Study on Effects of Metro Tunnel Enlarged from Air Defense Tunnel on Adjacent Piles and Control Measures

Abstract

Based on project in which the existing air defense tunnel was enlarged to build a metro tunnel adjacent to bridge piles in Harbin, the 3-D numerical simulation using FEM was conducted to analyze the internal forces and deformations of piles. The results show that the internal forces and deformations on the right side are larger than those on the left after the enlarged excavation on a single side on sidewalls. The maximum value as well as its position differs according to the distance between the pile and tunnel. After the enlarged excavation on the invert, the increase in the horizontal displacement is smaller than that after the excavation on the sidewall. As to the vertical displacement and axial force, the increase is prominent and the increasing value is larger than the excavation on the sidewall. After the reinforcement measures of advanced pre-supporting and radial grouting are used, According the results, the internal forces and deformations of piles decreases after measures were taken. Compared with measured data on site, the control effect is good.