| With the rapid development of shield tunnel in the field of rail transit and municipal engineering,the problem of uneven longitudinal settlement of tunnel is becoming more and more prominent,and consequent problems such as water leakage,structural damage and internal distortion gradually cause people's attention.Through theoretical analysis and numerical simulation,this dissertation corrects stiffiiess further based on perfecting longitudinal equivalent continuous model,providing a reference for practical engineering on this background.Firstly,considering the effect of longitudinal axial force on the neutral axis,the expressions of longitudinal stiffness,the opening of the circumferential seam and the curvature radius of the segmental structure of shield tunnel are deduced,and they are verified correctly for No.147 drilling section at Shiziyang Tunnel on Foshan-Dongguan Intercity Railway by comparative analysis.Furthermore,the effects of the influential coefficient of the longitudinal joints,effective coefficient of lateral rigidity and staggered installation coefficient on the longitudinal effective rigidity ratio are discussed.The results show that:the neutral axis position depends on the size of the equivalent eccentricity;the horizontal stiffness of segmental lining and staggered joint erection are significant for increasing the longitudinal effective rigidity ratio.Then,the communication channel,shaft,wall after the hollow,mined and inner segment lining are introduced for further analysis.The linear relationship between longitudinal effective rigidity ratio and displacement in the affected area(-30m,30m)is established to analyze the force and deformation of segmental lining in the imfluencc of accessory structure and special circumstances,and this longitudinal mechanical properties are amended for above special stated case.The results show that:the accessory structure and the special circumstances can produce local stress concentration,which can significantly change the longitudinal rigidity of the structure,and the degree of influence is controlled by the joint type and the section length,so it's neccessary to carry out flexible treatment in the special section of transition zone(-10m,10m).Finally,taking Shiziyang Tunnel on Foshan-Dongguan as a study project,selecting the sections where overlying strata or substratum is uneven,strata suddenly changes,and alternating hard and soft rock exist,considering the separate calculation and combining calculation of water and soil pressure,the displacement and internal force distribution of the tunnel are calculated.In addition,for the highest and lowest water level in a hundred years,the loading and unloading effects of water buoyancy,river scouring and shore structures on tunnels during operation are analyzed.The variations of the deformation and internal force of vault,haunch and arch bottom of the tunnel are proved,which show that:the stress suddenly changes where strata suddenly changes,and the longitudinal axial force of the underwater tunnel cannot be neglected in the longitudinal design.In the context of longitudinal stiffness,through the formula deduction,correction at special area and finite element analysis on specific engineering case,this dissertation mainly studies the longitudinal settlement and the law of changes of longitudinal axial force and bending moment of tunnel.And the enlargement factor of longitudinal stiffness is obtained finally,which makes up the shortcomings of the vertical structure and deformation design of underwater shield tunnel.It has important engineering value and guiding significance. |
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