| Most of the South China belongs to karst geology,the karst itself has various complexity.The development of karst will bring many unknown engineering problems to shield construction.Therefore,based on the engineering construction of karst section of Shenzhen rail transit,the research contents and results are as follows:(1)Taking a subway section of Shenzhen rail transit Line 16 as the research object,the numerical simulation software Midas GTS NX is used.Assuming that the unloading process is linear,the load is linearly unloaded within a certain period of time by applying normal excavation pressure and jack force on the tunnel wall,which fully reproduces the dynamic process of shield excavation construction.The dynamic process of construction is reproduced completely.Reliability analysis of numerical simulation calculation results and measured data are carried out to study the influence of different shield tunneling speeds on the ground settlement,the influence of different shield tunneling pressures on the ground settlement,and the influence of the vibration of the shield cutter head on the ground structures.(2)Based on the karst section of Shenzhen Rail Transit Line 16,the research on the safety control technology of subway shield tunnels in karst areas is carried out mainly through literature collection,simulation analysis,reliability verification,sensitivity analysis and other research methods.According to the geological exploration data,a 3D shield tunnel model is established by using Midas GTS NX to analyze the sensitivity analysis factors of the distribution of karst caves,the size of karst caves and the relative relationship between karst caves and tunnels.In addition,the different effects of single line tunnel and double line tunnel on the stress around the tunnel and surface settlement in karst area are studied,and the influence of the distribution of karst caves near the central axis of double line shield tunnel and the size of karst on double line tunnel is deeply studied.The theoretical safe distance between the top cave and the tunnel is studied by taking the rock combination of fixed beam as an example.(3)Under the same constitutive model,the factors that may affect the ground settlement and surrounding rock deformation of shield tunnel are studied.The impact of five parameters including soil cohesion c,friction angle φ,elastic modulus E,poisson’s ratio v and shield tunnel buried depth H on shield tunnel excavation,not only ensures the smooth construction of the supporting project,At the same time,it has great theoretical value and practical significance for guiding the design,construction and disease treatment of similar projects.These studies provides a guiding reference for future projects.(4)Based on the geological survey data from Longping station to Shuanglong station and the results of numerical simulation and theoretical analysis of shield construction safety control technology in karst area,the karst cave treatment measures are summarized in karst areas.According to the distribution position and the size of the shape,the relationship between the karst distribution depth and the structural floor is evaluated. |
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