Study On Settlement Law And Control Standard Of Shield Tunnel Crossing Railway Subgrade

Shield tunneling plays an increasingly important role in tunnel construction because of its advantages such as small effect toenvironment and high precision etc.However,it will inevit ably lead to the deformation of railway subgrade and track structure when shield tunnels are passing through railway projects,thus affecting the normal operation of trains.Therefore,it is necessary to study the influencing factors and settlement control standards of Railway Subgrade in the construction process to ensure the safe operation of trains.this paper,Fuzhou Rail Transit Line 1 underpass Fuzhou Railway Station as a typical project was taken to study the influencing factors of subgrade settlement during under-through construction.In addition,data of 18 existing shield tunnels crossing the railway in China were collected to analyze the settlement value of subgrade.The settlement control value of Railway Subgrade under shield tunneling was discussed by referring to relevant specifications.Sugges ted values of subgrade settlement control standards under different railway grades were put fo rward.The main work listed as follows:(1)Finite element analysis software MIDAS/GTS was used to analyze the law of roadbe d settlement caused by shield tunnel construction in different soil layers,different tunnel burial depth and different double-track tunnel spacing.In order to study the influence of parameters on Subgrade settlement,the sensitivity analysis of parameters was carried out based on tunnel depth,spacing of double-track tunnel and soil compression modulus of tunnels.(2)Based on the measured data of 18 existing shield tunnels crossing the railway in China,the factors such as strata,reinforcement measures,tunnel depth and settlement of roadbed were analyzed,and the ratio of width coefficient of settlement trough to tunnel depth was obtained by back analysis.(3)MIDAS/GTS was used to analyze the variation of the width of settlement trough in different tunnel depths and different soil layers.The relationship between the width coefficient of settlement trough and the depth of tunnel in cohesive soil and sand-gravel soil layers was obtained by regression analysis.Besides,the recommended values of subgrade settlement control standards for shield tunnels passing through the two kinds of soil layers under different rail way grades were put forward according to the requirement of track smoothness.It has certain reference value for the settlement control standard of shield tunnel underpass railway subgrade.