Evaluation of shear strength parameters of rail track ballast in Sri Lanka

Abstract

In Sri Lanka the ballasted rail tracks are the most preferred by the railway authority due to low initial investment and it continues using crushed rock as rail track ballast. Regardless of the frequent usage of these aggregates as track ballast in Sri Lanka, their shear strength characteristics have not been scientifically measured or used in design. The primary purpose of this paper is to present the investigation of shear strength properties of fresh and fouled rail track ballast in Sri Lanka using a large-scale direct shear device, which accommodates actual size ballast particles. The shear stress–strain and dilation behaviour of fresh and fouled ballast were obtained and the internal friction angle was estimated. The results showed that the shear strength of fresh ballast is higher than that of the fouled ballast and the shear strength envelope better resembled non-linear behaviour. Also it was revealed that the internal friction angle of ballast tends to reduce with age. More realistic shear strength parameters as proposed by the test results would promote state-of-the-art practice for the design of ballasted rail track foundations.