Risk Assessment Of Collapse In Construction Of Mountain Railway Tunnel

With the rapid development of tunnel construction in China,the collapsed accident in the mountain railway tunnel construction process has become a significant problem.Because of the complex and changeable terrain and geomorphologic environment and severe natural conditions,collapsed accidents occur continually in the construction process of the mountain railway tunnel,so that cause great economic losses and casualties.It is of great practical significance for researching collapsed exposure rating of the mountain railway tunnel.Hence,this paper promotes mathematical model and theoretical analysis as the primary research means,explores and proposes a new evaluation method,and pus into use it to engineering practice for proving the viability of this way.Based on the above,through the statistical analysis of a mass of examples on mountain tunnel collapsed aspect,choose the primary factors of the tunnel collapsed,and the mountain railway tunnel collapsed risk model is established based on criterion system and method of evaluation,Bayesian network analysis way and extension evaluation way.The main work contents and research results are as follows:(1)Based on the statistical analysis of many cases for railway tunnel collapse in mountainous areas,the risk factors affecting tunnel collapse are obtained,covering four aspects: geological elements,design factors,construction elements and management factors.The impact of all kinds of factors on tunnel collapse is analyzed qualitatively.On this basis,united with the construction peculiarity of the mountain railway tunnel and the accident causation theory,the primary factors inpressing the collapse were deemed as surrounding rock classification,underground water,fault fracture zone,geological exploration and monitoring measurement,etc.,(2)Mountain railway tunnel structure collapsed incident Bayesian network model is established,the vague set theory is used to quantify the risk elements of tunnel structure,the Bayesian simulation software Netica was used for quantitative research,and diagnostic reasoning of risk accidents,the probability of tunnel collapse accident was obtained by prior probability inference,the importance sort of risk elements was obtained by posterior probability inference,and the sensitivity of risk elements to top events was obtained by susceptibility analysis.(3)A multi-level extension evaluation model for landslide risk assessment in mountain railway tunnel construction is established,the influence weight of each risk factor on tunnel collapse is calculated based on the extension assessment measure of AHP,the relevant function in extension mathematics is applied to delineate the risk class of the model assessment indicator,and the multi-level extension evaluation is proceeding.(4)Taking a tunnel as the research object,the above theoretical and risk assessment models are used for comprehensive example verification.Acquired the quantitative assessment consequence.Thus the reasonability and practicability of the risk assessment model are demonstrated.