Study On Mechanical Properties Of Common Joints Of Shield Tunnel Under Static And Dynamic Action

Shield tunnel structure has been in underground environment for a long time.The surrounding terrain conditions become more complex,and the uncertain factors are increasing day by day.The influence of earthquake is becoming more and more obvious.Therefore,the comprehensive analysis and quantitative optimization of mechanical properties of shield tunnel structure has become a key research topic,and the importance of seismic analysis of shield tunnel structure under seismic load is significant.How to evaluate the safety performance of shield tunnel structure under seismic conditions is very important.Lining joint is the key part to ensure the stability and integrity of the whole shield tunnel structure.It is an important research direction to explore the mechanical properties of commonly used joints of shield tunnel under static pressure and seismic excitation.In addition,as the key index to evaluate the bearing capacity and deformation capacity of tunnel structure,the flexural rigidity of joint is discussed in detail,which provides theoretical basis and technical guidance for the design,construction and safety evaluation of lining joint structure.Based on the theory of damage mechanics and structural mechanics,combined with the existing test results,this paper conducted a detailed study on the common joints mechanical properties of shield tunnels under static pressure and earthquake excitation by theoretical analysis and numerical simulation.Firstly,based on the finite element ABAQUS software,a three-dimensional refined numerical simulation model of common bolt joints was created,focusing on the stress and deformation characteristics of different types of bolt joints(bending bolt joints,straight bolt joints and inclined bolt joints)under the static pressure of surrounding rock.Suggestions for determining bending stiffness of three types of bolt joints under different tunnel burial depth and applicability of different types of bolt joints were put forward.Secondly,a threedimensional numerical calculation model of lining Ring-Bending bolt joint were built.The effects of tunnel burial depth,tunnel crossing stratum conditions,joint sealing gasket and shim on the mechanical properties of the joint were studied for the bending bolt joint.Thirdly,by constructing the three-dimensional numerical model of stratumstructure and using time-history analysis method,the dynamic response of tunnel lining under different seismic excitation directions and different seismic acceleration peak conditions were discussed,and the most disadvantageous stress location of tunnel structure under earthquake were determined,and the dynamic response characteristics of different types of bolted joints were obtained.The results show that the deformation of different types of bolt joints,the vertical displacement of the whole structure,the bolt tension and the bolt stress all decrease with the increase of the axial force and increase with the increase of the bending moment.Joint deformation is an important factor affecting structural instability and waterproofing failure.Adding shims can reduce radial convergence deformation of lining ring,but joint deformation increases.Checking the maximum internal force of lining structure during earthquake is the key link to prevent structural damage.The bending moment of segment joints is easily affected by the direction of seismic excitation,and the influence of seismic lateral excitation on the deformation of tunnel lining cross section is more disadvantageous.