminum

Filler

Shock from the detonation of a blasting cap or

Actuation method

the primer of the M81 igniter

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonator assemblies, nonelectric

UN serial number

0500

NSN

1375-01-415-1231

DODAC

Live: MN03

Inert: none

NEW (per cap)

13 gr

DOT container marking

Drawing

12972629

Specification

QQA-1459

Pre-1999: 4 units per cardboard box; 6 boxes per

wooden box (24)

Packaging

Post-1999: 4 units per fiberboard box; 5 boxes

per wooden box (20); 4 wooden boxes per pallet

(80)

Pre-1999 production: 46 by 21 by 21 in

Dimensions

Post-1999 production: 48.75 by 19.8 by 20.75 in

Pre-1999 production: 11.74 cu ft

Cube

Post-1999 production: 11.41 cu ft

Packing box

Pre-1999 production: 0.298 lb

NEW

Post-1999 production: 0.2486 lb

Gross weight of

Pre-1999 production: 169 lb

package

Post-1999 production: 176 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

2-42

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

M23 NONELECTRIC BLASTING CAP WITH A 1,000-FOOT

MINISHOCK TUBE

2-81. The M23 consists of a high-strength blasting cap precrimped to a 1,000-foot length of minitube. The

M23 is about one-third the size and weight of the M13. The M23 has a modified M81E1 igniter moisture

cap with a protected ignition primer factory-crimped that is installed to an in-line initiator on the minitube.

The M23 has a M9 holder already connected to the high-strength cap (Figure 2-40).

Figure 2-40. M23 MDI 1,000-Foot Shock Tube Component

USE

2-82. The M23 is used to transmit a shock tube detonation impulse from an initiator (or another relay cap).

Unlike the M13, a high-strength blasting cap or booster will not have to be added as part of the

transmission line. The M23 high-strength cap can be secured into an M9 holder to provide the capability to

initiate up to five additional shock tubes or five low-strength detonating cords or one strand of detonating

cord. The M23 high-strength cap can also be used to prime military explosives.

FUNCTIONS

2-83. The M23 functions by sending an initiating shock or small detonation through the shock tube to the

blasting cap. This blasting cap then actuates five shock tubes, five low-strength detonating cords, or one

strand of high-strength detonating cord held by the plastic connector. The M23’s shock tube must be

initiated by another blasting cap or by the M81E1 in-line initiators. Table 2-5, page 2-44, shows the M23

characteristics.

11 July 2007

FM 3-34.214

2-43

Chapter 2

Table 2-5. M23 Characteristics

Tabulated Data

Aluminum-tube

Length

2.25 to 2.35 in

detonator

Diameter

0.230 to 0.241 in

Material

Various plastics

Shock tube

Length

1,000 ft

Diameter

0.09 in

Detonator

Lead azide, PETN

Filler

Shock tube

HMX and aluminum

Actuation method

Impulse from attached minitube

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonating, assemblies, nonelectric

UN serial number

0500

NSN

1375-01-494-6941

DODAC

Live: MN90

Inert: none

DOT container marking

NEW (per cap)

19 gr

Drawing

12999561

Specification

QAA-1430

4 units per fiberboard box; 5 boxes per wooden

Packaging

box (20); 4 wooden boxes per pallet (80)

Dimensions

44 by 16.38 by 17.38 in

Cube

5.25 cu ft

Packing box

NEW

0.22 lb

Gross weight of package

17 lb

References

TM 9-1375-213-12

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M14 NONELECTRIC BLASTING CAP WITH A DELAY

2-84. The M14 is a high-strength blasting cap, factory-crimped to about 7 ½-foot length of time fuse. The

M14 is marked with yellow or black bands that represent a nominal 1 minute of burn time instead of having

a yellow band every 18 inches as on the M700 time fuse. The free end of the fuse is moisture-sealed and

must be cut off to the selected time band when being prepared for ignition (Figure 2-41).

2-44

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-41. M14 Time Fuse Component (Various Vendors)

USE

2-85. The M14 is used to detonate military explosives and initiate shock tube, low-strength detonating

cord, and detonating cord after being ignited. In dual initiation, an M14 can be connected to a line main or

transmission line and be used as the primary or secondary initiation system.

FUNCTIONS

2-86. The M14 functions by sending an initiating flame (from a time-blasting fuse igniter or a match)

slowly through the length of the time-blasting fuse to the blasting cap. The 1-minute bands on the time fuse

have been factory-calibrated. The burn time will increase with altitude and colder temperatures. The M14

has been designed to allow a nominal 5-minute delay, under all weather and altitude conditions, to allow

personnel to move to the minimum safe distance (MSD) from the explosive charges being detonated. If

greater time accuracy is required under specific altitude and weather conditions, an M14 from the same lot

should be tested. The M14 being tested should be timed to the detonation of the cap to provide an actual

burn time. This will allow the operator to adjust the time for the detonation of the explosive system or main

charge. Table 2-6, page 2-46, shows the M14 characteristics.

11 July 2007

FM 3-34.214

2-45

Chapter 2

Table 2-6. M14 Characteristics

Tabulated Data

Length

2.25 to 2.35 in

Aluminum-tube detonator

Diameter

0.230 to 0.241 in

Material

Plastic-covered fiber

Time-blasting fuse

Length

About 7.5 ft

Diameter

0.25 in

Detonator

Lead styphnate, lead azide, PETN

Filler

Time fuse

Black powder

Actuation method

M81 fuse igniter or flame from a match

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonators, nonelectric

Pre-1999: 0455

UN serial number

Post-1999: 0500

Pre-1999 production: 1375-01-415-1233

NSN

Post-1999 production: 1375-01-482-7380

DODAC

Live: MN06

Inert: MN37

DOT container marking

Pre-1999 production: 16 gr

NEW (per cap)

Post-1999 production: 16 gr

Drawing

12982929

Specification

QAA-1424B

Pre-1999 production: 10 units per fiberboard

box; 6 boxes per wooden box (60)

Packaging

Post-1999 production: 10 units per fiberboard

box; 4 boxes per wooden box (40)

Dimensions

26 by 18 by 11 in

Cube

2.8 cu ft

Packing box

Pre-1999 production: 1.554 lb

NEW

Post-1999 production: 1.6 lb

Pre-1999 production: 57 lb

Gross weight of package

Post-1999 production: 86 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M18 NONELECTRIC BLASTING CAP WITH A DELAY

2-87. The M18 is a high-strength blasting cap, factory-crimped to about 30-foot length of time-blasting

fuse. The black bands represent 1 minute of burn time. The free end of the fuse is moisture-sealed and must

be cut off to the selected time band when being prepared for ignition (Figure 2-42).

2-46

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-42. 20-Minute Burn Time M18 Component

USE

2-88. The M18 is used to detonate all standard military explosives. It is also used to initiate shock tube

blasting caps and detonating cord up to 20 minutes after being ignited.

FUNCTIONS

2-89. The M18 functions by sending an initiating flame (from a fuse igniter or a match) slowly through the

length of the time-blasting fuse to the factory-crimped blasting cap. The 1-minute bands on the time fuse

have been calibrated at sea level at a temperature of 125°F. The burn time will increase with altitude and

colder temperatures. The M18 has been designed to allow a nominal 20-minute delay under all weather and

altitude conditions. This allows personnel to move to the MSD from the emplaced explosive charges being

detonated. Table 2-7, page 2-48, shows the M18 characteristics.

11 July 2007

FM 3-34.214

2-47

Chapter 2

Table 2-7. M18 Characteristics

Tabulated Data

Aluminum-tube

Length

2.25 to 2.35 in

detonator

Diameter

0.230 to 0.241 in

Material

Plastic-covered fiber

Time-blasting fuse

Length

30-ft approximate length

Diameter

0.25 in

Detonator

Lead styphnate, lead azide, PETN

Filler

Time fuse

Black powder

Actuation method

M81 fuse igniter or flame from a match

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonators, nonelectric for blasting

UN serial number

0345

NSN

1375-01-449-9602

DODAC

Live: MN41

Inert: none

DOT container marking

NEW (per cap)

16 gr

Drawing

12982929

Specification

QAA-1424B

2 per barrier bag; 5 barrier bags inside box;

Packaging

4 boxes in overpack (40)

Dimensions

26 by 18 by 11 in

Cube

2.8 cu ft

Packing box

NEW

0.104 lb (for 60 caps NEW = 1.57 lb)

Gross weight of package

57 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M15 NONELECTRIC BLASTING CAP WITH A DELAY

2-90. The M15 consists of two blasting caps, factory-crimped at each end of a 70-foot length of shock

tube. The blasting caps are slightly different in size and contain different delay elements. The shorter, low-

strength blasting cap is designed to initiate another piece of shock tube in the firing system, while the

longer high-strength blasting cap is designed to prime explosives. Since the M15 high-strength blasting cap

is commercially used in boreholes, two brightly colored plastic flags are attached to the shock tube near the

detonator. A red flag is attached 1 meter from the longer high-strength blasting cap, and a yellow flag is

attached 2 meters from the low-strength blasting cap (Figure 2-43).

2-48

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-43. M15 Delay Blasting Cap

DANGER

The M15 can only be used belowground in quarry operations

according to FM 3-34.465. Failure to comply may cause death or

permanent injury.

USE

2-91. The M15 is used to provide a delay element in a combination firing system to obtain staged

detonations. Delayed and staged detonations are essential in quarrying operations but are also used in

relieved-face cratering.

FUNCTIONS

2-92. The M15 sends an initiating shock (or small detonation) through the shock tube to both of the

blasting caps. These contain pyrotechnic-delay elements. The delay times in the two detonators are

different; one is 25 milliseconds (low-strength, smaller cap with a shock tube connector), and the other is

200 milliseconds (higher-strength, larger cap with a shock tube connector). The high-strength blasting cap

is slightly larger in diameter than a standard blasting cap and will not fit in a standard cap well. The M15

shock tube must be initiated by another MDI component. Table 2-8, page

2-50, shows the M15

characteristics.

11 July 2007

FM 3-34.214

2-49

Chapter 2

Table 2-8. M15 Characteristics

Tabulated Data

Length (low strength)

2.5 in

Length (high strength)

3.5 in

Diameter (low strength)

0.296 in

Aluminum-tube detonator

Diameter (high strength)

0.296 in

Low strength: 3 gr

NEW (per cap)

High strength: 15 gr

Material

Various plastics

Shock tube

Length

70 ft

Diameter

0.118 in

Detonator

Lead azide, PETN

Shock tube

HMX and aluminum

Filler

Shock from the detonation of a blasting cap or

Actuation method

detonating cord

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonator assemblies, nonelectric

UN serial number

0500

NSN

1375-01-447-2049

DODAC

Live: MN07

Inert: MN38

DOT container marking

NEW (per cap)

1.36 gr

Drawing

12972631

Specification

QAA-1425

Packaging

60 units per wood box; 4 boxes (240) per pallet

Dimensions

46 by 21 by 21 in

Cube

11.74 cu ft

Packing box

NEW

0.18 lb

Gross weight of package

118 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M151 BOOSTER DEMOLITION CHARGE

2-93. The M151 is a nonelectric, insensitive initiation system that is factory-assembled by crimping a

secondary explosive booster onto a 10-foot length of low-strength detonating cord to allow the user to

2-50

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

preprime explosives for military operations and bury explosives primed with M151. The M151 has a

detonating cord clip like other MDI components for easy attachment to a line or ring main detonating cord.

A pentagonal-shaped tag affixed to the low-strength detonating cord identifies it as an M151 to preclude

incorrect connection within a firing system.

CAUTION

Do not use M151 low-strength detonating cord as a line or ring main.

The M151 is only used as a branchline and cannot be substituted for

standard detonating cord. Personal injury or damage to equipment

may result from long-term failure to follow correct procedures.

USE

2-94. The M151 is used to prime charges in situations where simultaneous initiation and detonation are

desired. Prepriming of charges allows a Soldier to transport the preprimed charge in the vehicle or on his

person. This also allows for the burial of an explosive charge.

WARNING

Never attach an M60 or M81 igniter to the M151. Failure to comply

could result in immediate personal injury or damage to

equipment.

FUNCTIONS

2-95. The M151 functions upon receiving an initiating shock from a blasting cap or other booster. When

the booster functions, it detonates the primed explosive charge. The M151 booster can be secured in the

M9 holder by using the small flap. Table 2-9, page 2-52, shows the M151 characteristics.

11 July 2007

FM 3-34.214

2-51

Chapter 2

Table 2-9. M151 Characteristics

Tabulated Data

Material

PETN

Aluminum-tube booster

Length

2.25 to 2.35 in

cap

Diameter

0.230 to 0.241 in

Black fiber, with an environmental seal on one end,

Material

5 to 7.5 gr per ft

Green pentagonal-shaped identification tag on both

ends of the assembly, marked M151 to distinguish a

Marking

low-strength detonating cord from other MDI

Low-strength detonating

components

cord

Length

10 ft

Diameter

0.150 in

Shock from the detonation of a blasting cap or

Actuation method

detonating cord when an M151 is used as a

branchline

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonator, assemblies, nonelectric

UN serial number

0410

NSN

1375-01-467-8646

DODAC

Live: MN68

Inert: none

DOT container marking

NEW

87 gr

Drawing

D10451-1 Ensign-Bickford drawing

Specification

None

Packaging

20 per cardboard box; 6 boxes per overpack (120)

Dimensions

None

Cube

None

Packing box

NEW

1.13 lb

Gross weight of package

46 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M152 BOOSTER DEMOLITION CHARGE

2-96. The M152 is a nonelectric insensitive initiation system that is factory-assembled by crimping a

secondary explosive booster onto a 30-foot length of low-strength detonating cord. This allows the user to

preprime explosives for military operations and bury explosives primed with M152. The M152 has a

detonating cord clip like other MDI components for easy attachment to a line or ring main detonating cord.

2-52

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

A pentagonal-shaped tag affixed to the low-strength detonating cord identifies it as an M152 to preclude

incorrect connection within a firing system (Figure 2-44).

CAUTION

Do not use M152 low-strength detonating cord as a line or ring main.

The M152 is only used as a branchline and cannot be substituted for

standard detonating cord. Personal injury or damage to equipment

may result from long-term failure to follow correct procedures.

Figure 2-44. M152 Low-Strength Detonating Cord Component

USE

2-97. The M152 is used to prime charges in situations where simultaneous initiation and detonation are

desired. Prepriming of charges allows a Soldier to transport the preprimed charge in the vehicle or on his

person. This also allows for the burial of an explosive charge.

WARNING

Never attach an M60 or M81 igniter to the M152. Failure to comply

could result in immediate personal injury or damage to

equipment.

FUNCTIONS

2-98. The M152 functions upon receiving an initiating shock from a blasting cap or other booster. When

the booster functions, it detonates the primed explosive charge. The M152 booster can be secured in the

M9 holder by using the small flap. Table 2-10, page 2-54, shows the M152characteristics.

11 July 2007

FM 3-34.214

2-53

Chapter 2

Table 2-10. M152 Characteristics

Tabulated Data

Material

PETN

Aluminum-tube booster

Length

2.25 to 2.35 in

cap

Diameter

0.230 to 0.241 in

Black fiber, with an environmental seal on one end,

Material

5 to 7.5 gr per ft

Green pentagonal-shaped identification tag on

Marking

both ends of the assembly, marked as M152

Low-strength detonating

Length

30 ft

cord

Diameter

0.150 in

Shock from the detonation of a blasting cap or

Actuation method

detonating cord when an M152 is used as a

branchline

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonator, assemblies, nonelectric

UN serial number

0410

NSN

Live: 1375-01-470-2399 Inert: 1375-01-467-8645

DODAC

Live: MN69

Inert: MN75

DOT container marking

NEW

197 gr

Drawing

D10451-2 Ensign-Bickford drawing

Specification

None

Packaging

20 per cardboard box; 3 boxes per overpack (60)

Dimensions

None

Cube

None

Packing box

NEW

1.44 lb

Gross weight of package

46 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M19 NONELECTRIC BLASTING CAP WITH A DUAL MINISHOCK

TUBE

2-99. The M19 consists of a 200-foot length of dual minitube with an in-line initiator built into one end of

each of the two minitubes and a nonelectric, nondelay high-strength blasting cap attached to the other end

of each minitube. The minitube is smaller in diameter and possesses all the same characteristics of a shock

tube. The M81E1 igniter is attached to each in-line initiator. M9 plastic holders are provided in the

packaging for each M19 to facilitate quick and easy attachment to the minitube of additional blasting cap

components (Figure 2-45).

2-54

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-45. M19 Dual-Minitube and Blasting Cap Component

USE

2-100. The M19 is used to initiate standard military explosives and demolition charges by inserting the

blasting caps directly into an explosive or the cap well of demolition charges. The M19 is particularly

suited for urban terrain missions when very high reliability is required.

