Unloading confining pressure tests of rock specimens with fixed displacement after conventional triaxial compression are conducted. Based on the complete procedure of unloading confining pressure, the failure features and strength of specimens are analyzed. The test results show that unloading fracture type is shear failure at the pre-peak and tensile-shear failure at the post peak. Failure phenomenon is easier to happen suddenly in the process of unloading confining pressure at the pre-peak than at the post-peak. In addition, the axial supporting capacity is very sensitive to the change of confining pressure. This is the result of the mosaic community between fractured rock blocks and reflects the structure effect along friction-sliding surface.
