Dynamics of a soil mass subjected to a deep source of gaseous energy

Abstract

Physical processes that take place in a soil layer subjected to the effects of chemical or nuclear energy sources are under rather extensive study at the present time. Specific mathematical models corresponding to the dynamics of the motion of a medium of known properties can be used for the numerical modeling of these processes on the basis of data on soil properties (incompressible saturated, compressible porous). This makes it possible to conduct numerical experimentation with higher accuracy and lower outlays, since use of universal mathematical models is less effective. The problem of substantiation and correctness of the use of some mathematical model to describe the evolution of a physical blast in soils, however, requires further development. The phenomenon of a sudden burst of energy of compressed gas from a source embedded deeply beneath a soil layer is understood to be a physical explosion for the case in question. A characteristic feature of this process consists in the fact that in contrast to a chemical or nuclear explosion, the action in question is accompanied by relatively insignificant parameter gradients. For a small degree of gas expansion, the process may be characterized as a gas-dynamic burst. It is obvious that the dynamics of the phenomenon in question during a camouflet burst has its own characteristic features to which the present experimental investigation is devoted. A schematic diagram of the experimental apparatus is shown in Fig. 1. Discharge channel (DC) 1, which is supercharged from unit 2 of compressed-air tanks through pneumatic panel 3, was mounted against the wall of a duct made of acrylic plastic. Pressure sensors 4 connected via pressure indicator 5 were installed at the level of the DC section. This made it possible to monitor the variation in the normal pressure in the layer and record it in five channels of N-145 mirror-galvanometer oscillograph 6. The other six channels of the oscillograph were operated under six autonomous electric circuits consisting of source 7, small lamps, and recorder 8, which is connected in series with galvanometer insert 9 of a dual-trace oscillograph, as well as contact couple 10. Six contact couples were rigidly mounted on the continuation of the vertical axis of the DC at a distance equal to the distance between pressure sensors - 65 mm apart. The distance from the first contact couple to the section of the DC was 50 mm. A 5-mm displacement of the layer of dry material caused the contact couples to break, and consequently, displacement of the oscillograph beam. The fields of pressure distribution over time and the displacement of the soil layers were therefore monitored synchronously by the oscillograph on a sheet of photographic paper. The displacement of the soil layers was duplicated by the cine-photograph recorded by high-speed ASK cine camera 11. TD visualize the displacement of the layers opposite each contact couple, a solid line was formed in the soil by placing thin layers of ground chalk near the transparent wall of the duct, and six small lamps reflecting the rupture of the contact couples and movement of the soil were also placed in view of the cine camera. The DC was hermetically sealed by a film of Iavsan plastic, the opening of which was accomplished by the burn through of a nichrome thread as voltage was delivered from power supply I2. The oscillograms obtained in five experiments under a DC charging pressure Pc = 8"105 Pa and DC embedment depth W = 0.4 m are presented in Fig. 2. The diameter of the DC and its outlet section were 0.05 m, and its length was 0.35 m. Quartz sand with the natural moisture contact, the bulk density of which p = 1400 kg/m 3, was used as the soil. We had previously described the distribution pattern of the pressure field in sand for the indicated scheme of investigations