The response mechanism of soil-immersed tunnel based on static pushover model test

The static pushover test of underground structures mainly concentrates on consistent deformation of soil, with scarcely any studies considering soil dislocation. This paper proposes a regional pushover method. The static pushover model test of soil-immersed tunnel was conducted. The deformation and mechanical features of soil and immersed tunnel were carefully analyzed. The failure mode of the immersion joint and the soil-immersed tunnel interaction mechanism have been revealed. The test results show that the immersed tunnel exhibits strong adaptability to soil deformation owning to the flexible joint. With the increase of soil dislocation, the earth pressure difference at the same depth of two tunnel elements near and away from the pushover plate can reach up to 71.6kPa, and obvious relative displacement occurs between two tunnel elements. Structural failure phenomenon is mainly concentrated at the shear key of the tunnel element near the pushover plate, and the story shifts of the two tunnel elements near and away from the pushover plate are 1/223 and 1/1024, respectively. The soil-immersed tunnel interaction can be divided into three stages: soil compacting stage, rapid development of differential deformation stage, and joint failure stage. The stiffness of the tunnel element maintains well, and the soil-structure interaction coefficients obtained from two observation surfaces develop slowly during the soil compacting stage. Obvious relative displacement occurs between two tunnel elements during the rapid development stage of soil dislocation. Meanwhile, the soil-structure interaction coefficient that near the pushover plate exceeds 1. Furthermore, the soil-structure interaction coefficient that away from the pushover plate still develops slowly. The soil-structure interaction coefficients near and away from the pushover plate are 3.10 and 0.67, respectively, during the joint failure stage. The study can provide experimental and technical support for the seismic analysis and risk assessment of immersed tunnels.