Study On Construction Risk Assessment And Countermeasures Of Tunnel Entrance Project Of High-speed Railway In Cold Region

With the construction of high-speed railway tunnels in cold regions,more and more construction risks are exposed.As the throat of the tunnel,the tunnel entrance section is often affected by rain,snow,strong wind and temperature changes.Therefore,the construction risk of the tunnel entrance section is even more severe,it is obvious that it is extremely critical to find the risk factors for the construction of high-speed rail tunnel openings in cold regions and formulate scientific and effective solutions.Relying on the construction of a tunnel on the Hamu passenger line,the risk assessment and countermeasures of the construction of the tunnel opening of the high-speed railway in the cold region were studied.Firstly,the composition and construction process of the high-speed railway tunnel entrance section are expounded.The construction safety accidents of typical tunnel entrance sections in China from 2000 to 2021 are counted,and the classification and analysis are carried out to determine the safety impact of high-speed railway tunnel entrance engineering construction in cold regions,factors to lay the foundation for further construction risk identification.The WBS-RBS method is used to identify risks in the construction of high-speed rail tunnel openings in cold regions.For the three stages of side(elevation)slope excavation and protection,end wall type opening construction,open-cut excavation and buffer structure construction,the WBS method is adopted.Decompose the work flow to obtain the work breakdown structure diagram;use the RBS method to decompose the construction risk from five aspects of man,machine,material,method and environment,and obtain the risk decomposition structure diagram;then carry out WBS-RBS coupling to establish each construction stage.Finally,a list of risk factor indicators at each stage is listed to determine the main risk sources that may occur in the construction of high-speed rail tunnels in cold regions.A construction risk evaluation model is established,4 first-level indicators and 42second-level indicators are set as the indicators of the risk evaluation system,and the weight of the indicators at all levels is determined by the analytic hierarchy process.Taking the construction of a tunnel entrance project on the Hamu passenger line as an example,the risk assessment is carried out,and the multi-level extension theory is used to divide the risk level domain,determine the classic domain and section domain of the risk assessment index,and then combine the weight of the risk index to calculate each the correlation degree of the grade index is used to determine the construction risk level of the tunnel entrance section as level 3,which is highly dangerous.Considering the measured data on site,the weight of each index and the risk level comprehensively,we propose countermeasures in terms of thermal insulation of Mingdong lining construction,excavation of frozen layer side(elevation)slope,support,waterproofing and drainage,up arch constructionas,well as construction quality and safety,so as to reduce safety risk level and economic loss,ensure the personal safety of construction personnel,and provide practical reference for subsequent similar projects.