Research On Ground Deformation And Effect Of Adjacent Piles Caused By Shield Tunnel Construction

This thesis has analyzed the theories of how to predict the ground deformation and estimate the influence to beside buildings after subway excavation. Aim at the inadequate of present theories, this thesis brings up the revised methods, which provide a scientific basis for solution the engineering problem during subway excavation. The main content of this thesis is as following.Firstly, aim at the traditional Peck method's calculation is narrower and deeper in shallow or rather shallow tunnel, this thesis established a calculation model that making the ground loss caused by metro excavation concentrated on a line which crossing the center of the tunnel. On basis of this modal, this thesis derived the formulas of 2D and 3D which are used to calculate the ground deformation caused by the tunnel excavation. Some practicality examples proved that the revision of Peck formula is right. The results show that revising Peck formula can reflect the influence of excavating section of the tunnel. In the same ground loss condition, the wider the horizontal width of the tunnel is, the smaller of the largest surface settlement. In shallow or rather shallow tunnel, surface settlement curve was "wider and shallower ", closer to surveying value.Secondly, According to the theory of stochastic medium didn't consider the ovalization deformation of tunnel section after excavation, a calculative model which considers the tunnel ovalization deformation is proposed to in this thesis. The deformation of the tunnel after excavation was considered as the sum of uniform radial displacement, ovalization of the tunnel and uniform vertical movement. Based on the model, the integral limits of the theory of stochastic medium formula were derived. And using a complex variable solution by Verruijt, the calculation formulas of three component of tunnel's ovalization were derived. The factors which impact the biggest surface settlement caused by the subway tunnel excavation were analyzed by a Fortran program, and the empirical formula which could calculate the largest settlement was derived.Thirdly, the numerical simulation method of shield construction was studied, including simulation method of the stress release, materials and loads during excavation. And non-uniform stress release method was brought up. It is found by analysis that uniform stress release method was not suitable for shield tunneling, otherwise the tunnel would upwarp. Non-uniform stress release method was accord with the actual conditions of shield construct, and its result was more reasonable. Finally, this thesis studied the influence to beside piles during tunneling excavation by FEM, analyzed the change law of pile displacement and force (include axial force, shear force, moment, and friction) and the influence to ground deformation under many different conditions (include different constraint condition on the top of pile, different pile length, and different difference between pile and tunnel).