Effect of Lateral Load on Vertical Bearing Capacity of Helical Piles—Part I. Numerical Simulation

Helical pile foundations are increasingly utilized in transmission line projects. The unique nature of transmission line loads necessitates that helical pile can provide adequate vertical bearing capacity under combined lateral and vertical loads. To investigate the influence of lateral load on the vertical bearing capacity of helical piles and establish a calculation methodology for their vertical bearing capacity, numerical simulations were conducted using the finite element software PLAXIS 3D. These simulations were based on previously documented indoor experiments found in the literature. After the numerical model was validated, numerical static load experiments were performed on helical piles under varying lateral-vertical load ratios. The load-vertical displacement curves and soil slip surfaces were obtained (as reported in this paper). Additionally, a theoretical study on the calculation method for the vertical bearing capacity of helical piles under combined loads was undertaken and is reported in a companion paper. The numerical simulation study yielded the following findings: Under combined loads, the vertical bearing capacity of helical piles decreases, with a more pronounced reduction in the compressive bearing capacity. Moreover, with an increase in lateral load, the main soil slip surface is shifted from the position of the pile helix to the upper part of the pile shaft. Furthermore, the soil slip zone at the position of the shaft increases in both size and depth.