Evaluation Study On The Puji Tunnel Safety Risk Of The New Tunnel

In recent years,with the rapid development of the transport industry,China has paid more and more attention to infrastructure and invested a lot of money on the road,the bridge and the tunnel construction.The tunnel has played a more and more important role for its convenience,time-saving,and little destruction on environment.Since the highway transport volume increases,the standard of highway alignment raises and the number of highway and tunnels has also increases.In this context,it appears that a lot of new tunnels are close to existing railway tunnels or in parallel,and results in an increase of construction difficulties,which is affected by excessive construction of tunnels,the limits of geology,terrain,space conditions and so on.The paper is based on Puji Tunnel in Yunnan Province.Its rock grade is third-level and belongs to weak rock.According to the data and information provided by the project,the survey,theoretical research and related calculations are conducted and the results are as follows.(1)The construction risk analysis is carried out in the open-cut tunnel section of the right line and it turns out to be the pit supporting construction with the highest level of risk(grade ?),the gob and coal strata construction with the medium level of risk(grade ?),and the supporting pile and front slope construction with the second level of risk(grade ?).(2)Based on t he geological conditions and construction method of Xinling Tunnel,the construction risk analysis is carried out in hidden-burying section,especially main risk factors like collapse,drainage,gas risk,and large deformation of the liner.Therefore,measures and suggestions to reduce the risk of Xinling Tunnel construction are proposed.(3)According to the actual geological conditions of the project,the new tunnel was analyzed by the numerical simulation software�ANSYS,and constructed by the bench cut method.According to the numerical analysis of three dimensional modeling,the stress concentrations at the local places of primary support and surrounding rock are observed.The force values of primary support and surrounding rock were lower than standard design ones,which satisfied the strength requirement.The displacements of primary support and surrounding rock both meet the requirement of the specifications.At last,the blast was analyzed and turned out that the blasting vibration was in the range of codes and had a small influence on vehicular traffic.