Influence of Installation Parameters and Geometric Configurations on the Uplift Capacity of Helical Anchors: An Experimental Investigation

Abstract

Recent studies have demonstrated that installation-induced soil disturbance, advancement ratio, and installation rate can substantially affect the subsequent axial response of helical piles. However, systematic experimental comparisons that simultaneously relate installation torque, axial thrust, and post-installation uplift capacity across multiple geometric and operational variables in clay remain limited. This study investigated the coupled effects of helix pitch, advancement ratio, penetration speed, and shaft style on the installation and uplift behavior of helical anchors in prepared clay. Laboratory model tests were conducted using grouped anchor configurations, and installation torque, installation thrust, and uplift load–depth responses were recorded. An area method was introduced to quantify accumulated installation resistance from torque–depth and thrust–depth curves. Within the tested fixed-advancement-ratio pitch series, the tested pitch–speed combinations produced comparatively moderate variations in installation resistance and uplift capacity when the helix plate diameter was fixed. The installation condition represented by the advancement ratio and corresponding penetration speed influenced penetration–rotation compatibility: lower advancement ratios increased repeated shearing and torque, whereas higher advancement ratios reduced torque but increased thrust. Increasing penetration speed markedly increased accumulated torque but reduced ultimate uplift capacity from 478 N to 315 N. The shaft-style tests showed differences in plugging, suction, and local penetration resistance, with limited variation in helical-anchor uplift capacity. These findings indicate that installation parameters and geometric configuration should be considered together when optimizing helical-anchor installation in clay. The findings provide model-scale references for selecting helical-anchor geometry and installation procedures in prepared kaolin clay under conditions comparable to those tested.