Multi-axis loading tests on a small-scale tree roots model

Trees can be considered as “living structures”, subjected to a complex combination of vertical, horizontal and toppling loads, mainly deriving from tree self-weight and external actions (e.g. wind). From a geotechnical perspective, the root plate works as a shallow foundation, providing the tree anchoring resistance within the soil. This paper presents a small-scale 1g testing campaign aimed at investigating root plate-soil interaction by means of a new multi-axis loading frame. A 3D printed simplified root model embedded in a<br/>medium dense sand is subjected to displacement controlled loading paths, combining vertical and toppling actions. The experimental data are then interpreted in the light of the well-known macroelement theory, and the discussion suggests that such method could be used to reproduce the system mechanical response for different loading directions. The bases of the definition of (i) the limit locus, (ii) the hardening rule and (iii) the plastic potential are also concisely presented.