基于主应力迹线分层的有限土体土压力计算

为了研究挡墙后有限土体的主动土压力，以墙后无黏性土体为研究对象，假定破裂面为通过墙踵的平面，且在挡墙平动模式下，墙后土体形成圆弧形小主应力拱。采用沿小主应力迹线分层的方法，将挡墙后土体划分为若干个圆弧形曲线薄层单元，考虑了单元体上下表面应力分布的不均匀性，提出了一种有限土体挡墙主动土压力计算方法，给出了主动土压力合力及其作用点高度的表达式，并验证了该方法的正确性。研究结果表明：采用曲线薄层单元法可以准确考虑单元体复杂的受力情况，能更好地反映挡墙后有限土体主动土压力的变化规律；有限填土时主动土压力沿墙高 呈非线性分布，土压力先随着土体深度增加呈单调递增趋势，然后在接近墙底位置处呈单调递减趋势。分析参数敏感性时取不同土体宽高比与墙背粗糙程度对挡墙主动土压力分布及合力作用点高度进行分析，结果表明：随着土体宽高比n的增大，主动土压力值逐渐增大，土压力分布曲线非线性越来越明显，合力作用点高度逐渐降低且恒大于 。当 0.71时，均趋于稳定。可将 0.71作为有限土体与半无限土体的临界宽高比。随着摩擦角 的增大，主动土压力值逐渐减小，土压力分布曲线非线性越来越明显，合力作用点高度逐渐增大且恒大于 。

Calculation of active earth pressure of finite soil based on layered principal stress trajectory

To study the active earth pressure of finite soil behind the retaining wall, the cohesionless soil behind the wall is taken as the research object. The fracture surface is assumed as the plane passing through the heel of the wall, and in the translational mode of the retaining wall, the soil behind the retaining wall forms an arc-shaped small principal stress arch. The soil behind the retaining wall is divided into several curve thin-layer elements by the stratification method along the small principal stress. Considering the inhomogeneity of stress distribution on the upper and lower surface of the element, a calculation method is proposed for the active earth pressure of finite soil retaining wall. The expressions of active earth pressure resultant force and the height of its action point are given, and the correctness of this method is verified. The results show that the curve thin-layer element method can accurately consider the complex stress condition of the element, and can better reflect the variation law of the active earth pressure of finite soil behind the retaining wall. The active earth pressure shows a nonlinear distribution along the wall height H, it firstly increases with the soil depth increasing, then decreases monotonically near the bottom of the wall. In parameter sensitivity analysis, the distribution of active earth pressure of retaining wall and the height of combined force applied point are analyzed with different width-height ratios of soil and wall back roughness. The results show that with the increase of width-height ratio n, the active earth pressure gradually increases, the curve of earth pressure distribution becomes more and more nonlinear, the height of resultant force application point gradually decreases, and it is always greater than . It tends to be stable when n is greater than 0.71, so 0.71 can be assumed as the critical width-height ratio of finite soil and semi-infinite soil. The active earth pressure decreases gradually with the increase of the frictional angle ; the curve of earth pressure distribution becomes more and more nonlinear, the height of resultant force application point increases gradually and is always greater than .