Moisture and soil strength monitoring of a railway embankment remediated with wicking geotextile

Abstract

A 45 m section of a railway embankment located at Fort Saskatchewan County in Alberta, Canada, was remediated as a part of the Canadian Pacific Railway’s (CP) Grade Stabilization/Remediation Plan. The embankment materials were replaced while a 4.6 m wide reinforcing geotextile (Mirafi® RS580i) and a 7.3 m wide wicking geotextile (Mirafi® H2Ri) were installed in the ballast and sub-ballast interface and between the subgrade and sub-ballast, respectively, aiming to address issues such as poor drainage and moisture retention. The studied site consists of an instrumented track including a remediated and an adjacent control section that provided the opportunity to measure volumetric water content (VWC) within the sub-ballast and clayey subgrade at both configurations. The VWC variation with seasonal weather change is continuously monitored by nine moisture sensors, and an antecedent precipitation index (API) model was developed to evaluate the influence of precipitation events on the VWC in both sections and to interpret the impact of the in situ VWC on the unsaturated strength of the soil according to the soil-water characteristic curve (SWCC) results. An initial evaluation of the moisture-suction relationship has shown that the subgrade soil strength is improving within the remediated section; nonetheless, these trends are anticipated to be more consistent with long-term observation.