Research On Accumulated Deformation And Resistance Evolution Characteristics Of Large Ramp Meter-gauge Ballast Bed

Meter-gauge railway in the Chinese western mountain areas is imminent.One metergauge railway that has been constructing runs through arduous mountain roads,which has the250‰ maximum designed ramp on this line.The ballast bed will bear a relatively large longitudinal load,deform under the long-term load of the train,and will also affect the resistance of the ballast bed.Therefore,this paper has carried out the research on the accumulated deformation and resistance evolution characteristics of the large ramp metergauge ballast bed through laboratory experiment and discrete element simulation.The use of discrete element software for simulation first needs to calibrate the micro-parameters of the ballast.Then the resistance changes of concrete sleeper and steel sleeper are compared and analyzed.And combined with ballast box test and simulation,the accumulated deformation characteristics of concrete sleeper and steel sleeper are analyzed separately.Finally,the large ramp meter-gauge ballast bed test was carried out,and combined with simulation,the accumulated deformation and resistance evolution characteristics of the large ramp metergauge ballast bed were analyzed.The specific research contents and results are as follows:(1)Based on the PFC discrete element software,the real ballast particles are established,which can reflect the occlusion between the ballast particles.The friction coefficient of the ballast is calibrated by the cylindrical pile bottom test,and the normal stiffness and shear stiffness of the ballast are measured by the compression test.And the meso-contact parameters of the ballast were obtained.(2)Through experiments and simulation comparisons,the difference in resistance performance between concrete sleeper and steel sleeper on the meter-gauge railway is analyzed.The concrete sleeper of the meter-gauge railway is stronger than the steel sleeper in terms of maintaining stability.The impacts of the height shoulder,the shoulder width and the ballast bed slope grade are explored on the ballast bed resistance of the meter-gauge concrete sleeper and steel sleeper,and the influence of the stiffened steel sleeper on the resistance of the meter-gauge steel sleeper ballast bed is analyzed.(3)Combined with the ballast box test and simulation,the accumulated deformation characteristics of the meter-gauge concrete sleeper and the steel sleeper ballast bed are analyzed.The results show that the settlement performance of the steel sleeper ballast bed is better than that of the concrete sleeper ballast bed.In addition,the influence of load frequency on the accumulated deformation of the two sleeper ballast beds and the vibration response law of the ballast under different load frequency are explored.The mechanism of the accumulated deformation of the ballast bed is explained from the angular velocity of the ballast rotation.The violent rotation of the particles leads to a rapid increase in the accumulated deformation of the ballast bed.(4)The test and simulation of ballast bed with steel sleeper on a large ramp of 250‰ have been carried out.The results show that the lognitudinal and lateral resistance of the steel sleeper on the large ramp with ballast beds does not change much before and after cyclic loading.The lognitudinal and lateral stability of the meter-gauge steel sleeper ballast bed is better at the 250‰ large ramp,and the final accumulated deformation of the large-ramp metergauge ballast bed is small.And the accumulated deformation and resistance characteristic of the meter-gauge ballast bed with large ramp and flat ramp are compared and analyzed.The influence of different ramps on the meter-gauge steel sleeper ballast bed is further studied,when the ramp exceeds 50‰,the porosity of the ballast bed will increase and the resistance of the ballast bed will decrease.Finally,the influence of passing load frequency on the accumulated deformation and resistance changes of the 250‰ large-ramp meter-gauge steel sleeper ballast bed is studied,and the passing load frequency and driving speed range that effectively suppress the accumulated deformation and resistance loss of the 250‰ large-ramp ballast bed are recommended.