Analytical modelling of skin resistance in sandy soils incorporating cranial asperity effects on pile surfaces

Predicting pile skin resistance in sandy soils is challenging due to the complex behavior at the pile–soil interface. This study presents a closed-form analytical model that incorporates the cranial asperity ratio (L/H) into classical formulations and validates it through laboratory tests. Steel piles with a 10 mm diameter and L/H ratios of 20, 26.67, and 33.33 were tested in uniform Brantas sand and compared with a smooth pile. Cranial asperities increased skin resistance by 601.37%, 469.45%, and 367.06%, with L/H 20 identified as the most effective configuration. One-way ANOVA showed significant differences among pile types (p < 0.05), while model–experiment comparisons revealed no significant discrepancy (p > 0.05). The findings indicate that interlocking and dilation induced by cranial asperities govern the mobilization of skin friction. The proposed model offers a validated basis for incorporating bio-inspired asperities into foundation design to enhance efficiency and promote sustainable construction.