چكيده به لاتين
The ballast tracks form a large part of Iran's railroads. The entry of fine aggregates (pollutants) into the ballast tracks weakens their performance and safety. Contamination commonly come come from breakdown of the ballast aggregate, outside contamination such as coal dust from coal trains and sand, or subgrade soil intrusion. Passing a significant portion of Iran's railroad tracks from desert areas is subjected them to contaminated with sandstone. The shear strength plays an important role in maintaining track stability and preventing accidents such as derailment. Adding water to these conditions can make the problem worse even lead to track instability. For this purpose, a laboratory plan basis on a large-dimensional direct shear test was carried out. Samples with 4 levels of contamination of 14%, 21%, 28% and 35%, and 4 different moisture content of 6%, 9%, 12% and 15% were tested. The results showed that increasing the amount of water injected into the specimen resulted in a decrease in shear strength at any given contamination level. Comparison with the results of this study with dry sand shows that with the presence of water, a decrease in shear strength is high. Expansion behavior of samples was also measured by measuring vertical deformation of samples during loading. In this case, the comparison of results with sand samples (dry) indicates that the presence of moisture decreases in the dilatation of the sample. Investigation of wet samples with different moisture content showed that by increasing the moisture content, the amount of dilution of the samples is reduced.
Keywords: Ballast, Wet sand, Large-scale direct shear test, Shear strength, Expansion behavior.
