Excavation and earth filling of foundation fundation pit under complicated geological conditions is one of the important problems in the underground engineering field. By considering complicated geological conditions

constrained conditions of structure and the interaction between structure and soils

this paper concerns about the nonlinear FEM numerical calculation of excavation and earth-filling of foundation pit by combining with the Western Long Tunnel Construction Project from Shenzhen to Hongkong. The characteristics and regularities of the calculated settlements in the excavation and earth-filling process are obtained. The results can be used as an important reference to the design and construction of engineering.