Numerical Analysis On The Law Of Surface Settlement In Zhengzhou Metro Shield Construction

With the rapid development of our country,the problem of traffic congestion in major cities has become increasingly serious.The construction of urban rail transit system has become an effective way to solve the problem of traffic congestion in more and more cities.The environment above the subway shield tunnel is complex,Heavy traffic,pipelines and important structures.Controlling surface settlement has become a key issue in shield tunnel engineering.Zhengzhou Metro shield tunnels pass through most of the sandy soil layers.It can be predicting the ground settlement caused by shield tunneling in sandy strata with different buried depths can provide certain technical guidance for subsequent subway construction in Zhengzhou.Based on the research background of shield tunnel construction in the Xi-Guo section,this paper studies the surface settlement laws of shield tunnels passing through sandy strata with different buried depths in Zhengzhou area,and gives suggested values of empirical parameters in the Peck formula under different buried depths.The main research methods are as follows:(1)Analyzing and summarizing the domestic and foreign literature on prediction of surface settlement in different buried depths of tunnels,and provide theoretical support for the research content.(2)Collect the monitoring data of surface subsidence in the interval between XiGuo section,and analyze the development law of lateral surface subsidence.According to the principle of least squares,the collected 2.5D(D is the tunnel diameter of 6.6m)buried depth surface settlement data are linearly fitted,and the empirical parameters of the Peck formula at the buried depth are obtained,which are compared with the actual measured settlement of the small monitoring section in the Xi-Guo Interval.The values are compared to prove the correctness of the Peck empirical parameter method obtained by linear fitting.(3)Using ABAQUS finite element analysis software to simulate 4 kinds of buried shield tunneling.First,comparing the 2.5D buried depth ground settlement data obtained by simulation with the actual measured ground settlement data of the project to verify the accuracy of the numerical simulation,and then analyzing the simulated four types of ground surface settlement laws with different buried depths are linearly fitted to numerically simulated surface settlement data at different buried depths,and empirical parameters of the Peck formula for different buried depths are obtained.(4)According to the principle of similarity model,design 4 kinds of indoor gravity shield model tests with equal depth(1:40),and compare the model test data with the same depth with numerical simulation data to verify the accuracy of the data.Then,linear fitting is performed on the surface settlement data of the model test with different burial depths,and the empirical parameters of the Peck formula for the model test with different burial depths are obtained.(5)The empirical parameters of the fitting Peck formula obtained from the actual measurement,numerical model and model test of the project.Between the three are mutually verified to give 4 kinds of empirical parameter recommended values for the buried depth,and the four buried depths are regarded as key nodes,and the buried depth is given.The range of empirical parameters of the Peck formula,which is deep in the range of 1D?1.5D,1.5D?2D,and 2D?2.5D.