Effect of an Embankment Reconstruction Using a Wicking Geotextile in the Drainage and Strength of Subgrade

  • Author / Creator
    Alvarenga, Camila B. S. De
  • Railways are essential for the transportation of goods and people and are an integral component of Canada’s economy (Leishman et al. 2017). As a part of the Canadian Pacific Railway’s (CP) Grade Stabilization/Remediation Plan, a 45 m section of a railway embankment located at Fort Saskatchewan County in Alberta, Canada, was remediated. The reconstruction consisted of replacing ballast and sub-ballast with clean materials and installing two geotextiles: a 4.6 m wide reinforcing geotextile (Mirafi® RS580i) and a 7.3 m wide wicking geotextile (Mirafi® H2Ri). The first was placed in the ballast and sub-ballast interface, while the second was placed between the subgrade and sub-ballast, aiming to address issues such as poor drainage and moisture retention. This site provided the opportunity of observing the enhancement of drainage brought by the performed reconstruction, as it enables testing adjacent remediated and control sections. This process facilitates the direct comparison between these locations. The site materials were tested in the laboratory. Both sections were instrumented with 5TE sensors, which can determine the volumetric water content (VWC), bulk electrical conductivity, and temperature from the soil around, aiming to compare the sections regarding their moisture levels directly. A Diviner 2000 probe was also used to read moisture profiles at each site visit. Precipitation data was acquired from weather stations near the study site and compared to the VWC levels seen at the site. A known method that relates the VWC and precipitation called the antecedent precipitation index (API) was used to ease the understanding of precipitation events' influence in the variation of moisture content and strength of the embankment at both sections.
    The key findings of the first year of monitoring are that the remediated section VWC levels were less sensitive to precipitation events than the ones from the control section. No changes were observed in VWC of the remediated subgrade, even with high amounts of precipitation. However, higher VWC levels were observed at the remediated subgrade compared to the control section in October/2020 after a long period without precipitation took place. A series of factors could contribute to this observation.
    The remediated section presented consistent strength levels throughout the study and presented a significantly higher minimum strength level than the control section. Therefore, the remediation done potentially improves the embankment bearing capacity during periods of heavy rainfall. This improvement may be beneficial for mitigating the issues seen at the site before the reconstruction.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.