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Permanent link (DOI): https://doi.org/10.7939/R39K4617B

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Axial and Lateral Behavior of Helical Piles under Static Loads Open Access

Descriptions

Other title
Subject/Keyword
Helical pile
axial load
lateral load
lateral behavior
axial behavior
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Li, Weidong
Supervisor and department
Deng, Lijun (Civil and Environmental Engineering)
Examining committee member and department
Cruz Noguez, Carlos (Civil and Environmental Engineering)
Bayat, Alireza (Civil and Environmental Engineering)
Department
Department of Civil and Environmental Engineering
Specialization
Geotechnical Engineering
Date accepted
2016-06-24T13:52:20Z
Graduation date
2016-06:Fall 2016
Degree
Master of Science
Degree level
Master's
Abstract
Helical piles have been used extensively in Western Canada to support the superstructures particularly with applications in power transmission towers, commercial buildings, camps, and so on. Extensive research in helical piles has been conducted using physical testing methods; however, there has been insufficient research in the numerical modeling soil-helical pile interaction in axial or lateral directions. The present research is thus carried out to bridge the knowledge gap. The first part of present research is aimed to investigate the behavior of helical piles subject to axial static loading using field load tests and numerical simulation based on Beam-on-Nonlinear- Winkler-Foundation (BNWF) methodology. Field load tests were conducted on 26 single-helix piles including 15 compression tests and 11 tension tests in two types of soils in Alberta, Canada. The soils in the two selected sites were classified as medium to stiff clay, and medium to dense sand respectively. Three sizes of helical piles whose shaft diameters varied from 7.3 cm to 11.4 cm were tested according to the same test procedures. The load-displacement curves were obtained to show the axial behavior of the helical piles under axial static load. Installation torque was recorded per foot penetration into the ground to portrait the correlations between the installation torque and bearing or uplift capacity. Cone penetration tests (CPT) were applied to develop soil profiles of the test sites to provide input parameters to the numerical models. The field tests provide case studies to the subsequent finite element analyses of axial soil-pile interaction. A BNWF model was developed on the platform of Open System for Earthquake Engineering Simulation (OpenSees). Soil reaction springs (p-y, q-z and t-z) were adopted by the developed model to simulate the integrated behavior of piles. It was found that the existing soil reaction spring implemented in OpenSees were capable of simulating the axial behavior of helical piles. The second part of present research is aimed to investigate the lateral soil-pile interaction using the BNWF model developed in OpenSees. In the literature, the effects of helix on the lateral capacity of helical piles have not been quantified. The numerical model was calibrated against published results of lateral load tests of helical piles. Systematic parametric analyses of helical piles using the BNWF models were conducted to observe the lateral capacity improvement due to the change of size and embedment depth of the helix, diameter and length of the bucket (partially enlarged pile shaft), and the soil classification (clay and sand). The effect of these geometric factors on the lateral capacity of helical piles was quantified, and the results of the parametric studies may be used for the practical design of lateral capacities of helical piles.
Language
English
DOI
doi:10.7939/R39K4617B
Rights
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
Citation for previous publication
Li, W., Schmidt, R., Li, B., and Deng, L. 2015. In-situ loading tests of small-diameter helical piles and evaluation of design methods. Annual Conf. Canadian Geotechnical Society, Quebec City, Que.Li, W., and Deng, L. 2015. OpenSees simulations of axial behaviour of single-helix piles. Annual Conf. Canadian Geotechnical Society, Quebec City, Que.

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