Risk Assessment Model Of Underground Construction In Karst Area Of Nanning City And Application

With the rapid increase in China's economic strength,the public transportation load in many cities has been increasing.The development of subways has become an important means to alleviate urban traffic problems.However,subway construction is a project with large investment,long construction period,and high risk,regardless of whether the station is large.There is a major source of risk in the foundation pit and the shield drive process.In recent years,various kinds of subway construction accidents in our country have become more frequent,which has brought invisible shadows to the development of urban subways.It has not only caused huge losses to the country and enterprises,but also seriously affected the life safety of constructors.Nanning is located in a carbonate karst development area in southwestern China.With the distribution of tertiary mudstones,high levels of groundwater levels,and hydrogeological characteristics,the construction of subways in the karst area of Nanning is more difficult and the risk assessment will be even greater.has practical significance.At the same time,it will have significant implications for the development of the following rail transit in Liuzhou.The main work and achievements of this paper are as follows:1.Firstly,the background and significance of the dissertation were introduced.The status quo of domestic and international research on risk assessment of subways was described.Based on this,the content and route of this paper were proposed.2.Describe the theoretical basis of the metro risk assessment,including the definition of risk,risk identification,risk estimation,risk assessment,and related evaluation methods,and introduce the grading standards and acceptance criteria of engineering risk.3.According to the existing Nanning Metro project construction data combined with the investigation of the Nanning subway construction site,two different construction techniques are applied to the station pit and shield drive,from the project's own risk,geological condition risk,and surrounding environmental risk.Carry out risk identification and establish a multi-level evaluation index system for the construction risk of subways in the karst area of Nanning.4.Using fuzzy comprehensive evaluation method to construct the risk evaluation model of subway construction in karst area of Nanning city,detailedly introduce the selection of risk assessment factors,the selection of evaluation sets,and the calculation method of membership degree,and obtain the weight of each riskindicator through the analytic hierarchy process.Finally,hierarchical fuzzy operations are performed.5.Apply the risk assessment model to Liangqing Station and Liangqing Station to Lutang Village Station of Line 4 of the Nanning Metro Line,and construct risk histograms of different risk types at stations and intervals through fuzzy calculations to quantify qualitative issues.,and then visualize.Explain the causes of the risks,and finally,according to the results of the relevant pre-control or control measures,the maximum possible reduction in risk losses.