Study On Water Leakage And Sand Leakage Disaster And Efficient Rescue Measures Of Subway Tunnel In Soft Soil Area

With the rapid development of China’s economy,the construction process of urban shield tunnel is greatly accelerated.In soft soil area of our country,if the tunnel leakage occurs,it is easy to cause the disaster of water and sand flooding,resulting in tunnel collapse and ground subsidence,bringing serious economic loss and bad social influence.In this paper,the evolution mechanism and rescue measures of water and sand inrush disaster of shield tunnel in soft soil area are studied in the following aspects:(1)The causes and classification of subway tunnel diseases at home and abroad and the classification of subway health degree are investigated and analyzed.The classification of health degree at home and abroad can be divided into three classification methods,four classification methods,five classification methods and ten classification methods.Combining with the disease characteristics of Tianjin metro and the previous research on the health degree of Tianjin metro tunnel,this paper puts forward a four-level classification method to grade the health degree of Tianjin metro tunnel.Based on the disease detection of Tianjin Metro Line 2,each section is graded and the disease disposal suggestions are put forward.(2)often occurs in the shield tunnel construction in the process of sand leaking accident,grouting is a common emergency treatment,due to the underground environment is often dynamic water condition,the double grout traditional grouting materials such as vulnerable to dilute scattered erosion of groundwater,so have very high request for grouting materials,grouting materials should be considered the setting time,water retention rate,the water plugging rate and other properties.In this paper,the present commonly used grouting materials such as double liquid slurry,polyurethane and other grouting materials,the comprehensive performance of the investigation and comparison,and independent research on a new type of grouting material-paste slurry,adding bentonite and fly ash in the traditional cement slurry,improve the ability of water erosion resistance of cement slurry.By studying the layering degree,consistency,expansion degree,bleeding rate,setting time,water retention,apparent density,cube compressive strength and other related technical indexes of different proportions of paste grout,a reasonable proportion of paste grout can be tested to be used in engineering emergency grouting.(3)Through small grouting test,the plugging performance of six grouting materials,such as ordinary double liquid slurry,paste double liquid slurry,two-component water-reactive polyurethane,Malisan,Super Absorbent Polymer(SAP),SAP and double liquid slurry combination,was studied.The plugging effect and mechanism of different grouting materials are analyzed.At the same time,it is shown that the combination of SAP and double liquid slurry and paste slurry double liquid slurry proposed in this paper have better cavity filling and plugging effect.(4)Through the simulation test device of large tunnel water leakage and sand leakage grouting,the tunnel,surrounding stratum and water leakage and sand leakage state are simulated more truly,the evolution mechanism of tunnel water leakage and sand leakage is studied,and the plugging effect of new grouting material is verified.When the boundary between clay layer and sand layer is located in the middle of the tunnel,water leakage and sand leakage occur at the bottom of the tunnel.After the leakage state is stable,a triangle cavity area will be generated on both sides in the middle of the tunnel to the bottom,and there is no obvious cavity at the bottom of the tunnel.SAP grouting can effectively fill the leakage cavity outside the tunnel and greatly slow down the leakage speed.On this basis,double liquid grouting can further seal the leakage.