APPLICATION OF THE ROCK BOREHOLE SHEAR TEST TO SOFT STRATA

The Rock Borehole Shear Tester (RBST) is a direct shear device used to evaluate rock shearing strength in situ. It is conducted on the rock surface of a borehole, and a Mohr-Coulomb envelope is defined by repeating the test at several applied normal stresses. Since laboratory testing of low strength rocks usually is biased because of incomplete core recovey, the use of the RBST would greatly reduce the difficulties of obtaining reliable values of rock strength. The application of the RBST to such materials was evaluated by testing the soft underclays and claystones underlying coal seams. In situ shear strength values determined by the RBST were compared with intact shear strength values determined by triaxial testing of cores from the boreholes. These results were then analyzed with respect to the results of plate bearing tests conducted at the test sites. The results indicated that the RBST could be adapted to testing low strength, poorly indurated rocks. Because of the very soft and fissured condition of the material tested, however, the initial design of the RBST had to be modified by addition of low range, high resolution gauges. In addition, testing procedures had to be varied to account for non-homogeneity within the strata. (Author)

• Supplemental Notes:
  • Proceedings of the Eighteenth Annual Engineering Geology and Soils Engineering Symposium, held at the Red Lion Inn, Boise, Idaho.
• Corporate Authors:

  Idaho Transportation Department

  3311 W State Street, P. O. Box 7129
  Boise, ID  United States  83707-1129

  University of Idaho, Moscow

  Department of Geology and Geological Engineering
  Moscow, ID  United States  83844-3025

  Boise State University

  Department of Geology and Geophysics
  Boise, ID  United States 

  Idaho State University, Pocatello

  Department of Geology
  Pocatello, ID  United States  83201

  Idaho State University, Pocatello

  Department of Geology
  Pocatello, ID  United States  83201
• Authors:
  • Higgins, J D
  • Rockaway, J D
• Conference:
  • Proceedings of the Eighteenth Annual Engineeing Geology and Soils Engineering Symposium, held at the Red Lion Inn, Boise, Idaho.
• Publication Date: 1980-4

Media Info

• Features: Figures; References;
• Pagination: p. 179-186

Subject/Index Terms

• TRT Terms: Boreholes; Clay; Cores (Specimens); Rocks; Shear strength; Shear tests; Soft rock; Triaxial shear tests
• Old TRIS Terms: Cores
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00334065
• Record Type: Publication
• Files: TRIS, STATEDOT
• Created Date: Sep 16 1981 12:00AM