Risk Management Of Foundation Pit Dewatering In Subway Tation In The Yangtze River Floodplain Area

In recent years,with the accelerating process of urbanization in China,the problem of traffic congestion has become increasingly prominent.In addition,the urban land resources have become more and more tense,and the way to develop and use underground space to build underground rail transit has been adopted to improve the current situation of urban traffic congestion.Complex geological conditions,the Yangtze river floodplain region of the Yangtze river floodplain area subway station foundation pit precipitation.Corresponding risk analysis and corresponding risk management measures for foundation pit dewatering in metro stations in the floodplain area of the Yangtze River are not only the guarantee for the smooth development of foundation pit dewatering construction,but also the basis for the successful completion of the entire foundation pit project,so it is of great significance.The Yangtze River floodplain area studied in this paper has complicated geological conditions.The corresponding risk analysis of the foundation pit dewatering of the metro station in this area and the corresponding risk management measures are the guarantee for the smooth development of the foundation pit dewatering construction and the completion of the entire foundation pit project.basisIn order to ensure the effective implementation of the foundation pit dewatering safety of the subway station in the floodplain area of the Yangtze River,this paper considers the special situation of the geological conditions in the floodplain area of the Yangtze River and considers the problem of the foundation pit dewatering safety accident during the foundation pit dewatering of the metro station in the area.The research work was carried out and the example was verified with the foundation pit dewatering project of High Temple Road Station of Nanjing Metro Line 7.This paper first introduces the domestic and international research and development status of the theory related to foundation pit dewatering,including the ground subsidence caused by foundation pit dewatering,the settlement of building(structure),the current status of seepage in foundation pit and the status quo of construction control technology,etc.In areas with complex geological conditions in the beach area,the risk management in the early stage of foundation pit dewatering,including risk analysis,risk identification,risk prevention and control,etc.,is less studied.This paper will use this as a starting point to propose a preliminary solution.Secondly,it analyzes the geology of the floodplain area of the Yangtze River and the characteristics of the foundation pit dewatering in the subway station.Based on the historical data of the foundation pit dewatering in Nanjing,according to the geological conditions of the foundation pit of the metro station,the nature difference and base of the underground aquifer.According to the different types of pit precipitating structure,the foundation pit dewatering of the metro station is divided into five types,which briefly describe the applicable stratum,the maintenance structure and the impact on the surrounding buildings,and the geology of the Yangtze River floodplain and the foundation pit dewatering of the metro station.The characteristics of the selection of reasonable subway station foundation pit precipitation risk assessment methods.Thirdly,based on the risk factors of the foundation pit dewatering in the floodplain area of the Yangtze River,combined with the site geological conditions of the High temple Road Station of Nanjing Metro Line 7,the nature of the underground aquifer and the surrounding environment,the foundation pit dewatering construction process of the entire metro station was determined.Possible risk factors.In this way,five risk indicators such as survey risk,design risk,construction risk,precipitation process risk and environmental risk were established,and the risk assessment index system for the foundation pit dewatering of High temple Road Station was established.In addition,taking the established subway station foundation pit precipitation risk assessment system as a guide,the triangular fuzzy function is selected as the language scale to collect the collected data through questionnaire survey,and the fuzzy network complementary judgment matrix is constructed.The risk weights are determined by the analytic hierarchy process.The fuzzy comprehensive evaluation method comprehensively evaluates the risk of foundation pit dewatering in subway stations,and establishes a risk assessment model for the foundation pit dewatering based on fuzzy network analysis method.Finally,taking the Nanjing Metro Line 7 High temple station as an example,the base pit precipitation risk assessment is carried out on the station.From the comprehensive evaluation results,it can be seen that the base station pit construction risk level of the subway station is Grade IV,which is a very serious grade.Among them,the construction quality of the foundation pit dewatering well is poor,the construction process of the precipitation is disorderly,the deformation of the building around the foundation pit is too large,and the diving well is not accompanied by excavation and precipitation is a key risk factor.Corresponding risk control measures are formulated for these key risk factors,and the risks are controlled within a reasonable range to ensure the safety of the foundation pit during the construction of the entire subway station.The smooth implementation of the foundation pit dewatering construction of High temple Road Station of Nanjing Metro Line 7 verified that the combination of fuzzy network analysis method and fuzzy comprehensive evaluation method has a good application prospect in the foundation pit precipitation risk management.