Shaft Resistance of Piles in Normally Consolidating Marine Clay Subjected to Compressive and Uplift Load

This paper presents 24 test results on instrumented hollow tubular aluminum close ended floating piles in laboratory to examine the mechanisms of load transfer between the piles surface and normally consolidating marine clay. Hollow aluminum tubes of 32mm external diameter and wall thickness of 1mm and length to diameter ratio of 10, 20 and 30 were used as model single piles. Compression and pullout tests were carried out at time periods of 0 to 6hr, 0 to 12 hrs, 0 to 18 hrs and 0 to 24hrs from the time of installation. Multiple neutral planes are observed along the depth of the pile, which is contrary to the present understanding of load transfer. The variation of skin friction with respect to maximum shear strength of soil in undrained condition is about 10 to 200 %. Design stipulations have been proposed based on model tests findings.