The uplift load capacity of an enlarged base pier embedded in dry sand
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ORIGINAL PAPER
The uplift load capacity of an enlarged base pier embedded in dry sand Ramli Nazir & Hossein Moayedi & A. Pratikso & Mansour Mosallanezhad
Received: 28 April 2014 / Accepted: 17 November 2014 # Saudi Society for Geosciences 2014
Abstract The purpose of this research is to determine the capability of (and the factors which affect the performance of) an enlarged base pier in resisting uplift capacity. Experiments were conducted in the reinforced bin box of an enlarged base pier with a shaft diameter ranging from 30 to 50 mm, base diameters between 75 and 150 mm and base angles of α = 30°, α = 45° and α = 60°. Tests were conducted in both loose and dense sand packing. A failure mechanism was studied in a glass box for loose and dense sand packing. A dry sand with a unit weight of γd = 14.80 kN/m3 and γd = 17. 0 kN/m3 was achieved for loose and dense packing, respectively. Increasing the bell angle and shaft diameter would result in a decrease of the net uplift capacity and failure displacement. This is due to the reduction in the amount of the sand column above the bell that resists the uplift of the pile. Failure displacements at a constant base diameter generally increased considerably with the increase of the embedment ratio but decreased with the increment of the sand density. It is thus apparent that the shaft diameter, bell diameter and bell angle are geometric factors which, together with the embedment ratio and the sand density, should be taken into account in the design of enlarged base piers.
Keywords Embedment ratio Large-scale modelling . Sand
. Enlarged based pier . . Uplift capacity . Belled pile
Abbreviations Ds Shaft diameter Db Base diameter α Base angle W Weight Pul Uplift load γ' Effective unit weight of soil γ Bulk unit weight N Porosity φ Internal friction angle Id Density index Ab Area of the soil Nu Breakout factor L Depth of embedment Qu Bearing resistance L/Db Embedment ratio
Introduction R. Nazir Department of Geotechnics & Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia H. Moayedi (*) Department of Civil Engineering, Kermanshah University of Technology, Kermanshah, Iran e-mail: [email protected] A. Pratikso Universitas Islam Sultan Agung, Semarang, Indonesia M. Mosallanezhad Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Over the past five decades, a wide variety of foundation anchor systems (belled pile, plate and pier, grillage, pedestal, pyramid, single and multi-helical anchor, grouted anchor, flute anchor, suction anchor) have been developed in order to satisfy the increasing demand for foundations with ever higher pull-out resistance (Ilamparuthi and Dickin 2001a, b). Enlarged base pier (belled piers) foundations for transmission line towers, with a slim high-rise structure, have proven to be an economical foundation type in providing resistance to extensive uplift load. They provide both compressive and uplift resistance (Hamza 1994).
Arab J Geosci
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