Microcracks development and porosity evolution in sandstone, Sichuan basin, China: An experimental approach

摘要: The process of fault rupture is closely related to the weakening of fault rock. The weakening process of fault rock from Sichuan basin was investigated when subjected to different loading levels and subsequently unloaded under uniaxial compression. With nuclear magnetic resonance, the transverse relaxation time spectra (T2) distribution and porosity characteristics of the sandstone were quantified; meanwhile, optical microscopic experiments were performed to explore the microcrack growth patterns. According to the growth curve of the normalized porosity, the degradation process of sandstone was divided into three phases. During the first phase, the normalized porosity grew at a small accelerating rate. The intergranular microcracks grew slightly, and there was no distinct change in the number of transgranular and transgranular-intergranular microcracks during this phase, suggesting the weakening was mainly …