Research on the Influence of the Construction of the Terminal Tower Base Bored Piles on the Adjacent Tunnel Structure

As an environment-friendly pile construction method, full-rotation casing bored piles are especially used in underground engineering construction due to their high pile quality, fast construction speed, small stratum disturbance and low environmental pollution. It is widely used in adjacent existing tunnels and foundation pit projects. Relying on a small clear distance transmission tower pile spanning subway tunnel project in Hefei, on the basis of theoretical analysis of the influence of the steel casing spinning construction on the tunnel deformation, the the influences of pile length, pile diameter, the pile-tunnel distance and the follow-up depth of the steel casing on the deformation of the adjacent subway tunnels is simulated. The deformation law of the tunnel structure caused by the construction of the pile foundation of the transmission tower under the condition of single parameter variation is researched. The results indicate that: Increasing the pile length increases the vertical deformation of the adjacent tunnel. On the basis of satisfying the bearing capacity of the pile, the pile length should be minimized. For the section where the horizontal displacement of the tunnel is strictly controlled, the situation where the ratio of pile length to tunnel depth is 1 should be avoided. The pile diameter factor has a great influence on the displacement of the adjacent tunnel. The total displacement value of the tunnel is negatively correlated with the pile-tunnel clear distance, and expanding the pile-tunnel distance is the best measure to control the tunnel deformation; The construction method of steel casing section-by-section spinning and borrowing has less influence on the surrounding soil disturbance, especially can reduce the horizontal deformation of adjacent tunnels. The half-casing hole-forming process should be avoided to prevent the secondary disturbance to the surrounding strata by the drilling construction below the casing.