Generation of High-Frequency P and S Wave Energy by Rock Fracture During a Buried Explosion.

摘要

We have developed a micromechanical damage mechanics model that is capable of predicting the nucleation, growth, and interaction of fracture damage at the high loading rates found in the non-linear source region of underground nuclear explosions. This model predicts the generation of strong S wave radiation in the non-linear source region whenever spherical symmetry is broken. Spherical symmetry is broken by the following: tectonic pre-stress, preferred orientation of pre-existing fractures (anisotropic rock fabric), and the lithostatic stress gradient. We are verifying this model by using it to predict the fracture patterns and S wave radiation generated by laboratory explosions in plates of candy glass . Candy glass (or break-away glass) is used in the movie industry to simulate glass fracture in stunts with no injury to the actors. We have measured the elastic velocities, density, fracture toughness, and the size and density of initial flaws of this material as required input parameters to our model. We have also used laser velocimeters (as high speed seismometers) to measure the seismic radiation generated by these laboratory explosions. The dynamic damage mechanics model gives a good simulation of the fracture pattern and associated elastic radiation in these experiments. We have recently extended the damage model to allow an anisotropic distribution of initial damage and used it to model the asymmetric fracture pattern and seismic radiation observed for a chemical explosion in a granite quarry in Barre, Vermont.