基于CSA和薄层单元法主动土压力计算方法

CALCULATION METHOD OF ACTIVE EARTH PRESSURE BASED ON CSA AND THIN-LAYER ELEMENT METHOD

土压力计算一直沿用经典朗肯和库仑土压力理论,所得土压力沿墙高呈三角形分布。而实际上认为挡土墙后土压力总是沿墙高呈三角形分布是不合理的,墙体位移量和形式不同,土压力分布将呈现不同的曲线形式,墙背与填土间的摩擦以及滑裂面的形状对土压力分布也有重要影响。假定挡土墙后土体潜在滑裂面由对数螺线滑动面和平面组合而成,根据挡土墙后土体薄层单元的平衡条件推导出粘性土层主动土压力的计算公式。通过在普通模拟退火算法中引入复合形法进行局部最优解搜索,得到了一种搜索性能更好的复合形模拟退火算法,并将其用于挡土墙后填土潜在最危险滑裂面搜索和相应的主动土压力计算,并给出了两个算例。其计算结果表明:与传统的朗肯和广义库仑土压力理论的计算结果相比,所提方法更符合实测结果。

It is not always reasonable that the distributing shape of earth pressure in the back of retaining wall is triangular along the height of the wall on the basis of the Rankine and Mohr-Coulomb theories. The distribution of earth pressure presents different curve shapes with different displacements and its form of the wall. The friction between the back of the wall and the filling plays an important role in earth pressure distribution. It is assumed that potential sliding surface of the soil in the back of the retaining wall is composed of logarithmic spiral arc and line. Based on the limit equilibrium of the soils＇ thin-layer elements in the back of retaining wall, calculation formula of the active earth pressure for the clayey soils is suggested. Complex simulated annealing （CSA） calculation method with better searching properties is attained by introducing complex method into simple simulated annealing method to search for local optimization solution. And it is used for searching for the potential sliding surface of the filling and computing the corresponding active earth pressure. Two case studies are given to verify the proposed method. The active earth pressures calculated by the presented method are more close to the in-situ ones comparing to traditional Rankine＇s and Mohr-Coulomb＇s theories.