Study on the Resistance of Bored Piles with Rings-Paper

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The study evaluates the load-bearing capacity of dry bored piles fitted with enlarged rings along their shafts. Developed for the soils of Maceió, Brazil, these piles are intended to increase capacity, reduce settlement, and offer an economical alternative to conventional bored piles.<br /><br />Researchers analyzed ten piles using two SPT-based semi-empirical methods—Décourt–Quaresma and Aoki–Velloso—and two methods that extrapolate pile load–settlement curves—Van der Veen and Décourt. Because the semi-empirical methods do not specifically account for rings, five modeling scenarios were tested, including piles without rings, assumed increases of 50% or 60% in shaft resistance, and representations of the rings as either a continuous enlarged cylinder or separate bases. Comparisons focused mainly on the 50% and 60% increase scenarios.<br /><br />The Décourt extrapolation method estimated higher ultimate capacities than Van der Veen for all ten piles. Aoki–Velloso generally predicted higher capacities than Décourt–Quaresma and, for the 50% and 60% scenarios, produced estimates closer to the extrapolation results—particularly Van der Veen. Its coefficient of variation was 0.17, compared with 0.27 for Décourt–Quaresma. The 60% shaft-resistance increase performed better than the commonly used 50% assumption. One pile, E4, showed unusually low estimates and was excluded from some statistical comparisons, possibly because of soil-classification error.<br /><br />Overall, the authors conclude that Aoki–Velloso, especially with a 60% increase in shaft resistance, was the most satisfactory of the tested approaches for predicting the capacity of ringed bored piles. The results support their potential as a viable, cost-effective foundation option in the Maceió region, while emphasizing the need to validate predictions against load tests.

Keywords

bored piles

load-bearing capacity

enlarged rings

shaft resistance

settlement reduction

Maceió Brazil

SPT methods

Aoki-Velloso

Décourt-Quaresma

pile load tests