Effects of scour-hole dimensions and bulb positions on the lateral response of under-reamed pile in soft clay

Abstract

The failures of pile foundations in water-borne structures are often attributed to the scouring phenomenon. Even though many studies are available on the countermeasures against scour around the pile, no attempt is made to increase the load-carrying capacity of pile foundation by changing the pile geometry. Therefore, in the present study, the effect of scouring on the lateral response of a single under-reamed pile in soft clay is investigated using three-dimensional numerical analysis. The variables considered in the present study are embedment ratio and bulb position of the under-reamed pile, depth, slope angle, and bottom width of the scour-hole. For a given scour-hole dimension, the lateral load-carrying capacity of the under-reamed pile increases; whereas, deflection, maximum negative shear force, and bending moment in the shaft portion reduce compared to the pile without bulb. A notable improvement in the pile response is found when the bulb is placed just below the scour-hole. The lateral load-carrying capacity of the under-reamed pile reduces with an increase in depth and bottom width of scour-hole from the pile surface and a decrease in slope angle of scour-hole. Pile responses reduce with the consideration of stress history due to excavation.