Effect of soil saturation conditions and helical configurations on compression capacity of screw piles

Abstract

Helical piles provide many advantages over other conventional piles system. Most studies focuses on the performance of these piles in the dry and fully saturated soils. Rare studies are curried out to evaluate the performance of helical piles in partially saturated soils. Small scale models of steel piles of 600mm length with single, double, and triple helices have been embedded in cohesion less soil a depth of 400mm, the inner pipe diameter (d) was 20 mm and the helix diameter (D) was 50mm with spacing between helices of 3D, (i.e wing ratio (S/D) of 3). The models were tested using different soil saturations conditions (dry, fully saturated, and partially saturated soils). A pipe pile model was tested as a reference for bearing capacity improvement ratio. The results showed that the helical pile models and the pipe pile in fully saturation condition have less ultimate capacity compared to other soil conditions. The increment of bearing capacity increased for partially saturated soils than that of fully saturated soil by 1.5 to 1.8 times. The percentage of improvement of bearing capacity for additional helices single double and triple, embedded within fully saturation soil were 33.3%, 45.0% and 108.3% respectively, than shaft pile only.