Effect of Helix Position on the Lateral Resistance of Battered Single-Helix Piles Located on a Sandy Slope Crest

Abstract

Helical piles are commonly used as foundations under electrical transmission towers, bridge abutments, highway signs, and light poles. The present experimental investigation focused on the lateral resistance of vertical and battered single-helix piles installed on the crest of Slopes 1V:2H and 1V:3H. The helix was placed at various positions below the ground surface, such as 0.25 Lp, 0.35 Lp, and 0.45 Lp (“Lp” refers to the embedment length of the pile), to analyze the influence of helix position on the lateral capacity of single-helix piles. The negative batter angle was varied as 7.5°, 15°, and 22.5° for all single-helix piles with different helix positions. The lateral capacity of the battered helical pile was compared with that of the vertical helical pile and the vertical regular pile (without helix) to assess the batter efficiency and net efficiency, respectively. A linear regression model was proposed to depict the variation of batter efficiency with several significant response variables like slope angle (α), batter angle (β), pitch (p), helix diameter (Dh), and shaft diameter (Dp). It was found that the battered single-helix pile with a helix at an embedment depth of 0.35 Lp is beneficial in improving the allowable lateral capacity for batter angles up to 15° on Slope 1V:2H. The helix position closer to the ground level (h = 0.25 Lp) was relatively efficient on Slope 1V:3H because higher lateral resistance mobilization occurs at a relatively shallow depth on the gentle slope. The allowable lateral capacity of the single-helix pile battered at 22.5° showed a remarkable improvement by 50%–53% on Slope 1V:2H and 22%–32% on Slope 1V:3H. The effect of helix was significant at smaller batter angles of 7.5° and 15° but turned marginalized at a higher batter angle of 22.5°.