Numerical Analysis of Degradation Characteristics for Heterogeneous Rock under Coupled Thermomechanical Conditions

Abstract

The effects of high temperature on rock strength and deformation, and hence the integrity of rock structure, have been a significant issue for rock mechanics and engineering. This article adopts a coupled thermomechanical (TM) solution method to explore the deterioration characteristics of heterogeneous rock under TM conditions. Based on the combination of damage mechanics and plasticity, a coupled material model with consideration of yielding, the plastic flow rule, damage evolution, the thermal effect, and heterogeneity was implemented in a commercial explicit finite-element code, LS-DYNA, through a user-defined material subroutine. Validation simulations indicate that the proposed model is capable of reproducing the mechanical behaviors of rock under unconfined compression and heating conditions. The effects of the heating temperature and homogeneity index on the mechanical properties were also investigated. The results indicate that rock exhibits prominent ductility characteristics with an increase in temperature regardless of the homogeneity index. With the same heterogeneity, monotonic reductions in unconfined compressive strength (UCS) and Young’s modulus and an increase in peak strain were observed with an increase in the temperature. A single oblique fracture dominated the failure of the rock with lower homogeneity, whereas two conjugate fractures developed in the rock with more homogeneous strength.