考虑邻近地下室外墙侧压力影响的平动模式挡土墙主动土压力研究

 对于挡土墙距既有地下室很近，墙后填土宽度有限的情形，采用经典的库仑、朗肯土压力理论计算挡墙主动土压力是不严格的。通过有限元数值分析发现，当挡墙平动、填土达到主动极限状态时，无黏性土滑动土楔与邻近地下室外墙并未脱开，地下室外墙上全深度承受侧压力；随着填土宽高比n的不同，挡墙与地下室外墙间土体内将形成一道或多道滑裂面，且最靠近地表的滑裂面与挡墙或地下室外墙交点以上的土压力近似为库仑主动土压力。由此建立新的土压力计算模型，给出了挡墙主动土压力系数 和第一道滑裂面倾角 的求解方法，采用水平薄层单元法，得到了挡土墙主动土压力的分布以及合力作用点相对高度 的理论公式，并通过典型算例，与经典土压力理论、前人理论方法及有限元数值解进行对比。研究发现，挡土墙土压力为非线性的鼓形分布，当土体内摩擦角 和墙土摩擦角 取定值且 0°时， 随着n的增大而增大，而 和 随着n的增大而减小，当 时， 和 值与库仑解一致；当 0°时，不论n取何值， 和 值恒等于朗肯理论解，且 。

STUDY OF ACTIVE EARTH PRESSURE ON RETAINING WALL SUBJECT TO TRANSLATION MODE CONSIDERING LATERAL PRESSURE ON ADJACENT EXISTING BASEMENT EXTERIOR WALL

In the case of retaining wall adjacent to existing basement and the backfill?s width is limited，it is not strict to use classical Coulomb or Rankine theory to calculate the active earth pressure. The results obtained from finite element method(FEM) show that when the retaining wall translates and the backfill is under fully active limiting state，the sliding soil wedge does not break away from the adjacent basement exterior wall；the lateral pressure from the basement exterior wall cannot be neglected. It also shows that multiple slip surfaces occur in the backfill if the backfill?s width is very small. The earth pressure above the intersection point between the last slip surface and the retaining wall or the adjacent basement exterior wall is approximately equal to the Coulomb active earth pressure. Based on the numerical results，a new theory model to calculate the earth pressure for limited soils is presented. The solving method for calculating the active earth pressure coefficient and the first slip surface inclination are provided. Using the horizontal differential element method，the theoretical formulae of the distribution of active earth pressures on retaining wall and the relative height of the application point of the resultant earth pressure are obtained. Comparisons of the calculated results with solutions obtained from the proposed method，the classical earth pressure theories，the other existing methods and FEM show that the proposed method can provide a good prediction of active earth pressure under this situation. It is shown that，the active earth pressures? distribution for limited soils is nonlinear. If the wall-soil friction angle 0°， increases，but and decrease with the increase in the aspect ratio of backfill ；and when ，the results are the same from Coulomb formulae. If 0°， ， and are coincident with Rankine theory.