Railroad subgrade stabilization using biaxial geogrid-geotextile composite: a case study

摘要

Construction of ballasted rail track-beds on saturated soft and compressible fine-grained soils involves significant design challenges. It needs to be ensured that under the repeated rail traffic loads, the track foundations do not cause problems due to excessive plastic deformation and progressive shear failure. Solutions include use of thick sub-ballast layer, excavation and replacement, soil stabilization and use of geosynthetics. This paper presents a case study where Canadian National Railway (CN Rail) used a biaxial geogrid composite to stabilize the poor subgrade comprising very soft and saturated clay in swampy conditions. The project is the additional 6-track extension for CN Rail at the Transcona yard in Winnipeg, Manitoba, Canada, where it was required to design and construct a competent formation on the weak subgrades. The solution proposed comprised placing a biaxial geogrid-geotextile composite on the poor subgrade. The product comprised a stiff polypropylene biaxial geogrid bonded to a polyester nonwoven geotextile. The composite combines the high tensile stiffness/modulus of the geogrid along with superior hydraulic characteristics of the geotextile and hence can function as a separator, filter and reinforcement. The proposed solution was found to be simple, easy to construct, effective, environmentally friendly and economical.