Observed Driving Performance of Open-Ended Steel Pipe Piles with and without Plugged Toes-Paper

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The paper examines the driving performance of 19 open-ended steel pipe piles installed at the Hunters Point South redevelopment in Queens, New York. The 16-inch-diameter piles were driven through highly variable fill and soft soils into glacial till or schist bedrock. Their penetration lengths ranged from 25 to 66 feet; ten reached bedrock refusal, while the others stopped in till at driving resistances of 2–8.5 blows per inch.<br /><br />All piles were monitored with a Pile Driving Analyzer (PDA), and the results were interpreted using the CASE method and CAPWAP signal-matching analysis. PDA measurements showed that hammer energy transfer was generally efficient and pile stresses remained below recommended limits, with no evidence of pile damage. Two piles were re-driven after a 17-hour waiting period and showed behavior suggesting that soil plugs had formed.<br /><br />CAPWAP results showed that toe resistance dominated capacity, accounting on average for 93% of total resistance in piles driven to bedrock, 83% in unplugged piles terminated in till, and 75% in plugged piles. Plugged piles had comparatively low toe resistance and a softer toe response. Estimated plug lengths were about 0.91–1.12 times the pipe’s internal diameter. Pile deformation depended strongly on toe conditions: piles seated on rock mainly shortened elastically along the shaft, whereas piles ending in till were more affected by toe movement.<br /><br />The CASE method generally overpredicted capacities for piles driven to bedrock refusal but provided more reasonable estimates for piles stopped after measurable penetration. The findings highlight the importance of recognizing soil plugging and toe conditions when interpreting dynamic test results and assessing the capacity and deformation of open-ended pipe piles.

Keywords

open-ended steel pipe piles

pile driving performance

Pile Driving Analyzer (PDA)

CAPWAP analysis

CASE method

soil plugging

toe resistance

bedrock refusal

glacial till

pile capacity