Kwajalein Drydock Pile Foundation Analysis.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
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The MCA 9206180 dry dock facility being constructed on Kwajalein Island of the Marshall Islands is to be supported by 12 groups of driven piles, 6 groups supporting each side of the dry dock. Each group contains 12 piles. Soil investigation reports of the calcareous coral sands and static pile load tests conducted near the headwall landside of the dry dock indicated that 20 in. by 20 in. by 85 ft long precast prestressed concrete piles embeded to a depth of 53 ft will adequately support the dry dock. Driving records of the production piles indicated that the penetration resistances of the piles at the final embedment depth became substantially less than expected as piles were driven further toward the lagoon end of the dry dock area. The penetration resistance N required for adequate bearing capacity using a Delmag 46-23 hammer rated at 60 kip-ft was determined to be 12 blowsft at the final toe tip elevation, but the actual N decreased to as low as 2 blowsft for piles driven near the lagoon end of the dry dock. The lower than expected penetration resistances observed during driving of the production piles were attributed to several mechanisms that include generation of excess pore pressures as a result of driving, encounter of loose weak sands or sands less dense at the lagoon end compared with those near the headwall, and destruction of cementation bonds in the coral sands.
- Structural Engineering and Building Technology
- Soil Mechanics