Spherically Symmetric Calculations of the SRI Grout Spheres Experiment for Four Different Laboratory Configurations

摘要

One-dimensional spherically symmetric finite difference calculations are presented which attempt to simulate the Stanford Research Institute (SRI) Containment experiments. In these experiments, 3.8 gm spherical PETN charges are detonated in 12-inch diameter spheres of grout placed in a water tank forming a cavity from which, subsequently, the spheres are hydrofractured using water or glycerol. The finite difference calculations simulate the formation of compressive residual stress fields around the explosively generated cavities. These calculations were made three types of grout; SRI rock matching grout (2C4), granite simulant (GS3), and a low density grout (LD2C4) which is a mixture of 2C4 grout with glass microspheres. The simulated cavity pressures at 100 microsec are considerably greater than the average fracture initiation pressure from the laboratory tests yet are contained without fracturing by the residual stress fields calculated using laboratory strength data for grout. If the finite difference calculations are correct, the strong implication is that the compressive residual stress fields must have decayed significantly in the time interval between the dynamic calculations and the beginnings of the hydrofracture process. The finite difference calculations have been compared with the experimental data relevant to the dynamic time scale, which consist of cavity radius measurements and of pressure and impulse measurements made by a quartz gauge in the wall of the water tank.