Research On Safety Risk Assessment And Its Application In Long And Large Tunnel Construction

The construction of long and large tunnels usually takes remarkable social and economic benefits, which also has great strategic significance. In recent years, a lot of long and large tunnels have been constructed in China. At the same time, the construction technique is developing quickly. The two properties of long and large tunnels respectively expressed as "long" and "large" represent more complex hydrological and geological conditions, more risk factors, higher construction difficulties and risks. Accidents occurred frequently during the construction of long tunnels. Therefore, construction risk assessment and management of long and large tunnels are necessary.In this paper, a construction risk assessment model of long and large tunnels is derived by using the method of literature research, field investigation, expert survey, statistical analysis, fuzzy mathematics and so on. The model is applied in Yakou tunnel which is a part of ChengKun railway. The main research contents and conclusions are as follows:(1) The influence factors of various typical accidents are summarized in detail based on the analysis of 296 tunnel construction accidents of China. The index system of risk assessment for the construction of the long tunnel is established by combining with the existing research results, project site surveys and expert advices.(2) Risk assessment model of long and large tunnel is established by using fuzzy AHP comprehensive evaluation method and expert investigation method. The risk probability level is estimated using the fuzzy AHP comprehensive evaluation method. The risk loss level is estimated using expert investigation method. The risk loss level is determined by analyzing the survey results.(3) A index system for tunnel risk evaluation is established based on the accident analysis and expert advice. The index weight is obtained by building comparison matrix, calculating eigenvectors of each matrix and checking their consistency. The membership function of the construction risk index is determined using trapezoid distribution function.(4) According to the existing tunnel risk assessment standards and guides, the risk assessment process, risk rating standard, index evaluation standard and risk control system of long tunnel are proposed.(5) The database of tunnel accidents, which can be used to input and query accident information, is established based on the SQL server. A long tunnel risk assessment program is developed using C# language.(6) The risks of Yakou railway tunnel is estimated using the assesment model derived in this paper. It reveals that the construction risk level of Yakou tunnel is Grade â…£ which belongs to a unexpected area. After taking control measures, the risk level reduced to Grade â…¢ for the reassessment, which is consistent with the conclusion assessed by experts.