Study On The Risk Identification And Prevention Of Water Gushing And Collapse In Tunnels With Rich Water And Weak Interlayer

At present,China’s transportation industry is developing rapidly,and a number of highway lines are being planned.To complete the construction of the planned road network,the key is the construction of some mountain roads.To build roads in these areas,it is necessary to build a large number of tunnels.Although the construction level of tunnels in China has been greatly improved,disaster events still occur from time to time when special geological conditions are encountered,One of the most common accidents is water gushing and collapse.Tunnel water inrush and collapse is often due to the existence of water rich and weak strata in the surrounding rock in front of the tunnel face.In the past,most of the researches focused on the mechanism of water inrush and collapse and the treatment measures after the accident,but it can not directly reduce the occurrence of such accidents.Therefore,it is urgent to carry out relevant research on the prevention and treatment system of water inrush and collapse in water rich and soft weak sandwich tunnel.Based on the above background,relying on the reconstruction project of ganhu road in Huidong County of Baihetan Hydropower Station,this paper makes a detailed study on the prevention and treatment system of water inrush and collapse of water rich weak interlayer tunnel by using the research methods of field investigation,literature review,theoretical analysis and numerical simulation.(1)Based on the statistical analysis of 100 tunnel collapse accidents in recent ten years,the influencing factors leading to the collapse are classified and summarized by using the statistical data,and the occurrence probability and influence law of each factor are analyzed in detail.(2)On the basis of accident statistical data,a decision-making model of fuzzy analytic hierarchy process(FAHP)for landslide risk occurrence is established,which can identify and evaluate the risk degree of landslide accident occurrence,and has been successfully applied in practical engineering.(3)Through the function of fluid structure coupling in FLAC3 D software,the construction process of tunnel with or without water rich weak interlayer is numerically simulated,and the critical instability criterion of water inrush and collapse accident of water rich weak interlayer tunnel is determined,and then the safety fortification distance of water inrush and collapse section of tunnel is determined.(4)In this paper,numerical model tests considering various factors are carried out to analyze the influence of common surrounding rock lithology and weak interlayer surrounding rock lithology,thickness,range,water pressure,buried depth and other factors on the safety protection distance.On this basis,the formula for determining the safety protection distance of water inrush and collapse of water rich weak interlayer tunnel is established,which has been applied and verified in practical engineering.(5)This paper puts forward a comprehensive prevention and control strategy for water inrush and collapse of water rich weak interlayer tunnel from two aspects of seepage instability and surrounding rock instability,divides the prevention and control measures into groundwater prevention and control measures and surrounding rock pre reinforcement measures,and analyzes the specific methods and action mechanism of each kind of measures.(6)The mechanical behavior of tunnel surrounding rock pre reinforcement measures is analyzed.Taking the pipe shed as an example,a pre reinforcement mechanical model which is more in line with the actual working conditions is established.The model is solved by MATLAB,and the pre reinforcement parameters are optimized by using the model,which is verified in the actual project.