Research On Construction Technology And Stratum Deformation Of Shield Tunneling Through The Main Canal Of South-to-North Water Transfer Project

In today’s era of rapid development,the travel of urban people is facing huge challenges,so the construction of subway tunnels is becoming more and more common.When the subway tunnel passes through the city,it will inevitably pass through the existing ground structures,such as houses,rivers,etc.,and the displacement and deformation of the ground soil caused by the ground settlement will cause damage to the existing structures on the ground and the soil,causing unnecessary loss.Therefore,during shield construction,it is necessary to predict the impact of shield construction on the ground and provide theoretical guidance for how to control the excavation parameters during the underpass construction process to ensure the safety of the ground structure and construction.Aiming at the construction technology and stratum deformation problems of subway shield tunnels under crossing existing rivers,relying on Zhengzhou Rail Transit Line 17 shield tunnels under crossing the main canal of the South-to-North Water Diversion Project,theoretical analysis,numerical calculation and on-site monitoring are used to study under water conditions.When the shield passes through the main canal of the South-to-North Water Transfer Project,the soil displacement changes at different depths are presented,and a reinforcement plan for the shield tunnel is proposed.The main research contents and results are as follows:(1)Combining the current domestic and foreign research status of the influence law of subway shield construction on soil displacement and deformation,introduce and summarize the factors of ground deformation caused by shield tunnel construction,analyze the change law of ground settlement and computer theory,and summarize the most commonly used minimum The calculation formula for the thickness of the covering soil and the reasons for the floating of the segment and the anti-floating measures.(2)Set up a shield test section before passing through the South-to-North Water Diversion,collect the excavation parameters during the tunneling process of the test section,and compare them with the earth pressure parameters calculated by the stratum,establish a three-dimensional finite element calculation model,and select appropriate parameters for calculation In the model,the calculated results are consistent with the actual measured data after the shield passes through the test section.While verifying the usability of the calculation model,it is simulated that the shield passes through the main canal of the South-to-North Water Transfer Project.(3)After simulating the double-line penetration of the shield,the settlement of the top of the main canal was analyzed,and it was found that the maximum settlement and uplift value did not exceed the limit value.Then it analyzes the vertical and horizontal displacement of the deep soil under the main canal,and summarizes the law of soil displacement at different depths.In engineering practice,attention should be paid to the resistance of the soil to the pipeline,pile foundation,etc.due to the change of the deep soil displacement during shield tunneling.Vertical and horizontal shear of soil structures.(4)The single variable method is used to study the influence of different excavation pressures on the settlement of the main canal and canal top.The effect of different elastic modulus slurries on the vertical displacement of the segment vault and arch bottom.The results show that the greater the excavation pressure,the surface settlement value the smaller the value,the greater the uplift value;the segment is affected by the unloading resilience,the greater the elastic modulus of the slurry,the greater the deformation of the arch bottom,and the smaller the elastic modulus is,the greater the deformation of the dome is affected by the buoyancy of the slurry.(5)When the shield crosses the river,the reinforcement measures in the tunnel are selected according to the actual situation of the site,and numerical simulation is carried out to analyze the changes in the vertical displacement of the ground surface and the segment,and compare the simulation results with the actual monitoring values.The results show that the grouting reinforcement can effectively control the deformation of the ground surface and the segment.The numerical simulation results have a small deviation from the actual monitoring,and the vertical displacement change trends of the two are basically the same,indicating that the reinforcement measures can effectively ensure the smooth progress of the shield tunneling project.