Thermo-mechanical FDEM model for thermal cracking of rock and granular materials

Abstract

A coupled thermo-mechanical (TM) model based on the combined finite-discrete element method (FDEM) was proposed to simulate the thermal cracking of rock and granular materials. For heat conduction, it links continuous and contact heat transfer simultaneously through the continuum and discrete thermal elements, and can handle thermal contacts explicitly. For thermally induced stresses, the new TM model uses the concept of multiplicative decomposition of deformation gradient, which is consistent with the finite strain theory used in FDEM – for handling large strains and rotations. For thermal cracking, the coupling of the new TM model occurs in two directions, such as cracking in mechanical calculation affects thermal conduction, and friction caused by contact interactions generates heat, thus can capture the dynamic process of thermally induced fracturing. Four verification examples were given to validate its performance in simulating the thermal expansion in the steady-state, thermal stress in transient states, thermal cracking, and complex-shaped multibody thermal contact. The new TM model exhibits attractive features: robust to capture heat transfer for multibody thermal contact problems; better handle large strains and thermal cracking; better capture the progressive process of fracturing affects thermal conductivity; applicable to not only the steady-state but also the transient TM response.