An Experimental Study on Vertical and Oblique Pullout Capacity of Belled-Wedge Piles in Cohesionless Soil

The study deals with the uplift and oblique pullout (inclined loading) capacity of tapered piles and tapered piles connected with an enlarged base at the bottom (belled-wedge piles). Two aluminum piles with taper angle of 1 degree and 2 degrees, each having a length of 300 mm, were used. The 1 degree tapered pile having a top diameter of 48 mm and bottom diameter of 37.5 mm, while the 2 degree tapered pile has a top diameter of 48 mm and bottom diameter of 27 mm. Bells (enlarged bases) at the bottom are made of aluminum and have different bell angles of 30, 45, and 60 degrees. The piles were placed into model tank of size 1200 × 720 × 750 mm filled with cohesionless soil medium. The model tank is made of mild steel. The pile combinations such as tapered pile, tapered pile connected with different bells at bottom are tested under three different loading angles namely 0, 30, and 45 degrees and uplift capacity of each combination was determined. The results indicated that uplift capacities of tapered piles are influenced by taper angles and Db/Ds (diameter of bell to average diameter of shaft) ratio. The oblique loading angles also play an important role in uplift and oblique pullout capacity of piles. The belled-wedge pile performs better under uplift loads. Conventional tapered piles are highly effective in resisting compressive loads due to the change in cross-sectional area and better material distribution along the length of the pile. Additionally, tapered piles play a significant role in reducing negative skin friction in loose and filled soils.