Measuring Rock Strength While Drilling Shafts Socketed into Florida Limestone
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 144, Issue 3
Abstract
The focus of this research was the real time assessment of rock strength during drilled shaft installations in Florida. Measures of unconfined compressive strength, a function of rock strength used commonly in shaft design, are provided through five monitored drilling parameters: torque, crowd, rotational speed, penetration rate, and bit diameter. This study is part of a larger project in which laboratory and field investigations were performed. This paper covers the laboratory portion of the investigation in which synthetic limestone blocks were cast at four design strengths representative of Florida limestone and drilled in a controlled environment. The laboratory drillings revealed that torque provides a better correlation with unconfined compressive strength than crowd force, which was found to be the case independent of drilling parameter groupings, and when groupings based on variations in bit diameter and the penetration rate to rotational speed ratio were enforced. During the analysis, multiple drilling equations were investigated, and a unique relationship was developed with Teale’s specific energy equation for nonpercussive rotary drilling using a rock auger.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors would like to express their sincere appreciation of the assistance of the FDOT’s State Materials Office, as well as the district and central geotechnical engineers. A special thanks is extended to all the FDOT participants who assisted in the development and production of Gatorock: Richard Delorenzo, Patrick Carlton, Patrick Gallagher, Thomas Frank, Dale Deford, Dan Pitocchi, and John Shoucair. The authors also would like to thank the University of Florida research team: Phillip Rodgers, Jerry Paris, Jordan Nelson, Shelby Brothers, Katie Maslak, Mike Stephenson, Tim Copeland, Matt Andrews, Aaron Hendricks, Michael Ferguson, Richard Booze, Ryan Mackey, and Vik Adams. Without your tremendous efforts, this research would not have been possible. This work was supported by the Florida Department of Transportation through Research Contract No. BDV 31 977 20.
Disclaimer
The opinions, findings, and conclusions expressed in this publication are those of the author(s) and not necessarily those of the Florida Department of Transportation or the U.S. Department of Transportation.
References
AASHTO. (2010). LRFD bridge design specifications, 4th Ed., Washington, DC.
ACI (American Concrete Institute). (2013). “Report on controlled low-strength materials.” ACI 229R-13, Farmington Hills, MI.
ASTM. (2002). “Standard test method for unconfined compressive strength of intact rock core specimens.” ASTM D2938-95, West Conshohocken, PA.
Brown, D. A., Turner, J. P., and Castelli, R. J. (2010). Drilled shafts: Construction procedures and LRFD design methods, FHWA, Washington, DC.
Bullock, P. (2004). “Insitu rock modulus apparatus.”, Univ. of Florida, Gainesville, FL.
Detournay, E., and Defourny, P. (1992). “A phenomenological model for the drilling action of drag bits.” Int. J. Rock Mech. Mining Sci., 29(1), 13–23.
Detournay, E., Richard, T., and Shepherd, M. (2008). “Drilling response of drag bits: Theory and experiment.” Int. J. Rock Mech. Mining Sci., 45(8), 1347–1360.
Hoberock, L. L., and Bratcher, G. J. (1996). “A new approach for determining in-situ rock strength while drilling.” J. Energy Resour. Technol., 118(4), 249–255.
ISO. (2016). “Geotechnical investigation and testing—Field testing—Part 15: Measuring while drilling.” ISO 22476-15:2016(en), Geneva.
Karasawa, H., Ohno, T., Kosugi, M., and Rowley, J. C. (2002a). “Methods to estimate the rock strength and tooth wear while drilling with roller-bits. 1: Milled-tooth bits.” J. Energy Resour. Technol., 124(3), 125.
Karasawa, H., Ohno, T., Kosugi, M., and Rowley, J. C. (2002b). “Methods to estimate the rock strength and tooth wear while drilling with roller-bits. 2: Insert bits.” J. Energy Resour. Technol., 124(3), 133–140.
Li, Z., and Itakura, K. I. (2012). “An analytical drilling model of drag bits for evaluation of rock strength.” Soils Found., 52(2), 216–227.
McVay, M., and Niraula, L. (2004). “Development of P-Y curves for large diameter piles/drilled shafts in limestone for FBPIER.”, Univ. of Florida, Gainesville, FL.
Ohno, T., Karasawa, H., Kosugi, M., and Rowley, J. C. (2004). “Proposed practical methods to estimate rock strength and tooth wear while drilling with roller-cone bits.” J. Energy Resour. Technol., 126(4), 302–310.
Sheppard, M., Bloomquist, D., Slagle, P., and Renna, R. (2006). “Rate of erosion properties of rock and clay.”, Univ. of Florida, Gainesville, FL.
Teale, R. (1965). “The concept of specific energy in rock drilling.” Int. J. Rock Mech. Mining Sci., 2(1), 57–73.
Viana da Fonseca, A., and Coelho, S. (2006). “Characterization of highly variable rock weathering by using DPR.” GeoShanghai Int. Conf., Shanghai, China.
Wolcott, D. S., and Bordelon, D. R. (1993). “Lithology determination using downhole bit mechanics data.” 68th Annual Technical Conf. and Exhibition of the Society of Petroleum Engineers, SPE, Houston, 769–778.
Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 144 • Issue 3 • March 2018
Copyright
©2017 American Society of Civil Engineers.
History
Received: Mar 17, 2017
Accepted: Sep 6, 2017
Published online: Dec 23, 2017
Published in print: Mar 1, 2018
Discussion open until: May 23, 2018
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.