车辆荷载在挡土墙上引起的附加土压力研究

Study on Additional Earth Pressure on Retaining Wall Caused by Vehicle Load

为了研究路面车辆在挡土墙上引起附加土压力的分布规律,结合330国道莲都至缙云段改扩建工程中悬臂式挡土墙的施工,在挡土墙的底板上方和立板内侧埋设了一系列的土压力盒,以工地施工用30 t自卸式货车为荷载源,采用定点停车方式加载,测试了路面车辆荷载(静载)引起的附加竖向和侧向土压力,并将测试结果与规范均匀分布法和弹性力学Boussinesq解进行了对比分析。结果表明:实测附加侧向土压力沿墙高呈非线性分布,峰值出现墙高的中部,峰值随车辆停车位置距挡土墙距离的增加而减小;底板上的附加竖向土压力在横断面方向上也为非线性分布;附加土压力实测值与现行公路设计规范采用的均匀分布法计算结果有较大的差异;若采用均匀分布法确定车辆荷载引起的附加侧向土压力,附加侧向土压力引起的弯矩或倾覆力矩可能被低估,使挡土墙下部的抗弯拉能力和抗倾覆能力不足,同时对于变截面挡土墙(墙身截面尺寸随高度增加而减小),可能造成墙身中上部抗剪强度过小而发生剪切破坏;实测附加侧向土压力的分布规律与Boussinesq解基本一致,但竖向附加土压力较Boussinesq解要大。建议在挡土墙(特别是重载道路挡土墙)设计时采用多车道同时作用有标准车辆时的Boussinesq解作为挡土墙的车辆附加荷载。

In order to study the distribution of additional earth pressure on retaining wall caused by vehicle load,combining with the construction of a cantilever retaining wall in Liandu-Jinyun section of 330 National Highway expansion project,a series of soil pressure boxes are embedded above the floor of the retaining wall and inside the vertical plate. By using a 30 t dump truck for construction as the load source and stopping and loading at designated places,the additional vertical and lateral earth pressures caused by vehicle（ static）load is tested,which is compared with the result calculated from standard uniform distribution method and the Boussinesq solution of elastic mechanics. The result shows that（ 1） The measured additional lateral earth pressure shows a nonlinear distribution along the wall height,the maximum value appears in the middle of the wall height,and the peak value decreases as the distance of the truck from the retaining wall increases.（2）The additional vertical soil pressure above the floor in the direction of the cross-section also obeys a nonlinear distribution.（ 3） There is a great difference between the measured value and the result obtained by the uniform distribution method used in current highway design code.（4） If the uniform distribution method isused to determine the additional lateral earth pressure caused by vehicle load,the bending moment or overturning moment caused by the additional lateral earth pressure may be underestimated,this will make the insufficient anti bending and anti overturning ability of the lower retaining wall. Meanwhile,for the variable section retaining wall（ the area of the wall section decreases as the height of the wall increases）,the shear strengths above the middle part of the wall may be too small and the shear failure may occur.（ 5） The distribution of the measured additional lateral earth pressures is basically the same as the Boussinesq solution,but the vertical additional earth pressure is larger than the Boussinesq solution. It is suggested that when designing the retaining wall（ especially heavy duty road retaining wall）,the Boussinesq solution with multiple lanes and standard vehicle loadings at the same time will be used as the additional vehicle load on retaining wall.