| With the development of transportation in mountainous areas in China,tunnels are indispensable in traffic construction.However,the construction of most tunnels inevitably encounters the problem of groundwater.The existence of groundwater has a great i MPact on the safety of tunnel construction and operation.Based on the Wufeng Mountain Tunnel in Enshi City,Hubei Province,this paper uses numerical simulation methods to focus on the deformation and hydraulic pressure distribution of the supporting structure during the initial construction of the tunnel.During the operation of the tunnel,the distribution and changes of the external water pressure of the lining in the case of failure of the drainage system were studied,providing relevant references for the safe construction of the tunnel and the operation and maintenance of the tunnel.The main research contents and results are as follows:(1)The research status of calculation theory of tunnel supporting structure at home and abroad,the study of water pressure outside the tunnel,and the calculation method of external water pressure are described.The influence of groundwater on the structure of the tunnel is discussed,and the prediction method of water inflow into the tunnel is clarified.(2)Based on the theory of fluid-structure interaction and the use of Flac3 D finite-difference software,a three-dimensional numerical model was established according to the Wufeng Mountain Tunnel project profile,which verified the necessity of considering the fluid-structure interaction in the tunnel project.The research results show that the deformation of each position of the primary support under the state of fluid-solid coupling is significantly larger than that when fluid-solid coupling is not considered.Ignoring the effect of fluid-solid coupling is more likely to bring construction safety risks.(3)The distribution of the initial support deformation and the external water pressure at different head heights,different grouting ring thicknesses,different grouting ring permeability coefficients,and different surrounding rock grades were studied.The initial support deformation curve and external water pressure were obtained.The distribution change curve determines the weakest position where the primary branch resists surrounding rock deformation and external water pressure.The results show that increasing the thickness of the grouting ring and decreasing the permeability coefficient of the grouting ring can reduce the initial support deformation and the external water pressure of the initial support,while the increase of the head height and the decrease of the surrounding rock grade have the opposite effect;The deformation of the supporting structure is mainly located in the arch top and the arch bottom,while the maximum external water pressure is located in the arch foot;The grouting circle with a thickness of 5m is used in the Wufeng Mountain Tunnel.When the permeability coefficient of the grouting circle is 1/50 of the permeability coefficient of the surrounding rock,the comprehensive effect of controlling the initial support deformation and external water pressure is the best.(4)Based on the complete failure of the drainage system of the Wufeng Mountain Tunnel,the distribution law of the external water pressure of the tunnel lining was investigated from three angles: the head height,the permeability coefficient of the grouting circle,and the surrounding rock grade.Curve,and get tunnel seepage in different conditions.The results show that the increase of the water head height and the decrease of the surrounding rock grade can significantly increase the external water pressure of the lining,while reducing the grouting ring permeability coefficient can well reduce the increase of the external water pressure of the lining and reduce the negative i MPact of the external water pressure on the lining. |
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