Squeezing Between Rock Cuts - The Route 128/I-95 Add-A-Lane Project, Dedham/Westwood, Massachusetts

In the 1950s the new Route 128/I-95 corridor was cut 10 to 50 feet into the granite bedrock. Over time, a lane was added along the shoulder. Now another is being constructed along the median. The result is tall rock cut slopes with narrow catchments. When this tight squeeze became apparent to the owner, GZA was asked to meet with project team and consider alternatives for rock slope stabilization and rockfall catchment. Initial observations revealed several areas at risk for rock fall into the travelway. A graduated approach was developed with limited field measurements and chart-based catchment evaluations for the lower risk slopes; and more detailed field mapping, kinematic analysis and computer-based catchment evaluation for the higher risk slopes. Over 1,400 discontinuities were mapped on nine rock exposures covering approximately 4,000 linear feet of cut. The field data were gathered via a GIS-based application on a tablet computer, tied to GPS locations, imported directly to spreadsheets, then directly into software to create stereographic projections, expediting kinematic and CRSP catchment evaluations. The team focused on unstable planes and wedges, and on irregularities that could serve as launch points for fallen rock. Scaling and local stabilization were recommended to mitigate the launch points and unstable areas along the median. Given the narrow width, permanent barriers were evaluated and recommended along the outside shoulders. Scaling is scheduled to begin in summer 2013. Observations and measurements during scaling will be used by GZA to design localized stabilization measures, and update CRSP analyses of the launch points.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 113-137
  • Monograph Title: Proceedings of the 64th Highway Geology Symposium (HGS 2013)

Subject/Index Terms

Filing Info

  • Accession Number: 01644017
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 8 2017 8:12PM