Study On Construction Safety Risk Assessment Of Underground Utility Tunnel In Collapsible Loess Area

With the continuous advancement of urbanization,the number of municipal pipelines,such as water,electricity and communication,is increasing,resulting in chaotic distribution and management of underground pipelines.Urban underground utility tunnel can make effective use of underground space,bring all kinds of pipelines into utility tunnel for unified planning and management,solve the problems of poor city image such as "road zipper" and "aerial spider web",and at the same time greatly improve urban disaster prevention ability and improve urban functions.Because the urban underground utility tunnel started late in China,and the construction in utility tunnel often faces the following complicated situations: long construction period,crossing existing buildings(structures)and special geology,etc.,which increases the construction difficulty.Especially in collapsible loess areas,safety accidents are more likely to occur in utility tunnel construction in this area due to the collapsible nature of loess,and the consequences are more serious.Among the existing research results,the research on the safety risk of pipe gallery construction characterized by collapsible loess area is in the exploratory stage,and there is still a lack of systematic theoretical and practical guidance.Therefore,this paper will study the mechanism of construction safety risk of utility tunnel in collapsible loess area,analyze the construction risk level of underground utility tunnel in collapsible loess area by using extension cloud method,deepen the understanding of risk,and then use Monte Carlo simulation to find out the key factors affecting the construction safety of utility tunnel in collapsible loess area,and then put forward corresponding control measures.Firstly,based on the risk analysis theory,this paper systematically analyzes the safety risk factors from five dimensions: man-made,management,construction technology,mechanical materials and environment.By means of questionnaire survey and literature analysis,the preliminary list of pipeline corridor construction risks is determined,and the risk index system of pipeline corridor construction safety system in collapsible loess area is constructed.Secondly,the data obtained from the questionnaire are sorted and analyzed,and the extension cloud model of multi-risk factors based on fuzzy rough set is constructed.By calculating and quantifying the risk levels of five-dimensional risk factors,16 high-risk factors are initially identified;Through the case analysis of a utility tunnel project in beilin district,Xi ’an,the above 16 key risk factors are quantified,and the Oracle Crystal Ball software is used to simulate and find out that there are 8 sensitive factors;The sensitivity of control variables to the whole system is analyzed,and the influence of risk factors on the development trend of the whole system risk level is dynamically observed.Finally,the risk control measures corresponding to sensitive factors are put forward,and the risk control measures are supplemented from three aspects: organizational measures,mechanism management and information technology guarantee,which further improves the research theory of construction safety risk in utility tunnel in collapsible loess area.