Design and Construction of a Temporary Rockfall Mitigation System at the Bellwood Quarry Reservoir Tunnel, Phase 1 Water Supply Program, Atlanta, Georgia

The City of Atlanta is commissioning a new 1-mile-long, approx. 13-ft. diameter, lined, water conveyance tunnel as part of Phase 1 of the Water Supply Program. The tunnel will be excavated through bedrock with a TBM and will provide the City with potable water from the soon-to-be-filled Bellwood Quarry Reservoir. Construction of the tunnel and ancillary features was initiated in spring of 2016 and is expected to be complete in 2018. The previously mined Bellwood Quarry will serve as a reservoir to impound and distribute the water. Prior mining activities have resulted in steep pit slopes, some as high as 350 ft., with an abundance of loose rock. In order to help maintain a safe and functional site for site access and tunneling, a temporary rockfall mitigation system was constructed (and is currently being maintained) above the main water supply tunnel and a secondary adit. Critical elements of the temporary system included post-scaling design and construction of draped netting, rock dowels, and two rockfall canopies. The draped netting and canopies were connected as part of a “slot” system, where falling rocks will be contained behind the drape and subsequently guided into (and arrested by) the canopy system. This paper details the elements of the temporary rockfall mitigation system being utilized during tunnel construction, and will describe the challenges associated with installation of near-horizontal rockfall canopies at elevated, difficult access locations.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References;
  • Pagination: pp 185-195
  • Monograph Title: Proceedings of the 68th Highway Geology Symposium (HGS 2017)

Subject/Index Terms

Filing Info

  • Accession Number: 01642817
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 13 2017 3:12PM