小净距叠行隧道先下后上法变形控制技术OA

In order to solve the problems of excessive deformation and structural damage of stratum and tunnel lining caused by excavation of small-clearance stacked tunnels,a three-dimensional finite element model was established based on the superimposed tunnel with a net clearance of 1.6 m on Suzhou Rail Transit Line 8 by using numerical simulation and engineering verification.The control effects of"synchronous grouting""stratum reinforcement""support trolley"and"stratum reinforcement+upport trolley"reinforcement schemes on stratum and tunnel deformation were compared and selected.The results show that single synchronous grouting cannot meet the requirements of stratum and tunnel deformation control.The ground reinforcement can significantly inhibit the surface subsidence(reduction 57％)and the floating of the downward tunnel(reduction of 63％).The reinforcement of the supporting trolley reduces the circumferential stress of the lining of the downward tunnel by 21％,and the adjacent stage of the new tunnel shield machine slows down the floating of the tunnel(a decrease of 51％);the combined reinforcement scheme of"stratum reinforcement+support trolley"has the best control effect.The surface settlement is 9.3 mm,the tunnel floating is 3.3 mm,and the clearance convergence is 3.6 mm,which is highly consistent with the measured data of the project.The research conclusions provide a valuable reference for the construction safety of similar small-clearance overlapped tunnels.