چكيده به لاتين
Ballast track is the most common track and infrastructure used in rail transportation. However, the settlement, deterioration and failure of the ballast aggregates leads to an increase in the maintenance and repair costs and, as a result, a decrease in the efficiency of the track due to its blockage. Extensive research has been done to improve the behavior of high-grade materials with the aim of increasing the useful life of the line. One of the ways to improve the properties of the ballast is to use worn-out tires. A review of the technical literature shows that railway engineers are facing a serious challenge for the use of crumb rubber in the ballast layer. In other words, laboratory studies show that the resistance and hardness of the ballast layer is often reduced due to the addition of rubber particles, which is a weak point worthy of consideration. On the other hand, the crushing, abrasion and energy absorption properties of ballast materials have been improved. Another important point is that the trend of the results obtained regarding the effect of adding crumb rubber on the high settlement in the studies of researchers are different and sometimes contradict each other. Therefore, in the present research, finding the optimal and selected gradation of rubber crumb according to the gradation of ballast in order to reduce breakage and wear of ballast aggregates and to limit the settlement of ballast layer affected by rubber crumb has been studied. In this regard, to check the settlement, hardness and damping of ballast materials, a cyclic loading test has been performed using a ballast box device. Also, the Los Angeles test has been used to check the fracture and abrasion of aggregates. It should be noted that the ballast samples prepared for the aforementioned tests contained 0, 5, and 10 percent by volume of crumb rubber with dimensions of 1, 10, 20, and 30 mm. The obtained results show that the volume percentage of rubber shards of 10% with a size of 10 mm as optimal crumb rubber can reduce the settlement of the ballast layer by 12.9%, and also the damping property of the ballast is increased by 87.5%, and the crushing of aggregates and their abrasion decrease by 12.1% and 13.2% respectively.
