Study On Safety Risk Assessment Of In-situ Expansion Tunnel

In recent years,with the increase of traffic volume,existing tunnels have been rebuilt and expanded to solve the traffic pressure.In-situ expansion is the excavation of existing tunnels to form larger-section tunnels.It is one of the main forms of tunnel reconstruction and expansion.Different from the new tunnel,existing linings need not only be dismantled but also maintain the stability of the surrounding rock.The construction process of the expansion process is complex,and the surrounding rock undergoes multiple disturbances,and the construction process is prone to safety risk accidents.This article analyzes the frequently occurring and hazardous landslide accidents in the construction process,based on the Decision Making Trial and Evaluation Laboratory analysis method to identify the main factors affecting the landslide accidents in in-situ expansion tunnels and the interpretative structural model analysis method to analyze the mutual influence relationships between various factors.Hierarchical structure is divided,a landslide risk assessment index system is established,and fuzzy fault tree theory is used to estimate the probability of occurrence and loss.Finally,apply the established model to the project instance.The research work done and the results achieved are:(1)Statistically analyze the project characteristics of the tunnel collapse project and the engineering characteristics of the in-situ expansion tunnel,and identify the accidental factors that affect the risk of landslides during the renovation and expansion tunnel.Based on the DEMATEL-ISM method of risk accident factor analysis model,the correlation between factors was analyzed.Through the hierarchical analysis of the results of the identification,the direct,transitional,and underlying factors affecting the collapse accident of the in-situ expansion tunnel are obtained,and the accident law of the collapse is analyzed.(2)A preliminary overall risk assessment system for the construction of in-situ expansion tunnels was used,and preliminary risk assessments were conducted prior to construction.(3)A special evaluation index system was established through a hierarchical model of risk factors.Based on the fuzzy fault tree theory,risk probability,risk loss.and fuzzy safet?importance were quantitatively analyzed to deterimine the risk level.(4)The risk assessment model and assessment proccse established in this paper are applied to an in-situ tunnel expansion project.The assessment results obtained are in great agreeement with the actual project conditions,verifying the established in-situ expansion tunnel risk assessment.The research results provide guidance for the safety of in-situ expansion construction,which has good practicability and feasibility,and at the same time enriches the risk assessment method system for tunnel reconstruction and expansion.