Evolution of mechanical properties and microstructure in thermally treated granite subjected to cyclic loading

Abstract

In high‐temperature geological engineering applications, cyclic loads induced by various factors (e.g., earthquakes, excavation, and blasting) can exacerbate the thermal damage of engineered rock formations. Therefore, this study investigates the mechanical properties and microstructure evolution of thermally treated granite subjected to cyclic loading. First, the mechanical property variations of thermally treated granite under cyclic loading were studied through cyclic loading experiments. Subsequently, nuclear magnetic resonance (NMR) was employed to examine the microstructure evolution of thermally treated granite under cyclic loading. Lastly, the effects of cyclic loading on maximum strain, Young's modulus, pore size distribution, and porosity of thermally treated granite were discussed. Results indicate that at the same number of cycles, maximum strain increases with increasing temperature, while Young's modulus decreases. For granite subjected to the same thermal treatment, the maximum strain increases as the cyclic number increases, while Young's modulus decreases. Concurrently, porosity and fractal dimension initially decrease and then increase with a rising number of cycles.