The Study Of Small Distance And Complx Position Caverns Tunnel Construction

As the development of underground space, build subway underground lead space to more and more shortage, it is hard to avoid nearly meet when build subway underground. The influence between nearly meet tunnels increased difficulties of it’s design and construction.How to choose distance between the nearly meet tunnels is become an important subject.This paper as the back ground of overlap peird of Chongqing rail transit line6a phase of the project (shangxin street to lijia)guangdianyuan station as interval as in and out of line as testing line tunnel project,use finite difference numerical simulation program FLAC-3D establish3d numerical calcaulation model to research the order of tunnel excavation, study the tunnel stability on the basis of strength reduction,and reduce the distance of two tunnels to analysis.The main research content as follows:(1)Build3d numearical calcaulation for several tunnels that the distance is small and the station is complex and overlap, in the two different order construction—"first the upper next the lower" and "first the lower next the upper "—to analysis surface subsidence and the rock’s deformation and stress around tunnels,through contrst the data,the conclusion is that the influence of the tunnel construction disturbance of "first the upper next the lower"is less than"first the lower next the upper ".(2)Contrast the site monitoring data and the numerical simulation data, validate the numearical calcaulation is reasonable or not.(3) According to the numerical simulation convergence judgment principle, using strength reduction analysis the stability for construction,the safety coefficient when mutations in rock deformation of tunnel surrounding is the tunnel safety coefficient.(4) With the same circumstances of depth, class of rock, excavation sequence (first the upper next the lower) and the construction method. Ensure the safety of tunnel construction,the same of Transverse distance and changing the vertical distance numerical simulation analysis, to select the optimal safety vertical distance.Then changing Transverse distance to numerical simulation analysis to determine the optimal Transverse distance. Finally obtains the final tunnel safetydiatance when the displacement mutation of the feature position.