Study of the effect of anchorage modes on the macro and micro shear characteristics of rock joints and its mechanism
With the continuous expansion of the scale of rock mass engineering and the increasing complexity of the occurrence environment,the phenomenon of rock joint shear slip causing rock bolt breakage is becoming more and more prominent.It is very important to recognize the shear characteristics and shear mechanism of bolted joints for the stability control design of rock mass engineering.In this paper,the effects of full anchor and end anchor modes on the macro and micro shear properties of rock joints and their mechanisms are systematically studied through shear tests and numerical simulation of anchored joints.The results show that the presence of anchoring agent can make the bolt play its"pin role"quickly in the full-anchor mode,while the bolt does not play its role until the shear displacement exceeds the gap between the borehole and the bolt in the end-anchor mode.Before the anchor rod fractures,the peak shear stress and breaking shear stress in the full-anchor mode are greater compared to the end-anchor mode.Under the same shear displacement,the number of cracks in the anchored joint is more in the full-anchor condition compared to the end-anchor condition.Under full anchoring method,the cracks are concentrated near the anchor rod,especially at the intersection of the anchor rod and the joint,while under end anchoring method,the cracks are distributed in the end bolted,the intersection of the anchor rod and the joint and the gasket.Under the same shear displacement condition,the shear stress of full-anchored bolt is much greater than that of end-anchored bolt,but its axial stress is mainly concentrated near the joint surface due to the restriction of anchoring agent.The axial stress of end-anchored bolt is fully mobilized and can effectively increase the normal stress of the joint after being transferred to the gasket.After the peak shear displacement,the deformation range of end-anchored bolt and full-anchored bolt increases continuously,but the deformation range of end-anchored bolt is significantly larger than that of full-anchored bolt.
rock mechanicsrock jointsbolted modemacro and micro view shear characteristicsnumerical simulation
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