The Application Of Classic Timoshenko Beam Theory In The Longitudinal Deformation Of Shield Tunnels And Related Research

In the long-term operation process of shield tunnels that have been completed,due to the influence of complex environmental factors,the tunnel structure has undergone uneven deformation along the longitudinal direction,which affects the safety and comfort of metro.Therefore,the longitudinal structural deformation of shield tunnels is necessary to be researched.As the shield tunnel is a complex assembled structure,the research on that of longitudinal mechanical properties is still a problem,so that it's studied by theoretical,experimental and numerical methods in the paper.The main contents are as follows:(1)The Timoshenko beam on the elastic foundation is used to simulate the longitudinal structure of the shield tunnel underground.The displacement,rotation angle,bending moment and shear force are taken as the initial parameters and the formula is solved by transfer matrix.The longitudinal structure calculation model of the shield tunnel which can consider both the shear effect and the bending effect is established,and the internal forces and deformation solutions under external loads in the longitudinal direction of the shield tunnel is obtained.(2)Based on the shield tunnel of Nanjing Metro Line No.1,a model tunnel with a similar ratio of 1:40 and a test loading system were independently designed and fabricated.The homogeneous tunnel and the model tunnel were subjected to loading tests.Through analysis of test data,the effective rate of equivalent bending stiffness is about 0.15-0.26.Through loading test of tunnels in model soil and the shear stiffness of the structure was inversely analyzed by the displacement data.The range of the equivalent shear stiffness correction coefficient is about 0.05-0.1.(3)Midas GTS and theoretical methods were carried out to calculate the structural deformation along the longitudinal direction of the shield tunnel under the conditions of the three soil layers.The results show that stress concentration at the interface of the soil layer because of the soil layer is not uniform.Meanwhile the cracking and displacement of the staggered benches are correspondingly increased.The theory of this paper is used to calculate the influence of the foundation pit project of Longyan Road,Nanjing,on the subway No.1 line.The result is close to the measured value,which partially proves the validity of the theory.