FUNCTIONS

2-101. The M19s minitube must be initiated by a blasting cap or by activating the firing assembly of the

M81E1 igniter. To actuate the M81E1, remove the cotter pin, and then pull the pull ring to the limit of its

travel. The pull ring rod then releases the firing pin. The firing assembly of the M81E1 igniter strikes the

M42C1 primer. The small detonation impulse (shock wave) from the primer is transmitted through the

minitube into a less sensitive explosive contained within its blasting cap. The blasting cap can actuate an

additional number of components held by the M9 plastic holder or can directly initiate explosive charges or

demolition devices. Table 2-11, page 2-56, shows the M19 characteristics.

11 July 2007

FM 3-34.214

2-55

Chapter 2

Table 2-11. M19 Characteristics

Tabulated Data

Aluminum-tube

Length

2.25 to 2.35 in

detonator

Diameter

0.230 to 0.241 in

Material

Various plastics

Shock tube

Length

200 ft (dual)

Diameter

0.09 in

Detonator

Lead azide, RDX

Filler

Shock tube

HMX and aluminum

Actuation method

Impulse from attached minitube

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Detonating assemblies, nonelectric

UN serial number

500

NSN

1375-01-494-6939

DODAC

Live: MN86

Inert: MN87

DOT container marking

NEW (per cap)

18 gr

Drawing

12999557

Specification

QAA-1431

Packaging

8 per fiberboard box; 5 boxes per wooden box (40)

Dimensions

44 by 16 by 21.5 in

Cube

8.76 cu ft

Packing box

NEW

0.31 lb

Gross weight of package

20 lb

References

TM 9-1375-213-12

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

M9 BLASTING CAP AND SHOCK TUBE HOLDER

2-102. Plastic holders allow the connection of several shock tubes to high-strength blasting caps and

boosters (Figure 2-46). The M9 holder helps secure the connection of up to five shock tubes or low-

strength detonating cords to high-strength caps or boosters. The M9 holder can also be used to connect

high-strength blasting caps and boosters to detonating cord. When using the M9 holder, tape it closed.

Note. Do not connect the shock tube, low-strength detonating cord, or detonating cord in the

same holder. Detonating cord functions at a higher velocity than the HMX and aluminum in the

shock tube and may cause a break in the shock tube.

2-56

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

1 to 2 shock tubes

Overhand knot

M9 holder (both MDI cap/booster

flaps open)

secured in an M9

(small flap closed)

3 to 5 shock tubes

Figure 2-46. M9 Blasting Cap and Shock Tube Holder

USE

2-103. The M9 can accommodate and ensure proper proximity for initiating up to five shock tubes, five

low-strength detonating cords, or one strand of detonating cord from the blasting cap or booster. The M9

can also be used to connect the MDI blasting cap or booster to a detonating cord line or a ring main.

FUNCTIONS

2-104. Shock tubes must be positioned straight through the holder with an overhand knot when using one

or more (Figure 2-46). The blasting cap or booster is inserted and secured by closing the smaller hinged

flap. Insert the ends of the shock tubes through the channels in the holder. Close the large flap to secure the

overhand knot. Use tape to secure the large flap in place. See Table 2-12, page 2-58, for the M9

characteristics. In the event an M9 holder becomes unserviceable or is not available, use tape to make MDI

connections. To attach a blasting cap to MDI components using tape, ensure that all strands of shock tube

or low-strength detonating cord being connected are in contact with the blasting cap or booster and is

secured with tape.

11 July 2007

FM 3-34.214

2-57

Chapter 2

Table 2-12. M9 Characteristics

Tabulated data

Length

3.0 in

Diameter

1.3 in

Thickness

0.7 in

One cap or booster per five shock tubes on

Accommodation

low-strength detonating cords

Material

Polyethylene

Color

Black

Dimensions (closed)

NSN

1375-01-415-1229

DODAC

1375-ML45

Drawing

12972626

Specification

QAA-1423

Gross weight of item

1 oz

Packaging

500 units per box

Gross weight of package

49 lb

Because this item is designed for one-time use, continued use in training will

Limitations

wear out the hinges very quickly.

M81 TIME-BLASTING FUSE IGNITER WITH SHOCK TUBE

CAPABILITY

2-105. The M81 igniter will initiate the time fuse and shock tube end of MDI components(Figure 2-47).

The M81 is almost identical to the older M60 igniter, except the M81 has a screw-end cap with a green

shipping plug and a silicon shock tube reducer. The cap allows the M81 to accommodate the standard

shock tube or the standard-diameter, time-blasting fuse (M700). Extra care is required when connecting the

shock tube to an M81 igniter to ensure proper initiation of an explosive system.

WARNING

Never attach an M151, M152, or detonating cord to the M81

igniter. Failure to comply could result in immediate personal

injury or damage to equipment.

2-58

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11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-47. M81 Fuse Igniter

USE

2-106. The M81 igniter is used to ignite a time-blasting fuse or to initiate a shock tube.

Note. The standard M60 igniter (which has an almost identical appearance to the M81) will not

secure or reliably initiate the shock tube.

FUNCTIONS

2-107. The M81 is actuated as follows:

Loosen the screw cap and remove the shipping plug when using shock tube. Remove both the

shipping plug and shock tube reducer when using a time fuse (Figure 2-47).

Insert the freshly cut end of the time-blasting fuse or shock tube in the hole from which the plugs

were removed.

Tighten the screw cap to secure the fuse or shock tube.

Remove the safety (cotter) pin by squeezing the safety pin ends together then pulling on the

cord.

Pull the pull ring to the limit of its travel.

Note. When the M81 reaches its limit of travel, the pull ring rod releases the firing pin. The

spring forces the pin into the primer. The primer fires with a flame, and an explosive shock

ignites the fuse or initiates the shock tube.

2-108. Table 2-13, page 2-60, shows the M81characteristics.

11 July 2007

FM 3-34.214

2-59

Chapter 2

Table 2-13. M81 Characteristics

Tabulated Data

Length

4.0 in

Pull ring: 1.2 in

Body

Diameter

Body: 0.75 in

Material

Plastic

M42 primer

Primer mix

NEW (per igniter)

0.00005 lb (0.000023 gr)

Filler

Impact of the spring-loaded firing pin

Actuation method

on the primer is affected by the

operator pulling the pull ring.

Shipping and Storage Data

DOD hazard class

1.4S

QD/DIV/SCG

DOT hazard class

1.4S

DOT label

Explosive

1.4S

Proper shipping name

Lighters, fuse

UN serial number

0131

NSN

1375-01-415-1235

DODAC

Live: MN08

Inert: none

Drawing

12972638

DOT container marking

Specification

QAA-1442

Drawing

12972628

Specification

QAA-1423

Five igniters per paperboard box;

Packaging

one to a barrier bag; 6 bags (300

igniters) per wooden box

Dimensions

21.5 by 12 by 14.5 in

Cube

2.16 cu ft

Packing box

NEW

0.03 lb

Gross weight (with contents)

65 lb

References

TM 9-1375-213-34&P

DOD Consolidated Ammunition Supply Catalog

2-60

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

SECTION V - EXPLOSIVE CHARGES PRIMED WITH MODERNIZED

DEMOLITION INITIATORS

2-109. There are three methods of priming explosive charges—nonelectric (MDI), boosters (MDI), and

detonating cord. Only nonelectric (MDI) and boosters are discussed in this section. Priming charges with

MDI M151 or MDI M152 components or detonating cord are the preferred methods for reserve demolition

targets, which allow charges to be primed at state of readiness—state 1 (safe).

NONELECTRIC PRIMING

2-110. Use high-strength MDI blasting caps or boosters for priming explosive charges that are emplaced

aboveground. For priming explosive charges belowground, use the M151 or M152 booster. Use the M12

and M13 only as transmission lines in firing systems (refer to Section VI of this chapter).

WARNING

Do not insert blasting caps in explosive charges until ordered to

do so. Failure to comply could result in immediate personal injury

or damage to equipment.

2-111. MDI priming is safer and more reliable than the current nonelectric cap priming methods. MDI

blasting caps and boosters are already factory-crimped to precut lengths of shock tube or time-blasting fuse.

Because the caps are sealed units, they are resistant to moisture and will not misfire in damp conditions.

However, once the system has been spliced, reliability will be significantly degraded due to moisture. Also,

the human factor of incorrect crimping is removed, making MDI blasting caps and boosters extremely

reliable. MDI blasting caps and boosters can be used with priming adapters or can be inserted directly into

the explosive charge and secured with tape. If using priming adapters, place them on high-strength blasting

caps and boosters as outlined in the note below.

Note. Older MlA4 priming adapters must be slid down the full length of the shock tube or low-

strength detonating cord to the high-strength blasting cap or booster. To slide the priming

adapter on the free end of the shock tube, it will be necessary to cut off the end of the shock tube

to remove the sealed end cap, and then slide the detonating cord clip off. The preferred priming

adapter is the M1A5 priming adapter, which has wider slots and can be placed over the shock

tube at a point near the blasting cap or booster.

TRINITROTOLUENE BLOCK DEMOLITION CHARGE

2-112. TNT blocks have threaded cap wells. A priming adapter is used to secure a high-strength blasting

cap or booster in the cap well of the TNT block as shown in Figure 2-48, page 2-62. When priming

adapters are not available, prime TNT blocks by inserting a high-strength blasting cap or a booster into the

cap well of the charge and secure it with tape.

11 July 2007

FM 3-34.214

2-61

Chapter 2

Figure 2-48. Priming a TNT Block With an MDI

MILITARY DYNAMITE

2-113. Military dynamite can be primed with MDI blasting caps or boosters using either the end- or side-

priming method. M2 crimpers or other nonsparking tools are used to make a cap well in one end of the

dynamite cartridge. If using the side-priming method, make the cap well in the side of the cartridge at one

end. The blasting cap or booster is inserted nearly parallel to the side of the cartridge. The explosive tip of

the cap should be near the middle of the cartridge. A blasting cap or booster is inserted into the cap well.

The shock tube, time fuse, or low-strength detonating cord is secured to the cartridge with tape to hold the

blasting cap or booster firmly in place (Figure 2-49). For quarry operations, see FM 3-34.465.

Figure 2-49. Priming M1 Dynamite With an MDI

M112 (COMPOSITION C4) DEMOLITION BLOCK

2-114. Use M2 crimpers or other nonsparking tools to make a hole in one end or on the side (at the

midpoint) of the demolition block. The hole should be large enough to hold a blasting cap or booster. Insert

2-62

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

a blasting cap or booster into the hole produced by the M2 crimpers. Do not force the blasting cap or

booster if it does not fit; make the hole larger. The blasting cap or booster is anchored in the demolition

block by gently squeezing the composition C4 plastic explosive around the blasting cap or booster. The

blasting cap or booster is secured by tape in the charge (Figure 2-50).

Figure 2-50. Priming a Composition C4 Demolition Block With an MDI

40-POUND CRATERING CHARGE

2-115. The 40-pound cratering charge is primed using one M151 or M152 booster and one M112

composition C4 or two M112 composition C4 as boosters attached to the side of the charge. Forty-pound

cratering charges should not be primed with blasting caps.

WARNING

Do not use the low-strength detonating cord of the M151 or M152

to lower 40-pound cratering charges into the holes. Failure to

comply could result in immediate personal injury or damage to

equipment.

M2A4 AND M3A1 SHAPED CHARGES

2-116. The M2A4 and M3A1 shaped charges have a threaded cap well at the top of the cone. A priming

adapter is used, if available, to secure a blasting cap or booster in the threaded cap well. If a priming

adapter is not available, use tape to secure the blasting cap or booster in the cap well (Figure 2-51,

page 2-64).

11 July 2007

FM 3-34.214

2-63

Chapter 2

Figure 2-51. Priming Shaped Charges With an MDI

Note. Charges will not be primed with blasting caps until the charges are placed on the target.

BANGALORE TORPEDO

2-117. The bangalore torpedo is primed using a blasting cap or a booster. Insert the blasting cap or

booster into the cap well in the end section of the charge, and secure it with a priming adapter. If a priming

adapter is not available, use tape to hold the blasting cap or booster firmly in place (Figure 2-52).

Figure 2-52. Priming the Bangalore Torpedo With an MDI

SECTION VI - INITIATING SETS AND FIRING SYSTEMS

INITIATING SETS

2-118. All MDI blasting caps and boosters can be used to initiate shock tube. Only use blasting caps or

boosters to initiate detonating cord or to prime and initiate explosive charges directly. MDI initiating sets

are used to initiate instantly. An M12, M13, M19, M21, and M23 or an M14 or M18 can be used to create a

delay. When using a combination (command and delayed) initiation system on the MDI, the command

initiation will be the primary initiation system, and the delay initiation will be the secondary initiation

system.

Note. Cover the secondary-initiation system blasting cap to reduce fragmentation hazards of the

cap.

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FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

2-119. If the primary initiating system fails, the secondary initiating system will function and initiate the

system when the time fuse burns down to the blasting cap. If the primary initiates the system, the secondary

blasting cap will detonate along with the other components of the firing system if it was connected to the

detonating cord. If the secondary blasting cap was connected to the shock tube or the low-strength

detonating cord, it will detonate when the time fuse burns down to the blasting cap. When using dual-delay

initiation systems, the shorter delay is the primary initiation system. When placing multiple charges, the

transmission line blasting caps and charges should be a sufficient distance apart to prevent fragments from

cutting other shock tube or low-strength detonating cord components before their planned ignition.

WARNING

Always observe the safe distances given in Chapter 6. Failure to

comply could result in immediate personal injury or damage to

equipment.

INSTANTANEOUS OR COMMAND INITIATION

2-120. To achieve the necessary safe distance from the explosive charges being emplaced, lay out one or

more M12s, M13s, M21s, or M23s. The blasting cap furthest from the initiation point is connected to the

MDI firing system or to the detonating cord ring main. When returning to the initiation point, visually

inspect the initiation system for possible misfire problems. This is the only test procedure for the MDI

initiation system. At the initiation point, the M81 igniter is secured to the M12 or M13 shock tube as

follows:

Loosen the M81 end cap three to four turns counterclockwise, and remove the hard, plastic

shipping plug. Pull the shipping plug out of the igniter ensuring not to remove the shock tube

reducer.

Cut off the crimped end of the shock tube at the desired length of the relay cap shock tube using

a sharp knife.

WARNING

Crimpers will not make a smooth enough cut to ensure that the

M81 will function the shock tube. Failure to comply could result in

immediate personal injury or damage to equipment.

Push the shock tube into the hole in the M81 end cap as far as it will go. Turn the igniter end cap

clockwise and finger tight to secure it in the device once the shock tube has seated (Figure 2-53,

page 2-66).

Ensure that all friendly personnel are at a safe distance from the explosive charge and that they

take appropriate cover.

Squeeze together the spread legs of the safety (cotter) pin. Use the safety pin cord to remove the

safety pin from the body of the igniter. Wear a leather glove, and grasp the igniter body firmly

with one hand, with the pull ring fully accessible to the other hand.

Actuate the igniter by sharply pulling its pull ring. Ensure that the pop of the igniter primer is

heard.

Note. The mechanism of the M81 is identical to that of the old M60 igniter. If the primer does

not fire, the M81 can be recocked and reactuated immediately. The igniter should be held firmly

and then the pull rod should be pushed back into the igniter until a click is heard or felt, and then

the pull ring should be pulled again sharply to actuate it. If the igniter primer fires, but the charge

does not, refer to Section VII, Misfires, in this chapter.

11 July 2007

FM 3-34.214

2-65

Chapter 2

Figure 2-53. M81 Fuse Igniter With a Shock Tube

DELAY INITIATION

2-121. The M14 delay blasting cap assembly has a 7 1/2-foot length of time fuse marked in nominal

1-minute increments giving a total delay of a nominal 5 minutes. Before attaching the M14 to the initiation

system, visually inspect the initiating sets for possible misfire problems. This is the only test procedure for

the MDI initiating set. The M14 is initiated by—

Step 1. Opening an M9 blasting cap holder.

Step 2. Inserting the M14 blasting cap.

Step 3. Snapping shut the smaller hinged flap to secure the M14.

Step 4. Placing up to five shock tubes, five low-strength detonating cords, or one strand of

detonating cord in the M9 holder if they are run straight through the M9 and are not looped.

Step 5. Tying the shock tube, low-strength detonating cord, or detonating cord ends into an

overhand knot.

Step 6. Placing the shock tube, low-strength detonating cord, or detonating cord in the M9

holder alongside the blasting cap and securing the M9 larger hinged holder flap.

Step 7. Securing the large flap with tape (Figure 2-54).

2-66

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-54. M9 Blasting Cap Holder in a Delay Initiation

2-122. A M14 time fuse is installed as follows:

Step 1. Use a sharp knife to cut 1/4 inch of the time fuse and the metal seal from the free end of

the M14 time fuse (if the maximum 5-minute delay is required). Cut at the marked bands to

reduce the delay, if so desired. Ensure that the delay on the time fuse allows for withdrawal to a

safe distance or allows time to take appropriate cover.

