The Analysis Theory For The Weak Connected Double Lining Of Shield Tunnels

Due to various factors such as the geological conditions,construction environment,and experience of construction technique,various tunnel diseases are becoming more and more prominent.To meet the requirements of structural durability and safety of major shield tunnel projects,more and more shield tunnel projects have started to use the double lining structure with the "segment lining+secondary lining"form.At present,scholars from various countries mainly use numerical methods and experiment methods when studying the double lining structure,but rarely use analytical methods.Therefore,it is necessary to carry out in-depth discussion on the analytical solution of the double lining structure.Based on the curved Euler beam theory,this paper presents an analytical solution for the double lining structure of shield tunnels,and the mechanical properties of the double lining under different conditions are studied,the main research and results are as follows:(1)Based on the theory of the curved Euler beam,a new approach of partial-interaction composite curved beam was presented to simulate precast concrete segments with secondary linings,where slippage could occur at the interface.(2)A new analytical theory to a double lining structure of shield tunnel was presented herein.Using the state space method,solutions for the internal forces and deformations could be derived efficiently and succinctly for varying conditions,such as arbitrary loading,joint distributions,and non-uniform stiffness at the lining-lining interface.In addition,as in the state space method,the internal forces and deformations were primary variables,and a trial-and-error procedure was performed to consider the effect of bending-direction-dependent joint stiffness,without recourse to traditional tedious procedures such as nonlinear iterative algorithms.(3)Based on the analytical theory of the double lining structure,the interaction between soil and structure was introduced,and two typical analysis models of the double lining structure on elastic foundation are established,namely elastic foundation model and simplified soil reaction model.The elastic foundation model is more suitable for deep-buried shield tunnels,and the simplified soil reaction model is more suitable for shield tunnels in shallow or soft soils.(4)The mechanical response of the double lining structure under different structural parameters was studied:three different joint distributions were compared;the effect of internal-force-direction-dependent joint stiffness was studied;the variation trends of internal forces and deformations with variable tangential stiffness at the interface and soil reaction stiffness were studied.(5)Based on the analytical theory to a double lining structure,analytical theories to a double-loop structure with double lining and a segmental lining structure reinforced by a semi-ring secondary lining were presented.The shear interaction between two adjacent lining rings is considered in the longitudinal double-loop model;By changing the local structural parameters,the model of the segmental lining structure reinforced by a semi-ring secondary lining can conveniently consider the effect of the track bed on the lining structure in a practical tunnel reinforcement project.