Research On Construction Technology Of Newly Built Subway Undercrossing The Existing Shield Tunnel

With the acceleration of urbanization in China,newly built tunnel pass below the existing tunnel engineering is constantly springing up.That how to choose the best construction method,further optimization in engineering design and construction has become the important topic to solve the tunnel engineering.In this paper,taking the Beijing Metro Line 6 underpass the existing tunnel line 4 as the background,Set numerical models of the stage bench with temporary inverted arch and the stage bench reserved core soil construction method,based on the analysis of the displacement field of the surrounding rock and the existing shield tunnel,the stress field of the new tunnel and the existing shield tunnel,it is considered that it is more appropriate and safe to use the stage bench reserved core soil construction method.The main conclusions are as follows: the effect of tunnel excavation has been extended to the surface,the maximum settlement value appears at vault,transverse influenced range caused by tunnel excavation is about 15 m;The minimum settlement at the top of the new tunnel is located directly above the orthogonal position of new tunnel and the existing shield tunnel;The displacement of and initial support maximum values of the stage bench with temporary inverted arch are greater than stage bench reserved core soil in each excavation stage;It can acquire the best effect when controls the distance between up and down steps in 3~7 m,the distance between the left and the right lines is above 20 m.Through the actual engineering and monitoring values comparison,the difference is not large,it confirmed that the numerical simulation method is feasible,and can provide reference for similar engineering.