富水软土地层隧道开挖失稳破坏机理与三维稳定性上限分析

In order to solve some problems in the existing face stability analysis of tunnels in water-rich soft strata, the authors conducts the research from two aspects. First, model tests are conducted, since it is a powerful tool in exploring the collapse mechanism of tunneling. The authors made efforts to improve the three-dimensional failure mechanism for the face stability of tunnel in water-rich soft strata. As in the existing 3D translational multi-block collapse mechanism, the intersection of the circular truncated cylinder with the tunnel face is an ellipse surface that does not cover the entire circular face of the tunnel. A new 3D upper-bound limit analysis method for the tunnel face stability in in water-rich soft strata is established. Second, by adopting FE numerical simulation, the influence of water table line on the distribution of pore water pressure around the shield tunnel face is studied, and the influences of water table line, tunnel diameter, and tunnel depth on the seepage force are obtained. By considering the average seepage force on the slide block, the face stability of shield tunnels is studied via a new proposed model, and a formula to calculate the limit support pressure under seepage condition is deduced. The study will provide experimental and theoretical bases for the design of the tunneling in water-rich soft soil, which will be great helpful to improve its application in the traffic engineering construction.

针对富水软土地层盾构隧道开挖面稳定性问题现有分析研究现状的不足，本项目从两个方面进行研究。一、通过模型试验技术，监测隧道开挖失稳过程中开挖面支护压力及土体变形的发展，揭示隧道失稳破坏的机理；基于模型试验的分析结果，构建能够反应隧道开挖面失稳流滑机理的破坏模式，并通过优化的方法得破坏滑动面形状和极限支护压力的最优上限解，建立软土地层隧道开挖面稳定性问题的三维上限分析方法，并与极限分析有限元的计算结果进行对比验证其可靠性。二、采用有限元数值模拟方法，分析水位高度、隧道埋深比等对开挖面渗流力、隧道开挖面失稳破坏模式的影响，得到考虑渗流影响的开挖面极限支护压力计算结果；建立渗流条件下的开挖面失稳破坏模式，得到渗流条件下砂土地层隧道开挖面稳定极限支护压力的上限解答。研究成果将为盾构隧道掘进施工提供试验和理论依据，促进其在富水软土地区交通工程中的应用和推广。