CONTACT MECHANICAL RESPONSE ANALYSIS OF SOIL-FOUNDATION SYSTEM UNDER THE INFLUENCE OF TUNNEL EXCAVATION

To realize the theoretical prediction for mechanical response of soil-foundation system due to new tunneling below, an analytical method for the mechanical response of the soil-foundation system under the disturbance of tunnel construction is established, considering the multi-body contact effect. In this method, the stratum is regarded as a homogeneous isotropic medium with linear-elastic property. Next, the contact theory is introduced into the derivation process to consider the contact effect between stratum and foundation, and a new analytical strategy, “exchanging the sequence between tunnel excavation and foundation action”, is proposed to determine the analytical expression of contact pressure in final state. Then, the difficulties of determining the contact pressure under the coupling action of tunnel excavation and multi-body contact are overcame. Finally, the proposed solution is obtained using the superposition of elasticity solution. The analytical results are in good agreement with the numerical results, which verifies the correctness of the analytical solution. Based on the proposed solution, the effects of stratum parameters, tunnel depth, radial displacement of tunnel boundary and external load concentration on the vertical displacement increment, contact pressure and internal force distribution of foundation are analyzed. The results show that the analytical method can accurately predict the mechanical response of the soil-foundation system, and it can realize the quantitative description of the complex contact mechanical behavior between the stratum and foundation. The effects of Young’s modulus and Poisson’s ratio of formation focus on deformation and stress respectively, while the variation of tunnel buried depth and radial displacements along the tunnel boundary lead to significant changes in deformation and stress. The ground displacement is the result of the coupling effect of tunnel excavation and multi-body contact, and the significant impact region is limited near the contact area. Under the influence of tunnel construction, the contact pressure will redistribute, which is characterized by “release in the middle and concentration at the end”. As a result, the internal force of foundation is found to increase greatly, and when the disturbance of tunnel construction is severe, it may even lead to incomplete contact phenomenon with discontinuous vertical displacement. The research has important theoretical significances and application values for the prediction of mechanical response of soil-foundation system caused by the construction of urban shallow tunnel.