Research on Settlement Laws and Reinforcement Schemes for Existing Tunnels During the Under-Crossing Construction of Double-Track Shield Tunnels in Composite Strata
The settlement control of operating subway tunnel tracks is stringent,and the construction of new tunnels beneath existing ones can potentially induce settlement in the latter,which is even more pronounced in composite strata.Therefore,the selection of reinforcement schemes is crucial for controlling the settlement of existing tunnels.This paper,relying on a specific shield tunnel under-crossing project,employs numerical simulation methods to investigate the deformation patterns of existing tunnels and reinforcement schemes arising from the construction of shield tunnels beneath them in composite strata.The results indicate that:1)After the construction of the new shield tunnel beneath,the longitudinal settlement curve of the existing shield tunnel exhibits a"W"-shaped pattern,with the maximum settlement occurring at the intersection point of the planes of the new and existing tunnels;2)Upon implementing the designed reinforcement measures,the shape of the settlement curve of the existing shield tunnel gradually changes from"W"to"U"as the reinforcement intensity increases,accompanied by a reduction in the maximum settlement;3)When reinforcing the soil layer within a 180° range along the arch of the new tunnel and extending radially by 2.7 meters,the settlement of the existing tunnel meets the control standard requirements.Under similar engineering conditions,the above reinforcement scheme is recommended.
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