Abstract
The main objective of this paper is to design, manufacturing and testing of new loading rig machine to install and testing (i.e. compression and tension load capacity) of screw pile models in both cohesive and cohesionless soil layers. The mainframe was fabricated from thick steel sections, 8mm steel plates that welded together to construct a heavy and strong frame, that able to resist the expected loads during installation (linear and rotational movement at the same time) and testing of the screw pile models (model of loading test). Two independent gearbox motors (actuators) are used to supply the rotational and vertical movement. To provide precise control of velocity, the master gearbox motor, that can convert the rotary motion to a linear motion for vertical displacement along two screw bars via two ball screw systems, and four stainless guided rods to prevent rotation or inclination the bearing plate (rig) which manufactured from high stiffness stainless-steel was used. The second gearbox motor (‘slave’) mounted on the bottom loading plate that rotates the multi-plate screw pile. It was observed that the measured compression and tension load capacity of screw pile models illustrated the actual behavior of such kind of piles and this machine can be used in both conventional piles (i.e. pipe piles) and screw pile model.
Highlights
Many studies were conducted on different soil specimens using principles of physical modeling to investigate different engineering problems, in the cohesionless soil in both dry and saturated state
To compared the results of capacity that investigate in single helix case, the pipe pile capacity is added to the curves (i.e. No helix pile or shaft model only), it was found that the screw pile model that has a wing ratio 4 (i.e. H1Dh=80 or helix diameter 80mm) was about 11.5 higher for a piles (H1D60 ) that have diameter 60mm whereas it was 31.5% higher than the measured value for the model that has diameter 50mm and 55% higher than the model of that has diameter 40mm while the load capacity was 130% higher than the conventional model that has a zero wing ratio
For multi-helix screw pile model groups, it was observed the same behavior that investigated in the single helix case; but the increase in compression capacity was found for the screw pile model that has a diameter 50mm was about 7.5% and 61.5% higher than the measured value for the model that has a wing ratio 2 (i.e. Dh=40mm) whereas it was 27% higher than the determined value of the model that has a diameters 30mm, while the compression capacity was 161% higher than the determined value for the pipe pile
Summary
Many studies were conducted on different soil specimens using principles of physical modeling to investigate different engineering problems, in the cohesionless soil in both dry and saturated state. Installation and testing of screw pile models are commonly investigated problems. The design of a screw pile involves the choice of its shaft length and diameter as well as a specific arrangement of flanges including their number, diameter, Dh, spacing to diameter ratio, S/Dh, and the embedment depth to diameter ratio (H/Dh) of the top flange. All these parameters can be influenced on the pile ultimate capacity (Wang et al, 2017). The design of screw piles involves the selection of a reliable method and consideration of specified performance and loading criteria
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