Field Testing of Axial Performance of Large-Diameter Helical Piles at Two Soil Sites

Helical piles are being used extensively in engineering applications in western Canada. There are insufficient studies on the axial load-transfer mechanism (ALTM) for helical piles, which require successful instrumentation of the piles. A field testing program, including two axial compression and two axial tension tests, was carried out on helical piles installed at two test sites consisting of clayey and sandy soils, respectively. The ALTM was investigated using strain gauges measurements. The development of the shaft and helix resistance as the axial displacement proceeded was established. The zone along the shaft where the shear resistance was not developed was estimated to be 2.5–5 times the helix diameter.