Study On The Influence Of Near-Fault Pulse Ground Motion On Ballastless Track Structure And Driving Safety

China has put forward the idea and task of further expanding the scale of highspeed railway construction in the new era.Combining with the actual situation that seismic zones are widely distributed and earthquakes occur frequently of in China,the technical requirements for high smoothness and stability of high-speed railway and the large proportion of ballastless track used in the construction of high-speed railway in China,it is necessary to research the seismic response and driving safety of ballastless track of high-speed railway.At present,there are few studies about the influence of ground motion characteristics on track seismic response,however,the near-fault ground motion has obvious pulse characteristics compared with the far-fault ground motion.Considering the above problems,under the assumption that no damage occurs on the under-rail foundation,CRTS II slab ballastless track structure on the subgrade is taken as the research object,and the following works are carried out:(1)The dynamic time history analysis method is selected to analyze seismic response in this paper.The finite element model of CRTS II slab ballastless track structure on subgrade is established.(2)Three groups of ground motion records are used in this study including the nearfault pulse-type records with forward-directivity pulse and fling-step pulses,and nonpluses records.The seismic responses of CRTS II slab ballastless track structure on subgrade are compared under the ground motions with and without pulse characteristics.The results show that the pulse effect of the near-fault ground motions can significantly increase the seismic responses of ballastless track structures.(3)Artificial synthesis of near-fault pulse-type ground motions is carried out,and the effectiveness of ground motion synthesis is verified by an example.The sensitivity of the seismic response of CRTS II slab ballastless track structure on subgrade to the three characteristic parameters of pulse peak velocity,pulse period and number of pulse is analyzed.The results show that different pulse characteristic parameters have different effects on the seismic response of ballastless track structure.(4)The vehicle-track dynamic analysis model under earthquake is established.Combining with relevant evaluation indexes,the driving safety under different nearfault pulse-type ground motion intensity and running speed conditions is analyzed.