Study of Interface Frictional Anisotropy at Bioinspired Soil-Structure Interfaces with Compliant Asperities

The transfer of load across soil-structure interfaces is of significant importance for the stability and service life of most geotechnical structures. Soil-continuum interfaces are relevant to many human construction activities; however, they also impact the likelihood of survival of numerous plants and animals. Through the process of evolution, many organisms have optimized load transfer across interfaces to fulfill their daily needs, such as hunting and feeding. The biological adaptation used in this research comes from the ventral scales on the underbelly of snakes. When a snake moves on a soil surface it generates enough propulsion force to initiate or maintain forward movement while it simultaneously minimizes the friction that opposes this movement. This feature is enabled due to the greater friction coefficient mobilized during backward (i.e. cranial) than during forward (i.e. caudal) movement. This characteristic is typically referred as friction anisotropy and is produced by the shape, stiffness, and angle of attack of the scales on the snake’s skin. This research explores the effect of asperity compliance and angle of attack of snakeskin-inspired surfaces on the shear strength and deformation behavior of sand-structure interfaces. The idealized snakeskin surface models are composed of asperities made from flexible plastic film of different stiffnesses embedded into a rigid base. The results from shear box interface shear tests highlight the effect of initial asperity angle, scale stiffness, and overburden stress on the shear strength and frictional anisotropy mobilized by the snakeskin-inspired surfaces.