| In the excavation and construction of subway tunnels in the strata under the river,water seepage and gushing are often encountered.The seepage effect in the water-bearing formation will greatly increase the difficulty of tunnel excavation construction.Therefore,how to ensure the safety of tunnel construction under the influence of seepage field is a very valuable research problem.In this study,combined with the shield excavation project of Changsha subway crossing the river tunnel,the numerical model of underwater tunnel excavation was established,and the fluid-structure coupling analysis of double line tunnel excavation was carried out by FLAC3 D finite difference calculation method.At the same time,the surrounding rock deformation and seepage laws during tunnel excavation caused by changes in parameters such as water depth,tunnel depth and spacing are summarized.The main work of this paper is as follows:(1)Combined with the actual engineering geological data,a detailed survey of the engineering site was carried out.The distribution characteristics of formation rock and soil are analyzed in detail by means of coring drilling.The basic property test of the geotechnical samples was carried out in the laboratory,and the real geotechnical parameters were obtained.(2)The basic process of numerical analysis of tunnel excavation using FLAC3 D is introduced.The derivation process of the differential equation for seepage calculation,the definite solution conditions of the differential equation and the calculation mode selection of fluid-solid coupling analysis are discussed in detail.(3)A double line tunnel excavation model is established,and a fully coupled calculation mode is used to simulate and analyze the tunnel excavation.The study found that after excavation,the top and bottom of the tunnel produced 7.8mm and 3.3mm of convergence deformation respectively,and the tunnel section developed towards an elliptical shape;After the excavation is completed,the pore pressures at the top and bottom are significantly reduced,the pore pressure rise areas are formed in the surrounding rocks on both sides,and the seepage effect on the side walls is the strongest.(4)The influence of water depth,tunnel burial depth and spacing on tunnel excavation is studied.The result is as follows: The change of water depth will have a significant effect on the seepage intensity of the tunnel surface,and the deformation of the tunnel wall also increases with the increase of water depth;With the increase of the buried depth,the deformation of the tunnel increases,and the settlement displacement of the surface decreases;When the tunnel spacing is less than 16 m,a superimposed pore pressure concentration area will be formed in the middle area.Then with the increase of spacing,the mutual influence of double-line excavation is weakened,and the seepage effect in the middle pore pressure concentration area is also weakened. |
PDF Full Text Request