Stability Analysis Of Surrounding Rock And Lining Optimization Design For Urban Long Water Conveyance Tunnels

The urban long water transfer project solves the urban residents'domestic water consumption and urban industrial water consumption by inter-regional water transfer,guarantees agricultural grain production,alleviates the pressure of urban groundwater exploitation,and supports for ecological environment protection.In this paper,based on the urban water conveyance project in Jilin Province,six typical sections of TBM and blasting are selected as the research objects in the construction scheme of the water mains.Two-dimensional numerical modeling was performed using Abaqus finite element software to analyze the surrounding rock stability and lining structure design.The lining optimization design is carried out by adjusting the thickness of the lining and the load distribution of the double lining.The main results are as follows:?Contrasting and analyzing the influence of drilling and TBM on the stability of surrounding rock after tunnel excavation,and reducing the physical and mechanical parameters of surrounding rock in the excavation section of drilling,simulating the damage of surrounding rock by drilling.In the section excavated by drilling,the principal stress value of the surrounding rock is discontinuous in the surrounding rock distrubed zone and the adjacent unaffected zone.Tunnel excavation results in a decrease in rock mass stiffness in the surrounding rock disturbance zone,making its minimum principal stress greater than that of adjacent unaffected areas.?After the excavation of the tunnel,the maximum principal stress and the minimum principal stress of the surrounding rock plane are both negative values,indicating that the surrounding rock units are under pressure and conform to the mechanical properties of the rock compressive strength greater than the tensile strength,calculating the surrounding rock safety factor F_s Value,and some sections have a safety factor less than one.?After the first lining is loaded,the tangential stress of first lining unit is negative,and the radial displacement of the surrounding rock is directed to the inside of the cave,which can fully exert the mechanical properties of the lining material.The safety factor of the surrounding rock unit in some sections is less than 1,indicating there is room for optimization in the preliminary lining design.After the lining of the secondary lining,due to the effect of internal water pressure,the tangential compressive stress of the lining is reduced,and the safety factor of the surrounding rock of each section is improved,indicating that the water-passing conditions contribute to the stability of the surrounding rock and lining.?Increasing the thickness of first lining,under the working conditions and water-passing conditions,the tangential stress of the lining is reduced,and the safety factor of the surrounding rock is increased to varying degrees.Under the same composite lining optimization scheme,the tangential stress of the lining is reduced with different rate.Under the water-passing condition,the thickness of first lining has a linear relationship with the average value of the tangential stress of the first and secondary linings.?Adjust the load distribution of the double lining so that the secondary lining can bear part of the surrounding rock load to make full use of the bearing capacity of the double lining.On the basis of the preliminary composite lining design,the appropriate first and secondary lining load distribution can reduce the tangential stress value of the lining under construction and water-passing conditions,so that it meets the material strength requirements and improves the surrounding rock safety factor.The radial displacement of the surrounding rock after the loading of first lining and before the loading of the secondary lining is set as the independent variable to optimize the lining design,under construction conditions and water supply conditions,the displacement value of surrounding rock and the average value of the tangential stress of the first and secondary linings are obviously linear.