Demolition Charges

These charges are used in general demolition operations, such as cutting, breaching and cratering. They are composed of high-velocity explosives RDX, PETN, amatol, composition B, composition C series, tetrytol and TNT, and the low-velocity explosive ammonium nitrate. Most charges are made in the form of rectangular blocks. Some are made in cylindrical form, such as the 1/4-pound TNT charge. Recent studies show that a thinner layer of explosive spread out over a larger area is more efficient than a thick block of the same weight. In line with these studies, newer demolition charges are thinner than the older charges and are fitted with pressure-sensitive adhesive on one side for quick emplacement on practically any surface. a. Cutting and Breaching Types.

(1) Tetrytol blocks. These blocks (fig. 8-1), composed of 75 percent tetryl and 25 percent TNT, have a threaded cap well in each end and a tetryl booster pellet. The threaded cap well is designed to receive a detonator, a primed firing device, or a priming adapter with an electric or nonelectric blasting cap. Tetrytol blocks are effec

Booster Pellet
Figure 8-1. Tetrytol demolition block.

tive as a cutting or breaching charge but not as a cratering charge. Tetrytol is only slightly soluble in water. It is brittle and breaks very easily. Each block is wrapped in olive-drab, asphalt-impregnated paper.

(2) Composition C2 or CS blocks. These blocks (fig. 8-2) are plastic explosives. They may be molded at temperatures between -20°F. and +125°F. Although composition charges are difficult to mold at temperatures below freezing, body heat can keep the material pliable. Gases emitted, however, under these conditions, cause sickening headaches. Plasticity of the material permits it to be molded by hand, like putty; confinement of the material, as in the case of packing it into irregular-shaped objects, gives it high demolition efficiency. Insoluble in water, block demolition charges of composition C2 and C3 are suitable for underwater demolition. Initiation may be by detonating cord tied in a double knot, with the plastic explosive molded into a ball around the knot or by a special blasting cap inserted into the explosive.

(3) Composition C4 blocks. Composition C4 has many advantages over composition C3: It is more powerful; it may be molded over a broader range of temperatures (-70°F. to +170°F.); it is more stable, less sticky and will not adhere to hands; and it is less subject to water erosion when used for underwater work. This explosive is issued in thin blocks (fig. 8-3) or packed in white plastic containers with a threaded cap well in each end.

(4) TNT blocks. Trinitrotoluene (TNT) is one of the most powerful of military explosives. It has a high detonating velocity and is therefore used in general demolitions for cutting and breaching. It can be burned in the open in small quantities without exploding. It is relatively insensitive to shock. TNT is insoluble in water and can be used in underwater charges. TNT block demolition charges are available in three sizes: 1/4 pound, 1/2 pound and 1 pound. The 1/4-pound block demolition charge is issued in a cylindrical, olive-drab, plastic container. The 1/2-pound and 1-pound charges are issued in rectangular, olivedrab, plastic containers. All three have threaded cap wells at one end to receive detonators, primed firing devices, and priming adapters with electric or nonelectric special blasting caps.

b. Cratering Type. Ammonium nitrate or H-6 blocks (fig. 8-4) are used for cratering operations. Ammonium nitrate is the least sensitive of military explosives. It has a low detonating velocity and is,

Improvised Electric Blasting Caps

ord D316

Figure 8-2. Plastic demolition charges.

ord D316

Figure 8-2. Plastic demolition charges.

Demolition Charges Army

* ord d15vi

Figure 8-3. Composition C4 block charge.

* ord d15vi

Figure 8-3. Composition C4 block charge.

therefore, unsuitable for cutting and breaching. c. Shaped Demolition Charges. These charges

However, the low detonating velocity produces a consist of cylindrical blocks of high explosive. They pushing or heaving effect. This makes it well suited for have a conical or hemispherical, metal-lined cavity in cratering and ditching operations. one end, and a conical shape with

Underwater Demolition Charge
Figure 8-4. Cratering-type block demolition charge.

blasting cap well at the other end. Detonation of the charge starts at the cap well and travels to the cavity. There, the detonation wave is focused to produce a narrow concentrated detonation jet. This results in penetration greater than that produced without the cavity. With this effect, called Munroe effect, boreholes can be blasted in steel, concrete and similar material. Maximum penetration of a shaped charge is obtained when it is exploded at a certain characteristic distance, called standoff, from its target. Standoff is provided for by a fiber sleeve or metal legs supporting the charge at the time of firing. See TM 9-1375-200 for precautions in use of shaped charges.

