Field Evaluation of the Installation and Pullout of Snakeskin-Inspired Anchorage Elements

Abstract

Soil nails and tieback anchors are used extensively for excavation support and slope stabilization; however, their performance can be complicated by limited pullout capacity or installation challenges. This paper presents the results of field load tests performed on anchorage elements with snakeskin-inspired surfaces that do not require grout and that can reduce the force required for installation. These tests evaluated the effects of the asperity geometry, soil type, and embedment depth on the anchor load transfer behavior and pullout capacity. The tests consisted of jacked installation and pullout loading in sites consisting of dense sand and structured silt. The test results in sand indicate that the installation force and pullout skin friction increase as the asperity height is increased and the asperity length is decreased. The pullout capacity of the snakeskin-inspired anchors in sand was between 1.2 and 4.2 times greater than the capacity of a reference rough anchor. In the structured silt site, disturbance during installation influenced the pullout behavior, resulting in a decrease in anchor capacity as the asperity height was increased. However, the anchor capacity with small asperity heights was greater than that of the reference rough anchor. The snakeskin-inspired anchors mobilized direction-dependent skin friction, resulting in pullout skin friction values that were as much as 3.0 and 4.5 times greater than those generated during installation in the sand and silt sites, respectively, due to mobilized passive resistances during pullout. The results indicate that the snakeskin-inspired anchors can outperform conventional driven anchors in sands. However, the possible effects of installation disturbance should be evaluated carefully in sensitive, structured soils.