Rock Slope Failure Mode Analysis and Mitigation Using LiDAR Data in Fairlee, Vermont

In May 2017, the Vermont Agency of Transportation (VTrans) asked GZA GeoEnvironmental, Inc. (GZA) to assess a recent rockfall that had left a mass of failed material above Interstate Route 91 (I-91) in Fairlee, Vermont. VTrans’ initial assessment identified the risk that release of the failed material could overwhelm the existing catchment and impact the interstate highway. GZA developed a comprehensive assessment that included LiDAR survey and hand measurements to characterize the failure area. The LiDAR data allowed characterization of the scarp behind and the base plane beneath the failed material while avoiding direct access on or beneath the unstable mass. Split-FX® software was used to create a mesh from the point cloud, assess bedrock structure and dimensions of key features, and develop detailed cross-sections. Most significantly, the Split-FX® mesh helped reveal the location and orientation of the scarp for use in kinematic analyses. Evaluations confirmed toppling instability as the predominant failure mode, and the orientation of the base plane indicated a combined sliding and toppling instability mode was the likely cause of instability of the Displaced Mass. GZA recommended scaling to remove the failed material, combined with passive dowels to stabilize the remaining scarp face against continued toppling. Catchment performance was evaluated for the proposed scaling, and for the proposed final slope configuration, using RocFall® software. LiDAR data was used extensively in these evaluations, as input to Split-FX®, which was used to evaluate the geometry of the failed rock mass, thickness of individual blocks, and cross-section dimensions for rockfall evaluations. The value of LiDAR for rock slope mapping was illustrated throughout the course of the project.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Maps; Photos; Tables;
  • Pagination: pp 71-93
  • Monograph Title: Proceedings of the 69th Highway Geology Symposium (HGS 2018)

Subject/Index Terms

Filing Info

  • Accession Number: 01719277
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 23 2019 9:01AM