Research On Mechanics Of Shield Tunnel Segments And Waterproof Performance Of Joint Gaskets In Rich Water Area

Shield tunneling has become the preferred mode of urban public and cross river and sea transportation due to its advantages such as short construction period,low weather impact,and strong resistance to natural disasters.With the continuous increase of shield tunnel construction scale and the increasing number of shield tunnels in water rich areas,the abundant groundwater not only seriously affects the normal construction of the tunnel,but also brings adverse effects on the safety of the tunnel lining structure during operation.This article is based on a certain section of the Jinan Metro project.Through theoretical analysis,numerical simulation,indoor experiments,and other methods,research is conducted on the mechanical properties of shield tunnel segments and the evolution law of joint sealing pad waterproof performance in rich water areas.The mechanical properties and deformation laws of tunnel entire ring segments and local segment joints under different groundwater levels are obtained,revealing the evolution law of sealing pad waterproof performance and the failure mechanism of waterproof performance,The main research content is as follows:(1)Based on actual working conditions,a numerical calculation model for shield tunnel integral segment was established using ABAQUS finite element software.The influence of groundwater level changes on the mechanical properties of the segment was studied,and the spatial distribution patterns of tunnel deformation,segment axial force,bending moment and other mechanical states were obtained.The most unfavorable working conditions were obtained,and the influence of changes in the position of the sealing block on the mechanical properties of the tunnel segment was studied using this working condition,The mechanical response characteristics of the tunnel segments with changes in the position of the sealing block were obtained,the most unfavorable load conditions were determined,and the stress danger zone was proposed.(2)Based on the most unfavorable load conditions,establish a refined model for the segment joint,and study the changes in mechanical parameters such as the opening amount,rotation angle,and bolt stress of the segment joint under combined compression and bending loads.On this basis,numerical analysis was conducted on the mechanical properties of the joint sealing gasket of the pipe segment under different working conditions,and the variation law of contact stress of the joint sealing gasket under different working conditions was obtained.In addition,in response to the characteristics of high groundwater levels in shield tunnels in water rich areas,a fluid solid coupling model for joint sealing pads was established using the AB AQUS CEL method.The deformation of the sealing pad,surface contact stress,and external water pressure evolution during the seepage process were studied.The four stages of water leakage through the sealing pad were obtained,and the surface contact stress and external water pressure variation characteristics of the sealing pad at different stages were obtained,Revealed the failure mechanism of waterproof performance of sealing gaskets under water pressure.(3)We conducted indoor experiments using the shield tunnel segment joint water force coupling leakage test device independently designed and developed by the research group.We studied the assembly stress and maximum water pressure variation of the segment joint sealing pad under adverse working conditions such as segment joint opening,assembly misalignment,load generated misalignment,and rotation angle.The main reasons for the waterproof performance degradation of the joint sealing pad were verified with numerical simulation data.