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| Experimental and numerical study on tensile-shear strength and rupture characteristics of sandstone#br# |
| CEN Duofeng，LIU Chao，HUANG Da#br# |
(School of Civil and Transportation Engineering，Hebei University of Technology，Tianjin 300401，China)
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Abstract High rock slope and underground engineering excavations can easily induce rock mass tension-shear failure disasters. A kind of rock tension and shear device，which can be used in servo-controlled compression and shear test machine to ensure the accuracy of load and displacement control，is designed，and uniaxial tension，tension-shear and compression-shear tests of sandstone were carried out. The tension-shear strength envelope of sandstone is nonlinear and can be described by Hoek-Brown criterion in the full normal stress zone. In view of the failure of conventional PFC parallel bond Mohr-Coulomb strength criterion to effectively simulate the nonlinear strength envelope of rocks，a parallel bond Hoek-Brown strength criterion was established based on the sandstone test results and programmed into the PFC program through a simple conversion method to effectively simulate the tensile-shear strength，fracture characteristics and mesomechanical mechanisms of sandstone. The cracks on the fracture surface is relatively thin and more tensional in the case of tension and shear，while the number of microcracks is relatively large and the damage is more intense in the case of compression and shear. With increasing the normal stress sn，the failure surface becomes less tensile and more shear. Due to shear dilation，however，tensile-shear cracks are still dominant under a smaller normal stress. Based on the numerical simulation results，the damage evolution process of rock under tension-shear or compression-shear stresses can be roughly divided into four stages including elastic deformation，stable rupture development，unstable rupture development and overall failure. When sn is larger，the stages of elastic deformation and unstable rupture development are relatively longer，the pre-peak plastic deformation is more and rock under tension and shear condition is more elastic-brittle.
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2020, Vol. 39 
