Abstract:

The strength of root-soil complex is significantly influenced by the morphology and spatial distribution of the root system. However, current studies have been limited to shear tests of root-soil complexes containing herbaceous roots and conventional indoor direct-shear tests. To investigate the impacts of root morphology and spatial distribution of perennial shrubs on root reinforcement, shearing experiments were conducted on in situ root-soil complex using a large-scale direct-shear apparatus (diameter 400 mm). The root morphological parameters (root area ratio RAR, root length density, root bulk density, and root surface area density), dilatancy and shear strength of the root-soil complex were measured. The distribution characteristics of root system along soil depth, the dilatancy of root-soil complex, and the correlation between root morphological parameters and shear strength were examined. Findings indicate that the root system exacerbates the dilatancy of the root-soil complex. Among the four evaluated root morphological parameters, RAR and root surface area density contribute the most to the shear strength. While Wu’s model effectively reflects the enhancement effect of root system on soil strength, it occasionally overestimates or underestimates the strength. The findings in the present research is conducive to promoting the application of root system in soil reinforcement.

Key words: shrub root morphology, root-soil complex, shear strength, dilatancy, large-scale direct-shear test