Step 2. Loosen the M81 end cap three to four turns counterclockwise so the hard, plastic

shipping plug can be easily removed. Pull the shipping plug and shock tube reducer out of the

igniter.

Step 3. Secure an M81 fuse igniter to the freshly cut end of the M14 time fuse (Figure 2-55).

Step 4. Squeeze the spread legs of the safety (cotter) pin together. Use the safety pin cord to

remove the safety pin from the body of the igniter. Wear a leather glove and grasp the igniter

body firmly with one hand, with the pull ring fully accessible to the other hand. Pull the igniter

pull ring sharply to actuate.

Step 5. Ensure that smoke is coming from the fuse or out of the vent hole in the igniter.

Step 6. Remove the igniter, and withdraw to a safe distance or to appropriate cover.

Figure 2-55. M81 Fuse Igniter With an M14 Time Fuse Installed

11 July 2007

FM 3-34.214

2-67

Chapter 2

SPECIAL CONDITIONS

2-123. The ambient temperature and the altitude of the site have an impact on the operation of the MDI.

Cold weather and high altitudes will extend the delay times on the M14 and M18. Precautions can be taken

when using MDI in extreme cold temperatures and/or high altitudes by dual-priming and dual-initiating the

charges to ensure proper initiation. When using MDI for ice demolitions, the same precautions must be

taken with one addition; if the charges are to be placed in the ice or under water in extreme cold conditions,

the same rules apply as if the target were stemmed or tamped. For these types of missions, use detonating

cord for priming and branchline construction.

Note. The M14 and M18 time-blasting fuses gives about a 5-minute delay and 20-minutes,

respectively, between lighting the fuse and initiating the detonator. Like the standard M700 fuse,

the burning time will vary with temperature and altitude. For example, operating at an altitude of

12,000 feet in cold weather will extend the delay time significantly. When exact detonation

times are required, command-detonation methods should be considered.

WARNING

When using an MDI in extreme cold temperatures and/or high

altitudes, dual-prime and dual-initiate the charges. Failure to

comply could result in immediate personal injury or damage to

equipment.

MODERNIZED DEMOLITION INITIATOR FIRING SYSTEMS

2-124. With the introduction of MDI components, there are two types of firing systems: a stand-alone and

a combination firing system. Both systems can be emplaced as single- or dual-firing systems. The choice of

which system to use for a particular demolition mission is left to the experience of the engineer

commander. However, the combination firing system is the preferred method for reserved demolition

targets. Whenever handling MDI components with blasting caps or boosters outside of their original

packaging, ensure that they are inserted into a foam protective cap or an M9 holder to prevent damage.

DISPOSAL

2-125. After the charges have been successfully fired, the unit commander is responsible for ensuring the

proper disposal of the residue. The used shock tube is nonrecyclable plastic and may be sent directly to an

approved landfill. However, the blasting cap residual is considered hazardous waste and must be removed

from the shock tube and disposed of according to local policy. Commanders must coordinate with the local

Directorate of Engineering (Department of Public Works) and/or the local Defense Reutilization and

Marketing Office (DRMO) for local disposal guidance and landfill information.

WARNING

Do not dispose of used shock tubes by burning them because of

the potentially toxic fumes given off from the burning plastic.

Failure to comply could result in immediate personal injury or

damage to equipment.

STAND-ALONE SYSTEM

2-126. The stand-alone firing system is one in which the initiating sets and transmission and branchlines

are constructed using only MDI components and the explosive charges are primed with MDI blasting caps

2-68

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

or boosters. It is important to ensure that the firing system is balanced. All charges must have the same

distance in the shock tube length and the low-strength detonating cord from the firing point to the charge.

Figure 2-56 shows the MDI single-firing system and Figure 2-57, page 2-70, shows the MDI dual-firing

system.

2-127. The disadvantages of a single-firing system are that if the transmission line is cut, charges down

line from the cut will not detonate. If there is a possibility of the transmission lines being cut (for example,

through artillery fires), a second firing system should be added as shown in Figure 2-57.

Figure 2-56. MDI Single-Firing System (Single-Primed and Dual-Initiated)

WARNING

When making multishock tube installations, ensure that the shock

tubes are protected from the effects of the nearby relay caps and

charges. The shrapnel produced by a cap or charge could easily

cause a misfire (partial or complete). When there are many shock

tubes involved in a shot, they should be carefully placed away

from the junction. Failure to comply could result in immediate

personal injury or damage to equipment.

2-128. The stand-alone MDI firing system is used for all types of demolition missions, including bridge

demolitions. The MDI firing system can be used to initiate reserved demolition targets. However, only the

M151 or M152 may be used to prime charges. Under current internationally agreed upon doctrine, charges

cannot be primed with blasting caps until a change of readiness from state 1 (safe) to state 2 (armed) is

ordered. Priming every charge with MDI blasting caps at this critical moment would take a considerable

amount of time and be unacceptable to the maneuver commander. Priming charges with MDI M151 or

MDI M152 components or detonating cord are the required methods for reserve demolition targets. The

charges in this case are now dual-primed, the transmission line is laid in the opposite direction of the first

transmission line, and the system is a balanced system.

11 July 2007

FM 3-34.214

2-69

Chapter 2

Figure 2-57. MDI Dual-Firing System (Dual-Primed and Dual-Initiated)

CONSTRUCTION SEQUENCE OF A MODERNIZED DEMOLITION INITIATOR USING A SHOCK

TUBE

2-129. The demolition site should be thoroughly reconnoitered before emplacing explosive charges on the

firing system. The following steps should be used:

Step 1. Identify the firing point, and observe the safe distances as given in Chapter 6.

Step 2. Emplace and secure primed explosive charges on the target.

Step 3. Begin with the set of explosive charges furthest from the firing point, and place a

sandbag or other easily identifiable marker over the transmission line blasting cap. Use an M11

or M152 if the distance between the sets of charges is less than 30 feet. Use an M151 if the

distance is less than 10 feet.

Step 4. Attach branchlines from the primed explosive charges to the transmission line using the

attaching method as shown in Figure 2-46, page 2-57. Secure the transmission and branchlines

by taping all the holders closed.

Step 5. Unreel the transmission line to the firing point. Achieve the necessary safe distance by

using several M12s, M13s, M21s, or M23s if needed. Use an M14 or M18 as an ignition element

of a transmission line to provide time to reach a safe distance without the need to lay and

connect multiple M12s, M13s, M21s, and M23s spooled components as transmission lines.

2-70

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Note. To effectively prevent a misfire, the shock wave in the shock tube must travel the same

distance to all charges. No more than five M11, M151, or M152 branchlines can be connected to

the transmission line blasting cap holder. If there are more than five charges, group the

branchlines from the charges, and connect them to the M9s blasting cap holder of another M11,

M151, or to an M152 branchline. The branchline is connected to the transmission line blasting-

cap holder as shown in Figure 2-46, page 2-57. The transmission and branchlines are secured by

a large, hinged flap and the flap is secured with tape.

Step 6. Perform a visual inspection of the firing system for possible misfire indicators while en

route to the firing point.

Step 7. Initiate the system at the firing point using the procedures in paragraph 2-121.

CONSTRUCTION SEQUENCE OF A MODERNIZED DEMOLITION INITIATOR USING AN M151

OR AN M152

2-130. The boosters are factory-crimped onto low-strength detonating cord. The booster is used to prime

charges that are either buried or aboveground by substituting, not eliminating, the present use of standard

detonating cord as a branchline or to prime charges. When an M151 or M152 is removed from an original

shipping container, a foam protector should be installed on the booster. As low-strength detonating cord is

used, additional procedures are involved in the use of an M151 and M152. These procedures include—

Removing any tape used to bundle an M151 or M152.

Spreading the low-strength detonating cord between the primed charge and the M9 holder of the

transmission line when charges are in the same general area.

Avoiding conditions where one or more cords are running alongside or twisted with other cords

or crossovers any low-strength detonating cord.

Ensuring that the cords are in contact with a blasting cap or booster.

2-131. Thoroughly reconnoiter the demolition site before emplacing explosive charges on the firing

system. Use the following steps:

Step 1. Identify the firing point, and observe the safe distances as given in Chapter 6.

Step 2. Emplace and secure primed explosive charges on the target.

Step 3. Begin with the set of explosive charges farthest from the firing point, and place a

sandbag or other easily identifiable marker over the transmission line blasting cap. Use an M11

or M152 if the distance between the sets of charges is less than 30 feet. Use an M151 if the

distance is less than 10 feet.

Step 4. Attach branchlines from the primed explosive charges to the transmission line. See

Figure 2-58, page 2-72. The attaching method is shown in Figure 2-46. Secure the transmission

and branchlines by taping all the holders closed.

Step 5. Unreel the transmission line to the firing point. Use several M12s, M13s, M21s, or M23s

to achieve the necessary safe distance needed. Use an M14 or M18 as an ignition element of a

transmission line to provide time to reach a safe distance without laying and connecting multiple

M12s, M13s, M21s, and M23s spooled components as transmission lines.

Step 6. Perform a visual inspection of the firing system for possible misfire indicators while en

route to the firing point.

Step 7. Initiate the system at the firing point using the procedures in paragraph 2-121.

11 July 2007

FM 3-34.214

2-71

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-59. Combination (MDI and Detonating Cord) Firing System (Dual)

2-133. Use the combination (MDI and detonating cord) firing system for all types of demolition missions.

It combines the advantages of MDI components with the simplicity and flexibility of detonating cord. The

combination firing system is the preferred method for reserved demolition targets, underwater operations,

and operations where subsurface-laid charges are used.

CONSTRUCTION SEQUENCE FOR MODERNIZED DEMOLITION INITIATOR SHOCK TUBE

COMPONENTS AND DETONATING CORD

2-134. Thoroughly reconnoiter the site before emplacing explosive charges on the firing system. Use the

following steps:

Note. M151s or M152s can be used to replace detonating cord when used as branchlines to

charges placed either aboveground or belowground.

Step 1. Identify the firing point, and observe the safe distances as given in Chapter 6.

Step 2. Emplace and secure the primed explosive charges on the target.

Step 3. Construct detonating cord line or ring mains according to the procedures in Section III,

of this chapter.

Step 4. Cover the blasting cap of the transmission line with a sandbag or another easily

identifiable marker at the connection between the detonating cord line and ring main to the MDI

initiating set.

11 July 2007

FM 3-34.214

2-73

Chapter 2

Step 5. Tie in any detonating cord branchlines to the line or ring main. Clip the branchlines to

the detonating cord line or ring main using the attached detonating cord clip if priming with

MDI. Do this by—

Looping the shock tube around and into the detonating cord clip (Figure 2-60).

Pulling the shock tube tight to prevent the detonating cord clip from slipping.

Clipping the detonating cord line or ring main into the detonating cord clip.

Laying the branchlines toward the charges if an M11 is used.

Figure 2-60. MDI Detonating Cord Clip

Step 6. Lay out an M11, M151, or M152 with an M9 installed as a transmission line from the

detonating cord ring main to the transmission line.

Step 7. Attach the M11, M151, or M152 to the holder on the transmission line blasting cap

holder, and secure with tape.

Step 8. Tie an overhand knot in the detonating cord of the ring main, and place it into the M9

blasting cap holder. Secure the large flap with tape.

Step 9. Perform a visual inspection of the entire firing system for any flaws, which might cause

a misfire.

Step 10. Initiate the system at the firing point using the procedures in paragraph 2-121.

SHOCK TUBE SPLICING

2-135. The MDI shock tube components are extremely reliable because all the components are sealed.

Unlike standard, nonelectric priming components, they cannot be easily degraded by moisture. Cut shock

tubes make the open ends vulnerable to moisture. Dampened explosive film on the inside of the shock tube

will stop a detonation from going beyond such a damp spot. Care should be taken when cutting and splicing

the shock tube. When cutting the shock tube, make a temporary moisture seal by bending it 2 inches onto

itself from the cut and taping it together along the open end with electrical tape. Splicing tubes are used to

repair a break in the shock tube of a transmission or branchline (for example, caused by shrapnel from

artillery fire). Every splice in the shock tube reduces the reliability of the firing system. The number of

splices in a shock tube line should be kept to as few as practicable.

Note. A fully sealed MDI component should be used to replace the broken shock tube. If a fully

sealed MDI component is not available, splicing is used as a last resort. When conducting water

or diving demolition missions, do not splice the shock tube.

2-74

FM 3-34.214

11 July 2007

Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

2-136. The following procedures are the proper way to splice the shock tube:

Step 1. Use a sharp knife to make a square cut about 3 feet from the previously cutoff end of the

shock tube, whether or not it was knotted according to the guidance above. Immediately seal off

the shock tube remaining on the spool by bending 2 inches of the shock tube end over on itself

and taping it in place to provide a temporary moisture seal. Tie a knot if no tape is available.

Step 2. Tie loosely the two shock tube ends to be spliced together in an overhand knot. Leave at

least 2 inches free at the end of each shock tube beyond the knot.

Step 3. Pull the shock tube lightly to tighten the knot, but not so tight as to significantly deform

the shock tube in the knot.

Step 4. Push one of the free shock tube ends to be spliced firmly into one of the precut splicing

tubes at least 1/4 inch.

Step 5. Push the other shock tube end firmly into the other end of the splicing tube at least

1/4 inch (Figure 2-61).

Note. It is not necessary for the two ends of the shock tube to meet; the detonation wave in the

shock tube will still generate over a small gap.

CAUTION

Taping two cut ends of the shock tube together does not make a

reliable splice. Personal injury or damage to equipment may result

from long-term failure to follow correct procedures.

Figure 2-61. Splicing a Shock Tube

SECTION VII - SAFETY PROCEDURES

MODERNIZED DEMOLITION INITIATOR CONSIDERATIONS

2-137. When conducting training and missions with the MDI, follow the general safety considerations for

demolitions as given in Chapter 6 and DA Pamphlet 385-63. When MDI components are removed from

their original packaging, install a foam protector onto the blasting cap or booster. Misfires occur when—

11 July 2007

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Chapter 2

The shock tube is cut using crimpers.

The M81 fuse igniter is not properly connected to the shock tube before initiation or the shock

tube is pulled after being secured in the M81.

The shock tube is cut by shrapnel during the initiation process.

The shock tube is incorrectly inserted into the holders on the M12 or M13 blasting caps or into

the M9 holder.

An overhand knot is not used to secure the spliced area. A splice without a knot can separate by

a small accidental tug on the shock tube.

2-138. MDI components, with factory-crimped blasting caps attached to a shock tube, in their original

packaging and subpackaging are marked according to Department of Transportation hazard class

explosives requirements. These items can be transported with other explosives provided they are

compatible. See DA Pamphlet 385-64 to identify the classes of explosives that can be transported in the

same vehicle.

MODERNIZED DEMOLITION INITIATOR MISFIRES

2-139. Working on or near a misfire is the most hazardous of all blasting operations. A misfire in the MDI

system is extremely rare if the following procedures are used:

Prepare and emplace all components of the firing systems. Use dual-firing systems where

appropriate. Ensure that the detonating cord, shock tube, or low-strength detonating cord in the

blasting cap holder is in contact with the blasting cap. Do not mix the detonating cord, shock

tube, or low-strength detonating cord in the same M9 holder.

Mark or cover MDI blasting caps with sandbags or other clearly identifiable markers to prevent

personnel from damaging the caps during setup.

Emplace and prime all charges safely.

Prime all buried charges with an M151, M152, or detonating cord.

Perform any tamping operation with care to avoid damage to the charges and the priming

system. Always tamp with a nonsparking tool.

Initiate charges according to the correct technique.

Inspect visually the firing system before initiation.

DANGER

Do not handle misfires down range until the required 30-minute

waiting period for both primary and secondary initiation systems

has elapsed and other safety precautions have been taken.

Failure to comply may cause death or permanent injury.

2-140. The most common cause of a misfire in a shock tube firing system is the initiating element, usually

an M81 igniter. The following misfire procedures are for both command-initiated and delay-initiated

systems(Figure 2-62):

A failure with the M81 will occur if the primer does not fire. If, after two retries, the M81 does

not result in it firing, cut the shock tube, replace the igniter with a new one, and repeat the firing

procedure.

Another misfire mode for the M81 is that the primer fires but blows the shock tube out of its

securing mechanism without it firing. This is usually due to the shock tube not having been

properly inserted and secured in the igniter. To correct this problem, cut a minimum of 3 feet

from the end of the shock tube. It is recommended that the shock tube be checked for the

presence of fine explosive powder following step 1 in the next paragraph. If powder is present,

replace the igniter and repeat the firing procedure.

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Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

Figure 2-62. MDI Misfire Procedures

2-141.

The following steps are used to correct misfire problems:

Step 1. If the igniter appears to have functioned properly (the primer pops or smokes), but the

charge did not fire, cut off the first 6 inches of shock tube and discard. Then cut a 1-foot section

from the shock tube. Hold the 1-foot piece of shock tube so that one end is over the palm of your

hand, then blow through the other end. If no powder is present, proceed to step 2. If a gray or

silver powder is blown from the shock tube, it has not fired. In this case, install a new igniter on

the freshly cut end of the shock tube, and repeat the firing procedure. If detonation does not

occur, proceed to step 3.

