Lateral Performance of Two-Section Helical Piles in Soft Soils-Article

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The study evaluates the lateral performance of two-section helical piles (TSHPs) in very soft organic soil over soft clay, comparing them with one-section helical piles. Nine full-scale lateral load tests were conducted near Conklin, Alberta, alongside cone penetration and portable soil probe testing. The soil profile comprised muskeg to about 0.9 m, soft clay to about 6.9 m, and compact sand below.<br /><br />Test results showed nonlinear load–deflection behaviour and soil yielding near the pile surface. Increasing the upper shaft’s diameter or length generally improved lateral resistance: larger-diameter piles resisted about 8%–40% more load, while longer upper sections increased resistance by about 14%–29%. Greater embedment also improved performance. At low deflections, two-section piles performed similarly to one-section piles of comparable embedment, offering a potentially more cost-effective option. At larger deflections, one-section piles that extended into compact sand could develop greater resistance, likely because the sand provided partial fixity near the pile toe.<br /><br />The piles primarily rotated under lateral loading, with the centre of rotation moving deeper as load and embedment increased. LPILE Plus 5 analyses using p–y curves agreed closely with measured resistance at low deflections; predictions at 12 mm were within roughly 4% of test values. The authors conclude that these analyses can reasonably estimate TSHP lateral resistance when load-test data are unavailable. Installation torque trends also helped identify soil layers and compare soil consistency.

Keywords

lateral performance

helical piles

two-section helical piles

one-section helical piles

very soft organic soil

soft clay

full-scale lateral load tests

p-y curves

installation torque

soil yielding