考虑中间主应力的非饱和土刚性挡墙抗倾覆稳定性

现有基于Mohr-Coulomb强度准则的饱和土基坑挡墙抗倾覆设计过于保守，本文基于非饱和土的平面应变抗剪强度统一解，考虑土体强度的非饱和特性与中间主应力效应，推导了满足不同抗倾覆稳定系数的刚性挡墙埋置深度方程，并探讨了中间主应力、基质吸力和稳定系数对埋置深度的影响特性。推求的闭合解为有序新解答的集合，可供不同类型和特点的基坑工程选择与优化。结果表明，中间主应力和基质吸力对埋置深度有影响，表现在随中间主应力效应和基质吸力的增加，埋置深度相应减小且显著；挡墙抗倾覆设计的强度理论效应明显，稳定系数越大对应要求的埋置深度越大，且埋置深度也与基坑开挖深度相关。研究成果为非饱和土基坑挡墙工作性能和安全储备的分析与评价提供了理论基础。

Anti-overturning Stability of a Rigid Retaining Wall in Unsaturated Soils Considering the Intermediate Principal Stress

The saturated soil mechanics theory, developed on the basis of the Mohr-Coulomb failure criterion, was often applied to the existing anti-overturning design for the retaining wall of a foundation pit. However, this design idea was very conservative. For this reason, use of the unified solution of shear strength in the plane strain condition for the unsaturated soils derived the embedment depth equations of a rigid retaining wall, which can meet different anti-overturning stability coefficients. The effects of the unsaturated characteristics and the intermediate principal stress on the shear strength were also taken into consideration. Direct use of these equations can plot the influences of the intermediate principal stress, the matric suction, and the stability coefficient on the embedment depth of a rigid retaining wall. The closed-form solutions are an orderly set of new results and these solutions provide more choices and optimizations for the design of foundation pits with different types and features. The results show that both the intermediate principal stress and the matric suction have obvious influences on the embedment depth of a retaining wall, i.e., the embedment depth decreases remarkably with the increase of the intermediate principal stress or matric suction. In addition, different failure criteria have an obvious effect on the anti-overturning design of a retaining wall; the greater stability coefficient designed, the greater is the embedment depth, which is also related to the excavation depth of a foundation pit. This paper provides a theoretical basis for the analysis and evaluation about the work performance and the safety reserve of the retaining wall of a foundation pit in the unsaturated soils.