Step 2. If the igniter or initiating element functioned properly and no powder was blown from

the shock tube in the previous step or its flash was seen, observe the burn time plus 30 minutes

before going downrange.

Step 3. After waiting the burn time plus 30 minutes, proceed downrange and check all the

components in the firing system. The most likely cause of a misfire is the incorrect placement of

the shock tube in the blasting cap holders (for example, the blasting cap detonated but failed to

initiate the shock tube of the next down-line MDI component). If a blasting cap has not fired, it

is likely that the shock tube was not initiated by the up-line blasting cap. To determine if the

shock tube has fired at a particular point, perform step 1 with a 1-foot section of shock tube cut

from the suspect area.

Step 4. If the shock tube still contains the explosive dust, attach a new component by cutting the

shock tube down line from the defective shock tube 1 foot past the blasting cap holder. Seal the

shock tube by bending it 2 inches from the cut and taping it. On the defective tube, move down

and cut it 10 feet from the blasting cap. Remove and dispose of the defective shock tube and cap

according to local misfire policies. Then, lay out the shock tube of the replacement component

back to the firing point, and repeat the firing sequence when it is safe to do so.

Step 5. If the shock tube contains no explosive dust because it has been fired, the problem is

probably with the blasting cap. The shock tube is cut down line from the defective blasting cap

1 foot past the blasting cap holder. Then, seal the shock tube by bending it 2 inches from the cut

and taping it. On the shock tube of the defective blasting cap, move down and cut it 10 feet from

the blasting cap. Remove and dispose of the defective shock tube and cap according to local

misfire policies. Then, lay out the shock tube of the replacement component back to the firing

point, and repeat the firing sequence when it is safe to do so.

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Chapter 2

DANGER

Never yank or pull hard on the shock tube. This may actuate the

blasting cap. Failure to comply may cause death or permanent

injury.

Step 6. If the first component of the firing train was not the one that failed, check out each

succeeding component until the failed one is found. Then, replace the failed or fired relay

components back to the initiating site as in steps 4 and 5.

Step 7. If the failed component appears to be the final high-strength blasting cap or booster,

replace if it is easily accessible. If it is used to prime an explosive charge, do not disturb it. Then,

place a new, primed 1-pound explosive charge next to the misfired charge and detonate it when

it is safe to do so.

Step 8. If the charges were primed with MDI M151 or MDI M152 components and buried,

follow the above misfire procedures to the low-strength detonating cord of an MDI M151 or

MDI M152. If the transmission line blasting cap has failed to function, use a nonsparking tool to

cut the low-strength detonating cord 1 foot past the failed transmission line blasting cap. Then,

walk back 10 feet from the defective blasting cap, and cut the transmission line shock tube.

Remove the defective shock tube, failed cap, and the length of low-strength detonating cord is

and dispose of them according to local misfire procedures. Lay out a replacement transmission

line to the firing point and then connect the remaining low-strength detonating cord to the

transmission line holder. Repeat the firing sequence to detonate the charge. If the buried charge

has failed to detonate, but the booster cord has functioned to the surface of the buried charge,

follow the procedures in Chapter 6, Section III.

SECTION VIII - MODERNIZED DEMOLITION INITIATOR USE WITHIN

COMMON DEMOLITION MISSIONS

FIRING SYSTEMS PLANNING

2-142. The MDI system has many components that make up a firing system. Because of this, it is critical

during the planning and resourcing phase of the operation that the firing system be planned in detail. The

process of planning the firing system from the charge to the firing point is critical to the success of the

mission. Demolition site reconnaissance is required and precise numbers of shock tube, holders, and other

devices must be determined before executing the demolition mission. All residue must be collected and

disposed of whenever possible. This is both an environmental and a tactical necessity.

2-143. A number of missions require charges to detonate simultaneously. To assure this, branchlines of

equal length must be attached to the initiating cap or booster or detonating cord ring main if used. Making

branchlines as short as is practical will further improve the simultaneous detonation of the charges. For

example, if the farthest distance for one of three branchlines is 15 feet, measure the three lines, tie an

overhand knot at this point, and connect the transmission line between the knot and the charge or move all

three J hooks to that point and connect.

STEEL-CUTTING CHARGES

2-144. Steel-cutting charges should be emplaced according to the procedures outlined in Chapter 3. See

Figure 2-63 for an example of steel I beam cutting charges.

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Initiating Sets, Priming Methods, Firing Systems, and Modernized Demolition Initiators

BRIDGE DEMOLITION CHARGES AND CONSTRUCTION

SEQUENCE USING SHOCK TUBE COMPONENTS

2-146. Bridge demolition charges should be emplaced according to the procedures outlined in Chapter 4.

TIMBER-CUTTING CHARGES

2-147. Timber-cutting charges should be emplaced and primed according to the procedures outlined in

Chapter 3.

EXTERNAL TIMBER CHARGE

2-148. Figure 2-66 shows external timber charges using dual initiation. The following steps are used when

placing external timber charges:

Step 1. Place explosives according to the procedures outlined in Chapter 3.

Step 2. Lay out transmission lines from the charge to the firing point.

Step 3. Lay out branchlines from the charges to the holder on the M12 transmission line. Insert

the branchlines into the holder, snap the hinged flap shut, and tape it closed.

Step 4. Prime the charges according to the procedures outlined in Chapter 3, using minimal

personnel on the site.

Step 5. Inspect the firing system while moving to the firing point once all charges have been

properly placed and primed. At the firing point, attach the M81 fuse igniter to the end of the

M12 or M13 transmission line and initiate the firing system.

Figure 2-66. External Timber Charges Using Dual Initiation

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FM 3-34.214

2-81

Chapter 2

INTERNAL TIMBER CHARGE

WARNING

Do not use MDI shock tube components for priming internal

charges. Use the M151 or M152. Failure to comply could result in

immediate personal injury or damage to equipment.

2-149. Figure 2-67 shows internal timber charges with dual initiation. The following steps are used when

placing internal timber charges:

Step 1. Place primed explosives according to the procedures outlined in Chapter 3.

Step 2. Lay out transmission lines from the charge to the firing point.

Step 3. Lay out branchlines.

Step 4. Tie the branchlines into the line main.

Step 5. Construct the line main according to the procedures outlined in Chapter 2.

Step 6. Connect the transmission line to the line main using an M9 holder, and tape it closed.

Figure 2-67. Internal Timber Charges With Dual Initiation

BREACHING CHARGES

2-150. Breaching charges are emplaced according to the procedures outlined in Chapter 3. See

Figure 2-68.

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Chapter 3

Charge Calculations and Placement

This chapter discusses charge calculations. Included are the six-step, problem-solving

formats for all types of calculations and the different methods for placing charges.

SECTION I - DEMOLITIONS

DEMOLITION PRINCIPLES

3-1. The amount and placement of explosives are key factors in military demolition projects. Formulas

are available to help an engineer calculate the required amount of explosives. Demolition principles and

critical-factor analysis guide a Soldier in working with explosive charges. The available formulas for

demolition calculations are based on the detonation effects, the charge dimension significance, and the

charge-placement significance.

DETONATION EFFECTS

3-2. When an explosive detonates, it violently changes into highly compressed gas. The explosive type,

density, confinement, and dimensions determine the rate at which the charge changes to a gaseous state.

The resulting pressure then forms a compressive shock wave that shatters and displaces objects in its path.

A HE charge detonated in direct contact with a solid object produces the following three detectable,

destructive effects:

Deformation. The shock wave charge deforms the surface of the object directly under the

charge. When the charge is placed on a concrete surface, it causes a compressive shock wave

that crumbles the concrete in the immediate vicinity of the charge, forming a crater. When

placed on a steel surface, the charge causes an indentation or depression about the size of the

charge contact area.

Spalling. The shock wave of the charge chips away at the surface of the object directly under the

charge. This action is known as spalling. If the charge is large enough, it will spall the opposite

side of the object. Because of the difference in density between the target and the air, the

compressive shock wave of the charge reflects as a tensile shock wave from the free surface if

the target has a free surface on the side opposite the charge. This action causes spalling of the

target-free surface. The crater and spalls may meet to form a hole through the wall in concrete

demolitions. On a steel plate, the charge may create one spall in the shape of the explosive

charge, throwing the spall from the plate.

Radial cracking. If the charge is large enough, the expanding gases can create a pressure load

on the object that will cause cracking and displacing of material. This effect is known as radial

cracking. When placed on concrete walls, the charge may crack the surface into a large number

of chunks and project them away from the center of the explosion. When placed on steel plates,

the charge may bend the steel away from the center of the explosion.

CHARGE DIMENSION SIGNIFICANCE

3-3. The force of an explosion depends on the quantity and power of the explosive. The destructive effect

depends on the direction of the explosive force. To transmit the greatest shock, a charge must have the

optimal relationship of the contact area and the thickness to the target volume and density. If a calculated

charge is spread too thinly, not enough space will be provided for the shock wave to reach full velocity

before striking the target. In improperly configured explosives (too thin or wrong strength), the shock wave

tends to travel in a parallel rather than a perpendicular direction to the surface. As a result, the volume of

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FM 3-34.214

3-1

Chapter 3

the target will be too much for the resulting shock wave. Additionally, a thick charge with too small a

contact area will transmit a shock wave over too small a target area with much lateral loss of energy.

CHARGE PLACEMENT SIGNIFICANCE

3-4. The destructive effect of an explosive charge depends on the location of the charge in relation to the

size, shape, and configuration of the target. For the most destructive effect, detonate an explosive of the

proper size and shape for the size, shape, and configuration of the target. Any significant air or water gap

between the target and explosive will lessen the force of the shock wave. Cut explosives (such as sheet or

plastic explosives) to fit odd-shaped targets. Whenever possible, place explosive charges to detonate

through the smallest part of the target. Use internal charges to achieve maximum destruction with minimum

explosives expense. Tamping external charges increases their destructive effect.

CHARGE TYPES

3-5. Internal and external charges are the two charge types. Internal charges are charges that are placed in

boreholes in the target. External charges are charges that are placed on the surface of the target.

INTERNAL CHARGES

3-6. Internal charges are confined with tightly packed sand, wet clay, or other material (stemming).

Stemming is the process of packing material on top of an internal borehole or crater charge. Stemming

material is filled and tamped against the explosive to fill the borehole to the surface. In drilled holes, tamp

the explosive as it is loaded into the hole. Stemming material should be tamped only with a nonsparking

tool.

EXTERNAL CHARGES

3-7. External charges are covered and tamped with tightly packed sand, clay, or other dense material.

Stemming material may be loose or in sandbags. To be most effective, make the thickness of the tamping

material at least equal to the breaching radius. Small breaching charges are tamped on horizontal surfaces

with several inches of wet clay or mud.

CHARGE CALCULATION FACTORS

3-8. The amount of explosives required is calculated for any demolition project. Charge calculations are

based on the following critical factors:

Type and strength of target materials. A target may be timber, steel, or other material.

Concrete may be reinforced with steel to increase the strength of the concrete.

Target size, shape, and configuration. These characteristics all influence the required type and

amount of explosives. For example, large or odd-shaped targets, such as concrete piers and steel

beams, are more economically demolished with multiple charges than with a single charge.

Desired demolition effect. The extent of the demolition project and the other desired effects

should be considered, such as the direction that trees will fall when constructing an abatis.

Explosive type. The characteristics of each explosive type determine its application for

demolition purposes. Table 1-1, pages 1-2 and 1-3, lists these characteristics.

Charge size and placement (Table 3-1). When using external charges without considering

placement techniques, use a flat, square charge with a thickness-to-width ratio of 1:3.

Charges should be fastened to the target using wire, adhesive compound, tape, or string.

Charges should be propped against targets with wooden or metal frames made of scrap or

other available materials or placed in boreholes.

Tamping method. If you do not completely seal or confine the charge or if you do not ensure

the material surrounding the explosive is balanced on all sides, the force of the explosive will

escape through the weakest spot. To keep as much explosive force as possible on the target, pack

material around the charge to fill any empty space. This material is called tamping material, and

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FM 3-34.214

11 July 2007

Charge Calculations and Placement

the process is called tamping. Sandbags and earth are examples of common tamping materials.

Always tamp charges with a nonsparking tool.

Priming direction. The direction in which the shock wave travels through the explosive charge

will affect the rate of energy transmitted to the target. If the shock wave travels parallel to the

surface of the target (Figure 3-1, Diagram 1), the shock wave will transmit less energy over a

period of time than if the direction of detonation is perpendicular to the target (Figure 3-1,

Diagram 2). For best results, prime the charge in the center of the face farthest from the target.

Table 3-1. Breaching Charge Thickness

Charge Weight (lb)

Charge Thickness (in)

Less than 5

5 to less than 40

40 to less than 300

300 or more

Note. If using TNT, use the approximate thickness.

Figure 3-1. Direction of Initiation

EXPLOSIVE SELECTIONS

3-9. Explosive selection for successful demolition operations is a balance between the factors listed in

paragraph 3-8 and the practical aspects; target type; the amount and types of explosives, materials (such as

sandbags), equipment, and personnel available; and the amount of time available to accomplish the

mission.

11 July 2007

FM 3-34.214

3-3

Chapter 3

CHARGE CALCULATIONS

3-10. Use the six-step, problem-solving format below for all charge calculations. This format is used to

determine the weight (P) of the explosives required for a demolition task in pounds of TNT. If using an

explosive other than TNT, adjust P accordingly by dividing P for TNT by the relative effectiveness (RE)

factor of the explosive you plan to use (Table 1-1, pages 1-2 and 1-3).

Step 1. Determine the critical dimensions of the target.

Step 2. Calculate the weight of a single charge of TNT by using the appropriate demolition

formula.

Step 3. Divide the quantity of explosive by the RE factor. Skip this step if using TNT.

Step 4. Determine the number of packages of explosive for a single charge by dividing the

individual charge weight by the standard package weight of the chosen explosive. Round this

result to the next higher, whole package. Use volumes instead of weights for special-purpose

charges (ribbon, diamond, saddle, and similar charges).

Step 5. Determine the number of charges based on the targets.

Step 6. Determine the total quantity of explosives required to destroy the target by multiplying

the number of charges (step 5) by the number of packages required per charge (step 4).

SECTION II - NORMAL CUTTING CHARGES

TIMBER-CUTTING CHARGES

3-11. Plastic explosives are the best timber-cutting charges for both internal and external placement. These

explosives make excellent internal charges because they are easily tamped into boreholes. They make

excellent external charges, because they are easy to tie, tape, or fasten to the target. Timber will vary

widely in its physical properties from location to location, requiring careful calculation. Therefore, make

test shots on the specific timber type to determine the optimal size of the timber-cutting charge.

INTERNAL CHARGES

3-12. The following formula is used to calculate internal cutting charges:

D²

P =

or P = 0.004D

250

where—

= TNT required per tree (in pounds)

= diameter or the least dimension of dressed timber (in inches)

Note. Diameter = circumference divided by 3.14

For trees that are up to 18 inches in diameter, use one hole to place the explosive. For larger trees, use two

holes drilled at right angles to each other without intersecting but as close together as possible. Two-inch

diameter holes should be drilled to a depth equal to two-thirds of the diameter of the tree. Evenly split the

required charge between the holes. This will allow enough room to place the explosive in the holes and

leave enough room to cap them with mud or clay (Figure 3-2). For dimensioned timber requiring two

boreholes, place the boreholes side by side. When placing the charges, form the plastic explosive to the

approximate diameter of the hole. To not reduce the density of the explosive, try to minimize the amount of

molding. The charge is primed with detonating cord (see Chapter 2, Section II) and placed in the hole. A

nonsparking tool is used to finish filling the holes by packing them with mud or clay. When using two

boreholes, connect the branchlines in a British junction

(Figure

2-33, page

2-29). For an example

calculation, see Appendix F (Figure F-1, page F-1).

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11 July 2007

Charge Calculations and Placement

Figure 3-2. Timber-Cutting Charge (Internal)

EXTERNAL CHARGES

3-13. To be most effective, external charges should be rectangular, 1 to 2 inches thick, and twice as wide as

they are high. Remove the bark to place the explosive in direct contact with solid wood and to reduce air

gaps between the charge and the wood. If the timber is not round or if the direction of fall is not important,

place the explosive on the widest face. This will concentrate the force of the blast through the least

dimension of the timber. Trees will fall toward the side on which the explosive is placed, unless influenced

by the wind or the lean of the tree (Figure 3-3, page 3-6). If the tree is leaning the wrong way or a strong

wind is blowing, place a 1-pound kicker charge on the side opposite the main charge, about two-thirds of

the way up the tree. The kicker charge is fired at the same time as the main charge. For the best results

when using composition C4, orient the longest dimension of the charge horizontally. Orienting the charges

vertically tends to allow gaps to develop between the charges. Use the following formula to determine the

amount of explosive needed for cutting trees, posts, beams, or other timber using untamped external

charges.

