Steel Plate Pile Slope Stabilization: Case History of a 250-ft Relief Clay Slope with Variable Rockhead-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes stabilization of an actively failing, approximately 250-foot-high clay slope near FirstEnergy’s Holloway Substation in Mead Township, Ohio. Since 2015, repeated slope movements, erosion, groundwater seepage, tension cracks, and bulges had threatened transmission-line foundations and substation infrastructure. Earlier repairs—including regrading, geogrid reinforcement, and drainage work—had not stopped the movement.<br /><br />The project used a patented steel plate pile system (SRTs). Closely spaced, staggered plate piles create horizontal barriers within the slope, allowing soil to arch between them and transferring slide forces to stronger underlying material. The system was selected to improve global stability while limiting earthwork and construction disruption. Design targeted factors of safety of 1.3–1.5.<br /><br />A total of 3,305 steel plate pile elements were installed across two areas. Design accounted for estimated slide depths of up to 8 feet in Area A and 15 feet in Area E, as well as varying slope angles and groundwater conditions. Installation took place from October to December 2025 and was completed on schedule and within the $1.08 million budget.<br /><br />The main construction challenge was highly variable shale-bedrock depth. Shallow rock frequently caused pile refusal, requiring piles to be shortened or removed and replacement piles installed nearby. The project’s key lesson was that more thorough subsurface exploration within the slide areas could better define rockhead elevations, improve pile-length design, and reduce rework, steel waste, costs, and safety risks. The SRT system stabilizes slope movement but does not control surface-water erosion, so drainage and erosion management must be addressed separately.

Keywords

slope stabilization

steel plate piles

landslide remediation

clay slope

groundwater seepage

transmission line foundations

substation infrastructure

patented SRT system

shale bedrock refusal

drainage and erosion control