Model test on the deformation of adjacent pile foundation caused by the excavation of a shield tunnel

Aiming at the difficulty of deformation observation of adjacent pile foundation during excavation of ultra-large diameter tunnel, a transparent soil test scheme was proposed for lateral penetration of pile foundation in ultra-large diameter tunnel. Fused quartz sand, mixed solution of n-dodecane and white oil were used as pore solution to provide transparent soil, and optical observation system and PIV processing system were combined. The soil displacement around pile caused by shield tunnel excavation is analyzed and the soil displacement field around pile under different conditions is obtained. The test results show that with the increase of the distance between piles and tunnels, the disturbance to the soil near the pile foundation will become smaller and smaller. When the distance between piles and tunnels reaches 1.5 times the tunnel diameter, the influence on the pile foundation will reach the critical value. With the increase of pile length, the vertical displacement of soil on the pile side shows a parabolic form, first increasing and then decreasing. With the increase of pile length, the horizontal displacement of soil on the side of pile will change from the upper part of pile foundation to the direction of tunnel to the upper part of pile foundation and the soil in the tunnel to the direction of tunnel. The closer the excavation face is to the pile foundation, the more severe the influence of excavation on the soil displacement around the pile.