基坑开挖与支护模拟的位移迭代法

将基坑支护体系分解为彼此独立又相互作用的3个模型，即支护结构外侧主动土体、支护结构本身和支护结构内侧被动土体。按平面问题进行有限元分析时，土体采用面单元，支护桩采用梁单元，若桩上有内支撑或锚杆，则将梁单元与杆单元结合。各模型可分别求解，但共享边界条件。以开挖后桩体侧向位移为零、两侧都为静止土压力作为初始条件，然后按位移迭代求解，前后两次计算位移值基本相等时迭代结束，此时的位移和相应荷载就是基坑支护结构稳定后的变形与受力。该方法能客观反映土与结构相互作用的动态过程，实例计算结果与实测结果很吻合。

Method of displacement iteration in numerical simulation of foundation pit

The support system of foundation pit is divided into three isolated models related by their boundary conditions,which include active soil around support structure,support system and passive soil under the bottom of the pit.As plane strain problem,the active and passive soils are meshed as solid elements,support piles are meshed as beam elements.If the piles worked with bolts or struts,the bolts and struts are meshed as truss elements connected with beam elements.Then each model could be solved respectively;but share common boundary conditions.Giving the initial condition as the horizontal displacement of the piles equal 0,then the displacement could be solved by iterative method.If the displacements between two loops are nearly same,the iterative process ended;and the forces and displacements of the piles in stable state could be achieved.Displacement iterative method objectively reflected the dynamic interaction process between soil and support structure.This method is applied to an actual case;the calculating results are well coincident with the measuring data.