BEHAVIOR OF SHEARING MECHANICS AND CHARACTERISTICS OF STRAIN SOFTENING OF FAULT GOUGE

Exploring the mechanical behavior of fault gouge is the basis of studying the engineering geology effects of fault zone. Taking the gouges of Shendaogou Fault in Yan'an as an object, the fabric characteristics of three color fault gouges are studied with particle analysis and X-ray diffraction(XRD). In addition, the mechanical behavior of remolded fault gouges under different water contents are analyzed with ring shear test. The results show that the gradation curve with single peak of fault gouge particle is significantly better than that with double-peaks. Quartz, mica and feldspar are the main non-clay minerals, while illite and kaolinite are the main clay minerals. The color difference of fault gouge is brought by the relative content of hematite and chloriter. The strain softening characteristics of fault gouge are mainly affected by water content and coarse particle content. The strain softening is first strengthened and then weakened with the increase of water content. When the water content is less than the plastic limit, the strain softening characteristics weaken with the increase of coarse particle content. Internal friction angle(φ) is the main mechanical parameter affecting strain softening characteristics. Peak internal friction angle and residual internal friction angle are negatively correlated with water content. The variation of φ is influenced by the mineral composition, which indicates that φ increases with the increase of non-clay mineral under 5% and 10%water content.