(1) 15-Pound shaped demolition charge. This charge (fig. 8-5) consists of an explosive charge of Composition B and a 50/50 pentolite booster in a moisture-resistant fiber container. The top of the charge has a threaded cap well for receiving a blasting cap and adapter or any standard firing device. A cylindrical fiber base slips on the end of the charge to hold the charge at the proper standoff distance. The cavity liner is a cone of highdensity glass. This charge will pierce 36 inches of reinforced concrete. In a wall of greater thickness, it will produce a hole 30 inches deep and 2 to 31/2 inches in diameter.

(2) 40-Pound shaped demolition charge. This charge (fig. 86) consists of a larger quantity of Composition B than the 15-pound charge, and a 50/50 pentolite booster in a metal container. The cavity liner is made of metal. A threaded cap well is provided for receiving a blasting cap and adapter or any standard firing device. A metal tripod for gaging correct standoff distance is shipped unassembled, nested with the charge in the same container. This charge will penetrate 60 inches of reinforced concrete, producing a hole tapering from 5 inches to 21/2 inches in diameter.

(3) Shaped demolition charge containers. These containers are used in opening explosive-

Lbs Crater Charge
Figure 8-5. 15-Pound shaped demolition charge.

filled ordnance by initiating low-order detonation. When containers are filled with plastic explosive, the liners mold the explosive to produce a shaped charge. Shaped demolition charge containers, available in several shapes and sizes, are designed for various types of operations.

d. Dynamite. Dynamite, the most common com-

Ammonia Dynamite Explosive
Figure 8-6. 40-Pound shaped demolition charge.

mercial high explosive, may be one of several types: straight dynamite, ammonia dynamite, ammonia gelatin dynamite and gelatin dynamite. These types are produced in various grades designated by a weight-strength marking expressed as a percentage. Dynamite is exploded by a No. 6 (or larger) commercial blasting cap or by military blasting caps termed Special. Dynamite is normally issued in paraffin-treated paper cartridges (also called sticks), packed 50 pounds per wooden box. The standard cartridge size is 11/4 inches in diameter by 8 inches long. The number of cartridges per box varies in inverse proportion to the density of the particular type and grade of dynamite. A cartridge of 40-percent dynamite for example, 11/4 inches in diameter by 8 inches long, weighs approximately 1/2 pound.

(1) Straight dynamite. The percentage designation of straight dynamite is the percent, by weight, of nitroglycerin it contains. (In other than straight dynamite, the percentage indicates equal strength, weight for weight, with straight dynamite containing that percent of nitroglycerin.) Straight dynamite consists of nitroglycerin absorbed in a porous material that contains other energy-producing ingredients. Increasing the percent of nitroglycerin decreases the amount of other energy-producing ingredients. Hence, the actual blasting power of the dynamite does not increase directly with an increase in the percentage designation. Fifty to sixty percent straight dynamite is roughly equivalent to TNT and may be substituted for it. This dynamite does not resist water as well as TNT, but may be used under water if fired within 24 hours after submersion.

(2) Ammonia dynamite. In ammonia dynamite, part of the nitroglycerin is replaced by ammonium nitrate. This change in composition results in less poisonous fumes, less fragmentation and less water resistance than for straight dynamite of the same strength. Ammonia dynamite is not satisfactory for underwater use.

(3) Ammonia gelatin dynamite. This is a plastic dynamite that has an explosive base of nitrocotton dissolved in nitroglycerin with ammonium nitrate added. It produces less poisonous fumes than straight dynamite, which it equals in water resistance.

(5) Gelatin dynamite. This dynamite is a plastic type that has an explosive base of nitrocotton dissolved in nitroglycerin. It is insoluble in water. Its high velocity, when confined, produces a quick, shattering action. It is used for submarine blasting and blasting in extremely hard rock.

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