STRESS PATH AND FRICTIONAL SLIDING OF ROCKS

Frictional sliding experiments with Jinan gabbro and Diancangshan marble are made by the bishear test method. There are two types of stress change in the experiments. Type A: The normal stress on the fault plane is increased first, then it is kept constant and the shear stress is increased until stick-slip happens; Type B: The normal stress on the fault plane is increased first, keeping it constant and the shear stress is increased to a certain value before stick-ship, then the shear stress is kept constant and the normal stress docreased until the happening of stick-slip. The experiments show that the frictional strength of rocks in type B experiments is higher than that in Type A, There is precusory increase of AE rate before stick-slip in Type A, but this has not been observed in Type B. It is suggested that there are two forms of dislock-ing of the locked faults: Dislcking by rushing, the fault movement is caused by an increase of the shear stress; Dislocking by relaxing, the fault movement is caused by a decrease of the normal stress. The form of stick-slip of faults is determined by the path of stress change in fault