Investigation on multi under reamed piles with small bulb diameter in clay

Abstract

ABSTRACT This paper presents a study conducted on a multi-under-reamed pile having a small bulb size, but more than two in number. The proposed design is aimed to mobilize the side friction along the cylindrical surface formed between the bulbs to a greater extent and thereby enhance the load-carrying capacity with the minimum use of concrete. Pile load test was carried out on full-scale models of the conventional pile, and the proposed multi-tiny bulb pile. Finite-element analyses were performed to analyse the capacity of the proposed pile and to compare it with conventional bored cast-in-situ piles tested in the field. The validated model was then used to study the effect of various parameters on load-deformation behaviour and to understand the deformation contours of Multi-tiny bulb pile and to compare it with other existing pile geometries. It was found that Multi-tiny bulb piles of bulb diameter equal to the shaft diameter of conventional piles mobilize almost the same capacity as that of a solid conventional pile of uniform shaft diameter equal to that of bulb diameter of the former. The volume of material consumed by a Multi-tiny bulb pile to attain this was only 42% of a conventional pile considered for the study. The study suggests that Multi-tiny bulb piles if properly employed in the field with quality control can effectively replace the conventional piles in clayey stratum and also is a cost-effective option in terms of material input.