Study On Mechanical Properties Of Universal Wedge Segments For Curved Section Of Shield Tunnel In Rapid Rail Transit

With the implementation of the national strategy of the coordinated development of Beijing,Tianjin and Hebei,the demand for rapid rail transit between the city center and satellite cities is increasing.More and more projects are under way and the scale of rapid rail transit projects is also growing.The underground tunnels of rapid rail transit are mostly constructed by shield method,which adopts small curve radius to bypass the underground structures such as urban building foundation and underground pipeline shield.Especially in the soft soil area,the mechanical behaviors and deformation of small radius shield tunnel lining structures is very complicated,which is the key issue in the design of shield tunnel for rapid rail transit.However,the current technical standards are only applicable to the railways with maximum train speeds of 80 km/h and 100 km/h.There is no corresponding technical standard applicable to the 120 km/h express railways.The design and construction parameter control of the curve segment of the rapid transit shield tunnel in soft soil area is still the blind spot of the current research.This thesis carry out research work on the following aspects mainly:(1)Longitudinal rigidity analysis of shield tunnels assembled by universal wedge segments.In this paper,the shell-spring model is used to simulate the longitudinal stiffness of shield tunnels,and the longitudinal load-deflection curve of tunnels are revealed.The relationship between the midpoint deflection and the external load in different positions of universal wedge segments is given.Finally,the influence of longitudinal seam and position of key block on the tunnel longitudinal stiffness is discussed.(2)Analysis of mechanical behaviors of straight section shield tunnel in construction stage.In this paper,the shell-spring model considering concrete damage plastic during the construction on straight-line of shield tunnels is established to reveal the influence of the segment width,geological conditions and jack eccentric thrust on the stress,deformation and damage of the universal wedge segments.(3)Analysis of mechanical performance of curve section shield tunnel in construction stage.In this paper,the shell-spring model considering concrete damage plastic in the construction of curved-line shield tunnel is established to reveal the influence of curve radius,segment width,geological conditions and jack eccentric thrust on the stress,deformation and damage of universal wedge segments.Based on Tianjin Z2 project,the software ABAQUS was used to study the influence of different curve radius,segment widths,geological conditions and jack eccentric thrust on the mechanical properties of the universal wedge segments during the construction of shield tunnel.The article gives the variation rules of the stress,deformation and damage of the universal wedge-shaped segment of shield tunnel under the different curve radius,segment widths,soil layer and jack eccentric thrust conditions.This research provide guidance for the design and construction of shield tunnel lining structure.