A multiscale peridynamic simulation on thermal-mechanical coupling behavior and damage failure mechanism of granite

In underground rock engineering, the propagation and coalescence of cracks in surrounding rock under high-temperature conditions exhibit highly complex mechanical behaviors. To address the challenge of simultaneously considering thermal damage and nonlinear mechanical responses within the peridynamics (PD) framework, this study proposes a novel computational framework for simulating the mechanical properties and damage mechanisms of granite at elevated temperatures. The framework integrates a thermal-mechanical coupling model comprising a nonlinear mechanical layer and a thermal damage layer, which are linked via a multi-layer computational strategy. To represent mineral-scale heterogeneity, a multi-parameter shuffle algorithm is incorporated, along with a nonlinear temperature evolution method and an OpenMP-based parallel computing strategy, significantly enhancing computational efficiency. The framework is calibrated and validated using laboratory test results, and analyses are conducted at both macroscopic and microscopic scales. The results indicate that increasing temperature markedly reduces the peak strength of granite, increases plastic deformation, and promotes the formation of a dense and interconnected thermal crack network, which is the primary cause of compressive strength degradation. Furthermore, the dominant failure mechanism shifts from stress concentration to the development of a thermal crack network, with the prevailing crack type transitioning from shear-dominated to tensile-dominated, ultimately producing a mixed fracture pattern. This study not only advances the numerical simulation of high temperature rock behavior but also provides a theoretical basis for understanding the failure mechanisms of high temperature rock masses in deep geothermal engineering construction.