Date of Award
Master of Engineering Science
Civil and Environmental Engineering
Dr. M. Hesham El Naggar
Helical piles represent an efficient deep foundation system that has many applications varying from use as anchors for transmission towers to supporting large compressive loads as well as lateral loads. Helical piles are made of steel shafts with one or multiple helices attached to it, and are installed by rotational force applied through a drive head.
The objective of this thesis is to evaluate the performance characteristics of helical pile groups subjected to axial compressive and lateral loads, independently. The effects of pile- soil-pile interaction (group effect) on both the ultimate capacity of the group in terms of group efficiency factors, and on the performance of the group in terms of settlement ratios and interaction factors, are investigated with the aid of three-dimensional nonlinear finite element analysis using the suite, ABAQUS/Standard.
Five axial compression load tests and three lateral load tests were conducted in northern Alberta site, representing sand, and in northern Ontario site, representing clay, using non instrumented full-scale piles. The test results were used exclusively to calibrate and verify the numerical models that were then used to perform a parametric study. The results of the calibrated numerical models were in good agreement with the field test data using representative soil properties and realistic modeling assumptions.
The parametric study involved piles installed in two types of soil: dry sand; and saturated clay. The soil strength ranged from loose to very dense sand and soft to very stiff clay. The piles configurations included two-helix piles with inter-helix spacing of 1, 2, and 3 helix diameters. The piles are spaced at five different distances: 2, 3, 4, 5, and 10 helix diameters. The results of the parametric study showed that the group effect for helical pile is relatively less significant than the case of conventional piles. It was also found that for the range of typical helical pile spacing used in industry (around 3 times the helix diameter), the group effect is insignificant.
Elsherbiny, Zeyad Hany, "AXIAL AND LATERAL PERFORMANCE OF HELICAL PILE GROUPS" (2011). Digitized Theses. 3273.