For

example

calculation,

see

Figure F-2, page F-2.

D²

P = or P = 0.025D

where—

= TNT required per target ( in pounds)

= diameter or least dimension of dimensioned timber (in inches)

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FM 3-34.214

3-5

Chapter 3

ABATIS

3-16. Fallen tree obstacles (Figure 3-6) are made by cutting trees that remain attached to their stumps.

Since trees vary in their physical properties, a test shot should be conducted if time and explosives are

available. The following formula is used to compute the amount of TNT required for the test shot:

D²

P = or P = 0.02D

where—

= TNT required per tree (in pounds)

= diameter or least dimension of dimensioned timber( in inches)

Figure 3-6. Abatis

Placement

3-17. External placement should be used with the charge 5-feet aboveground level. The tree will fall

toward the side where the explosive is attached unless influenced by the lean of the tree or wind.

Special Considerations

3-18. The following should be considered when creating an abatis:

Place a 1-pound kicker charge on the side opposite the main charge, about two-thirds of the way

up the tree, if the tree is leaning the wrong way or a strong wind is blowing. Fire the kicker

charge at the same time as the main charge.

Ensure that the obstacle will cover at least 75 meters in depth.

Ensure that the individual trees are at least 2 feet in diameter. Smaller trees are not effective

obstacles against tracked vehicles.

Fell trees 3 to 5 meters apart to create a condition to prevent tracked vehicles from driving over

the top of the obstacle.

Fell the trees at a 45° angle toward the enemy.

Simultaneously detonate the charges on one side of the road at a time and then fell the trees on

the other side of the road.

Enhance the obstacle with the use of wire, mines, and booby traps.

HASTY TIMBER CALCULATIONS

3-19. The situation sometimes require the use of hasty timber calculations. Table 3-2 lists the required

number of composition C4 packages for cutting timber with internal, external, and abatis charges.

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11 July 2007

Charge Calculations and Placement

Table 3-2. Timber-Cutting Charge Size

Packages of Composition C4 (1.25-lb packages) Required by

Charge

Timber Diameter (in)

Type

Internal

External

Abatis

—

Note. The packages required are rounded up to the next whole package.

STEEL-CUTTING CHARGES

WARNING

Steel-cutting charges produce metal fragments. Proper

precautions should be taken to protect personnel. Failure to

comply could result in immediate personal injury or damage to

equipment.

3-20. In order to prepare steel-cutting charges, the target factors and the explosive factors must be known.

The paragraphs below discuss the target and explosive factors.

TARGET FACTORS

3-21. Target configuration and target materials are critical in steel-structure demolitions, more so than with

other materials.

Target Configuration

3-22. The configuration of the steel in the structure determines the type and amount of charge necessary for

successful demolition. Examples of structured steel are I beams, wide-flange beams, channels, angle

sections, structural Ts, and steel plates used in building or bridge construction.

Target Materials

3-23. In addition to its configuration, steel also has a varied composition. It includes—

High-carbon steel. Metalworking dies and rolls are composed of high-carbon steel and are very

dense.

Alloy steel. Gears, shafts, tools, and plowshares are usually composed of alloy steel. Chains and

cables are often made from alloy steel; however, some chains and cables are composed of high-

carbon steel. Alloy steel is not as dense as high-carbon steel.

Cast iron. Some steel components (such as railroad rails and pipes) are composed of cast iron.

Cast iron is very brittle and easily broken.

Nickel-molybdenum steel. Nickel-molybdenum steel cannot be cut easily by conventional

steel-cutting charges. The jet from a shaped charge will penetrate it, but cutting requires multiple

charges or linear-shaped charges. Nickel-molybdenum steel shafts can be cut with a diamond

charge, but not with the saddle charge. Therefore, use some method other than explosives to cut

nickel-molybdenum steel, such as thermite, acetylene, or electrical cutting tools.

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FM 3-34.214

3-9

Chapter 3

EXPLOSIVE FACTORS

3-24. In steel-cutting charges, the type, placement, and size of the explosive are important. Confining or

tamping the charge is rarely practical or possible. The type, placement, and size are factors that are

important when selecting steel-cutting charges.

Type

3-25. Plastic explosive (composition C4) and sheet explosive are the best explosives for steel cutting.

These explosives have very effective cutting power and are easily cut and shaped to fit tightly into the

grooves and angles of the target. These explosives are particularly effective when demolishing structural

steel, chains, and steel cables.

Placement

3-26. See Figure 3-7. To achieve the most effective initiation and results, ensure that—

The charge is continuous over the complete line of the proposed cut.

There is close contact between the charge and the target.

The width of the cross section charge is between one and three times its thickness. Do not use

charges more than 6 inches thick, because better results can be achieved by increasing the width

rather than the thickness.

The long charges are primed every 4 to 5 feet. If butting composition C4 packages end-to-end

along the line of the cut, prime every fourth package.

The direction of initiation is perpendicular to the target (Figure 3-1, page 3-3).

Figure 3-7. Placing Charges on Steel Members

Size

3-27. The size of the charge is dictated by the type and size of the steel I beam and the charge type

selected. Either composition C4 or TNT block explosives can be used for the cutting steel; composition C4

works the best. Each steel configuration requires a unique charge size.

Block Charge

3-28. The following formula will give you the charge size necessary for cutting I beams, built-up girders,

steel plates, columns, and other structural steel sections. When calculating cutting charges for steel beams,

the area for the top flange, web, and the bottom flange should be calculated. Built-up beams have rivet

heads and angles or welds joining the flanges to the web. The thickness of one rivet head and the angle iron

must be added to the flange thickness when determining the thickness of a built-up beam flange. The

thinnest point of the web is used as the web thickness (the rivet head and angle iron thickness should be

3-10

FM 3-34.214

11 July 2007

Charge Calculations and Placement

ignored). The lattice of lattice girder webs are cut diagonally by placing a charge on each lattice along the

line of the cut. Use Table 3-3 and Table 3-4, page 3-12, to determine the correct amount of explosive

necessary for cutting steel sections. The following formula is used to determine the required charge size

(Table 3-3 is based on this formula) (see sample calculations in Appendix F, Figures F-3 and F-4, pages

F-3 and F-4):

P = (

) A or P = 0.375A

where—

= TNT required (in pounds)

= cross-sectional area of the steel member (in square inches) cross-sectional area for a circular

target (A = π r² [π = 3.14])

Table 3-3. Hasty, Steel-Cutting Chart for TNT

Average

Pounds of Explosive (TNT) for Rectangular Steel Sections of Given Dimensions

Thickness

of Section

Height of Section (in)

(in)

1/4

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.5

1.7

1.9

2.1

2.3

3/8

0.3

0.5

0.6

0.7

0.9

1.1

1.2

1.3

1.4

1.6

1.7

2.0

2.3

2.6

2.8

3.1

3.4

1/2

0.4

0.6

0.8

1.0

1.2

1.4

1.5

1.7

1.9

2.1

2.3

2.7

3.0

3.4

3.8

4.2

4.5

5/8

0.5

0.7

1.0

1.2

1.4

1.7

1.9

2.2

2.4

2.7

2.9

3.3

3.8

4.3

4.7

5.2

5.7

3/4

0.6

0.9

1.2

1.4

1.7

2.0

2.3

2.6

2.8

3.1

3.4

4.0

4.5

5.1

5.7

6.3

6.8

7/8

0.7

1.0

1.4

1.7

2.0

2.4

2.7

3.0

3.3

3.7

4.0

4.6

5.3

6.0

6.6

7.3

7.9

0.8

1.2

1.5

1.9

2.3

2.7

3.0

3.4

3.8

4.2

4.5

5.3

6.0

6.8

7.5

8.3

9.0

11 July 2007

FM 3-34.214

3-11

Chapter 3

Table 3-4. Hasty, Steel-Cutting Chart for Composition C4

Follow these steps to use this table:

1. Measure each rectangular section of the total member separately.

2. Find the appropriate charge size for the rectangular section from the table. Use the next larger dimension if the

section dimension is not listed in the table.

3. Add the individual charges for each section to obtain the total charge weight.

Weight of Composition C4 Required for Rectangular Steel Sections

Section

(height or width, in inches)

Thickness (in)

1/4

0.2

0.3

0.4

0.5

0.6

0.8

0.9

1.0

1.2

1.3

1.5

1.6

1.8

3/8

0.3

0.4

0.5

0.6

0.7

0.9

1.1

1.3

1.5

1.8

2.0

2.1

2.4

2.6

1/2

0.3

0.5

0.6

0.8

0.9

1.2

1.5

1.8

2.1

2.3

2.6

2.9

3.2

3.4

5/8

0.4

0.6

0.8

0.9

1.1

1.5

1.8

2.2

2.5

2.9

3.2

3.5

3.9

4.3

3/4

0.5

0.7

0.9

1.1

1.3

1.8

2.1

2.6

3.0

3.4

3.8

4.3

4.7

5.1

7/8

0.6

0.8

1.1

1.3

1.5

2.1

2.5

3.0

3.5

4.0

4.5

5.0

5.5

5.9

0.6

0.9

1.2

1.5

1.8

2.3

2.9

3.4

4.0

4.5

5.1

5.6

6.2

6.8

Note. Round up to the nearest 1/10 pound when calculating charge size.

High-Carbon or Alloy Steel

3-29. The following formula should be used to determine the required charge for cutting high-carbon or

alloy steel:

P = D²

where—

= TNT required (in pounds)

= diameter or thickness of section to be cut (in inches)

Steel Bars, Rods, Chains, and Cables (Up to 2 Inches)

3-30. The size of these materials make proper charge placement difficult. For example, Figure 3-8 shows a

charge placement on a chain. If the explosive is long enough to bridge both sides of the link or is large

enough to fit snugly between the two links, use one block. If the explosive is not large enough to bridge

both sides, two blocks should be used. The following amount of explosive should be used:

One pound of explosive for materials up to and including 1 inch in diameter or thickness.

Two pounds of explosive for materials between 1 and 2 inches in diameter or thickness. Prime

both charges so they will detonate simultaneously.

Note. Experience has shown that a link filled with explosive will be severed by detonation. See

Appendix G for the underwater method.

3-12

FM 3-34.214

11 July 2007

Charge Calculations and Placement

Figure 3-8. Charge Placement on Chains

Steel Bars, Rods, Chains, and Cables (Over 2 Inches)

3-31. When the target diameter or thickness is 2 inches or greater, the equation for high-carbon or alloy

steel should be used. When the thickness or diameter is 3 inches or greater, half of the charge should be

placed on each side of the target, and the placement should be staggered to produce the maximum-shearing

effect (Figure 3-9).

Figure 3-9. Charge Placement on a Steel Cable (3 Inches or Larger)

Railroad Rails

3-32. The height of the railroad rail is the critical dimension for determining the amount of explosives

required. For rails 5 inches or more in height, such as rail crossovers or switches, 1 pound of explosives

should be used. For rails less than 5 inches high, use 1/2 pound of explosives (Figure 3-10, page 3-14).

Railroad frogs require 2 pounds of explosives. If possible, charges should be placed at vulnerable points,

such as frogs, switches, and crossovers. Charges should be placed at alternate rail splices for a distance of

500 feet and on the inside of the rails.

11 July 2007

FM 3-34.214

3-13

Chapter 3

Figure 3-10. Charge Placement on Railroad Rails

SECTION III - SPECIAL CUTTING CHARGES

PURPOSE

3-33. When time and circumstances permit, special cutting charges (ribbon, saddle, and diamond charges)

should be used instead of conventional cutting charges. These charges may require extra time to prepare,

since they require exact and careful target measurement to achieve optimal effect. With practice, an

engineer can become proficient at calculating, preparing, and placing these charges in less time than

required for traditional charges. Special cutting charges use considerably less explosive than conventional

charges. Plastic-explosive (M112) or sheet explosive (M186) charges should be used as special charges.

Composition C4 requires considerable cutting, shaping, and molding that may reduce its density and,

therefore, its effectiveness. Using special cutting charges requires considerable training and practice.

RIBBON CHARGE

3-34. Ribbon charges are used to cut flat, steel targets up to 3 inches thick (Figure 3-11). The charge

thickness is made one-half the target thickness, but never less than 1/2 inch. The charge width is made three

times the charge thickness and the length of the charge is equal to the length of the desired cut. Ribbon

charges are detonated from the center of the C-shaped charge and the center of the top and bottom flange

charges when placing on I beams or wide-flange beams. When using the ribbon charge to cut structural

steel sections, the charge should be placed as shown in Figure 3-12. The detonating cord branchlines must

be the same length and must connect in a British junction (Figure 2-33, page 2-29). Figure F-5, page F-5,

shows how to calculate steel-cutting charges for steel plates. The charge thickness, width, and length is

determined as follows:

Charge thickness. The charge thickness equals one-half the thickness of the target; however, it

will never be less than 1/2 inch. The thickest part of the target is used to calculate the charge

thickness.

Charge width. The charge width equals three times the charge thickness.

Charge length. The charge length equals the length of the desired cut.

3-14

FM 3-34.214

11 July 2007

Charge Calculations and Placement

Figure 3-11. Using a Ribbon Charge

Figure 3-12. Placing a Ribbon Charge on Structural Steel

SADDLE CHARGE

3-35. This steel cutting method uses the destructive effect of the cross fracture formed in the steel by the

base of the saddle charge (the end opposite the point of initiation). This charge is used on mild steel bars,

whether round, square, or rectangular shaped, up to 8 inches in diameter (Figure 3-13, page 3-16). The

charge is made 1 inch thick. The dimensions, detonation, and the placement of the saddle charge is

determined as follows (see Figure F-7, page F-7, for an example calculation on steel cutting charges for

steel bars):

Dimensions.

Thickness. The charge should be made 1 inch thick (the standard thickness of M112 block

explosive).

Base width. The base width should be made equal to one-half the target circumference or

perimeter.

Long-axis length. The long-axis length should be made equal to the target circumference

or perimeter.

Volume (cubic inches). The volume is computed as: Long axis x base x 0.5 = volume.

Detonation. Detonate the saddle charge by placing a blasting cap or detonating cord knot at the

apex of the long axis.

11 July 2007

FM 3-34.214

3-15

Chapter 3

Placement. Ensure that the long axis of the saddle charge is parallel with the long axis of the

target. Cut the charge to the correct shape and dimensions, and then place it around the target.

Ensure that the charge maintains close contact with the target by taping the charge to the target.

Figure 3-13. Using a Saddle Charge

DIAMOND CHARGE

3-36. This stress-wave method employs the destructive effect of two colliding shock waves. The

simultaneous detonation of the charge from opposite ends (Figure 3-14) produces the shock waves. The

diamond charge is used on high-carbon or alloy steel bars that are up to 8 inches in diameter. The

dimensions, placement, and priming are determined as follows (for an example calculation on steel-cutting

charges for high-carbon steel, see Figure F-8, page F-7:

Dimensions.

Thickness. The charge should be made 1 inch thick (the standard thickness of an M112

block explosive).

Long-axis length. The long-axis length should be made equal to the target circumference.

Short-axis length. The short-axis length should be made equal to one-half the long axis.

Volume (cubic inches). The volume is computed as: Long axis x short axis x 0.5 = volume.

Placement. Place the explosive completely around the target so that the ends of the long axes

touch. Slightly increase the charge dimensions to do this, if necessary. Tape the charge to the

target to ensure adequate contact with the target.

Priming. Prime the diamond charge (Figure 3-14) with two detonating cord branchlines using

one of the following methods:

Detonating cord knots (Figure 2-15, page 2-15).

Two caps.

3-16

FM 3-34.214

11 July 2007

Charge Calculations and Placement

Note. When using a British junction, ensure that the branchlines are the same length.

Figure 3-14. Using a Diamond Charge

SECTION IV - BREACHING CHARGES

CRITICAL FACTORS

3-37. Breaching charges are used to destroy bridge piers, bridge abutments, and permanent field

fortifications. The size, shape, placement, and tamping or confinement of breaching charges is critical to

success. The size and confinement of the explosive are the most critical factors, because the targets are

usually very strong and bulky. The intent of breaching charges is to produce and transmit enough energy to

the target to make a crater and create spalling. Breaching charges placed against reinforced concrete will

not cut metal reinforcing bars. After the concrete is breached, remove or cut the reinforcement with a steel-

cutting charge.

COMPUTATION

3-38. When performing a computation for breaching charges, the formula to determine the size of the

charge must be known. The breaching radius, the material factor, and the tamping factor must also be

known.

FORMULA

3-39. The following formula is used to determine the size of the charge required to breach concrete,

masonry, rock, or similar material:

P = R³KC

where—

= TNT required (in pounds)

= breaching radius( in feet)

= material factor, which reflects the strength, hardness, and mass of the material to be demolished

(Table 3-5, page 3-18)

= tamping factor, which depends on the location and tamping of the charge (Figure 3-15, page

3-18).

