Study On The Investigation And Risk Assessment Of Open-Cut Subway Station In Karst Area

With the continuous development of the subway construction, the construction of the subway station in the karst area has become an inevitable problem. Karst caves, karst water and karst collapse are the three main types of hazard. If the survey measures are not appropriate, it will affect the risk assessment of the open pit excavation station, it will affect the construction of the supporting structure and the karst and other construction problems. Treatment is not wonderful easily lead to water gushing in pit, ground subsidence and other problems, not only to dig station or the surrounding environment caused a tremendous impact and leave security risks and even cause serious economic losses. In view of the above problems, this paper in Karst District of Guangzhou city open cut metro station construction project as the background, on the basis of theoretical research and engineering data, put forward a set of guiding method, main contents and research results are as follows:(1)Through the research on the mechanism and the investigation method of karst hazard, it is considered that the exploration of the subway station in the karst area should be based on the method of the combination of the test and in situ test. On the basis of the original survey content, focus on the karst hole, groundwater and other aspects of the investigation, the key areas of karst development through the encryption of drilling or geophysical prospecting. In geophysical prospecting method, the CT method of high density resistivity method and cross hole seismic method is better for the development of karst.(2)Through the research on the risk assessment theory, based on the survey results, the risk assessment system is established by using the method of chromatography analysis and fuzzy comprehensive evaluation. Construction risk assessment of the station, the risk of occurrence probability, risk loss and risk level.(3)Through the research on the selection of the supporting structure and the karst construction of the open cut station in karst area, the selection of supporting structure in the karst area should be adopted in the form of continuous wall and internal support. The open cut subway station in the construction of the cave, retaining structure collapse and leakage of water, water gushing in pit and ground subsidence and other problem put forward the corresponding processing method.(4)Taking Guangzhou Metro Line 9 as an example, according to the above method to dig the station to carry out the investigation. Combined with the survey results of the risk assessment, evaluation results determine the risk management measures. The station supporting structure selection and treatment of karst cave is described that filling and grouting, rock surface grouting and mound column method of solution hole treatment effect is better.