Finite Element Analysis Of Stress And Deformation Of Water Conveyance Shield Tunnel Composite Structure

With the continuous development of shield tunneling technology and the acceleration of urbanization,the underground pipe network facilities have been gradually improved.In addition to the subway,shield tunnels have been widely used in water pipelines,such as water resource allocation,water storage and drainage,and more and more aqueducts.Water conveyance tunnel is often used for water resource allocation,which can supply high-quality drinking water to urban residents.At the same time,it can improve the water quality,optimize the allocation of water resources,improve the utilization efficiency of high-quality water resources and resist the risk of urban water supply.With the increasing scale of water tunnel,the traditional single-layer lining and double-layer lining tunnel structures face with load effect,water leakage,concrete cracking and other problems under long-term service,and are gradually unable to meet the requirements of high internal water pressure of new large-scale water conveyance tunnel projects.The exploration of new lining structure of water conveyance tunnel has become an urgent need.In this thesis,a new three-layer composite water conveyance tunnel is taken as the research object.Through the establishment of refined finite element models,the mechanical characteristics of the structure under high internal water pressure and uneven settlement are studied,which provides the reference for the design and protection of the water conveyance tunnel structure.The main research contents are as follows:(1)The development process and typical engineering cases of the shield tunnel are introduced.The characteristics of the existing tunnel structure and related calculation methods are described.The significance of stress and deformation analysis of the three-layer composite shield tunnel structure is explored.The research status of the mechanical performance of the tunnel structure is summarized,and the research work of this thesis is given.(2)The buckling analysis method and loading mode of water delivery steel pipe are introduced.The finite element buckling analysis of a single water conveyance pipe under different working conditions is carried out.The influence of internal water pressure,pipe wall thickness and stiffener on the buckling of water conveyance pipe is studied.The research shows that the greater the internal water pressure,the thicker the pipe wall,the stronger the longitudinal buckling resistance of water conveyance steel pipe.The influence of stiffener and its spacing on the longitudinal buckling of steel tube is not obvious.(3)Considering the influence of the segment joint bolts,a refined finite element model of the three-layer composite shield tunnel with outer lining segment-inner lining concrete-water conveyance steel pipe is established.The respective mechanical situations of segment,bolt,inner lining concrete and steel pipe under different internal water pressure are studied.The influence of staggered weld on the stress of steel pipe is analyzed.The results show that under the condition of normal water supply,the water convayance tunnel can meet the stress demand,and the water pressure can be transferred to the segment through the lining concrete,reducing the vertical convergence deformation of the segment.(4)The structural stress changes of water conveyance tunnel with different concrete filling range and stiffener spacing are analyzed.The results show that the deformation of a-type structure is the smallest,but the tension of bolt axis is larger.The maximum stress of the three kinds of steel pipes is less than the allowable value.The research results can provide guidance for the optimization of structural forms of three-layer composite water conveyance tunnel.(5)In this thesis,the mechanical properties of the components of the water conveyance tunnel with different structural forms under the uneven settlement are studied.The results show that when the uneven settlement rate is 0.02%,the segment,lining concrete and joint bolt of the water conveyance tunnel begin to be damaged in tension,and the water conveyance steel pipe will not yield until the uneven settlement continues to increase.The water conveyance steel pipe in the c-type structure reaches the yield strength at the earliest,while the influence of stiffener spacing on the maximum stress of steel pipe is not obvious.