11 July 2007

FM 3-34.214

3-17

Chapter 3

Table 3-5. Material Factor (K) for Breaching Charges

Material

Earth

All values

0.07

Poor masonry

Less than 1.5 m (5 ft)

0.32

Shale

1.5 m (5 ft) or more

0.29

Hardpan

Good timber

Earth construction

0.3 m (1 ft) or less

0.88

Good masonry,

Over 0.3 m (1 ft) to less than 0.9 m (3 ft)

0.48

Concrete block

0.9 m (3 ft) to less than 1.5 m (5 ft)

0.40

Rock

1.5 m (5 ft) to less than 2.1 m (7 ft)

0.32

2.1 m (7 ft) or more

0.27

0.3 m (1 ft) or less

1.14

Over 0.3 m (1 ft) to less than 0.9 m (3 ft)

0.62

Dense concrete

0.9 m (3 ft) to less than 1.5 m (5 ft)

0.52

First-class masonry

1.5 m (5 ft) to less than 2.1 m (7 ft)

0.41

2.1 m (7 ft) or more

0.35

0.3 m (1 ft) or less

1.76

Over 0.3 m (1 ft) to less than 0.9 m (3 ft)

0.96

Reinforced concrete (factor does not consider

0.9 m (3 ft) to less than 1.5 m (5 ft)

0.80

cutting steel)

1.5 m (5 ft) to less than 2.1 m (7 ft)

0.63

2.1 m (7 ft) or more

0.54

Figure 3-15. Tamping Factor (C) for Breaching Charges

BREACHING RADIUS

3-40. The breaching radius for external charges is equal to the thickness of the target being breached. For

internal charges placed in the center of the target mass, the breaching radius is one-half the thickness of the

target. If the charge is placed at less than one-half the mass thickness, the breaching radius is the longer of

the distances from the center of the charge to the outside surfaces of the target. For example, when

breaching a 4-foot wall with an internal charge placed 1 foot into the wall, the breaching radius is 3 feet

(the longest distance from the center of the explosive to an outside target surface). If placed at the center of

the wall mass, the breaching radius of the explosive is 2 feet (one-half the thickness of the target). The

3-18

FM 3-34.214

11 July 2007

Charge Calculations and Placement

breaching radius is 4 feet for an external charge on this wall. Values of R are rounded to the next higher

1/4-foot distance for internal charges and to the next higher 1/2-foot distance for external charges.

MATERIAL FACTOR

3-41. The material factor represents the strength and hardness of the target material. Table 3-5 gives values

for K for various types and thicknesses of material. When the target material cannot be positively

identified, assume that the target consists of the strongest material type in the general group. Always

assume that concrete is reinforced and masonry is first-class unless the exact condition and construction of

the target materials is known.

TAMPING FACTOR

3-42. The tamping factor depends on the charge location and the tamping materials used. Figure 3-15

shows the methods for placing charges and gives the values of C for both tamped and untamped charges.

When selecting a value for C from Figure 3-15, do not consider a charge tamped with a solid material (such

as sand or earth) as fully tamped unless the charge is covered to a depth equal to or greater than the

breaching radius. The water depth must be greater than the radius to use 1 as C.

REINFORCED CONCRETE BREACHING

3-43. Table

3-6, page

3-20, gives the number of composition C4 packages required for breaching

reinforced concrete targets. The breaching-charge formula does not factor in cutting the steel. The

remaining steel is cut using steel-cutting charges. The amounts of composition C4 in the table are based on

the formula in paragraph 3-39, page 3-17. To use the table, do the following:

Measure the concrete thickness.

Decide how the charge will be placed against the target. Compare the method of placement with

the diagrams at the top of Table 3-6. Use the column that lists the greatest amount of explosive if

in doubt about which column to use.

Select the amount of explosive required based on the target thickness, using the column directly

under the chosen placement method. For example, 200 packages of composition C4 are required

to breach a 7-foot, reinforced concrete wall with an untamped charge placed 7-feet aboveground.

Note. See Figure F-9, page F-8, for an example calculation on breaching charges for a

reinforced-concrete pier.

MATERIALS BREACHING

3-44. Table 3-6 can be used to determine the amount of composition C4 required for other materials by

multiplying the value from the table by the proper conversion factor from Table 3-7, page 3-21. The

following procedure can be used:

Determine the material type in the target. Assume that the material is the strongest type from the

same category if in doubt.

Determine from Table 3-6 the amount of explosive required if the object is made of reinforced

concrete.

Find the appropriate conversion factor from Table 3-7.

Multiply the number of packages of explosive required (Table 3-6) by the conversion factor

(Table 3-7).

11 July 2007

FM 3-34.214

3-19

Charge Calculations and Placement

Table 3-7. Conversion Factors for Material Other Than Reinforced Concrete

Material

Conversion Factor

Earth

0.1

Ordinary masonry

Hardpan

Shale

Ordinary concrete

0.5

Rock

Good timber

Earth construction

Dense concrete

0.7

First-class masonry

NUMBER AND PLACEMENT OF CHARGES

3-45. When preparing breaching charges, the number and placement of the charges must be known. The

paragraphs below discuss how to determine the necessary information needed.

NUMBER OF CHARGES

3-46. The following formula is used for determining the number of charges required for demolishing piers,

slabs, or walls:

N =

where—

= number of charges (If N is less than 1.25, use one charge; if N is 1.25 but less than 2.5, use two

charges; if N is equal to or greater than 2.5, round to the nearest whole number and use that many

charges.)

W = pier, slab, or wall width (in feet)

= breaching radius (in feet)

PLACEMENT OF CHARGE

3-47. Before a charge is placed, the limitations and configuration of the charge must be known. The

paragraphs below describe the limitations and configuration of the charge placement.

Limitations

3-48. Piers and walls offer limited locations for placing explosives. Unless a demolition chamber (space

intentionally provided in a structure for the emplacement of explosive charges) (JP 1-02) is available, place

the charges against one face of the target. Placing a charge aboveground level is more effective than

placing one directly on the ground. When the demolition requires several charges to destroy a pier, slab, or

wall and elevated charges are to be used, the charges should be distributed equally no less than one

breaching radius high from the base of the target. This takes maximum advantage of the shock wave. If

possible, place breaching charges so that there is a free reflection surface on the opposite side of the target.

This free reflection surface allows spalling to occur. If time permits, tamp all charges thoroughly with soil

or filled sandbags. The tamped area must be equal to or greater than the breaching radius. For piers, slabs,

or walls partially submerged in water, charges should be placed at a distance equal to the breaching radius

and below the waterline (Figure 3-15, page 3-18).

11 July 2007

FM 3-34.214

3-21

Chapter 3

Configuration

3-49. For maximum effectiveness, place the explosive charge in the shape of a flat square. The thickness of

the charge depends on the amount of explosive required (Table 3-1, page 3-3).

Placement

3-50. The first charge is placed R distance in from one side of the target. The remaining charges are spaced

at a distance of 2R apart, center to center (Figure 3-16).

Figure 3-16. Charge Placement

COUNTERFORCE CHARGES

3-51. This special breaching technique is effective against rectangular masonry or concrete columns 4 feet

thick or less. It is not effective against walls, piers, or long obstacles. The obstacle must have at least three

free faces or be freestanding. If constructed of plastic explosives (composition C4), properly placed and

detonated, counterforce charges produce excellent results with a relatively small amount of explosive. Their

effectiveness results from the simultaneous detonation of two charges placed directly opposite each other

and as near the center of the target as possible (Figure 3-17).

Figure 3-17. Counterforce Charge

CALCULATION

3-52. The thickness or diameter of the target determines the amount of plastic explosive required. The

amount of plastic explosive equals 1 1/2 times the thickness of the target in feet (1 1/2 pounds of explosive

per foot). Round fractional measurements to the next higher half foot before multiplying. For example, a

concrete target measuring 3 feet 9 inches thick requires 6 pounds of plastic explosive (1 1/2 pounds per foot

times 4 feet). For an example calculation on counterforce charges, see Figure F-10, page F-8.

3-22

FM 3-34.214

11 July 2007

Charge Calculations and Placement

PLACEMENT

3-53. When placing a counterforce charge, split the charge in half. The two halves are placed directly

opposite each other on the target. This method requires accessibility to both sides of the target so that the

charges will fit flush against their respective target sides.

PRIMING

3-54. On the face farthest from the target, prime a counterforce charge. The ends of the detonating cord

branchlines are joined in a British junction (Figure 3-17, page 3-23). The length of the branchlines must be

equal to ensure simultaneous detonation.

SECTION V - CRATERING AND DITCHING CHARGES

FACTORS

3-55. To be effective obstacles, craters must be too wide for track vehicles to span and too deep and steep-

sided for any vehicle to pass through. Blasted craters will not stop modern tanks indefinitely. A tank,

making repeated attempts to traverse a crater, will pull soil loose from the slopes of the crater, filling the

bottom, and reducing both the depth and slope angle of the crater.

SIZES

3-56. Craters are effective antitank (AT) obstacles if a tank requires four or more passes to traverse the

crater, thereby providing enough time for AT weapons to stop the tank. Craters should be large enough to

tie into natural or constructed obstacles at each end. The effectiveness of blasted craters can be improved

by placing log hurdles on either side, digging the face of the hurdle vertically on the friendly side, mining

the site with AT and antipersonnel (AP) mines, filling the crater with water, or using other means to further

delay enemy armor. Craters should be cut across the desired gap at a 45° angle from the direction of

approach. To obtain this 45° angle, the following formula should be used:

width x 1.414 = length of crater

3-57. To achieve enough obstacle depth, place craters in multiple rows. To enhance some other obstacle,

such as a bridge demolition, single or multiple rows should be used. When creating more than one row of

craters, they should be spaced far enough apart so that a single armored-vehicle-launched bridge (AVLB)

will not span them.

EXPLOSIVES

3-58. All military explosives can create AT craters. When available, use a 40-pound, composition H6,

cratering charge (Figure 1-4, page 1-8) for blasting craters.

CHARGE CONFINEMENT

3-59. Cratering charges or explosives should be placed in boreholes. Then, tamp them.

HARD-SURFACED PAVEMENT BREACHING

3-60. Hard-surfaced pavements are breached so that holes can be dug for the cratering charges. This can be

done by exploding tamped charges on the pavement surface. A 1-pound charge of explosive is used for

each 2 inches of pavement thickness. Charges are tamped twice as thick as the pavement thickness. Shaped

charges are effective for breaching hard-surfaced pavements. A shaped charge will readily blast a small-

diameter borehole through the pavement and into the subgrade. Blasting the boreholes with shaped charges

will speed up the cratering task by eliminating the need to breach the pavement with explosive charges.

After blasting, a hole should be dug for the cratering charge. Do not breach concrete at an expansion joint

because the concrete will shatter irregularly. Table 1-3, pages 1-11 and 1-12, lists hole depths and the

optimum standoff distances when using 15- or 40-pound shaped charges against various types of material.

11 July 2007

FM 3-34.214

3-23

Chapter 3

Shaped charges do not always produce open boreholes capable of accepting a 7-inch diameter cratering

charge. To accommodate the cratering charge, some earth may need to be removed or narrow areas

widened. Widen deep, narrow boreholes by knocking material from the constricted areas with a pole or rod

or by breaking off the shattered concrete on the surface with a pick or crowbar and posthole diggers.

HASTY CRATER METHOD

3-61. The hasty crater method takes the least amount of time to construct, based on the number and depth

of the boreholes. However, it produces the least effective barrier because of its depth and shape

(Figure 3-18). The hasty crater method forms a V-shaped crater about 6 to 7 feet deep and 20 to 25 feet

wide, extending about 8 feet beyond each end borehole. The sides of the crater slope should be 25° to 35°.

Modern U.S. tanks require an average of four attempts to breach a hasty crater. To form a crater that is

effective against tanks, boreholes must be at least 5 feet deep with at least 50 pounds of explosive in each

hole.

Figure 3-18. Hasty Crater Charge Placement

BOREHOLES

3-62. All boreholes are to be dug the same depth (5 feet or deeper is recommended). The boreholes are

spaced at 5-foot intervals, center to center, across the area to be cratered. The following formula is used in

the six-step, problem-solving format (Section I), to compute the number of boreholes:

L - 16

N =

+ 1

where—

= number of boreholes (Round fractional numbers to the next higher, whole number.)

= length of the crater (in feet) (Measure across the area to be cut. Round fractional measurements to

the next higher foot.)

= combined blowout of 8 feet on each side

5-foot spacing

factor to convert from spaces to holes

CHARGE SIZE

3-63. Boreholes are loaded with 10 pounds of explosive per foot of borehole depth. When using standard

cratering charges, supplement each charge with additional explosives to obtain the required amount. For

example, a 6-foot hole would require one 40-pound cratering charge and 20 pounds of TNT or 16 packages

of composition C4.

3-24

FM 3-34.214

11 July 2007

Charge Calculations and Placement

FIRING SYSTEM

3-64. Dual-firing systems should be used (Figure 2-26, page 2-25). They are initiated with an M12, M13,

or M14. The 40-pound cratering charge is dual-primed as shown in Figure 2-21, page 2-20.

BOREHOLE TAMPING

3-65. All boreholes should be tamped with suitable materials.

DELIBERATE CRATER METHOD

3-66. Figure 3-19 shows the deliberate crater method. This method produces a more effective crater than

the hasty method. Modern U.S. tanks require an average of eight attempts to breach a deliberate crater.

Placing charges deliberately produces a V-shaped crater about 7 to 8 feet deep and 25 to 30 feet wide with

side slopes of 30° to 37°. The crater extends about 8 feet beyond the end boreholes. The following steps are

used to create a deliberate crater:

Step 1. Determine the number of boreholes required, using the same formula as for a hasty

crater. Place two adjacent 7-foot boreholes in the middle when there is an even number of holes

(Figure 3-19).

Step 2. Dig or blast the boreholes 5 feet apart, center to center, in a line across the area to be cut.

Make the end boreholes 7 feet deep and the other boreholes alternately 5 and 7 feet deep. Never

place two 5-foot holes next to each other.

Step 3. Place 80 pounds of explosives in the 7-foot holes and 40 pounds of explosives in the 5

foot holes.

Step 4. Use dual-firing systems (Figure 2-26). Dual-prime the 40-pound cratering charge as

shown in Figure 2-21.

Step 5. Tamp all charges with suitable materials.

Figure 3-19. Deliberate Crater Charge Placement

Note. For an example calculation on cratering charges, see Figure F-11, page F-9.

RELIEVED-FACE CRATER METHOD

3-67. The method shown in Figure 3-20, page 3-26, produces a crater that is a more effective obstacle to

modern tanks than the hasty crater. This technique produces a trapezoidal-shaped crater about 7 to 8 feet

deep and 25 to 30 feet wide with unequal side slopes. In compact soil, such as clay, the relieved-face

cratering method will create an obstacle such as the one shown in Figure 3-20. The side nearest the enemy

slopes about 25° from the surface to the crater bottom. The opposite (friendly) side slopes about 30° to 40°

11 July 2007

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Chapter 3

from the surface to the crater bottom. However, the exact shape of the crater depends on the soil type. The

following procedures are used to create a relieved-face crater:

Drill two lines of boreholes 8 feet apart, spacing them at 7-foot centers on dirt- or gravel-

surfaced roads. Drill the two lines of boreholes 12 feet apart on hard-surfaced roads. Use the

following formula to compute the number of boreholes for the friendly-side row:

L - 10

N =

+ 1

where—

= number of boreholes (Round fractional numbers to the next higher, whole number.)

= crater length (in feet) (Measure across the area to be cut. Round fractional

measurements to the next higher foot.)

= combined blowout of 5 feet on each side

= spacing of holes

= factor to convert spaces to holes

Stagger the boreholes in the row on the enemy side in relation to the holes in the row on the

friendly side (Figure 3-20).

Note. The line closest to the enemy will always contain one less borehole than the friendly line.

Make the boreholes on the friendly side 5 feet deep, and load them with 40 pounds of explosive.

Make the boreholes on the enemy side 4 feet deep, and load them with 30 pounds of explosive.

Use a dual-firing system for each line of boreholes. Prime 40-pound cratering charges as shown

in Figure 2-21, page 2-20.

Tamp all holes with suitable material.

3-68. There must be a 0.5- to 1.5-second delay in detonation between the two rows of boreholes. An M15

may be used as the delay detonation system. On the enemy side first, detonate the row. Then fire the

friendly-side row while the earth from the enemy-side detonation is still in the air.

Figure 3-20. Relieved-Face Crater on Dirt- or Gravel-Surfaced Roads

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Charge Calculations and Placement

MISFIRE PREVENTION

3-69. The shock and blast of the first row of charges may affect the delayed detonation of the friendly-side

charges. To aid in preventing misfires of the friendly-side charges, protect the detonating cord lines by

covering them with about 6 inches of earth.

