Deformation Control of Shield Short-distance Crossing Existing Tunnels in Silt Reclamation Stratum
Research purposes:This study aims to ensure deformation control of a newly constructed shield tunnel crossing above an existing tunnel with short distance in silt reclamation stratum during both construction and operational phases.Based on the construction case where Line 5 of the Shenzhen Metro crossing above Line 11,a series of numerical simulations were employed to evaluate different soft stratum reinforcement schemes.Consequently,the corresponding deformation control strategies were proposed,and the effectiveness of the reinforcement scheme was verified through deformation monitoring during the construction process.Research conclusions:(1)The reinforcement scheme of the ground jet grouting pile based on improving the long-term anti-deformation ability of tunnels is proposed.It shows that the effect of the increase of the width on the horizontal convergence of the tunnel is not obvious when the reinforcement width is greater than 5 m.(2)Compared with the unreinforced case,the floating deformation of existing underlying tunnels and surface settlement are reduced by 44%and 86%after reinforcement,respectively,which can meet the deformation control requirements during the construction period.(3)The measured data of the construction period shows that the maximum floating deformation of existing tunnels is 3.2 mm,and the maximum surface settlement along the line is 5 mm,which meets the deformation control requirements,indicating that the proposed stratum reinforcement measures are effective.(4)The research results have certain reference significance for the construction of shield tunneling crossing existing projects in silt reclamation stratum.
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