Non-Linear Fracture Mechanics Model for Spallation and Coupling of NuclearExplosions Detonated in Hard Rock

摘要

The primary objective of the work was to look into the scaling relations indamage accumulation near failure in order to help interpret the Russian fracture data near large nuclear explosions in granite. The damage mechanics model we are currently using gives a good description of the accumulation of fracture damage up to the critical point, but does not treat the multiscale cascade process which characterizes the failure and post failure behavior. Recent simulations by the Maxwell Labs group have shown that a better description of the post failure behavior is essential if we are to model the unusual waveforms produced by nuclear explosions in hard rock. In collaboration with theoretical physicists in Nice, France, we have developed a 'critical point' model for brittle failure which is based on the mathematical techniques used by statistical physicists to describe chemical and magnetic phase changes. As applied to the brittle failure of rock, this theory predicts a cascade process in which the temporal and spatial scaling of the accumulating damage can be accurately characterized using renormalization group techniques. Our first application of this method was toward an understanding of the spatio-temporal patterns of regional seismicity. We are now working closely with the Maxwell Labs group to apply these methods to damage accumulation in the explosion problem.