Pullout responses of root-inspired anchors from dry granular media: effect of material stiffness, embedment depth, and geometrical complexity via centrifuge modeling

Abstract The development of tree root-inspired anchors aims to improve their mechanical performance by mimicking the architecture of tree roots while using less material than conventional ground anchors. This study explores the effects of material stiffness, embedment depth, and architectural complexity on the pullout performance of root-inspired anchors. Root anchor models were made with a wide range of material stiffnesses and architectural complexity. These models were subjected to pullout at three different depths while maintaining the same vertical effective stress through centrifuge tests. The results reveal that high material stiffness leads to greater initial stiffness and peak capacity for a given architecture. In contrast, low material stiffness results in longer duration of sustained resistance and greater residual capacity. Greater embedment ratio increases the peak resistance, but reduces the influence of laterally extended branch structures and thus architectural complexity. Comparisons with previous studies show that tree root-inspired anchors exhibit a greater pullout resistance than conventional plate-type anchors through soil arching, particularly at low embedment depth. Furthermore, a dimensionless criterion is proposed to capture the interplay among the material stiffness, anchor geometry, overburden stress, and embedment depth, which predicts whether anchors are expected to produce flexible or rigid pullout behavior. These findings demonstrate that tree root-inspired anchors show unique flexible pullout responses that are promoted by branches with greater lateral extent, deeper embedment, and lower material stiffness. This study provides deeper insight into the load transfer mechanisms of root-inspired anchors and advances the understanding of the factors that influence the type of behavior (i.e., rigid versus flexible) of embedded structural elements.