Norfolk Southern, Gulf States Lead
The Geopier GeoSpike℠ system was used to reinforce the subgrade at a section of jointed track with vertical profile issues and ballast pumping. GeoSpike reduced dynamic deflection by 85% without removing the track, ties or ballast.
- Owner: Norfolk SouthernCanadian National
- General Contractor: Holden Contracting
Norfolk Southern (NS) was looking for an alternative option to solve subgrade issues that are prevalent around the railroad’s network. NS historically used either grout injection, dig out/replace and add ballast/tamp methods to remediate subgrade issues. Geopier was selected to provide a solution unlike methods used in the past. An onsite inspection was performed focusing on a 200ft section of track having a history of surface defects and repeated maintenance. The site inspection revealed soft, wet subgrade conditions below the ballast that were indicated by mud pumping and soil bulging at the toe of the ballast line. Geotechnical investigation provided evidence of adequate bearing soils 6 feet below the ballast line. The site inspection also included a motion capture of vertical deflection using a laser and high-speed camera. The test showed 1” of vertical deflection.
The Geopier solution for this project consisted of 6-8 ft GeoSpike℠ elements installed so that the GeoSpike apexes were 1-1.5 ft below the existing ties. The GeoSpike elements were installed in pairs spaced every other tie to resist a Cooper E-80 derived working load of 16 kips per GeoSpike. Approximately 120 GeoSpikes were installed in the 200’ section in about a day and a half using a hyrail excavator with vibratory driver. After the installation a sample load test was conducted on an installed element, resulting in 0.14” deflection at 150% design load. The track was surfaced prior to the installation of the GeoSpikes and other than back filling the installation locations no other surfacing was performed.
A Load Test was performed following installation to confirm that elements were supporting the measurable load without deflection. Results were as expected. A follow up inspection was performed six months after installation. The inspection included a motion capture of the vertical deflection using a laser and high-speed camera. The test showed 1/8” of vertical deflection. This was an 85% reduction in vertical deformation of the track under train load.