Research On Key And Difficult Engineering And Control Measures Of Shield Tunnel Of Pazhou Intercity Railway Branch Line

Nowadays,shield tunneling is more often used in tunnel construction,and the complicated engineering geological conditions have great constraints on the safe construction of shield tunneling tunnels.Due to the special engineering geological conditions,there are many initial accidents of shield construction in guangzhou and shenzhen,and many times of underpassing the pile foundation of bridge.Therefore,in the background of Hualong station-Lianhua station of Pazhou intercity railway extension project,the paper analyzes the pile foundation of shield tunneling and shield tunneling.The research results are of great significance for the shield tunnel with similar engineering geological conditions.The research work and conclusions are as follows:(1)Through the analysis of geological conditions along the tunnel,it is found that the construction of the project is difficult and risky.Through comparative analysis,a composite earth pressure balance shield is selected for tunneling.It is twokey and difficult engineering to determine the origin of shield construction and its crossing beside the pile foundation of bridge.(2)According to the theory of elastic plate and plastic loose ring,the reasonable reinforcement range of shield end is determined.Numerical simulation method is used to compare and analyze the degree of formation disturbance caused by the construction of the primary end reinforcement and the unconsolidated end reinforcement.It is found that the formation displacement of the primary segment is controlled obviously after the end reinforcement.It is found that the smaller the distance between two tunnel excavation palmface is,the more significant the effect is.(3)By analyzing the influence of shield tunneling on pile foundation,it is necessary to apply isolation pile between shield tunnel and bridge pile foundation in order to protect pile foundation.A comparative analysis is made of the two cases of isolation pile applied and no isolation pile applied.After the protection measures are applied,the maximum deformation of pile foundation of bridge is 5.6mm caused by shield construction.Pile foundation deformation is effectively controlled.After adding advanced grouting,the maximum deformation value is 3.95 mm.The deformation value meets the specification and construction requirements.(4)The whole process from tunnel construction to train operation is simulated.The results show that under the same velocity,the dynamic loads of 1,2 and 3 times are applied respectively.When the dynamic load of the train is smaller,the pile foundation is less disturbed.The maximum displacement value of the whole process is 6.44 mm,which meets the requirements of specifications and construction.(5)Combined with the theoretical analysis and numerical simulation results,the control measures of shield construction starting and passing by the pile foundation of the bridge is worked out.It is used to reduce the ground and building disturbance caused by construction reasons.