Effects of cross-section shape on cyclic lateral response of steel piles in residual soil

The lateral cyclic loaded piles' behaviour in bonded residual soil is still poorly understood by classical geotechnics. Currently used models reproduce the behaviour of residual soils based on those from other unstructured soils, resulting in a conservative design. This paper thus proposes to evaluate the behaviour of three different shapes of steel piles embedded in bonded residual soil when submitted to cyclic lateral loading tests. These tests encompassed 10 mm displacements performed on the top of the piles (considering service (working) displacements). The piles, with a length of 2·0 m, were equipped with strain gauges at ten levels. The evaluated cross-sections have circular, square and H shapes, all with similar inertia moment and diameter/edge of 0·15 m. The effect of cyclic loading has shown a degradation of available lateral load, mostly in the first 30 cycles. This degradation is also seen at the bending moments obtained. The piles have also shown a short free-headed behaviour that rotates from a certain depth. Finally, the study showed that the square cross-section-shaped pile had the best performance under service (working) cyclic displacements when embedded in bonded residual soil, followed by H cross-sectioned pile and finally the circular cross-sectioned pile.