INSITU ROCK MODULUS APPARATUS

Drilled shaft foundations socketed into limestone support many Florida structures and bridges through weak overburdened soils. The current design method for side shear capacity of drilled shafts in the highly variable Florida limestone uses compressive and tensile strength tests of rock cores. However, these tests represent only the recovered, intact portion of the rock core, not the rock mass. The pressuremeter measures rock strength in situ, and should accurately reflect the properties of the rock mass while reducing lab-testing effort. This research includes pressuremeter tests in both laboratory and field tests to estimate the strength and stiffness of Florida limestone. It also includes the measurement of modulus and strength on rock core samples by the Florida Department of Transportation and the University of Florida (UF). It includes Probex-1 and Texam pressuremeter tests performed by UF, eight tests in the lab at Gatorock, a synthetic limestone developed for this research, and 31 tests in the field at the SR20 Blountstown Bridge adjacent to two test shafts. This report compares the pressuremeter modulus, yield pressures and limit pressure to similar core test results. It presents a database of 419 comparisons of unconfined compressive strength versus splitting tensile strength, and 173 comparisons of unconfined compressive strength versus the pressuremeter modulus of the geomaterial, based on limestone core tests from six bridge sites. Pressuremeter tests in the lab proved quite successful, but tests using the Probex-1 in the field compared poorly with core tests and with the capacity of the adjacent test shafts. Site variability and weak rock affected these comparisons. An empirical design method provided the best estimate of the drilled shaft unit side shear, but it requires further calibration before design use in Florida.

• Record URL:
  https://fdotwww.blob.core.windows.net/sitefinity/docs/default-source/research/reports/fdot-bc354-13rpt.pdf
• 
• Corporate Authors:

  University of Florida, Gainesville

  Department of Civil and Coastal Engineering
  Gainesville, FL  United States  32611-6580

  Florida Department of Transportation

  605 Suwannee Street
  Tallahassee, FL  United States  32399-0450

  Department of Transportation

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Bullock, P J
• Publication Date: 2004-8-23

Language

• English

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 146 p.

Subject/Index Terms

• TRT Terms: Bridge foundations; Bridges; Compression; Compressive strength; Cracking; Design methods; Field tests; Laboratory tests; Limestone; Modulus; Pressure gages; Rock core; Rock drilling; Rock mechanics; Rocks; Samples; Shear modulus; Shear strength; Soils; Stiffness; Strength of materials; Synthetics; Testing equipment; Weak rock
• Uncontrolled Terms: Drilled shafts; Limit pressure; Side shear capacity; Yield pressure
• Geographic Terms: Florida
• Subject Areas: Bridges and other structures; Design; Geotechnology; Highways; I43: Rock Mechanics;

Filing Info

• Accession Number: 00980530
• Record Type: Publication
• Report/Paper Numbers: Final Report
• Contract Numbers: BC-354
• Files: TRIS, USDOT, STATEDOT
• Created Date: Oct 11 2004 12:00AM