Evolution Mechanisms of Lateral Earth Pressure against Rigid Retaining Structures Adjacent to Composite Foundations

With the rapid development of urban underground space utilization, an increasing number of problems arise, requiring foundation pit–supporting projects to be constructed adjacent to existing buildings. The calculation method of lateral earth pressure (LEP) acting on retaining structures adjacent to natural foundations has been systematically researched and standardized. However, the mutual influences between foundation pit–supporting systems and neighboring rigid pile composite foundations (RPCFs) are still unclear, demanding further studies and experimental verification of methods that are stipulated empirically in certain provincial standards. Considering this, the present article systematically analyzed the distributions and changing patterns of LEP on retaining structures during foundation pit excavation, as well as the changing mechanisms of LEP through large-scale indoor model tests. In addition, an approach based on the Mindlin and Boussinesq elastic solutions was established to estimate the at-rest earth pressure and active earth pressure distributions on rigid retaining walls close to RPCFs, under translation and wall rotation about the bottom mode of failures. The proposed method adopted a superposition approach to account for the effects of the vertical stress transfer mechanism of the adjacent RPCF. A comparison of the large-scale model test findings with the proposed analytical method showed good agreement on LEP distribution patterns; however, the proposed approach overstated the additional lateral stresses exerted by the RPCF. The advantages of the proposed method lie in its computational simplicity and convenience of application in practice, as it requires only a limited number of soil mechanical properties and the RPCF’s mechanical behaviors.