Study On Stratum Deformation Law Caused By EPA Shield Construction In Chengdu Water Rich Sandy Cobble Stratum

At present,the subway tunnel mainly adopts the EPB shield construction,will inevitably cause of formation losses caused by surface subsidence,surface subsidence of shield construction in different soil of the law is not the same,and most of the research results for the cohesive soil formation,the current study about the problem of ground settlement caused by EPB shield construction in water-rich sandy pebble stratum is few,pebble soil loose,low cohesion,high strength properties caused by the particularity of the sandy pebble stratum,the stratum settlement lag is very obvious,and even lead to the construction of the ground suddenly collapse of the accident,it has a great influence on the construction and monitoring.For water-rich sandy pebble stratum in Chengdu,systematically analyzes the deformation law of stratum caused by EPB shield construction,provide reference for shield construction.With the construction of Chengdu Metro Line 3 and line 7 shield tunnel as the background,for water-rich sandy pebble stratum,through the method of a large number of field measurement data statistical analysis、classification and comparison、regression fitting、numerical simulation and correction of empirical formula parameters,combined with the Chengdu metro shield construction site experience,study the influence of shield parameters on surface subsidence,the reasonable range of shield parameters is proposed;discusses the formation conditions for the influence of surface subsidence,the influence law of the internal friction angle on the ground settlement are obtained;and from stratified subsidence above tunnel、cross-sectional surface subsidence、longitudinal surface subsidence,study and analyze the deformation and subsidence law of stratum,obtained the main distribution of surface subsidence,The control value of surface subsidence in sandy cobble stratum is 20mm,The main influence area of formation deformation is about 12m of the central line of the tunnel,The damage process and form of the soil above the tunnel during shield tunneling,summarize the experience formula for the prediction of surface subsidence trend,verify the rationality of the formula which is suitable for Chengdu water-rich sandy pebble stratum,corrected the O’Reilly&New formula for the settlement groove width,it is applicable to the calculation of the settlement groove width of the EPB shield construction in Chengdu sandy pebble stratum,Systematically and comprehensively summarizes the deformation law of stratum caused by EPB shield construction in sandy pebble stratum.