平移模式下刚性挡土墙三维被动滑裂面的确定与土压力计算方法研究

Determination of three-dimensional passive slip surface of rigid retaining walls in translational failure mode and calculation of earth pressures

挡土墙后三维被动滑裂面的空间形态难以确定。基于数值模拟,取墙-土接触面摩擦角比值δ/Ф=0(δ为墙-土接触面摩擦角,?为土体内摩擦角),采用薄板光顺样条函数搜索出不同土体内摩擦角下挡土墙端部三维滑裂面,类比地基承载力破坏对不同土体内摩擦角下挡土墙端部三维滑裂面进行函数方程的拟合,拟合效果较好,并归纳总结挡土墙端部三维滑裂面方程。在刚性挡土墙平移模式、墙背直立、填土水平且为无黏性土、δ/Ф=0等条件下,基于挡土墙端部三维滑裂面方程,求出三维滑裂面的体积。通过力学分析推导了一种三维被动土压力计算方法,并对该方法进行了验证分析。分析结果表明:相较于Soubra被动土压力系数,计算方法得出的三维土压力系数更加接近数值模拟被动土压力系数。三维计算被动土压力系数和朗肯被动土压力系数在挡土墙长深比小于4的时候有明显的差异。随着挡土墙的长深比的增大和土体内摩擦角的减小,三维计算被动土压力系数趋向朗肯被动土压力系数,三维计算被动土压力合力作用点的位置趋向朗肯被动土压力合力作用点位置。

It is usually difficult to determine the spatial form of three-dimensional passive slip surfaces behind retaining walls.Based on numerical simulation,this paper assumes friction angle ratio of the wall-soil contact surface to be zero(δ/Ф=0),and uses the thin-plate smoothing spline function to search for the three-dimensional slip surface at the end of retaining wall under different internal friction angles of soil mass.By analogy with the failure of foundation bearing capacity,an equation is proposed to curve fit the three-dimensional slip surface,and the equation for three-dimensional slip surface at the end of the retaining wall is summarized.For translational failure mode of rigid retaining walls with upright wall back,horizontal filling level and non-cohesive soil,δ/Ф=0,the volume of sliding body behind the wall is calculated based on the three-dimensional slip surface equation.The calculation of three-dimensional passive earth pressure is deduced,and verification is carried out.The results are obtained as follows:(1)Compared with the Soubra passive earth pressure coefficient,the three-dimensional earth pressure coefficient obtained by the proposed method in this paper is closer to the numerical simulation result;(2)There is a significant difference between the three-dimensional passive earth pressure coefficient and Rankine passive earth pressure coefficient when the length-to-depth ratio of the wall is less than 4.0.As the length-to-depth ratio increases and the soil internal friction angle decreases,the three-dimensional passive earth pressure coefficient reduces to the Rankine’value,and the position of the three-dimensional passive earth pressure resultant action point tends to be the position of the Rankine’s point.