Effect of Installation Techniques on the Allowable Bearing Capacity of Modeled Circular Piles in Layered Soil

Abstract

The results of a comprehensive study on the effect of installation techniques on the allowable bearing capacity of modeled circular piles in layered sandy clay soil are presented. These results show the influence of driving by hammering and drop weights as well as boring techniques on load carrying capacity of modeled wooden piles driven or bored through layers of inter-bedded sandy clay soil. The investigation was carried out to study the influence of both driving and boring techniques on 20 mm diameter and 200 mm long modeled circular piles, driven/bored through specially conditioned layered sandy clay soil in a specially designed multi-purpose testing device in the laboratory. The piles were subjected to axial compressive load on incremental basis till failure. Modeled reinforced concrete instrumental test piles of diameters 200mm, 250mm, and 300mm were driven and bored through layered soil at a construction site. The effect of driving and boring on the pile-soil interaction and behavior as well as bearing capacity of these piles were also studied. Under similar conditions, driven piles have lower bearing capacity than identical bored piles. In addition, the overall settlement of bored piles is lesser than the corresponding driven piles, but the latter recorded a lesser settlement at lower depth beneath the pile cap than the former. In all, driven piles recorded less bearing capacity than the corresponding bored piles by approximately 12 - 18 % but are more easily handled and effective especially in a more cohesive soils