Research On The Ground Settlement Induced By Shield Tunnel Construction

Shield tunneling, an important construction method in Metro engineering in China, is widely applied in urban subway tunnel construction due to its characteristic of security and advancement. To some extent, however, the shield tunneling is prone to arouse ground settlement, which will have severe influence on economic and social development. Especially the excessive ground settlement will endanger the safety of surrounding buildings and underground tubes.The paper analyzed a large number of practical engineering monitoring data, researched the developing rule of ground settlement and influence basin in the shield tunneling process. The L-V model and V-G model were proposed and applied to the forecast of the ground settlement caused by shield construction. Using ABAQUS soft simulate ground settlement in the process of shield tunnel heading, researched the influence rule of soil deformation with change of heading face support stress when shield was tunneling in clay soil. Meanwhile, the paper discussed that depth of tunnel, tunnel diameter and soil parameter were effect on the stability of heading face, then following the conclusions:(1) When the shield is not up to a designated section, this section slightly ground settlement, and when the shield in the designated section ground produced clear sinking. The ground crosswise setting tank development rule complies with Peck formula.(2) L-V model and V-G model has played a very good prediction effect, the prediction precision far better than single Logistic model Von-Bertalanffy model and Gompertz model, R2reached0.9986.(3) The horizontal displacement and ground settlement of heading face soil ahead increased significantly with the support of the reduction of stress. Heading face support stress inadequate caused the largest displacement in the top of the tunnel in the deep soil, reduced gradually from the tunnel top to the surface. Limit support stress of heading face and crosswise setting tank coefficient increased with the depth and diameter of tunnel increased. Internal friction angle had more significant effect on support stress of heading face than cohesion.