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.

Research on the Strength Variation of Root-Clay Systems under Freeze-Thaw Action

“…Bourrier et al established a numerical model for the direct shear tests of discrete soils and determined the interaction mechanisms of various reinforced soils [10]. Kim et al used a vertical RR model to quantify the rootto-soil enhancement [11]. Mao et al used a finite element method and discrete element method to simulate threedimensional direct shear tests to evaluate the RR model and compare the two numerical methods [12].…”

Shallow Landslide Assessment Considering the Influence of Vegetation Cover

“…Tree roots are known to reinforce soil by increasing soil shear strength. However, few studies have quantified soil reinforcement by tree roots because of some experimental difficulties (Kim et al, 2010b). Quantitatively analyzing the soil reinforcement caused by roots has many difficulties because root structures are easy to be destroyed during the assessment.…”

“…Mechanical effects, such as root reinforcement, act directly whereas hydrological effects, such as water uptake, act indirectly (Kim et al, 2010b). Among the two, the latter factor is not particularly important for shallow landslides that occur during an extended rainy season (Sidle & Ochiai, 2006).…”