基于双剪统一强度理论的无黏性土非极限主动土压力分析

Analysis of non-ultimate active earth pressure in cohesive soil based on unified strength theory of double shear

针对传统Coulomb土压力理论与Rankine土压力理论在用于计算时未考虑中间主应力(σ_(2))的问题,对于平移模式下的墙背垂直挡土墙,假定墙后填土为无黏性土,基于双剪统一强度理论建立了考虑中间主应力、土拱效应、土体内部水平剪应力等因素的无黏性土主动土压力计算模型,求得了非极限主动土压力解析解。将计算结果与试验数据对比后发现:适当考虑中间主应力系数(b)后得到的极限与非极限主动土压力计算值与试验数据吻合较好,当b取值为0.50左右时二者吻合最好;墙后土体内摩擦角(φ)、潜在滑裂面倾角(β)受挡土墙实际水平位移比(η)、中间主应力系数(b)的影响较大,η越大则φ与β越大,b越大则φ与β的初始值越大;适当考虑中间主应力后得到的静止土压力、非极限主动土压力、主动土压力与传统土压力计算方法相比平均下降10%左右。

The traditional Coulomb earth pressure calculation method and Rankine earth pressure calculation method do not consider the influence of the intermediate principal stress(σ_(2)),which inevitably leads to larger calculation results than the actual monitoring ones and is not conducive to make full use of the strength characteristics of geotechnical materials.For the vertical retaining wall at the back of the wall in translation mode,assuming that the filling soil behind the wall is non-cohesive,a calculation model of the active earth pressure of the non-cohesive soil is established based on the unified strength theory of double shear,taking into account the intermediate principal stress,soil arching effect,and horizontal shear stress in the soil,and the analytical solution of the non-ultimate active earth pressure is obtained.By comparing the calculation results with the test data,it is found that:the calculated values of the ultimate and non-ultimate active earth pressure obtained after considering the intermediate principal stress coefficient(b)are in good agreement with the test data,and the best agreement is obtained with a b value of about 0.50.The friction angle(φ)and the inclination angle(β)of the potential slip surface behind the wall are greatly affected by the actual horizontal displacement ratioηand the intermediate principal stress coefficient(b).The largerηis,the largerφandβare.When b is larger,the initial values ofφandβare larger.The static earth pressure,non-ultimate active earth pressure and active earth pressure obtained by appropriately considering the intermediate principal stress(σ2)are reduced by about 10%on average compared with the traditional earth pressure calculation method.