Performance of Pile Foundations with Internal Diaphragm in the Red Sea Formations-Paper

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Coral and carbonate formations in the Red Sea are highly variable, making site characterization and pile-capacity predictions uncertain. Conventional soil-mechanics methods may overestimate capacity, so design should use conservative limiting values and, where possible, site-specific load-test data.<br /><br />This paper examines two offshore, open-ended pipe piles driven near the west coast of the Red Sea. Each pile had an internal diaphragm intended to promote soil-plug formation and fully mobilize end bearing, while retaining the easier installation of an open-ended pile. A 100 mm opening in the diaphragm allowed drainage of the soil column. The piles were approximately 914 mm in diameter, penetrated about 23 m into the coral formations, and had diaphragms positioned 18 m above the toe. Their estimated ultimate capacity was about 2,600 kN.<br /><br />GRLWEAP drivability predictions were compared with field driving records. For both piles, blow counts increased noticeably once the diaphragm engaged. Actual driving resistance exceeded theoretical predictions, indicating greater resistance than the analysis anticipated. The authors attribute this partly to soil densification and reduced disturbance near the toe as the plug formed, and partly to potentially underestimated end-bearing and lateral earth-pressure parameters.<br /><br />The results suggest that an internal diaphragm can help achieve soil plugging and mobilize pile base resistance while avoiding the cost and installation difficulties of alternative plugging methods. The approach contributed to reduced construction time and project costs by avoiding longer or additional piles. However, pile behavior in coral formations remains difficult to predict. The authors recommend accounting for construction-induced changes in soil behavior from the outset and conducting comprehensive site investigations, including measurements of compressibility, to improve characterization and design.

Keywords

Red Sea

coral formations

open-ended pipe piles

soil plug formation

pile capacity

pile drivability

GRLWEAP

end bearing

offshore foundation

site investigation