Bearing Capacity Factors of Helical Piles Embedded in Cohesive Soils

Helical pile is a deep foundation system consisting of a central steel shaft, with helical-shaped steel plates affixed to its body by welding. Helical piles have been used in construction for over a century, especially in developed nations, but they have had limited applications, such as in transmission towers. However, with advancements in their design and the development of high-torque machinery, they have now garnered widespread recognition as a practical foundation solution. Many developed nations, alongside helical pile manufacturing companies, have introduced comprehensive codes and manuals covering various aspects, including design, manufacturing, installation, testing, and operational guidelines. Nevertheless, several ongoing research endeavors are being carried out to refine the helical pile design, accurately ascertain their load-bearing capacity, and establish regulatory codes in India. This study employs two-dimensional axisymmetric finite element analyses to scrutinize the performance of helical piles when embedded in cohesive soils. The failure criteria, failure mechanism, influence zone, and displacement contours generated under static axial loads have been assessed. In addition, a comparative study is conducted by employing analytical formulae based on limit equilibrium method. The results from finite element analyses, coupled with those derived from analytical expressions, were used to determine the bearing capacity factor N q and breakout factor N u . Subsequently, meticulous regression analyses were carried out to formulate simplified expressions for calculating N c and N u values.