Effect of pile group size on its behaviour in sand underlain by compressible soil

Experimental investigation was carried out to throw the light on the behaviour of pile groups in sand underlain by compressible soil. Four groups 1x2, 2x2, 2x3 and 3x3 besides the single pile were manufactured. The pile shaft was cylindrical steel tube of 27.5mm outer diameter, d, and its length was variable ranging between 15d and 30d. The piles were instrumented by load cells at its tips. The soil medium was sand underlain by Foam layer representing compressible soil. The test results showed sever reduction in the ration of end bearing to total loads as a result of the presence of the compressible layer. This reduction depended mainly on the dimensionless distance t/B and the group size, B. A comparison between the loads of piles in sand only and that in sand underlain by compressible soil was performed to show the feasible effect of the compressible soil on the bearing capacity of the piles.