| As the running speed of high-speed trains continues to increase,the shortcomings of ballastless tracks in high-speed railways have begun to become prominent.As the traditional track structure of railways and one of the important forms of high-speed railways,it has unique advantages in applicability,construction cost and maintenance.However,flying ballast,which is ubiquitous in ballasted tracks,poses a major threat to the safety and service life of high-speed trains and must be effectively controlled.It is necessary to study the generation mechanism and movement characteristics of flying ballast.In this paper,a single ballast model is first established,the dynamic and static numerical simulations of single ballast particles are carried out,and the movement laws of flying ballasts are studied,and the influencing factors of its movement characteristics are analyzed.Then,the aerodynamic simulation model of the high-speed railway ballasted track-car body coupling system was established,and the wind pressure and the surface wind pressure of the high-speed train and the ballast bed under cross-wind and random wind conditions were studied under the conditions of single-vehicle open-line and double-line crossing conditions.Wind speed distribution,analysis of the environmental conditions required to produce flying ballast.Finally,the ballasted beds with different size parameters are simulated,and the optimal ballasted track ratio that helps avoid flying ballasts is analyzed.The results show that in the static simulation of single ballast particles,flying ballast hazards are likely to occur when the wind speed increases,followed by the decrease of wind speed,and the ballast particles are not easy to move when the wind speed is constant compared to when the wind speed changes.The mass of three-dimensional ballast and flat ballast is directly proportional to the critical speed and inversely proportional to the moving distance.The critical speed of three-dimensional ballast and flat ballast is inversely proportional to the moving distance;three-dimensional ballast with a mass greater than 160 g and less than 130 g has a mass Flat ballasts larger than 75 g are not prone to flying ballasts.Ballasts of this type should be used on high-speed railway ballast beds.Under the open-line working condition of a cross-wind bicycle with a vehicle speed of 350m/s and a crosswind speed of 13.8m/s,the front,rear and car body bogies are likely to cause instability of the track surface ballast,and the wind pressure varies from-560 Pa to 380 Pa.The wind pressure fluctuates between-77 Pa and 340 Pa in the crosswind double-track working condition;the wind pressure and wind speed at the top of the ballast shoulder fluctuate the most drastically when the train passes.The maximum wind pressure is 430 Pa,the maximum The wind speed reaches 27m/s.When the wind field is random wind,the wind pressure distribution on the surface of the track bed satisfies: the small area negative pressure in the process of increasing wind speed under random wind is lower than that under cross wind,and the high pressure in large area is also higher;the wind speed under random wind decreases.In the process,the positive pressure in the small area is higher than that under the cross wind,and the low pressure in the large area is also lower.At the same time,the random wind strengthens the environmental pressure distribution when the two leading cars intersect and around the car body.Compared with the maximum positive pressure in the cross wind,the maximum positive pressure increases from 340 Pa in the cross wind to 1780 Pa,and the positive pressure range becomes larger;it also weakens The pressure distribution of the car body and its surrounding environment when the two trains and the tail cars are separated is compared with the minimum negative pressure in the cross wind from-77 Pa in the cross wind to-3729 Pa,and the negative pressure range is reduced.No matter in cross wind or random wind environment,the height of the ballast shoulder is 150 mm,the ballast height of the ballast bed center is 0mm,compared with the ballast shoulder height of 100 mm,the ballast height of the ballast bed center is 40 mm,and the flat ballast type ballast is easier.Cause flying ballast.That is to say: Compared with the flat ballast type,the pointed shoulder type is more likely to produce flying ballast on the surface of the ballast bed;the higher the height of the ballast shoulder,the lower the ballast at the center of the ballast bed,and the more likely it is to cause flying ballast hazards. |
