Shaft and Base Capacity of Snakeskin-Inspired Piles from Centrifuge Pile Tests

Many deep foundation applications require large shaft resistances for tensile loading, such as reaction piles and caissons. A suitable analog for designing surfaces whose load transfer response depends on the direction of loading is the skin along the underbody of snakes. Snakes have developed scales that minimize frictional resistances when they move forward (caudal direction, along the scales) and maximize frictional resistances when they move backward (cranial direction, against the scales). Previous studies show that surfaces designed based on such analogues exhibit directional dependence in terms of both interface friction angle and dilation. In order to assess the shaft and base capacity generated by piles with such surfaces, a series of centrifuge load tests were conducted on model piles with internal strain gages to evaluate the mobilization of shaft and base resistances. It was found that piles installed in the caudal direction mobilized smaller installation forces and similar pullout capacities compared to the rough pile, whereas piles installed in the cranial direction generated greater installation forces and a similar pullout capacity compared to the smooth pile. In addition, spatial variability in the model was assessed using CPT soundings and it was found that the shaft texturing had a negligible effect on the unit base resistance during installation. The results presented highlight that the surface of piles can be designed to reduce skin friction mobilized during installation relative to the skin friction generated during tensile loading resistance.