Effects of existing pile foundation on parameters of shield tunneling

The shield tunneling adjacent to bridge pile foundation has become a hot issue at present. In view of the application value of parameters of shield tunneling in projects, the vertical additional stress of the pile foundation is analyzed by using a three-dimensional elastic-plastic finite element method. The mathematical expressions for pile length and proportional coefficient are derived. The radii of impact area and non-impact area of piles are defined by comparing the influence area of additional stress generated by piles with the influence radius put forward by Randolph. The optimal values of tunnel face pressure and grouting pressure in the non-impact area of piles are obtained through three-dimensional elastic-plastic finite element analysis based on the theoretical values of tunnel face pressure and grouting pressure. The expression for calculating the ground loss is introduced under the condition that the soil loss per unit length equals the area of settlement trough. By combining the optimal values of the parameters of shield tunneling in the non-impact area and the additional stress generated by piles, the mathematical expressions for the parameters of shield tunneling in the impact area are achieved. The results show that when the soil pressure resistance of tunnel face equals the static soil pressure of tunnel face and the grouting pressure equals 1.1 times the soil and water pressure on the top surface of tunnel, the disturbance of the soil strata is relatively slight.