Seismic Mechanical Behavior And Anti-Seismic Measures Of Circumferential Joint Of Shield Tunnel

The shield tunnel is an assembled structure composed of segments and connecting bolts.Under the action of earthquakes,especially when the site conditions are poor,the tunnel is not uniformly loaded along the longitudinal direction.As the main area where longitudinal deformation of the tunnel happens,the circumferential joint is more likely to suffer vibrating damage such as concrete spalling,water seepage,and segment rupture,etc.This dissertation focus on the seismic mechanical behavior of circumferential joint of shield tunnel and its corresponding anti-seismic measures.Relying on the practical engineering case of utility tunnel of Sutong GIL project constructed by shield method,this dissertation has researched and discussed the seismic response characteristics of circumferential joint,the influence of bolt types on the seismic response of circumferential joint,the influence of joint measures on the anti-seismic performance of shield tunnels,and the measures to enhance the seismic bearing capacity of circumferential joint.Various analyzing methods such as theoretical analysis,full-scale test,and numerical simulation are adopted.The main work and related results obtained are as follows:1.Relying on building model of practical engineering case,the distribution law of the internal force between the rings of shield tunnel under seismic condition is obtained.The stress and deformation characteristics of the circumferential joint are calculated by using the whole rings model and the circumferential joint model based on the longitudinal equivalent continuous model respectively.The results show that the calculation results from longitudinal equivalent continuous model are safe and have good accuracy,proofing that it can be used as the basis for the full-scale test of the circumferential joint.Based on this,a full-scale test of the circumferential joint is carried out,the stress-bearing characteristics of the segment and the bolt under cyclic loading are studied,and the final failure mode of the oblique bolt circumferential joint is given.2.Taking the bolt length as a constant,the overall and local seismic response characteristics of shield tunnels with different types of connecting bolts(straight bolts,oblique bolts,and curved bolts)are studied.The influence of bolt types on joint opening,acceleration and structural stress is proved.Comparing the bearing capacity and failure mode of oblique bolt joints and straight bolt joints,a strength validating method that suitable for straight bolt joints and oblique bolt joints is proposed.Compared with the traditional method,the strength validating method proposed in this paper better considers the detailed structural characteristics of the shield tunnel.3.The effects of joint preloading force and elastic washer on the longitudinal anti-seismic performance of shield tunnel are studied respectively.Different from the traditional reinforcement measures for surrounding rock foundations of shield tunnels,this study focuses on the effect of longitudinal stiffness changes of tunnels on seismic performance.Firstly,the longitudinal stiffness of the tunnel under the action of the joint preloading is deduced,and then the distribution characteristics of the internal force between the rings are studied by using an iterative algorithm,meanwhile the distribution of the joint opening along the longitudinal direction of the tunnel is given.After the compression test,polyurethane is selected as the gasket material,the longitudinal stiffness of the tunnel after using the elastic gasket is deduced,and the stress and deformation characteristics of the circumferential joint under different parameters(peak seismic acceleration,gasket thickness,gasket application method)are studied.4.By means of full-scale model test,measures to improve the seismic bearing capacity of circumferential joint are studied,including the screw-in rate of bolts,the enhancement of the connection between the sleeve and the segment,and the improvement of the segment strength.The first two measures are only applicable to oblique bolt joints,and the last measure is applicable to every type of joints.The test studies the variation characteristics of joint bearing capacity,segment stress,reinforcement stress,bolt stress and final failure form under these different measures.This dissertation studies the seismic mechanical behavior of shield tunnels from the whole to the local joints,and proposes a strength validating method for circumferential joint.Anti-seismic measures that suitable for the longitudinal direction of the shield tunnel are also proposed,which can provide a reference for the longitudinal seismic safety design of shield tunnels.