Research On The Deformation Law And Control Measures Of The Shield Tunnels Crossing Existing Railway Facilities

With the rapid development of Subway track engineering in China,the phenomenon of approaching construction of shield tunnels becomes more and more prevalent,and the shield tunnels crossing existing railway are more and more.The subgrades,rails and other facilities are influenced by tunnel construction,then the driving safety problems are caused.So studying the deformation law of existing railway facilities and taking effective measures to ensure the safe construction or operation of the existing railway above subway tunnels and shield tunnels has important significance.Based on Line 6 of Tianjin Metro,the deformation law of existing railway facilities and deformation control measures are studied.The main works and research results of this paper are listed as follows:(1)in the paper,based on the engineering practice,two three-dimensional finite element models were builded to study and summarize the deformation law of existing railway facilities;(2)Based on the numerical simulation,space-time evolution regularities of surface and subgrades are analyzed and discussed,and the results show that deformation law correspond with each other,and the vertical settlement is the Gaussian distribution.As the ground loss had attenuation in the transfer process from the top of the tunnel to the railway subgrade in the process of decay,so the surface settlement was slightly larger than subgrade.(3)The vertical settlement and high-low deformation of rails was“S-type”distribution in the shield tunnel construction process.Alignment deformation,Gauge deformation and horizontal deformation all were“W-type”distribution because of the twin-tube shield tunnels construction in succession.Excavation had great influence on the surface and the existing facilities over the tunnels,so the vertical settlement of26~#,27~#and 28~#overhead lines larger than 25~#and 29~#overhead lines.the gradient of all overhead lines was less than the control standards.(4)Effective measures in design and construction phase are adopted to protect the surrounding buildings because of the ground loss caused by shield tunnel construction.Previous research,real-time supervision and parameter optimization were studied and summarized in this paper.And numerical simulation was used to study the effect of secondary deep hole grouting to control deformation.The result shows that the measure had great effect of uplifting,and deformation control indicators of all facilities can meet the standard requirements after using this method.It plays a great effect on deformation control.(5)The trace compensation grouting after segments and reinforcing grouting were used to control the surface deformation than secondary deep hole grouting in the shield tunnel construction.In this paper,the control deformation effect was studied by using the secondary deep hole grouting to and provide reference for the construction of similar projects.