Influence of Shaft Configuration and Method of Installation on Load Carrying Capacity of Pile Foundations

Abstract

The load carrying capacity, otherwise known as the bearing capacity of pile foundations has been reported to be influenced by many factors. Theoretically and from empirical pile baring capacity equations, the shape or configuration of the piles as well as method of installation employed during construction affect its bearing capacity. This article presents the results of laboratory and field investigations on the influence of shaft configuration and method of installation on the bearing capacity of modeled piles carried out on soils in the metropolis of Minsk, Belarus. Conical piles, with tapered cross section have higher bearing capacity in fairly homogenous soils, (either soft or stiff). In sandy and silty sand soils, especially where fine sand overlaid a stronger coarse sand layers, driven piles (installed by hammer or vibrator) have higher bearing capacity than bored piles, whereas the latter have higher bearing capacity where soft soil layers sandwiched between stronger strata. Cylindrical piles installed by boring method have higher bearing capacity in sandy soils than prismatic pile installed by driven, but the latter gave higher bearing values in layered soil with thicker stiff silty clay above sandy layers. In addition to this, the results, show bearing capacity increments of 10% in bored piles, 21% in hammered driven piles, and 26% in vibrated driven piles. The bearing capacity of conical piles with tapered cross section is 2-3 times higher than cylindrical piles and 1.5 – 2 times higher than prismatic piles respectively. Pile driving (by hammer or vibrator) yielded higher result in sandy soils, boring is better in cohesive clay and silty clay soil.