基于土拱效应的非饱和土主动土压力计算方法

Method for Calculating Active Earth Pressure of Unsaturated Soil Considering Arching Effect

基于扩展的非饱和土抗剪强度公式,假定墙后土体小主应力拱为圆弧拱,分别建立了水平微分单元平均竖向应力、层间剪切力与墙体水平反力的关系,进而通过静力平衡方程推导出非饱和土主动土压力计算公式。分析过程中考虑了水平微分单元体层间剪切作用,弥补了传统土拱效应方法中水平微分单元体受力不平衡的不足。与经典方法获得的非饱和土土压力公式相比,该方法考虑了墙后土体主应力偏转现象,所得主动土压力呈非线性分布,能够反映土体的真实应力状态;与传统的考虑土拱效应的土压力解析解相比,该方法较全面地分析了主动土压力影响因素,考虑了非饱和土物理力学性质、地下水位的影响。该结果可为非饱和土土压力研究提供理论依据,对工程设计有一定参考意义。

With the assumption that the trace of the principal stress arching is a semicircle,the relationships of average vertical stress and interlaminar shear stress of soil differential element vs. counterforce of wall were established,respectively. Then,a static equilibrium equation based on the extended unsaturated soil shear strength formula was set up to solve the active earth pressure. The interlaminar shear action was considered in the process,to make up the shortage of force imbalance of traditional static equilibrium equation. Compared with the earth pressure formula of unsaturated soil deduced from classical approach,principal stress deflection is considered in this study,and the active earth pressure is nonlinear along the height which is closed to the true stress distribution. Compared with the conventional earth pressure calculations considering arching effects,factors on active earth pressure are analyzed in the new method. These factors include the properties of unsaturated soil and groundwater level. The result can provide theoretical basis for earth pressure study and reference for the design of retaining wall.