Helical anchors are increasingly being considered for use in offshore floating facilities, such as floating wind turbines and wave energy devices. Some studies have explored the installation behaviour of helical anchors with varying advancement ratios (AR) in offshore environments. However, the specific contributions of different helix sections such as the top and bottom helix surfaces to installation resistance at varying pitch to helix diameter ratios (p/D) remain underexplored. This paper investigates the effects of these contributions on the installation resistance of helical anchors in uniform clay. Using 3D finite element (FE) analysis with large deformation and the Coupled Eulerian - Lagrangian (CEL) method in Abaqus, we examine that, under a constant vertical installation velocity of 0.21 m/s and rotational speed of 0.5 revolution per second (rps), the impact of different pitch to helix diameter ratios (p/D), hence different advancement ratios (AR). The underlying mechanisms of installation resistance are explored through examination of the behaviour of both the top and bottom helix surfaces. It is shown that the helix generates most of the soil resistance for all p/D ratios investigated. The pullout resistance has also been studied which shows that changing p/D ratios does not affect the capacity significantly for the perfectly plastic undrained condition considered here.