Investigation of axial loading effect on the behavior of helical piles with numerical analysis methods in cohesionless soils

Helical piles are factory-manufactured steel foundation elements, typically consisting of a central shaft, a conical tip, single, double or multiple helical plates, extension sections, and couplings, which can be installed into the soils by rotation through the application of a torque. In this thesis study, the behavior of helical piles embedded in cohesionless soils and subjected to axial compressive loading was investigated using numerical analysis methods. Within this scope, the load-displacement behavior, failure mechanisms, and ultimate axial bearing capacities of model helical piles with various structural configurations embedded in both dense and loose sand have been investigated by subjecting numerically to axial compression loads. The novelty and original contribution of this thesis lie in the analysis of axially loaded helical piles in sands of varying densities using multiplier elastoplastic analysis (MEPA), incorporating problem-specific mesh adaptation within OPTUM G2 geotechnical software. Two-dimensional axisymmetric numerical models were designed, discretized into finite elements with an automatic adaptive mesh refinement, and subjected to axial loading in the multiplier elastoplastic analysis mode. The ultimate compressive bearing capacities of the piles were determined from the numerically derived load-displacement curves based on a %5D limit displacement criterion, and the results were compared against experimental and analytical outputs. Following validation with test data, parametric studies were conducted to examine the effects of medium-dense sand and model scaling. In conclusion, it has been demonstrated that OPTUM G2 software yields successful and reliable results for modeling and analyzing helical pile-cohesionless soil interaction under axial loading conditions.