Crack propagation under compression of rocks and cracks in the rock are mainly tensile. Shear band can be formed as the result of interaction of tensile cracks; and shear failure finally occurs with propagation and interaction of cracks in the rock. It has been found that progressive failure process of rocks is affected by mineralogical composition

grain size

texture and foliation

etc. External factors such as the confining pressure and excavation disturbance also have great effect on progressive failure process of rocks. The influence of water pressure on crack propagation of sandstone is studied. Feature of each stage in progressive failure process of sandstone is researched; and stress thresholds—crack initiation stress and crack damage stress are summarized. Then the influence of water pressure on progressive failure process of sandstone is studied experimentally. It is indicated that with increase of water pressure at both ends of the rock sample

crack initiation stress has a tendency to increase and crack damage stress and peak stress decrease gradually. With increase of the confining pressure

stress thresholds during progressive failure process of sandstone decrease gradually.