Improved correlation between Texas cone penetrometer blow count and undrained shear strength of soft clays.

Details

• Creators:
  Garfield, Scott M. ; Varathungarajan, David A. ; Wright, Stephen G.
• Corporate Creators:
  University of Texas at Austin. Center for Transportation Research
• Corporate Contributors:
  Texas. Dept. of Transportation. Research and Technology Implementation Office ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Undrained shear strength
  • Soft clays
  • Cone penetrometers
  • soil shear strength
  • soft clay
  • geotechnical engineering
  • penetration tests
• Publication/ Report Number:
  FHWA/TX-09/0-5824-1
• Resource Type:
  Tech Report
• Geographical Coverage:
  Texas
• Corporate Publisher:
  Texas Department of Transportation. Research and Technology Implementation Office
• Abstract:
  The objective of this project was to develop an improved correlation between Texas Cone Penetrometer (TCP) ; blow count and undrained shear strength for soft, clay soils in the upper approximately 30 feet of the ground. Subsurface ; explorations were carried out by Tolunay-Wong Engineers, Inc. (TWEI) at six sites in the Texas Gulf Coast region where ; soft soils were expected to exist to obtain the data necessary to establish the improved correlation. A series of borings was ; made at each site with TCP tests, conventional (“Dutch”) piezocone penetration tests, thin-walled tube sampling, and vane ; shear tests. Laboratory testing was subsequently performed at The University of Texas at Austin on the thin-walled tube ; samples obtained in the field. The results of these field and laboratory tests were used to develop average, lower- and ; upper-bound undrained shear strength profiles for each of the sites (Varathungarajan, 2008). The data were used to ; evaluate existing correlations between TCP blow count and undrained shear strength as well as to establish an improved ; correlation. The following improved correlation was proposed: ; su = 300 + 60N ; where su is undrained shear strength in lbs. per square foot (psf) and N is the TCP blow count. ; To evaluate the improved correlation, bearing capacity analyses were performed using the computer software ; UTEXAS4 (Wright, 1999) to compute factors of safety for undrained strength profiles developed using the improved ; correlation as well as for the undrained strength profiles developed by Varathungarajan (2008). Factors of safety computed ; using undrained shear strengths based on the improved correlation generally showed good agreement with the factors of ; safety determined using the strength profiles developed by Varathungarajan (2008). ; The improved correlation is recommended over the existing correlations and is intended primarily for soft, ; shallow (less than 30 feet) clays with undrained shear strengths of 1200 psf (approximately 0.47 atmospheres) or less (TCP ; blow counts of 15 or less). Accordingly, this correlation should be used cautiously. Significant benefits can also be realized ; by performing more extensive field and laboratory testing, rather than relying on simple, approximate TCP correlations.
  More +
• Format:
  PDF
• Funding:
  0-5824
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/16781/dot_16781_DS1.pdf
• File Type:
  [PDF - 3.60 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:0163e6fcc1bc40f9d5d9478fb3bd1507a45c682d9513d10c261f737b2f53c096