Mechanism of influences of shield construction nearby friction pile foundation on its bearing capacity and its controlling techniques

Aiming at the disturbance problem of the adjacent friction pile foundation buildings caused by shield tunneling, based on the changes in the stress field of the strata before and after shield tunneling, an analytical calculation model for the bearing capacity of the existing friction pile foundation under the interaction of tunnel, stratum and pile foundation is established, revealing the influence mechanism of shield tunneling on the bearing performance of friction pile foundation. Taking the construction of an old building with friction pile foundation at the side of a subway shield tunnel as the engineering background, the deformation characteristics of the friction pile group under the disturbance of shield tunneling are analyzed, and the effectiveness of ground reinforcement in controlling the deformation of adjacent pile foundations is demonstrated. The research results indicate that the changes in horizontal and shear stresses in the strata after tunnel excavation are the fundamental reasons affecting the bearing performance of friction pile foundations. The loss of bearing capacity of pile foundation is directly proportional to the loss rate of formation during tunnel construction. The ground reinforcement can effectively control the ground loss caused by tunnel construction, thereby reducing the deformations of the ground and the existing pile foundations.