Safety Risk Management And Control Of Deep Foundation Pit Construction Of A Subway Station In Dalian Based On DMAIC Model

With the continuous development of society and the continuous increase of urban population,the problem of road congestion is already the biggest problem to be solved in each city,and the development of the subway can effectively alleviate this problem.Due to the characteristics of large scale,high risk and great interaction with surrounding environment,it is particularly important to establish a scientific and efficient construction risk management and control system to realize the closed-loop management of risk identification,evaluation and control in the whole process of subway construction.This study takes the deep foundation pit project of a subway station in Dalian as the research object,based on DMAIC(Define,Measure,Analyze,Improve,and Control)models,combined with the actual situation of the project,realize the scientific,process and layering of safety risk management for the construction process of the deep foundation pit project of the subway station.(1)Based on WBS-RBS coupling matrix method,the safety risk list of deep foundation pit construction process was established: Combined with the actual situation of the project,the WBS work breakdown structure is used to divide the station deep foundation pit construction process into six stages;The RBS risk decomposition structure is used to analyze the risks of the deep foundation pit construction process of the station from the aspects of personnel and equipment.Construct a WBS-RBS coupling matrix to identify 39 safety risk factors that affect the normal operation of deep foundation pit construction,and build a safety risk list for subway deep foundation pit construction on this basis.(2)Based on rough set theory,a safety risk assessment index system for the construction process of deep foundation pits is constructed: On the basis of the safety risk list,the attribute reduction of the initial safety risk list is carried out by using the rough set theory,and 22 key risk factors are screened out.On this basis,the safety risk evaluation index system of a station deep foundation pit construction process of Dalian Metro Line 5 is constructed.(3)Based on the improved matter-element extension model,a safety risk assessment model for the construction process of deep foundation pits is constructed: The matter-element extension model was improved,and the entropy weight method was used to determine the index weights in the improved matter-element extension model.The results show that except for the construction of casing occluded piles and steel bracing,the other construction processes and the overall safety risk level of the station are all lower.Therefore,the corresponding improvement suggestions and countermeasures are proposed for the construction phase of casing bite piles and steel support.(4)Build an information platform for risk grading management and control of hidden foundation pits and investigation of hidden dangers:Combined with the dual prevention mechanism,establish the information platform of risk level management and control andhidden danger investigation and treatment,carry out closed-loop management on the risks and hidden dangers in the construction process of deep foundation pit,and realize the function of supervision,inspection and timely feedback on the implementation of safety risk improvement measures and hidden danger investigation in the construction process.