BEHAVIOR OF HELICAL PILES – AS A GEOENVIRONMENTAL CHOICE – BY FRUSTUM CONFINING VESSEL
Javad Khazaei 1  
,  
 
 
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Department of Civil and Environmental Engineering, Amirkabir University of Technology (AUT), Tehran, Islamic Republic of Iran
CORRESPONDING AUTHOR
Abolfazl Eslami   

Amir Kabir University, Hafez ave, 1969754113 Tehran, Iran
Publish date: 2016-09-01
 
Adv. Sci. Technol. Res. J. 2016; 10(31):8–22
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ABSTRACT
Helical piles are environmentally friendly and economical deep foundations that, due to environmental considerations, are excellent additions to a variety of deep foundation alternatives available to the practitioner. Helical piles performance depends on soil properties, the pile geometry and soil-pile interaction. Helical piles can be a proper alternative in sensitive environmental sites if their bearing capacity is sufficient to support applied loads. The failure capacity of helical piles in this study was measured via an experimental research program that was carried out by Frustum Confining Vessel (FCV). FCV is a frustum chamber by approximately linear increase in vertical and lateral stresses along depth from top to bottom. Due to special geometry and applied bottom pressure, this apparatus is a proper choice to test small model piles which can simulate field stress conditions. Small scale helical piles are made with either single helix or more helixes and installed in fine grained sand with three various densities. Axial loading tests including compression and tension tests were performed to achieve pile ultimate capacity. The results indicate the helical piles behavior depends essentially on pile geometric characteristics, i.e. helix configuration and soil properties. According to the achievements, axial uplift capacity of helical model piles is about equal to usual steel model piles that have the helixes diameter. Helical pile compression bearing capacity is too sufficient to act as a medium pile, thus it can be substituted other piles in special geoenvironmental conditions. The bearing capacity also depends on spacing ratio, S/D, and helixes diameter.