Optimization Analysis of Protection Schemes for Shield Tunnel Undercrossing Existing Tunnel
The construction of shield tunnel has an obvious effect on the upper tunnel.There are significant construction risks and control and protection should be carried.Based on one shield tunnel undercrossing the existing tunnel,three-dimensional FEM models of three rein-forcement schemes,which are MJS horizontal reinforcement,pipe-shed grouting reinforcement and ground sleeve valve pipe grouting rein-forcement,are built.The horizontal and vertical displacement characteristics of the existing tunnels under three reinforcement schemes are ana-lysed in detail.And a comparative analysis was conducted from the aspects of deformation control,construction method shortcomings,feasi-bility,and engineering costs to determine the optimal reinforcement scheme.Some conclusions have been drawn.Firstly,the displacement of existing tunnels is mainly vertical displacement,which is the key index for tunnel deformation control.Secondly,displacement control of ex-isting tunnels,the scheme of MJS horizontal reinforcement is the best and ground sleeve valve pipe grouting reinforcement has the worst ef-fect.Thirdly,based on four factors,the scheme of pipe-shed grouting reinforcement.Fourth,the soil strength has been improved after rein-forcement treatment and the of the right tunnel construction has little effect on the size and position of maximum displacement.Finally,with the distance between the excavation faces of double tracks is more than 2.5 times the tunnel diameter,the construction disturbance can be re-duced to a certain extent.The conclusion can provide reference for similar undercrossing project.
new built tunnelexisting tunnelreinforcementMJS horizontal reinforcementpipe-shed grouting reinforcementsleeve valve pipe
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