Centrifuge Modeling to Estimate p-y Curves in Unsaturated Cohesionless Soils

The p-y curve method is widely used in geotechnical engineering to understand the behavior of laterally loaded piles. Relatively little experimental research has been done to assess the lateral response of piles in unsaturated sands using the p-y curve method. This paper presents p-y curves obtained from centrifuge tests to show the influence of the unsaturated soil on the lateral resistance and, consequently, the p-y curves. A solid cylindrical steel pile was used to evaluate the lateral response of piles when embedded in F-75 Ottawa Sand. The centrifuge test setup was subjected to 50 g at the mid-depth of the embedded pile length to assess the lateral behavior of the pile in the prototype scale. Thus, a prototype pile with a diameter of 0.5 m and an embedded length of 9.5 m was simulated. The pile was laterally loaded using a loading actuator mounted on the centrifuge setup. The p-y curves were obtained using the strain gauges instrumented along the circular pile surface. The lateral resistance was obtained by double differentiation of the bending moment profile, while the lateral displacement profile was obtained by double integrating a fitted curve on the curvature data with the necessary boundary conditions. Experiments included saturated and a mix of unsaturated-saturated soil. The water table was lowered to the desired elevation in-flight prior to lateral loading for the unsaturated-saturated soil test. This paper discusses a fundamental understanding of how water table fluctuation can influence the behavior of laterally loaded piles for a performance-based design.