Ashraf Nazir

Designing pile foundations to resist uplift forces is becoming of increasing concern, and is especially prevalent in the design of lightweight steel frame buildings or on sites with residual soils. This paper introduces a modern pile-modification strategy known as winged pile that increases pile-tension capacity by providing an affirmative anchorage close to the pile tip. In this study, a nonlinear 3D analysis with an elastic plastic soil model, an elastic pile material and interface elements are used to model the modified pile–soil interaction. A numerical study using finite element analysis PLAXIS-3D was run on piles without/with wings. Studies were done by changing the wing-width ratio (Dw/dp = 2, 3, 4 and 5), number of wings (nw = 0.0, 2 and 4). The effect of sand relative densities were also considered. Results indicated that the adopted wings at the pile end have a considerable effect in increasing the uplift capacity with lesser deformation. It has been found that, for the same wing-width ratio (Dw/dp), the wing efficiency for uplift capacity increases as the sand relative densities increase. For the wing-width ratio (Dw/dp of = 5) and number of wings of (nw =4) the improvement in the uplift capacity are found to be (2.2, 2.33 and 2.45) times of normal pile without wings for sand density of (30, 50 and 80%) respectively. The existence of such wings at the lower part of the piles was provided an ideal anchorage system because of the significant locking-up effect of the soils within the wings, resulting in increased uplift capacity.

This paper presents an experimental study of the behavior of an eccentrically loaded model ring footing resting on a compacted replaced layer of sand that overlies an extended layer of loose sand. Particular emphasis is placed on the potential benefits of reinforcing the replaced sand layer with geogrid reinforcement. Load configuration was designed to simulate ring footings under vertical loads and overturning moment caused by lateral loads. Several configurations of geogrid layers, number, and stiffness were used to study ring footings with different inner-to-outer-diameter ratios and load eccentricities. The effect of the depth and the relative density of the replaced sand layer was also investigated. Test results indicate that the behavior of an eccentrically loaded ring footing significantly improves with an increase in the depth and the relative density of the replaced compacted sand layer. However, the inclusion of soil reinforcement not only leads to a significant reduction in the depth of the rep...