Model Study on the Performance of Single-Finned Pile in Sand under Tension Loads

Abstract

A variety of structures similar to marine dolphins, dock-fendering systems, tower foundations, inundated platforms, and abutments are installed on deep foundations, which are subjected to uplift loads. This paper introduces a modern pile-modification strategy known as finned pile that increases pile-tension capacity by providing an affirmative anchorage close to the pile tip. The alteration consists of four fins welded at the bottom of a pile around the circumferential area. Comparative small-scale model uplift tests were performed on normal piles without fins and on piles with fins. Investigations were done by changing the fin-width ratio (b/D), fin inclination angle (β), pile length-to-diameter ratio (L/D), and soil density. Results indicate that there is a considerable increase in uplift capacity of the piles when using fins at the end of the piles. When fins were installed with effective width equal to the pile diameter and at an inclination angle (β) of 90° for sand, with relative density (Dr) of 50%, the improvement in uplift capacity reached 1.82, 3, and 6 times that of the normal pile with L/D stiffnesses of 15, 20, and 30, respectively. It was also found that fins should be installed with an optimum fin inclination angle (β) equal to or greater than 45° to achieve the beneficial effect. The existence of such fins at the lower part of the tested piles provided an ideal anchorage system because of the significant locking-up effect of the soils within the fins, resulting in increased uplift capacity.