In high-rate failure models for geological and rock-like materials, heating due to inelastic deformation is often neglected or accommodated incompletely through the use of an isentropic elastic response. However, for realistic prediction of geomaterials response to high-rate large deformations with significant released energy (such as buried explosive), dissipation caused by the initial mechanical work of the blast wave results in a non-negligible entropy generation that must be accounted for in constitutive modeling. In this study, thermal effects in the vicinity of a buried explosive in partially saturated soil are investigated using the Jones-Wilkins-Lee (JWL++) detonation model of High Explosive (HE) material, along with coupled multiphysics balance equations in an open-source massively parallel computational framework (Uintah) via Material Point Method (MPM) and Implicit, Continuous fluid, Eulerian (ICE) for compressible multi-material formulation of fluid-structure interactions (including highly pressurized explosive gaseous products). The temperature is allowed to evolve according to thermo-plasticity equations (derived from dissipation inequalities and basic conservation/thermodynamics laws) and thereafter, the state of internal variables (porosity, entropy, yield stress, etc) and stress in the partially saturated soil are determined for the obtained temperature. In order to account for material hardening from pore collapse, a yield surface based on Gurson’s upper bound theory evolves with stress, temperature, and internal state variables in plastic phase. Comparisons of soil response to blast loading are provided to quantify the importance of thermal effects.
Furthermore, geomaterials develop anisotropy in their response to deformation caused by prompt high-pressure shock waves. Thermodynamic admissibility implies that the fourth-order tangent stiffness tensor of geomaterials must develop a recoverable deformation-induced anisotropy (RDIA) even if the material is initially isotropic. This effect is significant for materials, like geomaterials, that have strongly pressure-sensitive strength. The degree of RDIA and the required additional terms in the form of deformation-induced anisotropy based on thermodynamics requirements in a high-temperature phenomenon are summarized for the region near the buried explosive source in partially saturated soil.
