Prediction Of Water Inrush From Karst In Shuangfengya Tunnel Of The Nuoshui River Scenic Spot And Its Environmental Impact

The tourism economy has become the third pole of China’s economic development and has played a role in releasing economic vitality,stimulating domestic demand,increasing GDP,and stimulating regional economic development.The Nuoshui River to Guangwushan Highway（Nuoguang Road）connects the two state-level scenic spots of Nuoshui River and Guangwu Mountain.It is a major traffic and tourism channel conducive to the development of the tourism industry and the settlement of outlying poverty areas.The proposed Shuangfengya Tunnel is a key control project for Nuoguang Road.The Shuangfengya tunnel is a deep-buried karst tunnel with a length of 8,520m and a maximum depth of 700m.The hydrogeological conditions along the line are complex.During the excavation,there will be large water inrush and mud hazards,as well as water pollution.The groundwater environment in the River Scenic Spot has a certain impact.In view of this,this paper studies the prediction of water inrush in the Shuangfengya tunnel,the risk assessment of water inrush from the tunnel karst and the analysis of the main landscape in the Nuoshui River Scenic Area,and proposes corresponding protection for the groundwater environmental impact caused by the tunnel construction process.Measures.Therefore,the research in this paper has certain guiding significance for the construction of Shuangfengya tunnel.In this paper,the karst hydrology of the Shuangfengyu tunnel is examined by consulting geological background data,on-site hydrogeological investigation,rock slice identification,chemical composition analysis,isotopic composition analysis,drilling water pressure test,groundwater connectivity tracer test,and numerical simulation.Geological conditions analysis.On this basis,the analytical method and numerical method are used to predict the water inflow from the tunnel and the characteristics of the seepage field,and the risk of water inrush from the karst storm is evaluated for the Shuangfengyu tunnel.The research results have not only reached the goal of water inrush prediction and risk assessment,but also made some progress in the optimization of groundwater resources protection in the preferred line and the Nuoshui River Scenic Area.The main research results are as follows:1)The Shuangfengya tunnel passes through the Triassic Jialingjiang Formation（T₂j）,the Tongtong Tongjie Formation+Feixianguan Formation（T₁t+T₁f）,the Upper Permian Wujiaping Formation（P₂w）,and the lower Maokou Formation.There are thick layered limestones in the Qixia Formation（P1m+P1q）and the Ordovician Middle Pagoda Formation（O₂b）.The karsts develop in the area,and the karst is mainly controlled by structural control along the east-west direction.The research area is bounded by Nuoshui River,Lianchang River and Huitan River,forming an independent hydrogeological unit.A groundwater tracer test was carried out in the Permian（P₂）karst hydrogeology unit in the tunnel crossing area to further determine the location of the underground watershed,which is located about 2500m west of the surface watershed.2)The Shuangfengya tunnel is designed with four comparison lines.The lengths of the lines are respectively 8520m（CK line）,8585m（B1K line）,8250m（K line）,and11180m（AK line）.Using the atmospheric rainfall infiltration method,the groundwater runoff modulus method,the groundwater dynamics method（Cosgakov formula,empirical formula in the railway survey code）,and the numerical simulation method to predict and evaluate the tunnel inflow of the four comparative lines.The optimal route for the Shuangfengya tunnel is identified as CK line.The predicted normal inflow is between 47458.84⁷8851.28m³/d,with an average of 63154.56m³/d.The maximum inflow is between 159634.10²37336.19m³/d.The value is 198485.145m³/d.3)According to the main influencing factors of water inrush from the Shuangfengya tunnel,the solubility of the rock,geological structure,surface environment characteristics,the karst zone of the tunnel,the depth of the tunnel and the groundwater level were selected as evaluation indicators,and the tunnel in the southwest was used.The gushing water risk assessment system evaluated the water inrush danger of each comparative line,and concluded that the extremely high risk zone of the CK line was the shortest,that is,the minimum risk of water inrush from the CK line was determined from engineering hazards.4)The environmental impact analysis of the main landscape of the Nuoshui River Scenic Area was carried out,and the construction of the tunnel affected some of the water landscape.The CK line has the smallest impact area,about 1.034km,accounting for 4.43%of the entire recharge runoff area,and the rest of the landform landscape,vegetation landscape,humanities.Landscapes and tourist facilities have no effect.5)Finally,based on the prediction of water inflow,risk assessment results,impacts on the main landscape of the scenic spot,and project settings,etc.,a comprehensive determination of the CK line as the optimal route from both engineering hazards and environmental impacts was conducted on the Nuoshui River Scenic Area.Longhudong River has the least impact.