Executive Summary : | Temperature-dependent behavior of rock materials is crucial for various rock engineering activities, such as shale gas extraction, deep geothermal energy exploitation, nuclear waste disposal, rock cutting, drilling, blasting, and post-disaster reconstruction. Rocks exposed to high temperatures may be subjected to rapid cooling treatment. Conventionally, water is used for cooling agents, but liquid nitrogen (LN₂)-cooling has gained attention as a substitute. LN₂ is also used as a potential fracturing agent in underground coal bed methane, shale gas, and geothermal energy exploration. Understanding rock properties under various thermal treatments is essential for designing safe, stable, and sustainable engineering structures. Most investigations have focused on single LN₂ or water thermal shocks, but the feasibility and prospect of cyclic fracturing techniques have not gained much attention. Quartzite, basalt, and gneiss exhibit similar characteristics, but their engineering properties under various thermal treatments have not gained significant attention. To study the influence of different cyclic heating-cooling/thermal treatments on physico-mechanical properties, three different cooling techniques (LN₂-, water-, and air-cooling) are proposed. Microstructural changes induced by thermal treatments will be investigated using photomicrographs, SEM images, and X-ray micro-CT images, and numerical modeling will be conducted to simulate thermal dependent microstructural changes in rock materials. |