抄録
This study has been carried out systematically and over a long period to clarify practical design problems for pile foundations to be constructed on a man-made island. Forty-one test piles in total were driven at six sites of the island. Of them, fifteen piles had their lower portions enlarged. The experiments conducted from 1977 to 1981 showed the following : (1) Settlement of the ground consisted of settlements of the fill, the alluvial clay and the diluvial layers. (2) A considerable number of blows was required to drive the piles through the sandy fill, although the dynamic stress during hammering was in any case below the allowable stress of pile materials. Pull-out tests of bitumen-coated piles showed little segregation of bitumen from the piles with enlarged lower portions. (3) Consolidation settlement of the alluvial clay layer caused settlement of the fill and, consequently, negative skin friction on piles. Frictional resistance of sandy soils was large. As generally known, negative skin friction was considerably reduced by the use of a bitumen-coated pile. (4) The bearing capacity of a pile driven into the bearing soil layer was attributed to the frictional resistance on the pile. (5) In case of a pile with enlarged lower portion, its lateral resistance could be maintained to a degree similar to that of a normal straight pile by filling the gap around the pile with sand.
