Abstract
Preliminary identification of plugging of open-ended pipe piles based on their dimensions, ahead of driving, is explored in this study using data analytics. Piles can be unplugged, plugged, or internally plugged, depending on their dimensions, and geotechnical conditions. Plugging of pipe piles influences both pile capacity and driving behavior; however, the classification assumed at the design time does not always manifest during driving, sometimes resulting in driving difficulties. The relationship between pile plugging and pile dimensions was investigated using a dataset of 74 load tests on pipe piles, where geotechnical profiles were also available. An analytics approach borrowed from data science was adopted. First, capacity was computed using four recognized designed methods considering the unplugged, plugged, and internally plugged conditions. Next, the calculated capacities were compared to capacities measured (interpreted) from static load tests. Finally, voting was employed to identify plugging based on the closeness of the computed capacity assumptions to the interpreted capacity. Most piles were found to be unplugged. A diameter criterion is proposed as a tool to give early insight into the plugging condition of a pile ahead of driving which resulted in a 70 ± 10% accuracy. The proposed criterion was validated once using a dataset of 23 piles with CPT data and a second time using 24 published driving records where plugging records were available and achieved similar accuracy, in both cases. It was concluded that piles larger than ~0.9 m (36 inches) in diameter have a higher likelihood of being unplugged, while piles smaller than 0.5 m (20 inches) have a higher likelihood of being plugged.
Highlights
Pipe piles are routinely used to support a variety of structures ranging from residential and commercial structures to infrastructure projects
The American Petroleum Institute (API) method uses the α-method for side resistance similar to the Federal Highway Administration (FHWA) and United States Army Corps of Engineers (USACE) methods, but uses its own set of equations to calculate the adhesion between the piles sides and the surrounding soil based on the ratio of undrained shear strength to effective overburden stress
These results suggest that the diameter criterion offers results that are as good as the interaction diagrams
Summary
Pipe piles are routinely used to support a variety of structures ranging from residential and commercial structures to infrastructure projects. The majority of piles that experience plugging during static loading do not plug during driving [5] This could be attributed to a combination of an increase in the bearing capacity factor, Nq, over its static value due to inertial effects [6]; Smith et al [7] claimed that the internal and external friction of a driven pile is mobilized intermittently during penetration, and the soil core advances up the pile. Methods to predict the contribution of the plug to the pile capacity have been developed [24,25]; the required information is typically not available during initial design required to size piles. The onset of plugging is identified by comparing the measured (i.e., interpreted) pile capacity to that obtained from static analyses; there is a great difference between the pile capacities computed with the many available design methods. Proposed toinforecast thetoplugging condition a pile on its geometrical dimensions in an effort to shed some light on the pile plugging phenomenon
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