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Abstract As the existing studies in failure modes of rock under different loading paths are less，uniaxial compression，conventional triaxial compression，pre-peak and post-peak unloading confining pressure tests of sandstone are respectively conducted with the MTS815 rigid servo-controlling testing machine. Based on test results，the failure modes of sandstone under different loading paths are studied. According to the energy analysis of sandstone specimens before and after failure，the reasons for existences of different failure modes under different loading paths are discussed by means of energy dissipation theory. The results show that the main failure mode of sandstone specimens in uniaxial compression tests is splitting failure，while single shear failure is complement. The main failure mode is single shear or splitting failure under low confining pressure in conventional triaxial compression and post-peak unloading confining pressure tests；when the confining pressure is higher，combination failure modes of single shear and splitting failure mainly occurs. Under the per-peak unloading confining pressure tests，combination failure modes of shear and transverse shear of sandstone specimens mainly occurs under low confining pressure. On the contrary，combination failure modes of splitting and shear mainly occurs under high confining pressure. With the increasing confining pressure，shear failure occurs easily under triaxial compression；but the probability of shear failure occurrence increases at first，then decreases under pre-peak and post-peak unloading confining pressure. The failure modes under different loading paths are related with the energy values of sandstone specimens before and after failure. When the energy value is low，single failure mode occurs easily with intact broken block. When the energy value is high，combination failure modes occur easily with crushed block.
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Received: 11 August 2010
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2011, Vol. 30 
