Abstract:A large commercial center has been built in Tianjin,China,and the main building is 218 m high. To construct the building,a pit of 15.3 m deep,60 m wide and 150 m long has to be excavated. During foundation pit excavation,the developed cracks will affect the stress and deformation of the retaining structure. The fracture strength theory is taken into account in the constitutive relation of cracked soils. An elastoplastic finite element computer program is developed in order to simulate foundation pit excavation procedure. The calculation results are compared with the observed data from a construction site. The analysis results show that during pit excavation,tensile stress zones are developed in the ground surface behind the retaining structure. Once the tensile stress becomes larger than the tensile strength of the soil,fracture will arise in the tensile stress zone. To some extents,the existence of these cracks may decrease the stress and stiffness of the retaining structure. At the same time,the passive earth pressure increases and the active earth pressure decreases. In the crack range the active earth pressure even decreases to zero. Under this condition,the fracture strength theory is more fit for the soils than the other conventional theories and the calculated results agree well with the test data.