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| Model test on the progressive failure characteristics of tunnel-type anchorage in soft rock |
| LIU Xinrong1，2，HAN Yafeng1，2，3，ZHOU Xiaohan1，2，DENG Zhiyun1，4，LI Zhuang5，LAI Guosen6，XIAO Yu1，2，LUO Weibang1，2 |
| (1. School of Civil Engineering，Chongqing University，Chongqing 400041，China；2. National Joint Engineering Research Center for Prevention and Control of Environmental Geological Hazards in the TGR Area，Chongqing 400045，China；3. School of River and Ocean Engineering，Chongqing Jiaotong University，Chongqing 400074，China；4. Department of Hydraulic Engineering，Tsinghua University，Beijing 100084，China；5. China Railway Development Investment Group Co.，Ltd.，Kunming，Yunnan 650217，China；6. China Railway Beijing Engineering Bureau Group Co.，Ltd.，Beijing 102308，China) |
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Abstract The model test and digital-image correlation technology were employed to investigate the initiation and propagation characteristics of rock mass cracks during loading of the tunnel-type anchorage installed in soft rock strata. The results indicate that the bearing process of the tunnel-type anchorage installed in soft rock goes through four states successively：approximate linear elastic deformation，nonlinear deformation，plastic deformation and failure state. The failure of the tunnel-type anchorage installed in soft rock strata gradually evolved from a single rock mass failure in the early stage to a double failure of the rock mass failure and debonding of the interface between the plug body and rock mass. The progressive failure process of the tunnel-type anchorage can be generalized as follows：In the plastic deformation state，the tunnel-type anchorage first enters failure stage I，which is mainly characterized by the shear cracks initiation in the surrounding rock near the back end of the plug body crown and invert. Subsequently，the tunnel-type anchorage enters the double failure stage II，which is mainly characterized by the compression-shear and tension-shear failure of rock mass and sliding failure of the interface. In the complete failure state，the tunnel-type anchorage enters the failure stage III in which the crack extends to the ground surface and the interface is debonded. In the process of propagation to the ground surface，the cracks in the surrounding rock of the upper part of the plug body go through the evolution process of shear failure，tension-shear composite failure，and tensile failure. The surrounding rock of the lower part of the plug body is dominated by shear cracks approximately parallel to the axis of the plug body. The ground surface cracks propagate in a direction approximately perpendicular to the vertical projection of the plug body on the ground surface. The ground surface cracks experience the evolution from tensile cracks to shear or tensile-shear composite cracks，to tensile cracks，and then to tensile-shear composite cracks during propagating. The block shape cut by the crack inside the rock mass gradually transits from strip-shaped to block-shaped from the back of the plug body to its front end. The vertical dislocation value between adjacent blocks decreases from backward to forward. The cracks shape in the deep part of the rock mass gradually changed from a convex trumpet shape to a concave arc shape with the increase of the peeling depth，and the damaged area gradually shrinks to the shallow surface and the front end of the plug body crown.
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2022, Vol. 41 
