Fractal analysis of pore structure of granite after variable thermal cycles

Thermal cycling can change the micro-structure of rock, and the change of pore characteristics is an important manifestation of its structural change. In this paper, the pore characteristics of granite under different thermal cycling conditions [i.e., variable thermal cycles (i.e., 1, 5, 10, 15, and 20); variable temperatures (i.e., 25, 250, 350, 450, 550, and 650 °C)] are studied by mercury intrusion technique under the research background of dry–hot rock development. The results show that the pore characteristic distribution curve of granite shows obvious bimodal characteristics. According to this, the pore of granite can be divided into two categories (i.e., 0.01 < r < 10 μm and 10 < r < 200 μm). According to the analysis of pore distribution under different thermal cycling conditions, the influence of thermal cycling on the pores is great, especially for the pores with pore diameter of 0.1–100 μm, its diameter and volume increase with the increase of temperature. In addition, the results of fractal dimension calculation show that the number of thermal cycles has little effect on pore structure, while temperature has a great influence on pore structure, which reduces the complexity of the pore structure with pore diameter of 0.01–10 μm and increases the complexity of the pore structure with pore diameter of 10–200 μm.