Modified Standard Penetration Test for Drilled Shaft Design in Weak Fine-Grained Rocks

Standard penetration tests (SPTs) have been used to estimate strength parameters of soils and weak rocks when it is difficult to obtain high-quality samples for laboratory shear testing. SPTs require 45?cm (18?in.) of split-spoon sampler penetration to determine the blowcounts per 0.3?m (1?ft), which is difficult to impossible to obtain in weak rock, that is, intermediate geomaterials. As a result, a modified SPT is presented here for sampler penetrations less than 45?cm (18?in.) in weak rocks. This new procedure is termed the modified standard penetration test (MSPT) and uses the penetration rate, not the sum of penetration blowcounts per 0.3?m, to estimate the unconfined compressive strength for the design of drilled shafts in weak fine-grained rocks. The penetration rate is the inverse of the linear slope of the penetration depth versus blowcount relationship. With this new test and interpretation procedure, 45?cm (18?in.) of sampler penetration is no longer required to estimate the unconfined compressive strength of weak rocks. An empirical correlation between MSPT penetration rate and laboratory-measured unconfined compressive strength is presented here for weak Illinois shale. This correlation could be used to estimate the unconfined compressive strength for the design of drilled shafts in weak rocks.

• Record URL:
  https://doi.org/10.1177/03611981211037895
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/03611981
• Supplemental Notes:
  • Timothy D. Stark https://orcid.org/0000-0003-2384-1868 © National Academy of Sciences: Transportation Research Board 2021.
• Authors:
  • Stark, Timothy D
  • 0000-0003-2384-1868
  • Baghdady, Ahmed K
  • Osouli, Abdolreza
  • Shoup, Heather
  • 0000-0001-6599-004X
  • Short, Michael A
  • 0000-0002-3156-7670
• Publication Date: 2022-2

Language

• English

Media Info

• Media Type: Web
• Features: References;
• Pagination: pp 176-185
• Serial:
  • Transportation Research Record: Journal of the Transportation Research Board
  • Volume: 2676
  • Issue Number: 2
  • Publisher: Sage Publications, Incorporated
  • ISSN: 0361-1981
  • EISSN: 2169-4052
  • Serial URL: http://journals.sagepub.com/home/trr

Subject/Index Terms

• TRT Terms: Compressive strength; Design; Rock drilling; Shaft sinking; Shale; Soil penetration test; Weak rock
• Subject Areas: Bridges and other structures; Design; Geotechnology; Highways;

Filing Info

• Accession Number: 01782032
• Record Type: Publication
• Files: TRIS, TRB, ATRI
• Created Date: Sep 20 2021 4:58PM