(1. School of Civil and Transportation Engineering，Hebei University of Technology，Tianjin 300401，China；2. State Key
Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400044，China)
Abstract：Under the influence of anthropogenic and natural factors such as underground engineering，slope excavation and valley cutting，the rock mass stress will release at least in one direction，which induces complex stress redistribution of rock mass. Such unloading easily induces rock mass engineering disasters，and the shear failure due to normal stress unloading is particularly prominent. The direct shear test with gradually unloading the normal stress but keeping the shear stress constant was performed to simulate the shear mechanical behavior of rock mass induced by excavating and unloading. The influences of the angle between the flaw and the shear direction and the stress level on deformation，strength and fracture evolution of single flaw sandstone under unloading normal stress were studied. It is revealed that，with increasing the angle from 0°to 180°，single flaw sandstone in sequence shows shear failure，tension failure，mixed tension-shear failure and shear failure. In the process of unloading，the normal and shear displacements increase with increasing the initial normal stress but decrease with rising the initial shear stress. The unloading normal displacement decreases firstly and then increases with increasing the angle，while the unloading shear displacement is not sensitive to the angle. The unloading amount at failure respectively increases，decreases，and decreases firstly and then increases with increasing the initial normal stress，the initial shear stress and the angle. The specimen is most prone to unloading shear failure when the angle is 60°. The correlation between the failure mode and the angle was presented based on the analysis of the stress state of the crack surface. The research results enrich the basic theory of unloading rock mass mechanics and have reference value for the prevention and treatment of excavation disasters in rock mass engineering.
黄 达1，2，郭颖泉1，朱谭谭2，张永发2. 法向卸荷条件下含单裂隙砂岩剪切强度与破坏特征试验研究[J]. 岩石力学与工程学报, 2019, 38(7): 1297-1306.
HUANG Da1，2，GUO Yingquan1，ZHU Tantan2，ZHANG Yongfa2. Experimental investigation on shear strength and failure characteristics of sandstone with a single preexisting flaw under unloading normal stress. , 2019, 38(7): 1297-1306.
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2019, Vol. 38 
