چكيده به لاتين
Absence of sub ballast layers in a railway track causes direct contact between the ballast and the substructure, and causes abrasion of substructure by ballasts. Such abrasion creates substructure abrasion and produces fine soil. The fine soil is combined with water and therefore mud will be produced, which can be pumped into the ballast and can generate a great number of problems. The use of Geotextile between the ballast and the substructure is one of the ways to prevent mud pumping into the ballast. The main and most common failures in the use of geotextile as a filter between the ballast and the substructure are clogging and blocking of the geotextile pores. Therefore, the evaluation of the effective age of the geotextile filter subjected to different conditions of mud pumping has a considerable importance in the analysis of the material used in railway track and their performance.
In this thesis an innovative apparatus—simulator mud pumping in the railway track—is used for the evaluation of the geotextile filter performance in different conditions of mud pumping. Parameters such as the slurry concentration (weight ratio of soil/water), the axle load, the train velocity, and the apparent opening size (AOS) of geotextile, which are known as the parameters that affect the filter age, are studied. (slurry volume crossing the geotextile)/(watter volume crossing the geotextile) is considered as a criterion to determine the ultimate age of the geotextile filter. The experimental results show that the ultimate age of the Geotextile filter decreases 86.6 percent as the slurry concentration increases from 1/15 to 1/2 . Also, results from investigating the influences of different axle loads demonstrate no effect of such parameter. In addition, it is observed that by decreasing the velocity from 300 to 100 km/h, the ultimate age of the Geotextile filter decreases 57 percent; and by reducing AOS from 0.2 to 0.06 mm, the ultimate age reduces 69 percent.
Key words: Geotextile filter, clogging of Geotextile, mud pumping simulator, slurry concentration, Apparent Opening Size (AOS), the ultimate age of geotextile.
