Mountain Tunnel Earthquake Damage Mode And Its Performance Index Research

Judging from the earthquake damage investigation of large earthquakes in the past,the underground structure of the tunnel has been seriously damaged,indicating that the design method of the tunnel underground structure can not fully meet the seismic demand.In view of the importance of urban rail transit,its performance-based seismic design has been developed,and some of its results have been incorporated into the norm.In comparison,the seismic design method of the mountain tunnel is still relatively backward,but it plays a role in the traffic network.The more important the role,the corresponding performance-based seismic design method should also receive more attention and research.In the performance-based seismic design,the difficulty is the quantitative index corresponding to different performance levels.In the urban rail transit underground structure,the rectangular and circular section structures are checked by the inter-layer displacement angle and the diameter deformation rate,but the mountain road tunnel Most of the structures are arched sections,and the structural sections have large differences,which directly determines that the deformation verification method cannot be copied rigidly.Therefore,this paper takes the arched section structure of the mountain highway tunnel as the research object,and draws on the existing research methods of quantitative indexing,and obtains the quantitative index of the different performance levels of the arched section structure of the mountain highway tunnel.The main results of the paper are as follows:1)Analyze the dynamic time history response of the mountain tunnel structure under earthquake action,analyze the calculation results of stress,equivalent plastic strain and stiffness damage;summarize the earthquake damage mode of the mountain tunnel structure by seismic damage investigation and literature review.The failure mechanism is compared and the failure mode and failure mechanism are compared with the dynamic time history calculation results to illustrate the reliability of the dynamic time history analysis modeling process.2)The differences between the calculation results of the dynamic time history method and the pushover method are compared and analyzed.The seismic calculation of the mountain tunnel structure is carried out by the pushover method,and the variation law is analyzed.The pushover method is used to resist the earthquake in the mountain highway tunnel structure.In the analysis,there is a high applicability.Based on the analysis method,the damage process of the tunnel lining structure is quantified based on the magnitude of the stiffness damage value.A variable four-hinge arch system for evaluating the overall failure of the tunnel lining structure is proposed.3)Qualitatively describe the four different performance levels of the tunnel structure according to the failure mode and failure sequence of the tunnel structure,and define the corresponding seismic performance index of the relative deformation rate.Use the pushover method to carry out the different buried depths and different surrounding rock parameters of the tunnel structure.The transverse seismic analysis of different concrete grades and different lining thicknesses,statistical analysis of the calculation results,and considering the structural response characteristics and the actual seismic damage types,preliminary determination of the quantitative control values of the performance indicators corresponding to different performance levels.In this paper,the quantitative index control values corresponding to the different performance levels of the arched section structure of the mountain tunnel are preliminarily obtained,which provides some meaningful references for the deformation check of the seismic design of the mountain tunnel.