Performance assessment of peat rail subgrade before and after mass stabilization

Abstract

Railway tracks over peat subgrades can experience large ground deformations, increased pore-water pressures, formation of pumping holes, and pumping of fines during the passage of trains, which can lead to accelerated track deterioration and risk of derailment. One approach to mitigate these issues is to improve the subgrade stiffness using mass stabilization, which involves mixing a binding agent, such as cement, into a soil to improve its physical properties. This paper describes the development and use of a method to calculate trackbed modulus to quantify the improvement due to mass stabilization at a site with peat subgrade. Track modulus was calculated using in-service freight trains by measuring track displacements using digital image correlation and wheel loads from a nearby wheel impact load detector. Because of the voids that existed between the rail, sleepers, and ballast it was found that using displacements of the ballast crib to calculate the trackbed modulus, instead of the overall track modulus using rail or sleeper displacements, provided a way to quantify the improvement of the subgrade that was not affected by the presence of voids. The results indicate the post-rehabilitation trackbed modulus was double the original baseline value for the track section, indicating that mass stabilization can be an effective rehabilitation strategy to improve the stiffness of problematic peat subgrades.