Vertical response analysis of adjacent existing single pile under tunneling

When the pile top is loaded, the load transmitted to the surrounding soil through the pile will inevitably change the stress state of the adjacent soil, so the displacement caused by tunnel excavation will be different from the free soil displacement field. To analyze the vertical response rules of the adjacent existing piles under the collective influences of tunneling and loads above pile, using the two-stage method, a simplified analytical method is proposed by introducing the model of BoxLucas1 exponent function to describe the nonlinear interaction between pile and soil, besides, the loads above piles are considered, which is ignored by the majority of the current researches. The results show that when there are no loads above pile, the axial force firstly increases and then gradually decreases along the pile, and the maximum axial force appears around the center of the tunnel by gradually adding loads above the pile. The skin friction of the lower pile will reach its limit earlier than that of the upper part. The axial force of pile foundation presents a "three-stage" descending law of "slowly decreasing, then sharply decreasing, and finally decreasing slowly".