SYMPOSIA PAPER Published: 29 July 2019
STP161120170160

Case Studies of Rebounds on Long, Slender Piles

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Large pile rebounds are typically associated with displacement piles that are driven into very low-permeable saturated materials. This paper examines case studies of steel H-piles driven into high-permeability materials that exhibited significant pile rebound—approximately 25 mm (1 in.) per blow—for cases that underwent both easy driving as well as practical refusal driving. Interestingly, the observed rebound or release of the portion of the pile above the ground surface is often mistakenly thought of as the soil rebound. The high rebound observed in our case studies may be attributed to the pile length (longer than 60 m [200 ft]) that experienced significant pile elastic compression during the hammer blow and the subsequent release of the pile's elastic compression (i.e., spring back) upon freeing of the hammer's compression impact force at the top of the pile. In the dynamic event, the pile elastic compression release is much more difficult to evaluate than in the static event because the upward- and downward-traveling waves interact. Based on the signal-matching CAPWAP® analyses results, it is determined that the soil rebound in these case studies is insignificant (less than 6 mm [¼-in.]) compared to the elastic rebound of the compressed pile. This paper presents recommendations on how to evaluate and differentiate elastic compression release and soil rebounds from the observed pile rebounds/releases using either signal-matching analysis, the Embedded Data Collector toe accelerometer gage, or approximate equations employing maximum forces in the case of dynamic load test instrumentation or stroke heights in the case of no instrumentation.

Author Information

Nguyen, Thai
University of Florida, Gainesville, FL, US
McVay, Michael, C.
University of Florida, Gainesville, FL, US
Herrera, Rodrigo
Florida Department of Transportation, Tallahassee, FL, US
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Details
Developed by Committee: D18
Pages: 640–650
DOI: 10.1520/STP161120170160
ISBN-EB: 978-0-8031-7668-3
ISBN-13: 978-0-8031-7667-6