Correlation Analysis Between Drainage Functions Of Drainage Holes And Main Tunnels In Water-rich Highway Tunnels In Mountainous Area

Water and mud inrush accidents are common in water-rich mountain areas during tunnels construction,and various water disasters regularly appear during the operation period.Therefore,the auxiliary drainage measures outside the tunnel came into being.Adding a drainage tunnel is one of the typical ways,but the related research is scarce.Especially before construction,due to the incomplete grasp of hydrogeological information,the construction of the drainage tunnel is lagging behind.Secondly,due to the lack of theoretical research,and there are no relevant specifications and standards of the discharge tunnel,resulting in the lack of theoretical support for the discharge and water pressure relief function.Furthermore,the discharge tunnel has the risk of excessive discharge.Many factors lead to the design of the discharge tunnel without quantitative data support and seriously lagging behind the actual production.The empiricism in the design implies many problems such as the unsafe and the uneconomical.Therefore,relying on the Xiaba Tunnel of Naqing Expressway,starting from the field hydrogeological investigation,the necessity of adding water discharge tunnel is discussed.Theoretical analysis,numerical test and field test are used to analyze the function of discharge and water pressure relief function,and the control measures of discharge are put forward based on numerical test.The main research contents and results are as follows:(1)Through field hydrogeological investigation,the groundwater system is divided according to the concept of hydrogeological zoning,and the risk of water inrush is qualitatively analyzed.Based on the principle of water balance theory,the tunnel water inflow is predicted,and the risk of water inflow is quantitatively analyzed combined by engineering analogy method.After considering the adverse hydrogeological factors along the tunnel,the necessity of adding drainage tunnels is judged.(2)Based on the mirror image principle and well flow theory,a two-dimensional calculation model is constructed,and compared with the numerical simulation model,the results are in good agreement.Based on this,the mechanism of discharge and water pressure relief is explored,and the influence of the position of the discharge tunnel,hydrogeological factors,and main tunnel support factors on the effect of discharge and water pressure relief is analyzed.The problem of "over drainage" of the discharge tunnel is revealed,and the "control drainage" effect of the grouting ring and the diameter of the discharge tunnel is analyzed.(3)To consider the fluid characteristics in the drainage cushion under the actual situation,a three-dimensional numerical model with drainage system is constructed.Considering the fluid-solid coupling effect,the matching degree between the drainage tunnel and the main tunnel with different waterproof and drainage forms is proved by taking drainage and water pressure of lining as the response indexes.On the basis of the former theoretical research,the effect of discharge and water pressure relief and discharge reduction effect under the different position of the discharge tunnel and the grouting parameter are further revealed,and the applicable scope of the grouting discharge reduction measures is proposed.(4)Based on the above results,a concept of " local drainage " is proposed,and two structures of " limited surface discharge " and " centralized limited line discharge" are designed.The discharge reduction effect is tested by numerical simulation.After position,length and longitudinal spacing of the discharge hole are optimized,a decentralized line discharge reduction structure based on the concept of "decentralized local drainage" is developed,which acquire the most optimal water pressure relief effect on the main tunnel and can effectively control its own drainage.The structure has high flexibility,the effect of discharge and water pressure reduction and discharge reduction can be adjusted by adjusting the length of the discharge hole.(5)By measuring the water pressure of primary support and collecting the water inflow data on the basis of Field test during construction,combined with the result of theoretical research and numerical research,the real discharge and water pressure relief function of the discharge tunnel is revealed.