The model adopts eight-nodes isoparametric quadrilateral element, Drucker-Prager ideal Elastic-Plastic stress-strain model and the contact element, which is used to simulate the interface between the wall and soil. Accordingly, A flow chart about the arithmetic of contact is introduced in this paper. 模型采用八结点等参平面四边形单元、Drucker-Prager理想弹塑性本构模型以及用接触面单元模拟了土与围护结构的相互作用,并给出了相应的接触面模拟的接触算法流程。