CRATERS CREATED IN PERMAFROST AND ICE

3-70. Permafrost and ice can be as hard as solid rock. Therefore, procedures must be adapted for blasting

or cratering to accommodate permafrost and ice conditions.

BLASTING IN PERMAFROST

3-71. In permafrost, blasting requires about twice as many boreholes and larger charges than for cratering

operations in moderate climates. Blasted frozen soil breaks into clods 12 to 18 inches thick and 6 to

8 inches in diameter. Because normal charges have insufficient force to blow these clods clear of the

boreholes, the spall falls back into the crater when the blast subsides.

Boreholes

3-72. Before conducting extensive blasting, the soil should be tested in the area to determine the number of

boreholes needed. Boreholes are dug with standard drilling equipment, steam-point drilling equipment, or

shaped charges. Standard drilling equipment has one serious defect—the air holes in the drill bit freezes.

There is no known method to prevent this freezing. Steam-point drilling is effective for drilling boreholes

in sand, silt, or clay but not in gravel. Immediately after withdrawing the steam point, the charges should be

placed. If you do not, the area around the borehole thaws and collapses. Shaped charges are also effective

for producing boreholes, especially when forming craters. Table 1-3, pages 1-11 and 1-12, lists borehole

sizes made by shaped charges in permafrost and ice.

Explosives

3-73. If available, low-velocity explosives should be used for blasting holes in arctic climates. The

displacing quality of low-velocity explosives will more effectively clear large boulders from the crater. If

only high-velocity explosives are available, tamp the charges with water and let them freeze before

detonating. Unless thoroughly tamped, high-velocity explosives tend to blow out of the boreholes.

BLASTING IN ICE

3-74. Access holes in ice are required for obtaining water and determining the capacity of the ice for

bearing aircraft and vehicles and integrating obstacles. To accommodate rapid forward movements, ice

capacities must be determined quickly. Blasting operations provide this ability.

Boreholes

3-75. Small-diameter access holes should be made using shaped charges. An M2A4 charge will penetrate

ice as thick as 7 feet, an M3A1 charge will penetrate over 12 feet of ice (Table 1-3), and an M3A1 can

penetrate deeper. This has only been tested on ice that is about 12 feet thick. If placed at the normal

standoff distance, the charges form a large crater at the surface and require considerable probing to find an

actual borehole. A standoff distance of 42 inches or more should be used with an M2A4 shaped charge to

avoid excessive crater formation. An M2A4 creates a borehole with an average diameter of 3 1/2 inches.

An M3A1 borehole has an average diameter of 6 inches. In late winter, ice grows weaker and changes color

from blue to white. Although the structure and strength of ice vary, the crater effect is similar, regardless of

the standoff distance.

Craters

3-76. Surface craters are made with composition H6 cratering charges. For the best results, the charges

should be placed on the surface of cleared ice and tamp them with snow. When determining charge size,

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Chapter 3

keep in mind that ice has a tendency to shatter more readily than soil, and this tendency will decrease the

size of the charge.

MAKING VEHICLE OBSTACLES

3-77. A vehicle obstacle can be created in ice by first making two or more rows of boreholes. The

boreholes are spaced 9 feet apart and staggered in relation to the holes in the other rows. M112 charges are

suspended about 2 feet below the bottom surface of the ice with cords tied to sticks, bridging the sticks over

the top of the holes. The size of the charge depends on the thickness and condition of the ice. Test shots are

used to find the optimum amount. This obstacle type can retard or halt enemy vehicles for about 24 hours at

temperatures near -4°F.

CRATERS CREATED FROM CULVERTS

3-78. Destroying a culvert less than 15 feet deep may also produce an effective crater. The charges are

primed for simultaneous detonation, and sandbags are used to tamp all charges thoroughly. Culverts that

are no deeper than 5 feet are destroyed by placing explosive charges the same as for hasty road craters.

Boreholes are spaced at 5-foot intervals in the fill above and alongside the culvert. Ten pounds of

explosives per foot of depth is placed in each hole.

CRATERS CREATED FROM ANTITANK DITCHES

3-79. AT ditches are excavated by either the hasty or deliberate cratering method. Refer to the information

on hasty and deliberate cratering in this section.

DITCHING METHODS

3-80. Explosives can create ditches rapidly. Ditches are sloped at a rate of 2 to 4 feet of depth per 100 feet

of run. Ditches are placed in areas where natural erosion will aid in producing the correct grade. If a ditch

cannot be placed in an area aided by erosion, the ditch should be made deeper, increasing the depth as the

length increases. The single-line and cross-section methods are used for creating ditches.

SINGLE-LINE METHOD

3-81. The single-line method (Figure 3-21) is the most common ditching method. A single row of charges

are detonated along the centerline of the proposed ditch, leaving any further widening for subsequent lines

of charges. Table 3-8 gives charge configurations for the single-line method.

Figure 3-21. Single-Line Ditching Method

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Chapter 3

Table 3-9. Cross-Section Ditching Explosives Data

Required Width (w) (ft)

Row

Charge

Borehole

Required

Number of Boreholes in Each Cross

Spacing

Serial

per Hole

Depth (h)

Spacing

Depth (d)

Section

(x)

(in lb)

(in ft)

(s) (in ft)

(in ft)

2.5

7.5

0.5

1.5

1.3

2.5

3.0

10.0

1.0

2.0

1.5

3.0

4.0

14.0

2.0

3.0

2.5

4.5

6.0

20.0

5.0

4.0

6.0

10.0

26.0

10.0

7.0

5.0

8.0

SECTION VI - LAND-CLEARING CHARGES

STUMP REMOVAL

3-83. Stumps have two general root types—taproot and lateral root (Figure 3-23). The stump diameter is

measured 12- to 18-inches aboveground level. Then the diameter is rounded to the next higher 1/2 foot.

One pound of explosive is used per foot of diameter for dead stumps and 2 pounds of explosive per foot of

diameter for live stumps. If the complete tree is being removed, 3 pounds of explosives per foot of diameter

should be used. If the root type cannot be identified, it is assumed that the tree has a lateral-root structure

and removal proceeds accordingly.

TAPROOTED STUMPS

3-84. Two methods are common for removing taprooted stumps. One method is to drill a hole in the

taproot and place the charge in the hole. Another method is to place charges on both sides of the taproot,

creating a shearing effect (Figure 3-23). If possible, the charges should be placed in contact with the root

and at a depth about equal to the diameter of the stump.

LATERAL-ROOTED STUMPS

3-85. When blasting lateral-rooted stumps, drill sloping holes between the roots (Figure 3-23). At a depth

equal to the radius of the stump base, drill the holes Place the charges as close to the center of the stump as

possible. Trees with large lateral roots may require additional charges. Additional charges are placed

directly underneath the large lateral roots.

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Chapter 3

Table 3-10. Boulder-Blasting Charges

Charge Size (lb)

Boulder Diameter (ft)

Snake Hole

Mudcap Method

Blockhole Method

Method

0.75

2.0

0.250

2.00

3.5

0.375

3.00

6.0

0.500

MUDCAP METHOD

3-88. With the mudcap method, the charge is placed in a crack or seam in the boulder (Figure 3-24, page

3-31). Then the charge is covered with 10 to 12 inches of mud or clay. Table 3-10 lists the required charge

sizes.

BLOCKHOLE METHOD

3-89. The blockhole method involves drilling a hole in the top of the boulder deep enough and wide

enough to hold the amount of explosive required (Table 3-10). The charge is primed with detonating cord

and is tamped firmly (Figure 3-24).

DETONATING CORD WICK OR SPRINGING CHARGE

3-90. A detonating cord wick or springing charge is a comparatively small charge for enlarging a borehole

to accommodate a larger charge. At times, two or more springing charges may have to be detonated in

succession to make the chamber large enough for the final charge. Wait at least 30 minutes between firing

successive charges to allow the borehole to cool, unless the hole is cooled with water or compressed air.

For soils, several strands of detonating cord should be used, 5 to 6 feet long, taped together to form a

multicord wick. For best results, the wick should be extended to the full length of the borehole. As a

general rule, one strand of detonating cord (single-cord wick) will widen the diameter of the borehole by

about 1 inch. For example, a 10-cord wick will create a 10-inch diameter borehole. The initial borehole is

made by driving a steel rod about 2 inches in diameter into the ground to the required depth. The wick is

placed into the initial borehole with an inserting rod or some other field-expedient device. The detonating

cord wick works best in hard soils (see Appendix D). If placing successive charges in the same borehole,

use water or compressed air, or wait 30 minutes for the borehole to cool before placing the next charge.

QUARRYING

3-91. Military quarries are generally open-faced and mined by the single- or multiple-bench method.

FM 3-34.465 gives detailed information on military quarries.

SECTION VII - SPECIAL APPLICATIONS

SURVIVABILITY POSITIONS

3-92. In many circumstances, using explosives can reduce digging time and effort. Explosives should only

be used in soil that would be excavated by a pick and shovel. Explosives are not recommended for

excavations less than 2 feet deep. To limit the dispersion of soil to as small an area as possible, use small

charges buried and spaced just enough to loosen the soil. Attempting to form a crater spreads soil over a

large area, affecting concealment and weakening the sides of the finished position. Explosives can create

individual-fighting positions and larger crew-served gun or vehicle positions. Explosives used in this

manner require some advance preparation. In the case of an individual-fighting position, the preparation

time may exceed the time required to prepare the position by traditional methods.

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Charge Calculations and Placement

DEPTH

3-93. Charges are placed 1 foot shallower than the required depth to a maximum of 4 feet. If the required

depth is greater than 5 feet, dig the position in two stages, dividing the required depth in half for each stage.

Boreholes are made with an earth auger, wrecking bar, picket driver, or other expedient device.

SPACING

3-94. For rectangular excavations, the boreholes are dug in staggered lines. For circular excavations, the

boreholes are dug in staggered, concentric rings. The spacing (denoted as s) (Figure 3-25) between

boreholes in each line or ring and between lines or rings should be between 1 and 1 1/2 times the depth of

the borehole. All charges should be at least 2 feet inside the proposed perimeter of the excavation. Also, an

8- by 8-inch channel should be dug around the outer perimeter of the proposed excavation with the outer

edge of the channel forming the outer edge of the finished excavation. Figure 3-25 shows layouts for

rectangular and circular excavations.

Figure 3-25. Borehole Layouts

CHARGE SIZE

3-95. To dig foxholes, use 1/4-pound charges of plastic explosive. For large excavations, use charges

between 1/2 and 1 1/2 pounds, depending on spacing and soil characteristics. A test shot is usually

necessary to determine the correct charge size.

CONCEALMENT

3-96. Reduce explosion noise and spoil scatter by leaving any sod in place and covering the site with a

blasting mat. Blasting mats can be improvised by tying tires together with natural or synthetic rope (steel

wire rope is unacceptable) or by using a heavy tarpaulin.

EQUIPMENT DESTRUCTION

3-97. The following paragraphs discuss how to destroy equipment, such as guns and vehicles.

DANGER

Steel-cutting charges produce metal fragments. Proper

precautions should be taken to protect personnel. Failure to

comply may cause death or permanent injury.

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3-33

Chapter 3

WARNING

Beware of potential radiological hazards associated with

ordnance (depleted uranium

[DU] and some weapon system

sights [foreign-tritium]). Take proper protective measures before

and after equipment destruction. Failure to comply could result in

immediate personal injury or damage to equipment.

GUNS

3-98. Gun barrels are destroyed with explosives or their own ammunition. Small components should be

removed or destroyed (such as sights and other mechanisms). The following procedures should be

performed when preparing a gun for demolition:

Block the barrel just above the breach. Solidly tamp the first meter of the bore with earth for

small-caliber guns that use combined projectile-propellant munitions. Load a projectile and aim

the tube to minimize damage if the round is ejected. For heavier guns that use projectiles,

separate from the propellants.

Refer to Table 3-11 for the charge size required for standard barrel sizes. Determine the required

charge size using the following formula (if necessary):

D²

P =

636

where—

= quantity of explosive (any HE) (in pounds)

= bore size of the barrel (in millimeters)

636 = constant used to compute P

Pack the explosive, preferably composition C4, into the breach immediately behind the tamping.

Place the plastic explosive in close contact with the chamber. Close the breach block as far as

possible, leaving only enough space for the detonating cord to pass without being bent or

broken. Place 15-pound charges on the drive wheels of tracked guns and on the wheels and axles

of towed guns, if time permits. Connect the branchlines in a junction box, or use a ring main.

Simultaneously detonate all charges.

Table 3-11. Gun-Destruction Charge Sizes

Serial

Barrel Size (mm)

Charge Size (lb)

105

120

155

203

Note. Determine the appropriate charge sizes for barrel sizes not listed by comparing them to

known barrel sizes. For example, use the explosive weight in Serial 3 for a 112-millimeter

barrel (23 pounds) and Serial 4 for a 152-millimeter barrel (38 pounds).

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Charge Calculations and Placement

VEHICLES

3-99. To destroy friendly vehicles, refer to the applicable TM. When destroying vehicle components, use

the following priorities:

Priority 1. Carburetor, distributor, fuel pump or injectors, and fuel tanks and lines.

Priority 2. Engine block and cooling system.

Priority 3. Tires, tracks, and suspension system.

Priority 4. Mechanical or hydraulic systems (where applicable).

Priority 5. Differential and transfer case.

Priority 6. Frame.

Armored Fighting Vehicles

3-100. Armored fighting vehicles (AFVs) can be destroyed beyond repair by detonating a 25-pound

charge inside the hull. The charge may be a bulk 25-pound charge or a number of smaller charges placed

on the driving, turret, and gun controls. To increase the amount of damage to the AFV, ensure that the

ammunition within the AFV detonates simultaneously with the other charges and that all hatches, weapons

slits, and other openings are sealed. If it is not possible to enter the AFV, place the two charges under the

gun mantle, against the turret ring, and on the final drive (Figure 3-26). If explosives are not available,

destroy the AFV by using AT weapons or fire or destroy the main gun with its own ammunition.

Figure 3-26. AFV Charge Placement

Wheeled Vehicles

3-101. When using the explosive method, wheeled vehicles can be destroyed beyond repair by wrecking

the vital parts with a sledgehammer or explosives. If HEs are available, 2-pound charges should be used to

destroy the cylinder head, axles, and frame.

3-102. When using the improvised method, the engine oil and coolant should be drained and the engine

ran at full throttle until it seizes. To finish the destruction, burn the vehicle (ignite the fuel in the tank).

UNDERWATER DEMOLITIONS

3-103. See Appendix G for use and placement of underwater demolitions. Appendix G outlines the

techniques, tactics, and procedures for underwater clearance.

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3-35

Chapter 4

Bridge Demolition

The purpose of bridge demolition is to create gaps in bridges by attacking key bridge

components. This makes gaps large enough to make repairs uneconomical and to

force the enemy to construct other bridges on other sites. The minimum gap required

must exceed the assault bridging capability of the enemy by 5 meters. For planning

purposes, use 25 meters as the minimum gap size, but 35 meters is preferred. The

complete demolition of a bridge usually involves destroying all the components

(spans, piers, and abutments). Complete demolition may be justified when the terrain

forces the enemy to reconstruct a bridge on the same site. However, complete

destruction is not required to meet the tactical objective. The attack method that

achieves the tactical goal should be selected with a minimum expenditure of

resources.

BRIDGE DEBRIS

4-1. Debris may cause enemy forces serious delays, if it obstructs the gap (Figure 4-1). Debris also

provides excellent concealment for mines and booby traps. Whenever possible, demolish bridges in such a

way that the resulting debris hinders reconstruction.

Figure 4-1. Debris Use

BRIDGE CATEGORIES

4-2. The first step in any efficient bridge demolition is to categorize the bridge correctly. The term

categorization has been adopted to avoid confusion with classification, which is concerned with the load-

carrying capacity of bridges. The correct categorization of bridges, coupled with an elementary knowledge

of bridge design, allows you to select a suitable attack method. All bridges fit into one of the following

three categories: simply supported, miscellaneous, and continuous.

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4-1

Chapter 4

SIMPLY SUPPORTED

4-3. In simply supported bridges, the ends of each span rest on the supports, and there are no intermediate

supports. The free bearing conditions shown in Figure

4-2 represent any bearing that allows some

horizontal movement (for example, roller bearings, sliding bearings, and rubber bearing pads).

Figure 4-2. Simply Supported Bridges

MISCELLANEOUS

4-4. Miscellaneous bridges form a small portion of bridge structures. The theoretical principles governing

these bridges determine the appropriate attack methods. Examples of bridges in this category are

suspension, lift, and cable-stayed bridges.

CONTINUOUS

4-5. If a continuous bridge does not fit the miscellaneous category and is not simply supported, categorize

it as a continuous bridge. Hence, continuous has a wider meaning than multispan, or continuous-beam

bridges, as is normally implied.

