Heating rate effect of thermal expansion in granite and implications for rock breaking

The influence of the heating rate on the thermo-mechanical response and damage evolution of rock is a critical factor limiting the safety and efficiency of engineering applications. Conventional models are limited, however, as they assume a static coefficient of thermal expansion (CTE) and ignore its dynamic nature under rapid thermal loading. This study confronts this knowledge gap using a synergistic experimental–numerical approach. A custom system combining induction heating and Digital Image Correlation was employed to measure the rate-dependent CTE of both bulk granite and its constituent minerals over various heating rates. These dynamic coefficients were then integrated into a high-fidelity numerical model to simulate microwave-assisted rock breaking. Results definitively show the CTE is strongly rate-dependent. While the quartz phase transition at ∼573 °C triggers critical damage, faster heating significantly amplifies strain localization and damage accumulation. Crucially, simulations revealed that under identical microwave loading, the model using dynamic CTE (530 °C/min) reached a 1000 mm 2 failure area 11 times faster than the model using quasi-static CTE (5 °C/min). This study fundamentally establishes rock’s CTE as a dynamic, rate-dependent property, providing a key scientific basis for advancing such thermal fracturing technologies.