Shear characteristics of soil specimens with high water content containing roots of exotic herbaceous plants using sodding method in the second year.

Abstract

Direct shear tests were conducted on high-water-content soil specimens containing roots of three exotic herbaceous species (KBG, CRF and MF) in the second year after sodding in Tokachi region, Hokkaido, to evaluate the effect of root-systems indices on strength parameters ( cohesion c and shear resistance φ). Shoot and root growth varied with construction timing and site conditions. Vegetation cover was higher on flat ground and north-facing slope, and root-system indices were more favorable in plots sodded in late September. Regardless of site condition and construction timing, ⊿c ( increase in c ) showed a positive linear relationship with root-system indices that passed through the origin, whereas ⊿φ ( increase in φ) showed a positive linear relationship with a non-zero intercept. These results suggest that a minimum root amount in the specimen is required to achieve slope-conservation effects indicated by ⊿φ.