Numerical Modelling of Thermal Spallation of Rock

Abstract

This paper presents a numerical study on thermal spallation of rock. In the present context, thermal spallation refers to fragmentation of rock surface material when subjected to rapid external heating. For modelling the rock fracture in thermal spallation, an embedded discontinuity finite element approach is chosen. In the present implementation, a displacement discontinuity (crack) is embedded perpendicular to the first principal direction in a CST element upon violation of the Rankine criterion. The heating due to mechanical dissipation is neglected as insignificant in comparison to the external heat flux. Thereby, the underlying thermo-mechanical problem becomes uncoupled the only input from the thermal part to the mechanical part being thermal strains. This problem is solved with explicit time marching using the mass scaling to speed up the solution. A thermal spallation problem of a rock sample under axisymmetry is simulated as a numerical example. Different heat flux intensities are tested to demonstrate the capability of the method.