Presto Geosystems
GEOWEB® Retaining Wall Eliminates Track Instability and Reduces Maintenance
This article first appeared in the Railway-News magazine Issue 4 Track & Infrastructure edition, November 2022.
Wet Soils Cause Site Problems, Embankment Stability
An area along a medium-tonnage route that had a minimum of 14 freight trains per day (at typical speeds of around 81 kilometres per hour) had been an ongoing maintenance challenge for years. The section of track was on a mainline curve beneath overhead electric wires, which not only complicated maintenance efforts due to limited overhead clearance, but below grade, the track was experiencing settlement issues and profile problems that reportedly coincided with wet weather periods.
During one flood event in May 2010, a portion of the west slope was washed out. Local crews temporarily repaired the area with riprap and dumped rock on the east slope. The problems subsided for a while, but eventually, the same issues resurfaced, leading to continuous and costly maintenance.
The cause of the instability appeared to be the steep inclination of the fill embankment and periods of wet weather contributing to the base of the fill becoming saturated and losing strength. Cross-level settlement of the rail resulted as the shoulder dropped and ballast was lost from head of tie, down the slope. Prior attempts by local crews to address the historic instability at this site included driving rail pile, which did not solve the problem.
Additionally, work from track level to drive additional piling would have been disruptive and required substantial co-ordination and site preparation efforts to facilitate equipment access, including temporary removal and rerouting of overhead electric lines.
GEOWEB Geocells Earth Retention Solution
After considering several options, project engineers determined that a passive crib wall system along the toe utilising the GEOWEB® Earth Retention System was the preferred option. The engineers based their decision on the GEOWEB system’s ability to be constructed less expensively and more quickly than the alternatives, with the added benefit of not disturbing train operations. The GEOWEB system was selected as the facing of the wall due to the system’s ease of installation, tolerance to settlement and ability to minimise downtime.
