چكيده به لاتين
The objective of this study is to investigate the effects of different stiffness values of Under Sleeper Pads (USP) and Unconfined Compressive Strength (UCS) values of mother rocks of ballast aggregates in the degradation of railway ballast. In the beginning the mechanical specifications of two types of soft and hard USP used in this research were presented. In the following, the physical and mechanical characteristics of the ballast aggregates of the three Shahriar, Anjilavand, and Kouhin quarries in Iran were obtained via a series of standard lab tests, such as the UCS and other characteristics, and the results were presented. The UCS of core specimens taken from the mother rocks of the mentioned queries were ranked as low value (159 MPa), medium value (216 MPa), and high value (285 MPa) respectively. Finally, by selecting the used grain size, 27 ballast box test laboratory experiments with presence of USPs with two different stiffness values and without USP under 200,000 loading and unloading cycles were carried out. Experiment results were extracted in the form of settlement, ballast breakage index (BBI), ballast stiffness, and ballast Damping Ratio (DR). The results illustrate for ballast of Shahriar quarry by increasing of the USP’s stiffness from hard to soft USP, settlement, BBI, and stiffness have decreased by 16.6%, 7.9%, and 34.6% respectively and DR has increased by 114.66 % while these reported percentages, i.e. settlement, Br, and Stiffness have decreased and DR has increased after strengthening the ballast mother rock in the cases of Anjilavand and Kouhin quarries. On the other side, based on the achieved results for all three categories of ballast strengths, the soft USP has shown the most suitable performance.
Keywords: Under Sleeper Pad, Ballast Box Test, PFC3D 0.5, Ballast Deterioration
