地面超载条件下覆跨比对浅埋隧道稳定性的影响

Affection Laws of Thickness-Span Ratio on Stability of Shallow Tunnels under the Condition of Ground Overload

以青岛地铁江西路站为工程背景,通过典型数值模型的计算与分析,研究了地面超载环境中覆跨比对浅埋隧道的变形与受力特征等开挖稳定性规律.结果表明:不同覆跨比下浅埋隧道的破坏形态相似,首先是拱肩部位的围岩发生剪切破坏,然后破坏面逐渐发展至地表,围岩的塑性区形状呈倒锥体;覆跨比大小对隧道的围岩稳定性影响显著,覆跨比小于0.2时,围岩的破坏程度严重,出现地表、拱顶沉降变形不收敛的现象;覆跨比增大,有利于加强围岩与支护的共同作用,可以控制地层的变形发展、降低围岩的应力扰动;地面超载值越高,隧道结构的变形与地表沉降越大,围岩的应力扰动也越严重.

This paper takes the Jiangxi Road station of Qingdao metro as engineering background to set up typical numerical models.By calculation and analysis of the models,laws of thickness-span ratio on stability of urban subway tunnel,including deformation behavior and stress characteristics in excavation,are studied under overloading.The results show that the damage forms of shallow tunnels under different thickness-span ratios are similar,which means that the shear failure develops initiates from shoulders of surrounding rock to the ground surface,and the final shape of the plastic zone is the vertebral body.The thickness-span ratio has a great effect on the stability of a tunnel.When the ratio is less than 0.2,the damage of the surrounding rock is serious,and settlement of some monitoring points shows great divergent trend.The interaction between surrounding rock and support is strengthened,and the deformation of stratum and disturbance of surrounding rock stress are reduced as the ratio increases.The deformation of tunnel structure and ground surface settlement and disturbance of surrounding rock stress will be serious,if the ground overload value gets bigger.