Vol. 52 No. 4 December 2021
Resilient Deformation Characteristics of Unsaturated Subgrade Materials of Rail Tracks under Cyclic Moving Wheel Loads
T. Ishikawa, B. Dareeju, C. Gallage, and L. Tianshu
ABSTRACT: Water content of rail track subgrade materials fluctuates throughout the year due to the number of wetting and drying cycles, introducing unsaturated properties into the subgrade. Conservative rail track design guidelines are, however, mainly based on two extreme saturation conditions: fully dried or fully saturated. Current knowledge on the effects of subgrade water content on residual and resilient behaviour of the track foundation under the effects of Principal Stress Axis Rotation (PSAR) is limited and the potential of expansibility of foundation materials further upsurge the complexities towards the designing of the rail tracks. This study demonstrates the contributions of the PSAR on the resilient behaviour of foundation materials. Three different materials, including an expansive soil type have been subjected to drained cyclic vertical and torsional shear tests in a Modified Multi-Ring Shear (MMRS) apparatus and it is concluded that the resilient behaviour of the foundation materials is functions of the PSAR, material type, water content, and potential of expansibility.
KEYWORDS: Unsaturated foundation materials, Principal stress axis rotation, Resilient behavior, Expansive potential.
