Research On Waterproof Performance Of Joints Of Segment Lining In Shiled Tunnels With High Hydraulic Pressure

With the continuous development of China’s economy and infrastructure,shield tunnels have been widely used in the construction of traffic network.In recent years,the underwater shield tunnels under planning and construction gradually present the characteristics of high hydraulic pressure,large diameter and complex geological conditions.The increasing external hydraulic pressure requires the shield tunnels to have better waterproof performance.Based on the Shangyuanmen river-crossing tunnel project,indoor tests and numerical simulation were used to research the waterproof performance of joints of segment lining in shield tunnels under high hydraulic pressure in this paper.The main work and achievements are as follows:(1)The assembly force test and waterproof pressure test were carried out for several gaskets.According to the growth rate of assembly force,the gasket compression process can be divided into three stages,and the assembly force increases most in stage III.Under the same segment groove,the greater the maximum assembly force and maximum compression of the gasket,the greater the waterproof pressure.The more gently the assembly force increases in the compression process,the greater the waterproof pressure,which makes the gasket have better waterproof performance when the compression is small.(2)Based on the model of the gaskets at the straight joints,some suggestions on the selection of constitutive model of rubber and the boundary conditions of gaskets were put forward by comparing the results of the numerical simulation and laboratory tests of the assembly force.Based on this,the numerical simulation of the waterproof performance of the gaskets at the straight joints and the T-shape joints of staggered jointed lining of shield tunnels was carried out.The assembly force and the contact stress on the contact surfaces of three kinds of gaskets with different cross-section forms under different staggering and opening distance were analyzed.It’s found that the top surface of the gaskets is prone to warp and produce large free surface when the staggering distance is 5～15mm,which reduces the assembly force of the gaskets and the average contact stress of the top surface of gaskets.Compared with the straight joints,the T-shape joints are easier to leak near the corner of the gaskets.And the waterproof performance of the longitudinal seams is less than that of the circular seams.(3)A calculation method of waterproof performance of sealing gaskets under superposition of water penetratration and extrusion effect was established in ABAQUS sorfware.The whole dynamic deformation process of sealing gaskets under water penetratration and extrusion could be simulated.The concept of "waterproof point" was proposed to describe and analyze the water penetratration process of sealing gaskets under different staggering distance in detail.By comparing the maximum waterproof pressure obtained by this method and the average contact stress of the top surface of the gaskets with the results of waterproof pressure tests,it can be found that the average contact stress method is not suitable for the evaluation of the waterproof performance of the gaskets with high hydraulic pressure and large deformation.And the influence of water pressure should be considered in the numerical simulation in order to predict the waterproof performance.(4)The influence of opening angle of longitudinal seams,assembly location of key segment,and surface state of gaskets on the waterproof performance of joints of segment lining in shield tunnels was analyzed through numerical simulation.There is a linear positive correlation between the absolute value of the opening angle of longitudinal seams and the tunnel ellipticity after segments were assembled.And the maximum opening angle of internal angles of all longitudinal seams is greater than that of external angles at the same ellipticity.The assembly force and average contact stress of the gaskets decrease with the increase of the opening angle of longitudinal seams.The waterproof performance of the gaskets is more affected by the outer angles of the longitudinal joints than inner angles.The waterproof performance of the gasket can be improved if the capping block is located on both sides of the vault.It can improve the assembly force of the gasket and the average contact stress of the contact surface to apply lubricant on the top surface of the gaskets and bond the bottom surface of the gaskets with the surface of the groove.With the time increasing,the top surface,bottom surface and back surface of the gaskets are gradually infiltrated by water,and the average contact stress between the gasket contact surfaces decreases gradually.