Search for: All records

Structures with deployable and compliant mechanisms are new to the domain of underground geotechnical systems. An anchor with rotationally deploying compliant thin-wall elements has been developed. This paper presents variations of this anchor that are targeted to increase the surface area associated with the anchor. This increased surface area correlates to higher skin friction to better resist tensile forces. The number and sizing of the deployable components, called awns, are investigated. The work presented here includes methods to change the deployment behavior of the awns by changing the shape of the awns and by using functionally graded materials for increased resistance when the anchor is subjected to uplift forces. Test members were fabricated from a combination of flexible and rigid polymers via additive manufacturing. Experimental testing included anchor deployment tests and awn tension tests. For deployment tests, torque was applied to an anchor placed in clear sand. Awn tension tests provided additional information about the deformation of functionally graded awns through isolated testing of the awns. The presented design and experimental methodologies give insights into the behavior of small-scale deployable anchors. 

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 geosystems to provide friction anisotropy and increase capacity.