A p-y Q-z Method for Analyzing Helical Piles under Lateral Loading

Helical piles are composed of steel prismatic shafts and individual or multiple helical plate elements attached to them. These elements are commonly used as foundations in diverse applications such as pipelines, solar renewable energy farms, aquaculture farms, lightweight buildings, pedestrian pathways, among others. Under some of these scenarios, the helical piles are often demanded under vertical loading, for which the strength is usually calculated with bearing capacity equations and then verified with field observations of the required installation torque. Lateral demand provided by wind, earthquake, or inclined loads is also often present in these elements representing the critical design conditions that cannot be as easily verified with close form bearing capacity solutions or field torque measurements. To overcome these design challenges, engineers often rely on more advanced methods such as the p-y method to analyze the response of helical piles shafts under lateral loads. This method has proven to be efficient for pure prismatic elements; thus helical piles are analyzed neglecting any effect from the helical plates. In this paper, a simplified methodology for analyzing helical piles under lateral loading, including the effects of helical plates, is presented considering p-y curves around the shafts in combination with Q-z curves around the plates. The presented methodology is validated with 3D finite element analysis at different cohesive soil conditions and displacement levels.