管棚预支护条件下水下隧道开挖面三维稳定性分析

为研究管棚预支护条件下水下隧道开挖面稳定性,基于塑性极限分析理论,建立考虑渗流力的管棚预支护条件下隧道开挖面三维稳定性分析模型,并据此确定开挖面的极限支护压力。结合深圳地铁实际工程,采用笔者提出的方法计算得到的开挖面极限支护压力较二维极限平衡法更符合实际情况,该方法的合理性得到验证。进而研究管棚预支护、地下水位和管棚剩余长度对隧道开挖面渗流力的影响。分析结果表明,渗流力对隧道开挖面稳定性有显著影响,渗流力与地下水位呈线性关系;采用管棚预支护能显著减小隧道开挖面处的渗流力,但当开挖面前方管棚剩余长度超过2倍洞径时,再增加管棚长度对减小开挖面渗流力的效果不明显。

Three-dimensional Face Stability Analysis of Underwater Tunnel with Pipe Roof Reinforcement

In order to study the face stability of underwater tunnel,based on the kinematic method of limit analysis,a three-dimensional model for expressing the face stability of underwater tunnel with pipe roof reinforcement was established.The proposed approach was employed to define the support pressure of tunnel face.For a certain tunnel excavation,the solutions computed by the proposed approach were compared with the results given by two-dimensional limit equilibrium method to verify the reasonability of the method.The proposed approach was also employed to study how the water level and the length of pipe affect the seepage pressure.The analytical results reveal that the existence of groundwater may seriously affect the face stability,and the linear formula is able to account for the influence of water level on seepage pressure.There was a relatively large reduction in the seepage pressure by adopting the pipe roof reinforcement technique.However,the studies also reveal that if the pipe length ahead of tunnel face is longer than 2 times of tunnel diameter,the effect of pipe roof reinforcement on reducing seepage pressure is not significant.