UNDERWATER EXPLOSIONS PART 5. MINIMUM WEIGHT OF AN EXPLOSIVE CHARGE FOR THE RELIABLE ENERGY MESUREMENTS

摘要

When establishing an underwater testing site for the energy measurements of the explosives, the dimensions of the measuring pool have to be measured to find out what is the maximum weight for the test charge. Secondly one has to decide the distance between the pressure gauge and the shooting point. Thirdly the pool has to be calibrated because of the reflections of the explosions by measuring the bubble periods of the calibration charges. The calibration shots can also be used to estimate the minimum weight of the explosive charge for the reliable energy measurements by calculating the shock, gas heave and total energy values and their standard deviations. Before the energy measurements can be started, the test site has to be established. The equipments of the site consist of pressure gauge, cable, measuring unit and the charges. The measuring pool also has to fulfil certain requirements concerning the depth and the free water space of the pond. The length of the measuring cable should be optimized and kept as short as possible because of the potential signal damping which may cause some interference for the shock energy measurements. It is possible to use the signal amplifiers, but if the length of the measuring cable can be optimized, there is no need for the amplifiers and the measuring system can be kept as simple as possible. One also has to make the decision what is the weight of a representative test charge. The weight of the test shots also effects to the selection of the distance between the pressure gauge and the charge. The pool calibration can be carried out by exploding a set of calibration charges, whose weight varies from a few hundred grams to several kilograms covering the whole weight range of the test charges. The test results of the pool calibration can also be used to estimate the minimum weight of an explosive charge for the reliable energy measurements.