Agata Iwan Candra, As’Ad Munawir, Yulvi Zaika, Eko Andi Suryo, Mahardi Kamalika Khusna Ali
Surface modification of pile foundations using cranial-oriented micro-asperities offers a novel bioinspired solution to improve pile-soil interaction in granular soils. This research examines the effect of asperity geometry ratio (L/H) and pile diameter on the mobilization of shaft resistance and the distribution of the lateral earth pressure coefficient (K). A series of laboratory tests was performed using steel model piles with diameters of 10 mm, 12 mm, and 15.85 mm, driven vertically to a depth of 240 mm in uniformly graded dry sand. CNC-fabricated piles were loaded vertically at 0.1 mm/s using a stepper motor controlled by Arduino R4; axial load and displacement were recorded in real-time using a Zemic load cell and a linear potentiometer. Cranial asperities with L/H ratios of 20, 26.67, and 33.33 were applied, while smooth piles were used as references. Among the tested configurations, L/H 20 consistently produced the highest Qs/σ′ and K values across all diameters. The improvement in skin friction exceeded threefold compared to the smooth pile, while the lateral pressure remained stable along the full embedment depth. Higher depth-to-diameter ratios (D/B) also supported the stability of K distribution at maximum penetration. ANOVA analysis confirmed that the influence of asperity geometry was statistically significant, with all configurations showing p-values below 0.05. These results provide a design reference for optimizing micropile performance in dry sandy soils, contributing to safer and more efficient pile design. This research advances the understanding of interface mechanics by integrating the anisotropic contribution of cranial asperity geometry and highlighting the role of active surface contact in reinforcing shaft friction mechanisms. © The Author(s) 2026.
Department of Civil Engineering, Kadiri University, 1 Selomangleng str, Kediri, 64115, Indonesia; Department of Civil Engineering, Brawijaya University, 167 MT. Haryono str, Malang, 65145, Indonesia
