Simulating the behavior of geologic materials under impact loading conditions requires the use of a constitutive model that includes the effects of bulking, yielding, damage, porous compaction and loading rate on the material response. This paper describes the development, implementation and calibration of a thermodynamically consistent constitutive model that incorporates these features. The paper also describes a computational study in which the model was used to perform numerical simulations of PILE DRIVER, a deeplyburied underground nuclear explosion detonated in granite at the Nevada Test Site. Particle velocity histories, peak, :1ocity and peak displacement as a function of slant range obtained from the code simulations compare favorably with PILE DRIVER data. The simulated attenuation of peak velocity and peak displacement also agrees with the results from several other spherical wave experiments in granite.
Modeling the dynamic response of rock materials is a challenging area of research. Since most strength measurements in rock materials are performed for intact samples under static conditions, the models based on these data should account for possible scale and rate effects when being applied to simulation of the dynamic response of large-scale rock masses. Unlike intact rock samples, rock masses may contain discontinuities that may reduce the strength. This paper describes the development and application of a thermomechanically consistent constitufive model for rock that accounts for these effects and also includes the effects of bulking, yielding, material damage, and porous compaction on the material response. Results of a computational study performed to investigate the behavior of granite under shock wave loading conditions are used to illustrate the model capabilities.
