Small-scale modelling of root-soil interaction of trees under lateral loads

Aim (1) To understand the tree root-soil interaction under lateral and moment loading using a physical modelling technique; (2) To detect the possible factors (e.g. root architecture, water condition, and stress level) influencing a tree's pushover behaviour; (3) To identify suitable scaling laws to use in physical modelling. Methods Two 1:20 scaled root models with different architectures (namely, deep and narrow, and shallow and wide) were reconstructed and 3D printed based on the field-surveyed root architecture data. Pushover tests were performed both in elevated-gravity (centrifuge 20-g) and normal-gravity (1-g) conditions. Results The shallow and wide model showed higher anchorage strength than the deep and narrow model. Regardless of the root architecture, the root anchorage strength measured from dry soil was higher than that from saturated soil. However, once the effective stress was the same, regardless of water conditions, the root anchorage strength would be the same. Conclusions The presence of water decreasing the soil effective stress and key lateral roots extending along the wind direction play a significant role on a tree's pushover resistance. Centrifuge tests showed comparable results to the field pullover measurements while 1-g model tests overestimated the root-soil interaction, which could be corrected for soil strength by using modified scaling laws. Keywords Root-soil interaction. Pushover . Centrifuge. Moment capacity. Root system architecture. Water condition Abbreviations ABS Acrylonitrile Butadiene Styrene CPT cone penetration test DBH diameter at breast height DSA direct shear apparatus ND narrow and deep (root model) PSD particle size distribution WS wide and shallow (root model) Plant Soi