الهه انديشمند

The development of railways in recent years, in turn, has increased the axial load, speed and frequency of loading of the passing trains and thus accelerated the deterioration of these tracks.In recent years, due to the deposition of worn tires and environmental issues, its use in crushed form in the composition of railway ballasts to reduce this deterioration of the track has been studied by experts in the field. In this dissertation, the ballast box test is simulated by developing a numerical model by discrete element method in EDEM software and the ballast is mixed with crumb rubber in this test by considering the real shape of the grains and with the aim of investigating effects such as the magnitude of the axial load and the loading frequency in the settlement, damping ratio and stiffness of the samples have been studied. For this purpose, the initial model of the ballast box was created by combining different percentages of ballast and crumb rubber in EDEM software and the loading results of 3 tons and 3 Hz of this layer up to the 1000th cycle were compared with the results of laboratory tests and valid eva‎luation. Then, the box with the optimal percentage of crumb rubber (5% by weight) based on the ballast composition was tested in the box and the effect of different types of loading (including magnitude and frequency of load) on it was studied. The output obtained from modeling was fitted to 1000 cycles and announced. The simulation results show that with increasing axial load and loading frequency of samples in the actual loading range of high-speed lines (80 to 240 km / h, equivalent to loading frequency of 11 to 33 Hz and axial load tonnage of 20 to 30 tons). The use of TDA of the same size as ballast grains maintains the settlement and stiffness of the ballast layer within the allowable range, and increases the damping ratio of the ballast layer by 2.5 to 18%, and also increases the stiffness of the line between 0.0504 and 0.1111 MN / mm. The results of the models indicate that the effect of cyclic load tonnage on the settlement rate of the ballast layer is more evident in the box test compared to the effect of the loading frequency. Also, the track stiffness decreases either with increasing loading frequency or with increasing axial load tonnage, although changes in line stiffness with lower loading frequency are less predictable. In addition, the damping coefficient of the samples at different loading tonnages at a loading frequency of 33 Hz is larger than at lower frequencies.

بالاست مخلوط با خرده لاستيك , آزمايش جعبه بالاست , روش اجزاء گسسته , نرم افزار EDEM , نشست

Ballast mixed with TDA , Ballast box test , discrete element method , EDEM software , settlement

elahe andishmand

dr. mortaza esmaeali