Velocity Variations in Cross-Hole Sonic Logging Surveys Causes and Impacts in Drilled Shafts

Federal Highway Administration2008PDFTech ReportRock, AlanZhang, RuningWilkinson, DavidUnited States. Federal Highway Administration. Central Federal Lands Highway DivisionHaramy, Khamis Y.Peabody, MichaelSurdahl, R.Greer, MattJalinoos, FrankUnited States. Department of Transportation. Federal Highway AdministrationUnited StatesGeophysical prospectingTomographyVelocityPile foundationsCrossheadingsQuality assuranceQuality controlNondestructive testsSonic testsCross-hole sonic loggingCSLDrilled shaftsDeep foundationGeophysical surveyTomographyVelocityAnomaliesFHWA-CFL-TD-08-009DTFH68-05-P-00056DTFH68-05-P-00089DTFH68-06-P-00105Haramy, KhamisCOTR: Khamis Haramy, FHWA-CFLHD. Advisory Panel Members: Michael Peabody and Roger Surdahl, FHWA-CFLHD; Matt Greer, FHWA-CO Division. and Frank Jalinoos, FHWA-TFHRC. This project was funded under the FHWA Federal Lands Highway Technology Deployment Initiatives and Partnership Program (TDIPP).Drilled shafts are popular deep foundation supports, as they can be constructed in a wider range of ground conditions with less noise and vibration than driven piles. Quality assurance and quality control of drilled shafts has become a concern due to difficulties in locating defects and determining load bearing capacity. Various non-destructive evaluation (NDE) techniques have been developed to estimate the integrity of the concrete. While NDE techniques provide a powerful tool and have been widely accepted, many variables and unknowns can affect the measurement results. Results are more difficult to interpret, leading to unnecessary litigation over shaft integrity. In addition, influences of surrounding ground, stress states under different load conditions, and crack development during concrete curing further complicate determination of shaft performance. This study identifies various conditions that affect the load bearing capacity of drilled shafts by modeling various conditions and analyzing them with numerical methods. The analysis first identifies design criteria and construction procedures, and reviews NDE techniques. This analysis uses results based on principles and theorems from engineering mechanics, geotechnical engineering, concrete chemistry, and geophysical engineering, which are analyzed numerically by the Geostructural Analysis Package (GAP.) GAP combines numerical methods of Discrete Element Method, Particle Flow Method, Material Point Method, and Finite Differencing, together with engineering mechanics constitutive models, concrete chemistry models, thermodynamics models, and geophysical tomography and holography for geotechnical engineering application. GAP has also been used successfully for ground characterization in highway engineering and mining operations. This study explores many concerns recently raised for drilled shaft design, construction and maintenance. Conclusions and recommendations offer engineers more information for a better understanding of drilled shaft foundations to revolutionize foundation design, concrete mix design, construction techniques, NDE measurement, and defect evaluation, to improve performance and efficiency.96