Structural Analysis Of Shield Tunnel Lining Based On The State Space Method

The shield tunnel technique is distinguished by several remarkable properties,such as low impact on the surface environment and high security and so on,and widely used in tunnel construction all over the word.Precast segmentation and highly mechanization produce extensive longitudinal joints and circumferential joints for shield tunnel which are considered to be vulnerable points of structure.In the primary planning and degign stage,a prerequisite task is to obtain the deformation and internal force of tunnel lining by a proper way.Thus,it is of great significance to further analyze and improve the structural design theory of tunnel lining for practical engineering especially when taking the influence of joints into account.The traditional solving strategies such as the force method and the displacement method,involve an elimination procedure to solve the problem within range of one type of variables.It leads to high-order differential control equations such that hard to deal with joints and soil-structure interaction simultaneously.The solutions are just available in some special scenarios and usually rely on symmetry assumption of load and structure or turn to the numerical framework.To improve and enrich the theoretical analysis of lining,the state space method was introduced to rearrange the control equations and unknowns into matrix form and obtain exact solutions for circular segmental lining subjected to arbitrary external loads and with arbitrary joint distribution within range of two types of variables,i.e.,both force and displacement.The main works and progresses involved in this dissertation are as follows.1.The state space method was introduced to acquire an exact solution for the response of a jointed free single ring model subjected to external loads,based on the beam-spring model and curved Euler beam theory.Rigorous theoretical proof was provided to eliminate the rigid body displacement and reveal the implicitly embedded self-balance condition of external load.The present solution was verified by a comparison with measurement of full-scale model test and laid a foundation for further involving the soil-structure interaction.2.The solution of a jointed single ring bedded on an elastic medium was obtained by the state space method and validated by comparisons with numerical approach,existed solution and scaled model test.Through a parameter study,the effect of joint stiffnesses and the characteristics of surrounding soil on the internal forces and deformations of lining was revealed.3.Two-directional shear spring was used to model the interaction between adjacent rings.The state space method was applied to acquire an exact solution for the response of a jointed free longitudinal dual-ring model subjected to external loads,which is applicable for both straight and staggered jointed tunnel linings.Rigorous theoretical proof was provided to eliminate the rigid body displacement and reveal the implicitly embedded self-balance condition of external load.The present solution was verified by a comparison with measurement of full-scale model test and existed analytical solution.4.The solution of a jointed dual-ring bedded on an elastic medium was obtained by the state space method and validated by comparisons with numerical approach.The effect of staggered assembly of adjacent rings,shear stiffnesses of circumferential joint and the characteristics of surrounding soil was analyzed through a parameter study.5.Combining the cavity expansion theory and multi-disc soli deposit model with a consideration of nonlinearity of soil,an explicit equation for soil reaction stiffness was established,which showed high efficiency,quick convergence rate and suitability for a preliminary simulation for the soil-structure interaction.