Claystone, Steep Slopes, and Water, Not Again! The SR 2018 West Smithfield Street Landslide Remediation, Allegheny County, Pennsylvania

Claystone beds commonly found throughout the geology of Southwestern Pennsylvania are generally soft, weak, and susceptible to landsliding. The Birmingham “Schenley” Redbed Claystone present at the SR 2018 West Smithfield Street project site in Allegheny County, Pennsylvania, is no exception. A landslide occurred above the roadway, cascading debris over the 40-to-50-foot near-vertical rock cut adjacent to the road. The size and volume of the landslide mass forced closure of the roadway. Gannett Fleming was tasked by the Pennsylvania Department of Transportation to provide a landslide treatment design that adequately stabilized the slope and prevented further debris from falling into the roadway. The “Schenley” Redbed Claystone encountered at the top of the near-vertical rock cut during the subsurface investigation measured up to 36 feet in thickness. Fluctuation of the groundwater table within the thick “Schenley” Redbed Claystone further softened and de-stabilized the claystone, complicating the task of stabilizing the slope. Several variations of the stability model were evaluated during the design phase to account for changing groundwater conditions. The final landslide treatment design incorporated flattening the slope to the edge of the near-vertical rock cut in combination with a soil nail slope treatment to provide additional reinforcement for the remaining soil and bedrock.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 184-201
  • Monograph Title: Proceedings of the 67th Highway Geology Symposium (HGS 2016)

Subject/Index Terms

Filing Info

  • Accession Number: 01628002
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Feb 25 2017 1:24AM