Rock Slope Design Criteria

Details

• Creators:
  Shakoor, Abdul ; Admassu, Yonathan
• Corporate Creators:
  Kent State University. Dept. of Geology
• Corporate Contributors:
  Ohio. Dept. of Transportation. Office of Innovation, Partnerships & Energy ; Ohio. Dept. of Transportation. Innovation, Research, and Implementation Section ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Slope stability
  • Slope failure
  • Rockfalls
  • Landslides
  • Cutting (Earthwork)
  • Ditches
  • Drainage
  • Rock slope design
  • Rockfalls
  • Undercutting
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• Publication/ Report Number:
  FHWA/OH-2010/11
• Resource Type:
  Tech Report
• Geographical Coverage:
  Ohio
• Corporate Publisher:
  Ohio. Dept. of Transportation. Office of Research and Development
• Abstract:
  Based on the stratigraphy and the type of slope stability problems, the flat lying, Paleozoic age, sedimentary ; rocks of Ohio were divided into three design units: 1) competent rock design unit consisting of sandstones, limestones, ; and siltstones that may exhibit discontinuity-related failures; 2) incompetent rock design unit consisting of shales, ; claystones, and mudstones that may exhibit raveling and gully erosion; and 3) inter-layered design unit consisting of ; both competent and incompetent rocks where differential weathering may result in undercutting-induced failures. Data ; regarding geological parameters (stratigraphy, joint orientation, joint spacing, bedding thickness, total thickness of rock ; unit), geotechnical parameters (point load strength index, slake durability index, plasticity index, geologic strength ; index, rock quality designation), and geometrical parameters (slope height, slope angle, catchment ditch width, ; catchment ditch depth) were collected for 26 cut slopes containing the three design units. Twenty three additional sites ; were later added to the study for a more detailed investigation of undercutting-induced failures within inter-layered rock ; sequences and the instability caused by raveling of incompetent rock. The data were used to perform slope stability ; analyses including kinematic analysis using discontinuity data, global stability analysis using the geological strength ; index (GSI) and the Franklin shale rating system, and an analysis for determining the stable slope angles using the ; approach described in the Ohio Department of Transportation Geotechnical Bulletin 3 (GB 3). ; Results show that slopes cut at 0.5H:1V and 0.25H:1V are adequate in minimizing the potential for discontinuity related ; failures in competent rock design units and second-cycle slake durability index (Id2) values can be used to select stable ; slope angles for incompetent rock and inter-layered rock design units. Based on Id2 values, these angles range from < ; 2H:1V to 0.5H:1V. RocFall analysis indicates that either a 13 ft (3.9 m) wide by 1 ft (0.3 m) deep ditch with a 10 ft (3 m) ; wide flat bottom and a 3H:1V foreslope or 16 ft (4.8 m) wide by 1 ft (0.3 m) deep ditch with a 10 ft (3 m) wide flat ; bottom and a 6H:1V foreslope would adequately contain at least 95 % of the rockfalls, as long as the slope height does ; not exceed a certain limit. For higher slopes, either rockfall barriers or wider and deeper catchment ditches will be ; required. The choice between a rockfall barrier and a catchment ditch will depend on economic considerations and/or ; space limitations. Based on these results, detailed cut slope designs, including slope angle, catchment ditch and bench ; design, and stabilization techniques, are recommended for each of the three design units.
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• Format:
  PDF
• Funding:
  134325
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/20528/dot_20528_DS1.pdf
• File Type:
  [PDF - 25.27 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:d4f39fe54602c503d7aa9a61f12b93fd5a8fab8f38330103777ae60d54bb4548ce45c06fc95068b199b0725bb5f01b5149f7cc81c230bcc5f0bb59b43217d413