Estimating Soil Reinforcement by Tree Roots using the Perpendicular Root Reinforcement Model

Abstract

Tree roots are generally understood to reinforce soil by increasing soil shear strength. However, few studies have quantified soil reinforcement by tree roots. This study estimated soil reinforcement by larch [Larix kaempferi (Lamb.) Carrière] and Korean pine (Pinus koraiensis Siebold et Zucc.) roots using the perpendicular root reinforcement model. Root area ratio (RAR) and root tensile strength were measured for each species to apply to the model. RAR ranges were 0.02-0.27% for larch and 0.08-0.23% for Korean pine. The root tensile strengths of larch and Korean pine ranged from 5.8-38.8 MPa and 8.3-75.6 MPa, respectively. The model indicated that roots increased soil shear strengths by as much as 3.9-28.2 kPa for larch and 13.5-35.4 kPa for Korean pine, implying that roots have substantial effects on slope stability. Moreover, results from the perpendicular root reinforcement model can be practically applied with a relevant reduction factor, considering the simplicity and limitations of the model.