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Salient. Victoria University Student Newspaper. Volume 36, Number 8. 19th April 1973

Counter Force

Counter Force

General. This charge will effectively breach dense concrete and occasionally certain timber targets up to 1.22 meters in thickness. Excellent results will be obtained with relatively small amounts of explosive when properly constructed, placed, and activated. The simultaneous activation of two diametrically opposed charges on the target causes the shock waves to meet at the target center. The resultant pressure causes internal damage.

Preparation and placement. The actual size of the charge is governed by the target thickness, in meters, of the target to be breached. Multiply the diameter or thickness of the target to be breached by the constant, 5, which gives the number of pounds of plastic explosive required for reinforced concrete. Round off to the next higher meter for any fractions less than I meter. For example if a concrete target pier measures 1.06 meters in thickness the total amount of plastic explosive required is 6 pounds (2.72 kilograms). Divide the required amount of explosives in half and place the halves diametrically opposite one another on the target. Both sides of the target must be accessible in order to position the two charges against the sides of the target. To secure the charges against the target one of the following methods may be used:
(a)Suspend the charges from ropes which pass over the top of the target (fig. 3)
(b)Construct a simple frame of a sire that will enclose the target. Secure the charges to both sides of the frame so that they are diametrically opposed. To secure the frame in position one side may be hinged and the frame wedged in place (fig. 4). The frame may also be suspended using ropes which pass over the top of the target.
(C)On relatively small targets, visual adjustment and placement may be employed. Charges are held in place by propping them with boards or poles.

Pruning, Simultaneous detonation of both charges is mandatory. The most common procedure is to crimp non-electric blasting caps to equal lengths of detonating cord; prime at the center rear of the charge; join the two free ends together at a point 15.24 centimeters from the end and tightly tape the blasting cap of the firing system to the parallel detonating cords.