Study On The Deformation And Control Effects Of Shield Under-crossing The Existing Metro Interval

Shield tunnel crossing is a common phenomenon in the construction of underground rail engineering.As a special type of under-crossing,the small angle under-crossing often poses high risks in construction.In this paper,the displacement or stress changes of the ground surface,the existing tunnel structure and other structures were analysised by the numerical simulation and the theoretical analysis in the context of the under-crossing project of the newly built line of Tianjin metro through the existing operating line.It also optimized some parameters of the construction by using the monitoring data.The main research contents and conclusions are summarized as mentioned below.(1)The Midas GTS NX finite element software was used to simulate the whole process of shield under-crossing,with the left line was first to be excavated,and by changing the excavation sequence to verify the secondary disturbance of the backline construction on the tunnel structure of the first line and the soil layer above.By comparing and analyzing the ground settlement curves at different depths,it was found that the shape of the ground settlement curves at different depths was related to the spacing and burial depth of the tunnel.The final settlement deformation of the existing line structure reached the warning line,and relevant measures need to be taken to deal with it.(2)The numerical simulation method was used to optimize the construction parameters of soil bin pressure and grouting pressure,analyze the correlation of the two parameters on the influence of the settlement deformation,and combine the five levels of the two parameters for the simulation analysis,give the optimized combination of construction parameters based on the simulation results,and compare the simulation results under the optimized combination of working conditions with the monitoring data for verification,The results show that the combination of parameters has a certain safety reserve for the prediction to the settlement of the existing tunnel structures,and has reference significance for the construction of subsequent sections and similar projects.(3)Based on the modified Peck’s formula,the settlement deformation of the structure caused by the under-crossing construction was calculated and analyzed.The effect of the metro train load under the operational condition was considered,and the elastic foundation short beam solution was used to solve the problem.The settlement deformation of the structure under the theoretical condition was superimposed and compared with the simulation results,from the results can be shown that the applicability of the settlement trough width geometry algorithm and the structural settlement superimposition algorithm.