Theoretical Analysis of Existing Tunnel Affect under Shield Tunnel Parallel Construction

It is important to study the affect of new shield tunnel construction on existing tunnel's deformation for protecting the existing tunnel.The complex variable function conformal mapping theory and the method of Schwarz alternate were used.First,the analytical solution of the influence of new shallow shield tunnel construction was deduced on existing tunnel's deformation.In this process,the initial stress field and the affect in different stages of new tunnel construction were considered.Second,the analytical solution formula calculation program was made by Matlab mathematical tool.And it was used to calculate the existing tunnel's deformation in new shield tunnel construction stage.Combined with the geologic conditions of project on the Renmin road cross-river tunnel in Shanghai,the additional stress and displacement of existing tunnel was analyzed in two process of new tunnel excavating: tail grouting and the tail void.The results show that the size of the clear distance between two tunnels has significantly influence to the existing tunnel's deformation.With the decrease of the clear distance,the existing tunnel's radial deformation increases rapidly.In the process of tail void,the deformation is biggest on the roof of existing tunnel;but the deformati on is biggest on the right waist of existing tunnel in the process of tail grouting.When it is the different hole diameter and same depth,with the increase of existing tunnel hole diameter,new tunnel excavating has greater influenceto the existing tunnel.To the same hole diameter and different depth,the affect of new tunnel to existing tunnel is weak.