ATTACK TYPES

4-6. When designing a bridge demolition, the first priority is to create a gap. This may require one or two

attacks to accomplish. Further actions to improve the obstacle may follow if the situation permits.

BOTTOM ATTACK

4-7. In a bottom attack, a hinge forms at the top. As the span falls, the cut ends at the bottom move

outward. The span may form a three-pin arch and fail to fall completely if the distance the cut ends must

move is greater than the total end clearance (denoted as E) between the span ends and the pier or abutment

faces (Figure 4-3). If a three-pin arch situation is likely, do not attempt a bottom attack.

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FM 3-34.214

11 July 2007

Bridge Demolition

Figure 4-3. Three-Pin Arch Effect

TOP ATTACK

4-8. In a top attack, a hinge forms at the bottom. As the span falls, the cut ends at the top move inward.

Some bridges may jam along the faces of the cut before the ends of the span fall off the abutments, forming

a cranked beam (Figure 4-4). The length of span (denoted as L_C) removed at the top should be enough to

prevent the formation of a cranked beam.

Figure 4-4. Cranked-Beam Effect

SUCCESSFUL BRIDGE DEMOLITIONS

4-9. There are two minimum conditions for successful bridge demolition. They are—

Condition 1 (a proper collapse mechanism design). Under normal conditions, a bridge is a

stable structure. In bridge demolitions, the goal is to destroy the appropriate parts of a bridge so

that it becomes unstable and collapses under its own weight. In other words, a collapse

mechanism is formed. This may involve either cutting completely through all structural

members or creating points of weakness in certain parts of the bridge. Figure 4-5, page 4-4,

shows an improper collapse mechanism and the hinges that have not been formed. At times,

making bridges unstable by attacking their piers rather than their superstructures is easier, but it

is still possible for bridges not to collapse, even though they lose the support provided by one or

more of their piers. To avoid this type of demolition failure, place the charges on the structural

members of the superstructure immediately above the piers being attacked.

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FM 3-34.214

4-3

Chapter 4

Figure 4-5. Improper Collapse Mechanism and Hinges

Condition 2 (an attacked span that moves freely and far enough under its weight and

creates the desired obstacle). Figure

4-6 shows a bridge demolition where the collapse

mechanism has formed but where it has failed to form the desired obstacle because the bridge

span has jammed before moving far enough. To complete the demolition in this example,

remove only a small portion of the abutment to allow the span to swing down freely.

Figure 4-6. Jammed Bridge Span

COLLAPSE MECHANISM TYPES

4-10. Figures 4-7 through 4-9 show the three basic collapse mechanisms. The three collapse mechanisms

are the seesaw, beam, and member without support.

Figure 4-7. Seesaw Collapse Mechanism

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11 July 2007

Bridge Demolition

Figure 4-8. Beam Collapse Mechanism

Figure 4-9. Member Without a Support Collapse Mechanism

EFFICIENT DEMOLITION METHODS

4-11. To ensure that a demolition achieves collapse with reasonable economy, consider the factors required

to achieve an efficient demolition. The best balance between these factors will depend on the particular

demolition under consideration. An efficient demolition should—

Achieve the desired effect.

Use the minimum amount of resources (time, manpower, and explosives).

Observe the proper priorities. The demolition reconnaissance report clearly states the priorities

and separately lists the requirements for priority 1 actions and priority 2 improvements (the

priorities are explained below). If enough gap will result by attacking bridge spans, do not

perform the priority 2 improvements unless the report specifies complete destruction or an

excessively long gap. If the total gap spanned by a bridge is too small to defeat enemy assault

bridging, consider the site as an unsuitable obstacle unless the gap can be increased. Engineer

efforts may be better applied elsewhere. To improve an obstacle, increase the gap by

demolishing the abutments and building craters on the immediate approaches. In this case, attack

nearby bypass sites (by placing mines and craters).

Priority 1. The desired obstacle should be created. The minimum gap required is 5 meters

greater than the assault bridging capability of the enemy. Ideally, demolition should be

accomplished with the first attempt. However, many reinforced- or prestressed-concrete

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FM 3-34.214

4-5

Chapter 4

bridges may require two-stage attacks. Attacking the friendly side of spans will permit

economical reconstruction of the bridge at a later date, if necessary.

Priority 2. Improvements to the gap should be made. This activity is performed only when

it is specified on the demolition reconnaissance report. When no reconnaissance report has

been issued and time permits, perform improvements in the sequence specified below.

Deviation from this sequence should only be made under exceptional circumstances or

when directed to do so by the responsible commander. The standard sequence of demolition

is to destroy and mine the blown abutment, to lay mines in likely bypasses, to blast craters

and lay mines in likely approaches, and to destroy the piers.

CONCRETE-STRIPPING CHARGES

4-12. Concrete-stripping charges are bulk, surface-placed charges designed for removing concrete from

reinforced-concrete beams or slabs and exposing the steel reinforcement. Although these charges cause

some damage to the reinforcing steel, the extent of this damage cannot be predicted. These charges are

effective against reinforced-concrete beams or slabs up to 2 meters thick.

Charge Effects

4-13. Figure 4-10 shows the effect of the concrete-stripping charge. Using the proper charge size for the

thickness of the target will—

Remove all concrete from above the main reinforcing steel.

Remove all concrete from below the main reinforcing steel (spalling).

Damage the main reinforcing steel to some extent.

Destroy the minor reinforcing steel near the surface under the charge.

Figure 4-10. Effect of a Concrete Stripping Charge

Charge Calculations

4-14. For all simply supported concrete bridges, removing all concrete over the required length of the span

removed will cause collapse. For beam or slab bridge spans (T beam and I beam bridges), determine the

charge sizes for the beams or slabs separately. The following procedure is used for determining charge

sizes for simply supported spans (see Figure F-12, page F-10, for an example calculation):

Calculate the mass of the charge required.

P = (3.3h + 0.5)^{3 (}3.3)

where—

= required charge size in pounds of TNT per meter of bridge width

3.3 = constant to determine P

= beam or slab plus roadway depth in meters (minimum is 0.3 meters and maximum is

2 meters)

0.5 = constant to determine P

4-6

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11 July 2007

Bridge Demolition

Calculate the width of the required ditch. (The charge will produce a ditch across the width of

the bridge.) Determine the width of this ditch using the following formula:

W_d = 2h + 0.3

where—

W_d

= ditch width (in meters)

= overall roadway or beam or slab depth (in meters)

Compare the required W_dwith the required L_C, and take the appropriate action.

If L_C is equal to or less than W_d, use one row of charges as specified by P.

If L_C is greater than W_d but less than twice W_d, increase the size of the charge by

10 percent.

If L_C is twice the W_d, double the charge and place them in two lines side by side.

Place charges in a continuous line across the full width of the bridge at the point of attack.

Ensure that the shape of the end cross section of the charge is such that the width is between one

and three times the height of the charge.

Tamp the charges, if required.

Note. No tamping is required for the concrete-stripping charge as calculated. If tamping with two

filled sandbags per pound of explosive, the calculated mass of charge should be reduced by one

third.

UNSUCCESSFUL BRIDGE DEMOLITIONS

4-15. A no-collapse mechanism and jamming are two possible reasons for unsuccessful bridge

demolitions. The formation of cantilevers (Figure 4-11) is a typical example of a no-collapse mechanism

being formed. The likelihood of this occurring is high when attacking continuous bridges. The span, once

moved by the collapse mechanism, jams before moving far enough to create the desired obstacle. The most

likely causes of jamming are the formation of a three-pin arch or a cranked beam (Figure 4-12, page 4-8).

When attacking bridge spans, always consider the possibility of jamming during bottom and top attacks.

Figure 4-11. Cantilever Effect

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Chapter 4

Figure 4-12. Causes of Jamming

SIMPLY SUPPORTED BRIDGES AND CONTINUOUS BRIDGES

4-16. The external appearance of a bridge can sometimes be deceptive. Whenever possible, consult

construction drawings to determine the correct bridge category. If drawings are not available and there is

any uncertainty about the category to which the bridge belongs, assume the bridge is of continuous

construction. Since more explosive is necessary to demolish a continuous bridge, assume that a continuous

construction will provide more than enough explosive to demolish a bridge of unknown construction. The

following describes some differences between simply supported and continuous bridges (Figure 4-13):

Continuity. In simply supported bridges, the entire superstructure is composed of a span or

multiple spans supported at each end. The main structural members (individual spans) meet end-

to-end, and each intermediate pair of ends is supported by a pier. The single ends are supported

by the abutments. In continuous bridges, the main structural members are formed into one piece

and do not have breaks over the piers, if any are present.

Construction depth. In multispan, simply supported bridges, the construction depth of the span

may decrease at the piers. In continuous bridges, construction depth frequently increases at the

piers.

Flange thickness. In simply supported, steel-girder bridges, the thickness of the flange

frequently increases at the midspan. In continuous bridges, the flange size frequently increases

over the piers.

Bearing. In multispan, simply supported bridges, two lines of bearing is needed at the piers. In

continuous bridges, only one is needed.

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Chapter 4

SIMPLY SUPPORTED BRIDGES

4-18. Figure 4-14 is a categorization chart for simply supported bridges. This chart is entered from the left,

and the lines and arrows are followed across to the right. The path selected must include all categorization

terms applicable to the simply supported bridge that is planned to be demolished. There are four main

subcategories:

Steel beam.

Steel truss.

Concrete beam or slab.

Bowstring.

4-19. The first three are further subdivided into deck bridges, which carry their loads on top of the main

structural members and through bridges. When dealing with deck bridges, note the locations of the bearing

(supporting the top or bottom chord or flange); this will influence the possibility of jamming.

Figure 4-14. Categorization Chart for Simply Supported Bridges

Steel-Beam Bridges

4-20. Steel-beam bridges may be constructed of normal steel-beam, plate-girder, or box-girder spans.

Figure 4-15 shows typical cross sections of these spans. For an example calculation, see Figure F-13,

page F-11.

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Figure 4-15. Typical Cross Sections of Steel-Beam Bridges

Steel-Truss Bridges

4-21. Figure 4-16 shows the side elevations for three normal steel-truss spans. Note that all truss bridges

have diagonal members in the trusses.

Figure 4-16. Side Elevation of Steel-Truss Bridges

Concrete-Beam or Slab Bridges

4-22. For categorization purposes, distinguish between reinforced- and prestressed-concrete bridges,

because the methods of attack are the same for both. Figure 4-17, page

4-12, shows midspan,

cross-sectional views of these bridge types. At midspan, the majority of steel reinforcing rods or tendons

are located in the bottom portion of the superstructure. The attack methods detailed in Appendix H take this

reinforcing condition into account.

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Chapter 4

Figure 4-17. Midspan, Cross-Sectional Views of Typical Concrete Bridges

Bowstring Bridges

4-23. Figure 4-18 shows the features of a normal bowstring bridge. The features of this bridge include the

following:

The bow is in compression.

The bow may be a steel beam, box girder, concrete beam, or steel truss. The depth (thickness) of

the bow is larger than or equal to the depth of the support members of the deck.

The deck acts as a tie and resists the outward force applied by the bow.

The deck is designed as a weak beam supported by the hangers.

Note. There is no diagonal bracing between the hangers.

Figure 4-18. Normal Bowstring Bridge

4-24. Occasionally, the bow and hangers are used to reinforce a steel-beam or -truss bridge. This bridge

type is categorized as a bowstring reinforced-beam or reinforced-truss bridge (Figure 4-19). In this type of

bridge, the depth of the bow will always be less than the depth of the support members of the deck.

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Bridge Demolition

Figure 4-19. Bowstring-Reinforced Truss Bridge

Reconnaissance

4-25. For simply supported bridges, use the following reconnaissance procedures:

Categorize the bridge.

Measure the bridge using the following measurements with Figure 4-20 as an example:

Length (L). Measure the length of the span to be attacked in meters.

Note. This distance is not the clear gap, but the length of the longitudinal members that support

the deck from end to end.

Depth (H). Measure the depth of the beam, truss, or bow in meters (include the deck with

the beam or truss measurement).

Total end clearance (E). Total the amount of end clearance at both ends of the span in

meters.

Average length of the bearing supports (L_S). Measure the average length of the bearing

supports from the ends of the spans to the faces of the abutments or piers in meters.

Determine the attack method (see Appendix H).

Determine the critical dimensions of the span required for charge calculations.

Figure 4-20. Measurements of Simply Supported Spans

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Chapter 4

Attack Considerations

4-26. Two considerations apply when attacking a simply supported span. They are the point of attack and

the line of attack.

Point of Attack

4-27. Simply supported bridges should be attacked at or near the midspan. This is done because—

Bending movements are maximum at the midspan.

The likelihood of jamming during collapse is reduced if the bridge is attacked at the midspan.

Line of Attack

4-28. The line of attack should be parallel to the lines of the abutments (Figure 4-21). This reduces the risk

that the two parts of the span will slew in opposite directions and jam. Do not employ any technique that

induces a twist in the bridge. If the line of attack involves cutting across transverse beams, reposition the

line of attack to cut between the transverse beams.

Note. For a sample calculation, see Figure F-14, page F-12.

Figure 4-21. Line of Attack

Attack Methods

4-29. See Appendix H, Table H-4, pages H-4 through H-8. Table H-4 lists in recommended order, by

bridge category, the attack methods likely to produce the most economical demolition. Within each

category are variations to accommodate the differences in construction materials, span configurations, load

capacities (road, rail, or both), and gap and abutment conditions. The three recommended ways of attacking

simply supported spans are bottom, top, and angled attacks. In all cases, ensure that jamming cannot occur

during collapse. Use Table H-4 to determine the charge location.

Bottom Attack Method

4-30. Use the bottom attack method whenever possible; it leaves the roadway open and enables you to use

the bridge, even when demolitions are at a ready-to-fire state (state 2). Reinforced and prestressed (tension)

beams are very vulnerable to a bottom attack, because the steel cables and reinforcing bars run along the

bottom portion of the beam and are covered by less concrete. The major disadvantages of the bottom attack

are the increased amount of time and effort necessary for placing and inspecting the charges. Because it is

generally impracticable to place enough explosive below a reinforced or prestressed slab to guarantee a cut

deeper than 0.15 meter, use the top or angled attacks listed in Table H-4 for these types of bridges. When

Table H-4 lists a bottom attack, determine the required end clearance (E_R) from Table H-1, page H-1, to

prevent jamming. If E is greater than E_R, jamming will not occur. If E is less than E_R, use a top or angled

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attack or destroy one abutment at the places where jamming would occur. Figure F-13, page F-11, explains

the method for bottom attack calculations.

Top Attack Method

4-31. See Appendix H. When Table H-4, page H-4, lists a top attack, L_C must be removed from the top of

the bridge to prevent jamming. From Table H-2, page H-2, determine L_C. In a V-shaped section, remove L_C

along the full depth of the target. For reinforced-concrete bridges, use a concrete-stripping charge

(discussed earlier in this chapter) to remove L_C from the top of the bridge. This action, by itself, should

cause collapse. There is no requirement to cut steel reinforcing rods. Figure F-14 shows the method for top

attack calculations.

Angled Attack Method

4-32. For angled attacks, cut all members (span, handrails, service pipes, and so forth) of the bridge. The

angle of attack should be made about 70° to the horizontal to prevent jamming. The location of the charge

should be between the midspan point and a point L/3 from the end (Figure 4-22). Although an angled attack

is effective on any bridge type, it is essential when the bridge must be kept open to traffic or when there is

ample time to prepare demolitions.

Figure 4-22. Location of an Angled Charge

CONTINUOUS BRIDGES

4-33. Figure 4-23, page 4-16, is a categorization chart for continuous bridges. This chart is used like the

chart for simply supported bridges. There are six main subcategories: cantilever, cantilever and suspended

span, beam or truss, portal, arch, and masonry arch. The first five categories differentiate between steel and

concrete construction, because each material has a different attack method. If a continuous bridge is of

composite construction (for example, steel beams supporting a reinforced-concrete deck), the material that

comprises the main, longitudinal, load-bearing members will determine the attack method.

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Bridge Demolition

Cantilever and Suspended-Span Bridges

4-35. If a cantilever bridge incorporates a suspended span (Figure 4-25) that is at least 5 meters longer than

the enemy assault bridging capability, this section of the bridge should be attacked. This requires less

preparation. Because suspended spans are simply supported, the attack method described for simply

supported bridges should be used (Table H-4, pages H-4 through H-8).

Figure 4-25. Cantilever and Suspended Span Bridges

Beam or Truss Bridges

4-36. For beam or truss bridges (Figure 4-26, Figure 4-27, page 4-18, and Figure 4-28, page 4-18),

differentiate between those bridges with spans of similar lengths and those with short-side spans because

this affects the attack method. A short-side span is one that is less than three quarters of the length of the

next adjacent span.

Figure 4-26. Steel-Beam Bridge Without a Short-Side Span

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FM 3-34.214 (FM 5-250) EXPLOSIVES AND DEMOLITIONS (July 2007) - page 2