Improved method for determining active earth pressure considering arching effect and actual slip surface

Abstract

To determine the distribution of active earth pressure on retaining walls, a series of model tests with the horizontally translating rigid walls are designed. Particle image velocimetry is used to study the movement and shear strain during the active failure of soil with height H and friction angle ϕ. The test results show that there are 3 stages of soil deformation under retaining wall translation: the initial stage, the expansion stage and the stability stage. The stable sliding surface in the model tests can be considered to be composed of two parts. Within the height range of 0.82H–1.0H, it is a plane at an angle of π/4+ϕ/2 to the horizontal plane. In the height range of 0–0.82H, it is a curve between a logarithmic spiral and a plane at an angle of π/4+ϕ/2 to the horizontal. A new method applicable to any sliding surface is proposed for active earth pressure with the consideration of arching effect. The active earth pressure is computed with the actual shape of the slip surface and compared with model test data and with predictions obtained by existing methods. The comparison shows that predictions from the newly proposed method are more consistent with the measured data than the predictions from the other methods.

摘要

为研究挡土墙主动土压力分布规律,本文开展了刚性挡土墙平动模型试验,利用颗粒图像测速 技术研究高度为H、内摩擦角为ϕ 的无黏性土体在主动破坏过程中的位移和剪应变发展规律。试验结 果表明,挡土墙发生平移时的土体变形可划分三个阶段:初始阶段,发展阶段和稳定阶段。稳定阶段 的土体滑裂面由两部分组成,在0.82H~1.0H 高度范围内,滑裂面为与水平面成π/4+ϕ/2 的平面,在 0~0.82H 高度范围内的滑裂面为曲面,该曲面处在对数螺旋面和与水平面成π/4+ϕ/2 的平面所夹区域 之中。本文考虑土拱效应,基于差分法提出了适用于任意滑裂面形状的主动土压力计算方法,并根据 实际滑裂面计算了土体主动土压力理论值。在此基础上,将本文方法得到的理论值与实验数据及其他 方法计算的理论值进行对比,验证了本文所提出方法的有效性。