Pullout responses of root-inspired anchors in transparent soil: visualizing anchor-soil interaction and correlation analysis

Abstract

Understanding the pullout responses of root-inspired branching anchors is essential for developing efficient bio-inspired anchorage and foundation systems. In this study, transparent soil modeling using both transparent sand and transparent cemented soil was employed to investigate the pullout capacity and anchor-soil interaction of anchors with varying branch configurations. The pullout response exhibited three stages: initial increase, peak resistance, and post-peak softening. Anchors in transparent cemented soils (TCS) achieved greater peak forces with larger displacements than in sand, and the pullout capacity increased with branch number, angle, and node in both soils. Particle image velocimetry revealed that soil deformation initiated locally around branch nodes and lateral branches and progressively expanded vertically, evolving into a soil mobilization dominated by soil arching as branch number increased. In TCS, shallow failure developed sequentially through surface heave, shaft cracking, branch cracking, and failure surface expansion, with more complex branch configurations mobilizing larger soil volumes and triggering earlier acceleration in mobilization. Correlation analyses among pullout mechanical indicators, soil failure metrics, and anchor morphological descriptors showed a strong linear relationship between peak pullout force and total mobilized soil volume. The vertical projected area (A_bearing) emerged as a robust first-order parameter linking anchor geometry, soil mobilization, and pullout capacity. These findings provide direct visualized insights into anchor-soil interaction mechanisms and offer guidance for the rational design of root-inspired anchorage systems.