Analysis on Influence of Metro Shield on Ground Subsidence

The shield tunnel construction inevitably disturbs the surrounding strata, which in turn causes ground subsidence, and the excessive sedimentation will endanger the normal use and structural safety of adjacent buildings. Based on the analysis of the ground subsidence during the construction of the shield tunnel, the settlement trough of the surface cross section in the process of metro shield is similar to the normal distribution curve. The maximum settling volume usually occurs within 5 meters from the center of the tunnel. The ground subsidence arising from shield construction can be roughly divided into three stages: firstly, before the shield machine reaches the observation section, the subsidence (-30m-0m) occurs, and the settling volume is about 10% to 20% of the total settlement; secondly, when the shield machine passes through the observation section, the subsidence occurs (0-30m), and the settling volume is about 40% to 70% of the total settlement; and finally, after the shield machine passes through 30m of the observation section, the later consolidation settlement of the section occurs, and the settling volume is 10% or less of the total settlement. The transverse influenced range of the ground subsidence is about 30 meters or less and the main influence area of shield construction is around 5 meters from the left or right of the tunnel axis. In the case of the shield pass-through or the shield tail pull-away, the ground subsidence is relatively larger, accounting for 30% to 50% of the maximum settlement value.