Analyzing Geosystems with Deployable Compliant Mechanisms for Enhanced Tension Capacity

Current research into deployable and compliant structures focuses on their applications above-ground. Deployable structures have benefits in the construction industry because they can be transported compactly and installed easily on site. These benefits can be extended to underground applications which have not been widely investigated experimentally. Geotechnical structures, loaded primarily in tension, risk brittle collapse or displacement accumulation under extreme loading. To address this concern, members are oversized or components are added. Deployable structures offer a way to resist extreme design loading while increasing system resiliency and decreasing material cost, transport, construction time, and environmental impact. The goal of this work is to develop compliant attachments to the exterior of tension-loaded geostructures that deploy passively and increase the bearing area and capacity. This novel arrangement consists of a tension-loaded member (a pile) and compliant components (awns). When twisted, the awns deploy, entrapping soil and increasing surface friction. This increases the tensile capacity of the pile. Test members are fabricated via additive manufacturing using rigid polymer and rubber from Stratasys. They are rotated in clear sand by manually pulling cables with a load cell to measure applied tension. Using a machine vision plugin, rotation data is collected from video footage during experimental tests. The performance of the geometry is evaluated based on predictable awn deployability and the tension load of the geosystem. This paper presents parametric studies and experimental tests of adaptive torque-driven underground structures at small scale. With both structural and sustainability benefits, the deployable attachments increase the tension capacity of ground anchors while decreasing the embodied energy of the anchors.