Abstract: The strength parameters of fault gouge is significant for the fault sealing of underground gas storage. In this paper, direct shear tests are performed for fault gouge composed of different contents of kaolinite(K), montmorillonite(M) and quartz(Q), thus obtaining the shear strength parameters (cohesion c and internal friction angle φ ) of various types of fault gouge. The results reveal that: (1) the cohesion of fault gouge is positively correlated with the content of montmorillonite and negatively correlated with the content of quartz. The cohesion of fault gouge specimens with high content of montmorillonite (≥40%) is positively correlated with the content of kaolinite; (2) The internal friction angle of fault gouge is negatively correlated with the content of montmorillonite and positively correlated with the content of kaolinite; (3) The cohesion of fault gouge is positively correlated with the plasticity index I_P, while the internal friction angle is negatively correlated with the plasticity index I_P; (4) The predicted shear strength parameters of fault gouge obtained by statistical methods match well with the experimental results, indicating that statistical method is feasible in predicting the shear strength of fault gouge.

Key words: fault gouge, shear properties, cohesion, internal friction angle, mineral composition