Influence of Pile Shape on Resistance to Lateral Loading

The lateral resistance of pile foundations has typically been based on the resistance of circular piles and most instrumented lateral load tests and cases history have involved circular piles. Some researchers have theorized that the lateral resistance of square piles will be higher than that of circular pile for various reasons, but there is no comparative test data to support these claims. To provide basic comparative performance data, lateral load tests were performed on piles with circular, square and H sections with similar width/diameter under the same granular fill conditions. Although the square and circular pile sections had nearly the same moment of inertia, the square pile provided greater lateral resistance. The lateral resistance of the H pile was smaller than the other two pile shapes but higher than what would be expected based on the moment of inertia. Increasing the effective width to account for the shape effect was insufficient to account for the increased resistance. To provide agreement with the measured response, p-multipliers of 1.2 and 1.35 were required using the program LPILE for the square pile and H piles, respectively. Using the back-calculated p-multipliers provided very good agreement between the measured and computed load-deflection curves.