Relationship between strength parameter and water content of fault gouge with different degrees of consolidation

The strength of fault is significently influenced by the strength parameters of fault gouge, which are closely related to the consolidation degree and water content. In this study, specimens of fault gouge with different consolidation degrees and water contents are subjected to the direct shear test to obtaincohesion c and internal friction angle phi, which are the dominant strength parameters of fault gouge. Based on the results of test, the relationships between the two strength parameters and consolidation degree and water content of fault gouge are analyzed and following conclusions can be drew. The internal friction angles of fault gouge specimens with different consolidation degrees decrease as the water contents increase, but the decrease of internal friction angle is slight. The trend between cohesion of fault gouge specimens of different consolidation degrees and the water content can be divided into three stages: ascent stage, steep descent stage and slow descent stage. These three stages are separated by the first inflection point and the second inflection point. As the consolidation degree increases, the internal friction angle of fault gouge increases gradually but slightly. Meanwhile, the descresing rate of the internal friction angle of fault gouge tends to descrese with the increase of the water content. As the consolidation degree increases, the water content of fault gouge whose cohesion is at the first inflection point increases rapidly, while the water content of fault gouge whose cohesion is at the second inflection point changes slightly. The relationship between consolidation degree of fault gouge and the water content of fault gouge whose cohesion is at the first inflection point can be described by a quadratic polynomial function.