Uplift Capacity Prediction of Continuous Helix Piles in Cohesionless Soils Using Cone Penetrometer Tests

Full-scale tests were performed on continuous helix piles in cohesionless soils. An investigation on the failure mechanisms is presented in this article. Prediction methods are also used for the estimation of the piles uplift capacity using CPT tests. For all tested piles, a cylindrical failure surface was found. The load–displacement curves highlighted that both the inter-helix spacing ratio S/Dh and the helix diameter Dh influence the uplift capacity. Using a statistical analysis, a new prediction method based on the CPT tests is proposed. This method permits to obtain the ultimate uplift capacity of continuous helix piles according to their geometrical parameters such as: inter-helix spacing ratio S/Dh, helix diameter Dh and shaft diameter d. The applicability of the proposed method was evaluated using four statistical criteria: (1) the best-fit line, (2) the arithmetic mean and standard deviation, (3) the cumulative probabilities, and (4) the log-normal and histogram distributions. Based on these criteria, the following conclusion can be made. The proposed method: (1) tends to underestimate the measured capacity of less than 1%, (2) the prediction probability of the ultimate load capacity within a 20% accuracy level is close to 96%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$96\%$$\end{document}.