Soil-Structure Interface Resistance Changes due to Rigid Awns

This paper presents a study on the impact of rigid awns and their deployment on interface friction. Awns are appendages attached to the exterior surface of a geo-system and bio inspired by grass seeds. Awns provide frictional anisotropy and assist the seed in self-embedding into the soil or clinging to animal hair. In geo-systems, like piles, deployable awns can provide frictional anisotropy reducing installation effort and increasing global capacity. In addition, flexible awns can be folded up to enable space saving for transportation. This paper presents the results from a set of interface shear tests in a modified direct shear device. Single rigid awns were tested at various angles, from horizontal, as a pseudo-static simulation of deployment, in loose and dense sand, in both the cranial (towards the head) and caudal (towards the tail direction). It is shown that awns opened at larger angles provide higher interface friction and that shearing in the cranial direction provided more resistance than in the caudal direction. This demonstrates that deployable awns could be used in geo-systems to provide friction anisotropy and increase capacity.