Identification And Treatment Of Leakage Disease Of Shield Tunnel In Water Bearing Stratum During Operation Period

In recent years,with the rapid development of national urbanization,urban land shortage is getting tense,and urban road congestion is gradually aggravating.At the same time,with the further needs of social and economic development and cultural exchanges,the demand for transportation is gradually increasing.Therefore,tunnel construction has naturally become the top priority of urban traffic construction,favored by many places.Among all kinds of tunnels,shield tunnel,due to its unique advantages,has become the preferred construction method for a large number of tunnel projects,especially in urban areas.But at the same time,in the middle and lower reaches of the Yangtze River or similar areas,under the condition of long-term high water pressure,the tunnel leakage problem occurs frequently,which not only reduces the driving safety of the drivers,but also causes a lot of waste of resources in the treatment of leakage.For many years,this kind of problem is extremely common,which perplexes the majority of engineering practitioners.Therefore,this paper focuses on a variety of leakage diseases of a highway shield tunnel under the Yangtze River during the operation period,mainly on the elastic-plastic design theory of shield tunnel structure,segment joint model,tunnel leakage property division,leakage treatment and other contents,to carry out the core problems of shield segment leakage treatment under the Yangtze River deep-water faced,that is,whether the leakage segment structure is stable,the judgment of the joint property of the leakage segment and the discussion of the principle of the treatment scheme for the leakage of the high-pressure tunnel with water.The main contents and achievements are as follows:(1)Based on the traditional elastic-plastic circular cavity expansion theory,considering the long-term high pressure of water bearing strata and the anisotropy of soil layer in the middle and lower reaches of the Yangtze River,combined with the circular cavity calculation theory in anisotropic soil layer by sun Jinshan and other scholars,the analytical derivation of the elastic-plastic calculation theory of shield tunnel during operation(i.e.the third stress state)is carried out.At the same time,the calculation results are compared with isotropic solution,modified routine method and numerical simulation solution to seek the calculation theory which can reflect the real situation of soil layer and is convenient for engineering application.The calculation results are used to preliminarily judge the overall stability of tunnel structure,so as to guide the next waterproof and plugging work.(2)Based on the joint interface model,through simple and reasonable mechanical assumptions,fully considering the opening stages of internal and external waterproof mat,concrete crushing cracking,bolt tensile yield,the bending mechanical model of segment joint is established.By dividing the seam opening into different stages,different calculation methods are given.With given external force,the opening state of the joint can be easily and quickly obtained by trial calculation,and the opening height,opening width and staggering deformation of the joint can be obtained.(3)The existing waterproof standards and leakage classification specifications in China are sorted out,and the waterproof design data of metro tunnels and large section shield tunnels in some cities in China are collected.This paper attempts to link the tunnel leakage with the different stages(Qualitatively)of joint opening and the height and width(Quantitatively)of joint opening,so as to establish the identification system of leakage property and provide the theoretical basis for the water plugging treatment.(4)In view of the current situation that there is no limit value for the joint opening in the existing specifications,combing the existing research results,as well as the monitoring data and leakage situation of the actual project,this paper puts forward relevant suggestions on the early warning value and limit value of the opening,in order to make full waterproof measures in the waterproof design stage,and strengthen the focus during the operation monitoring,so as to reduce the occurrence of leakage.(5)Based on the existing treatment materials and schemes,the frequently-used segment leakage treatment materials(such as polyurethane,modified epoxy resin and composite acrylate)and their related construction process characteristics are systematically combed and evaluated.The grouting materials suitable for leakage treatment of shield tunnel with high water pressure in Yangtze River region are selected through comprehensive comparison of physical and mechanical properties.In this paper,the mechanism of sealing rubber strip caulking waterproof,combined with the grouting technology,as well as bolt hole waterproof treatment and lane board plugging treatment are described in detail.Based on the specific engineering practice in Nanjing,this paper discusses the comprehensive leakage treatment method combined with drainage for tunnel under high water pressure.With the treatment effect and follow-up monitoring results,reference is provided for similar projects.