چكيده به لاتين
The study of ballast material degradation processes is crucial for predicting and extending the lifespan of these materials, reducing pollution, minimizing maintenance operations, and consequently lowering replacement costs. Generally, ballast stabilization and improvement methods can be classified into two categories: mechanical (e.g., the placement of geogrids, geosynthetics, rubber strips, etc.) and non-mechanical (e.g., asphalt injection, asphalt-cement grout injection, etc.). In recent years, rubber strips have been used as geogrids for soil stabilization. One of the important considerations before using recycled rubber in soil is assessing its environmental impact, particularly in terms of pollution. To date, there have been few studies on the use of rubber strips for ballast stabilization. This study focuses on the impact of rubber strips, which are made from recycled belts and known as Geo-Scraps, on the shear behavior of stone-slag ballast. The study was conducted on Geo-Scraps with a mesh size of 5×5 cm, placed at a depth of 12 cm from the bottom of the box in a large-scale direct shear test. A total of 30 tests were conducted on 0%, 25%, 50%, 75%, and 100% stone-slag ballast mixtures, both in normal and reinforced conditions, under three normal stresses (50, 100, and 150 kPa) with a horizontal loading rate (shear strain rate) of 1 mm/min on ballast grading group 4, as per the 301 publication of the Management and Planning Organization. The aim of this experiment was to determine the quantities of shear strength, vertical displacement, internal friction angle, and dilation angle. The results showed that with the reinforcement of the ballast and an increase in the stone-slag ballast mixture percentage in all tests, the maximum shear strength and internal friction angle increased, while the peak vertical displacement and dilation angle decreased. It can be stated that with an increase in the ballast mixture percentage from 0% to 75% in the unreinforced state, the maximum shear strength increased by 26%, vertical displacement decreased by 24%, the internal friction angle increased by 10%, and the dilation angle decreased by 25%. Furthermore, with the reinforcement of the 75% ballast mixture compared to the unreinforced state, the maximum shear strength increased by 24%, vertical displacement decreased by 28%, the internal friction angle increased by 7%, and the dilation angle decreased by 20%.