Effects of helix shapes and locations on compression capacity of helical piles for offshore foundations

Piles are widely used in marine projects where inappropriate soils are present and soil replacement is not justified economically. Among various pile types, helical piles have been considered as a potential substitution for driven piles in offshore applications. The present paper investigates numerically the effects of tapered helices and inter-helix spaces to achieve the maximum compression capacity in homogeneous and in-homogeneous soil profiles. Both individual and cylindrical failure mechanisms were studied. Tapered helices with decreasing diameters from the top to bottom instead of the same number of identical helices were also studied. Results show that the best inter-helix spacing to helix diameter ratio is two to achieve the greatest pile capacity. Also, the compression load corresponding to 10% of the pile head settlement was found to be reasonable for computing the pile capacity. The results show that tapered helix piles offer better compression capacity than uniform helix piles with the same number of identical helices. In addition, tapered helix piles have almost similar load-settlement variation to solid frustum shape helix piles while in the latter more steel is consumed. In general, the present research highlights that using tapered helices due to their technical and economic performance is advantageous.