Experimental and numerical study of the bulb's location effect on the behavior of under-reamed pile in expansive soil

Abstract In this experimental and numerical analysis, three varieties of under-reamed piles comprising one bulb were used. The location of the bulb changes from pile to pile, as it is found at the bottom, center, and top of the pile, respectively. PLAXES 3D was used to conduct the research. In expansive soil, the under-reamed piles were 350 mm long, with the pile tip in dense sandy soil. The experiment was carried out in both saturated and unsaturated circumstances. The influence of the bulb location on the pile's bearing capacity for vertical and lateral loads, as well as the amount of swelling pressure and upward movement owing to swelling, was investigated. The results showed that in the unsaturated state, the bulb at the top of the pile gives bearing that is higher than the bulb at the bottom of the pile and near to the bulb in the center. In the case of unsaturated soil, the closer the bulb is to the top, the larger the bearing capacity, whereas in the event of swelling, the bearing capacity is highest when the bulb is in the middle of the pile. The same is true of the pile's upward movement, which is greater when the bulb is at the top than when it is at the bottom.