RES2020-14: Design Considerations and Limitations of Rock Dowels/Anchors Loaded in Shear

In Tennessee, cut rock slopes with exposed discontinuities are often reinforced with grouted steel anchors installed across the discontinuity to stabilize the system by immobilizing the rock material above the sliding surface. These elements resist shear loading rather than function in tension. Yet, the steel bar may bend in cases where the discontinuity is sufficiently large. The purpose of this study was to investigate the performance of simulated un-tensioned dowel-jointed rock block systems subjected to shear loading and evaluate whether bending likely occurred as well as its contribution to the reduction in dowel capacity. Variables studied were aperture size (joint spacing), dowel diameter, and dowel angle of inclination with respect to the joint normal. Physical experiments were conducted using large concrete blocks to simulate the jointed rock material, steel rebars to simulate the dowels, and tested in a large-scale direct shear apparatus. A numerical model was developed to extend the dowel size and joint thickness. A dowel shear capacity design chart was also developed. The chart identifies the threshold between the pure shear capacity and the reduced capacity due to bending effects as a function of joint thickness and bar size. Conclusions from this study include (1) rebar double bending phenomenon was inferred from strain gage data in the case of a large aperture size, (2) bending starts at an aperture size relative to bar diameter and strength, and reduces the dowel shear capacity by a quantity related to bar size and aperture size, (3) all results from physical and numerical analyses show sufficient agreement with the governing equations for theoretical dowel shear and bending conditions to warrant the conservative use of the developed design chart (4) dowel inclination angle had little influence on ultimate shear resistance, and (5) free and fixed dowel placement show no significant difference in resistance.

• Record URL:
  https://www.tn.gov/content/dam/tn/tdot/long-range-planning/research/final-reports/res2020-final-reports/RES2020-14_Final_Report_Approved.pdf

Language

• English

Project

• Status: Completed
• Funding: $163207
• Contract Numbers:

  RES2020-14

• Sponsor Organizations:

  Tennessee Department of Transportation

  James K. Polk Building
  Fifth and Deaderick Street
  Nashville, TN  United States  37243-0349
• Managing Organizations:

  Tennessee Department of Transportation

  James K. Polk Building
  Fifth and Deaderick Street
  Nashville, TN  United States  37243-0349
• Project Managers:

  Beaver, Ann

• Performing Organizations:

  University of Tennessee, Knoxville

  Knoxville, TN  United States 
• Principal Investigators:

  Palomino, Angelica

• Start Date: 20190801
• Expected Completion Date: 20220531
• Actual Completion Date: 20220531
• USDOT Program: Transportation, Planning, Research, and Development

Subject/Index Terms

• TRT Terms: Anchors (Structural connectors); Bending; Dowels (Fasteners); Rock jointing; Rockslides; Shear properties; Thickness
• Subject Areas: Design; Geotechnology; Highways;

Filing Info

• Accession Number: 01771491
• Record Type: Research project
• Source Agency: Tennessee Department of Transportation
• Contract Numbers: RES2020-14
• Files: RIP, STATEDOT
• Created Date: May 11 2021 6:22PM