基坑潜在隆起破裂面的Dijkstra组合优化搜索法

运用弹塑性有限元程序计算基坑围护结构与土体任意一点在开挖前后的应力状态，根据选定的屈服准则计算其极限状态函数值，通过有限元网格节点及其坐标，采用“人机对话”的优化方法选择坑底最大可能的隆起破裂面的起点和终点，通过Dijkstra算法找出基坑土体最可能发生坑底隆起破坏的潜在破裂面的形状及位置，并求出相应的安全系数。大量数值计算和实测资料表明：潜在破裂面终点的位置对围护桩插入比不敏感，而潜在破裂面起点位置则随围护桩入土深度的增加而逐渐靠近围护桩。搜索法得到的潜在破裂面突破了以往人为给定破裂面形状和极限土压力假定的限制，工程算例证实了基于组合优化Dijkstra算法的潜在破裂面搜索法的有效性和实用性。

Study on composite optimization based on Dijkstra algorithm in searching potential bulge fracture plane of foundation pit

Stress state of supporting structure and the retained soil was analyzed with elastoplastic FEM in foundation pit; and the value of limiting state function of retained soil was calculated. Based on the nodes and meshs, with “artificial participation” optimization, the shape and position of potential bulge fracture plane in foundation pit were searched with the DIJKSTRA optimization algorithm; and the relative safety factor was calculated. Large scale numeric calculation and in situ measurements show that the end point of potential fracture plane is insensitive to the insertion ratio of supporting pile, but, the start point of potential fracture plane is close to the supporting pile when the insertion of pile is increasing; and that the method of potential bulge fracture plane searching proposed in this paper is not restrict to the man-made fracture plane shape and limiting earth pressure assumption. The in-situ measurements show the availability and utilization of method of the potential bulge fracture plane searching based on the DIJKSTRA algorithm in composite optimization.