Load Transfer Mechanism of Screw Piles in Sandy Soils
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ORIGINAL PAPER
Load Transfer Mechanism of Screw Piles in Sandy Soils Hossein Soltani-Jigheh1 • Pouya Zahedi1,2
Received: 5 December 2019 / Accepted: 9 April 2020 Ó Indian Geotechnical Society 2020
Abstract In this research, the response and behavior mechanisms of screw piles and their correlations under compressive loading in sandy soils are analyzed. The results revealed that the bearing mechanism of screw pile can be extracted from the pile response curve. At nonlinear part of the pile response curve, screw pile acts individually and the shear strains within the soil are concentrated near the helix plates. The displacement and the load where changes in pile bearing mechanism occur were identified and named as transition displacement and phase transition load, respectively. The shear strains of the soil around the screw pile develop around the helix plates and move to each other as the load increases to merge a soil cylinder between the helix plates. Bearing mechanism of the screw pile changes to cylindrical mechanism, when the applied loading value passes phase transition load. The main parameters of the pile response curve such as phase transition displacement, phase transition load, initial slope of nonlinear part and slope of linear part depend on the pile geometry and soil specifications. Keywords Screw pile Bearing mechanism Pile response Soil properties Pile geometry Numerical modeling
& Hossein Soltani-Jigheh [email protected] Pouya Zahedi [email protected] 1
Department of Civil Engineering, Faculty of Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran
2
Researcher of East Azarbaijan Science and Technology Park, Innovation Center of Aras, Jolfa, Iran
Introduction Screw piles are used to resist axial compression, axial tension and lateral loads. Main parameters of these piles are pile length (L), inter-helix spacing (S), helix number (n) and helix diameter (Dh) (Fig. 1). The performance of screw piles depends on the interhelix spacing (S/Dh). For the piles with S/Dh greater than 3.0, under compressive loading, the helix plates act individually and the bearing capacity of the pile is determined by the summation of the individual bearing capacities of helix plates [1, 2]. For the piles with S/Dh lesser than 3.0, the soil between helix plates acts as a rigid cylinder and the frictional force between the soil cylinder and the surrounding soil as well as end bearing of lower helix resist against loading [3]. Zhang [4] showed that, in cohesionless soil, for S/Dh \ 2.0, the soil between helix plates behaves like cylinder and failure will be cylindrical. For these soils, Donal and Calyton [5] and Canadian and European offices [6] reported when S/Dh [ 3.0 each helix plate behaves independently. Failure mechanisms of the soil between the helix plates have been investigated experimentally by Hoyt and Clemence [2], Narasimha and Prasad [7], Meyerhof and Adams [8] and Bella [9]. Moreover, the failure mechanism of the soil around the helix plates in various soils has been studied
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