Thermal fracture modelling of borehole-heated rocks: A focus on inhomogeneities, physical properties, and heating rates

Abstract

The thermal cracking characteristics of borehole-heated rocks are significantly affected by inhomogeneities, physical properties, and heating rates. While most current numerical methods using Weibull-based models account for material inhomogeneity, they often overlook the simulation of real cracks. Although the finite discrete element method (FDEM) is effective for fracture simulation, this study enhances the process by integrating Voronoi diagrams and Weibull distributions to model rock inhomogeneity. Additionally, the finite discrete element method coupled with thermo-mechanical damage (FDEM-TMD) is employed to simulate realistic thermal cracking processes. This comprehensive model considers the distribution of temperature and thermal stress fields throughout the entire process from crack initiation to propagation. The model’s validity is confirmed through analytical solutions, experimental data, and other numerical simulations, which collectively demonstrate the influence of inhomogeneities, physical properties, and heating rates on rock fracturing. The results show that varying degrees of inhomogeneity can affect rock rupture behavior, while physical properties can impact energy consumption and heat transfer, ultimately influencing fracture efficiency. Furthermore, rapid heating may prolong stress accumulation and increase the probability of cracking. These insights enhance our understanding of heating-induced fracturing mechanisms and offer valuable theoretical guidance for applications in nuclear waste disposal, geothermal energy extraction, and laser-assisted rock fragmentation.