Evaluation of the effect of water saturation on the strength of individual railway ballast aggregate

Decreasing the hydraulic conductivity of railway ballast course can lead to the saturation of aggregate which can adversely affect the proper performance of this structural layer. The main objective of the present study is to investigate the effect of saturation on the strength and failure behavior of ballast material. For this purpose, the point load test (PLT) characterized as a simple portable test method for evaluation of the strength of rock material is carried out on both dry and saturated hexahedron-shaped individual ballast particles to assess the effect of water saturation on mechanical properties of aggregate. The ballast aggregate samples obtained from different quarries are sieved into three specific size fractions. In addition, saturation period of one and three weeks is separately established to further consider the influence of the saturation on the ballast strength. Obtained results show decrement of estimated point load strength index by increasing the size of individual ballast particle for both dry and saturated aggregate. Although, the strength of material is less size dependent for saturated ballast samples. Furthermore, saturation of specimens changes the failure pattern of particles as such the saturated ballast aggregate are mainly split into two segments.