Effect of Lateral Load on Vertical Bearing Capacity of Helical Piles—Part II. Theoretical Study

The utilization of helical pile foundations in transmission towers is increasingly prevalent. This foundation must endure both vertical and lateral forces imposed by the transmission towers. However, there is insufficient theoretical research and calculation methodology to assess the impact of lateral loads on the vertical bearing capacity of helical piles. This paper explores the influence of lateral load on the vertical bearing capacity of helical piles through theoretical analysis. A practical calculation approach for the vertical load-bearing capacity of helical piles under combined loading conditions is proposed. This method considers the impact of lateral loads on both the pile shaft and pile helix vertical bearing capacity, using distinct discount factors denoted as k1 and k2, respectively. When a small lateral load is applied, it affects the bearing capacity of the shaft initially. The discount factor k1 is used to adjust the shaft bearing capacity. When a substantial lateral force is exerted, resulting in the rotation point of the helical pile descend, it impacts the load-bearing capacity of the helix. The discount factor k2 is utilized to modify the load-bearing capacity of the helix. The values for k1 and k2 are derived from numerical model tests reported in a companion paper. The effectiveness of the proposed computational approach is validated by comparing it to experimental outcomes documented in the existing literature.