Role of Acacia tree root’s reinforcement in hill slope stability

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4. Role of Acacia tree root’s reinforcement in hill slope stability

Bio-engineering techniques such as planting trees/grass along hill slopes to prevent rainfall-induced slope failures is gaining worldwide acceptance. Such environment-friendly and cost-effective techniques can be an alternative slope stabilization solution in remote and rural hilly regions. Although non-native, Acacia trees have been recently used to re-vegetate barren scars in savanna grasslands in Guam with the aim to restore its degraded ecosystem. However, the exact quantification of the root reinforcement provided by the Acacia tree on the Island of Guam has not been investigated. In this study, laboratory and field studies combined with numerical analysis were performed to quantify the role of Acacia tree roots in improving the stability of the hill slopes in southern Guam. Root samples from various depths were collected and tested for their tensile strength and root morphological characteristics, namely root area ratio (RAR). A power-fit relationship was obtained between root diameter and tensile strength offered by the Acacia roots. In general, the offered root tensile strength ranged between 10-173 MPa and it increased with decreasing root diameter. Root bundle theory was used to translate the tensile strength offered by the roots into additional shear strength to predict the root-enhanced mechanical shear strength by the soil-root matrix. Results from the analysis show that the factor of safety increased many folds due to the inclusion of root fibers in the soil matrix as compared to the barren hill slope and that the Acacia roots provided a decent amount of stability through an increase in factor of safety via root reinforcement during extreme precipitation events, which are common to the Island of Guam.      

9th International Congress on Environmental Geotechnics (ICEG2023)

Human-Induced and Natural Disaster Mitigation