The Geotechnical Group returned to the CUNY Recital Hall in Manhattan for its fifth lecture of 2007-2008 on February 20, 2008. The lecture introduction by Dr. Terry Holman included a brief moment of silence in memory of the recent passing of Dr. Ralph Peck, one of the founding fathers of the field of geotechnical engineering. The lecture focused on dynamic testing of deep foundations installed by non-impact methods, and included a summary of dynamic testing theory, examples of load testing on drilled and cast-in-place foundations, and a brief discussion on integrity testing.
Presented by: Frank Rauche, Ph.D., GRL Engineers, Inc.
Dr. Rauche began the lecture with a brief discussion on the purpose of dynamic load testing, its project cost and scheduling benefits, and its usefulness given recent FHWA requirements for LRFD design.
Dr. Rauche continued with a discussion on the theory and general application of dynamic testing. The discussion included a brief history of the development of dynamic testing, and the equipment and setup employed for measurement, and collection of data using Pile Driving Analyzer® (PDA). He then discussed CAPWAP® which performs signal processing to further refine the results of the PDA data. A case history from Melbourne, Australia was presented wherein both static and dynamic data were obtained and compared. APPLE, a single impact ram developed to impart large dynamic loads on drilled shafts and cast-in-place piles, was presented. PDA and CAPWAP data from tests performed at Amherst test shafts were also discussed.
Dr. Rauche then went on to present various case histories, documenting the correlation between static and dynamic load test data on drilled shafts in Florida and California, and on micropiles in Karst formations. An additional example was presented for ACIP piles in Alexandria, Egypt.
Non-destructed integrity testing methods including Pile Integrity Testing (PIT) and Cross Hole Sonic Logging (CSL) were introduced. The basic operating principals and theories were discussed and specific results presented. Mathematical methods for interpretation of the data were also discussed.
In conclusion, Dr. Rauche explained that the value of dynamic testing method lies in its relatively modest costs, ability to perform testing on “production” foundations, and the greater amount of data that can be obtained for the same cost. His experiences with dynamic testing have demonstrated that often, structures founded on drilled shafts have little redundancy in foundation design due to the high shaft capacities, and that contract documents should be clear as to remedies for failed or defective piles.