Stability Analysis of Plant-Root-Reinforced Shallow Slopes along Mountainous Road Corridors Based on Numerical Modeling

Abstract

Engineering methods such as soil nails, geosynthetic reinforcement, retaining structures, gabions, and shotcrete are implemented to stabilize road cut slopes along mountainous areas. However, these structures are not environmentally friendly and, particularly in Ethiopia, it is impossible to address all road problems due to financial limitations. Nowadays, soil reinforcement with plant roots is recognized as an environmentally sustainable alternative to improve shallow slope failure along mountainous transportation corridors. The aims of this study was, therefore, to conduct slope stability analysis along a road corridor by incorporating the effect of plant roots. Five plant species were selected for the analysis based on their mechanical characteristics. Namely, Eucalyptus globules (tree), Psidium guajava (shrub), Salix subserrata (shrub), Chrysopogon zizanioides, and Pennisetum macrourum (grasses). The roots' tensile strength and soil parameters were determined through tensile strength testing and triaxial compression tests, respectively. The factor of safety of the slope was calculated by the PLAXIS-2D software. The study showed that when the slope was reinforced with plant roots, the factor of safety (FOS) improved from 22-34%. The decreasing effect of vegetation on slope stability was observed when soil moisture increased. The sensitivity analysis also indicated that: (1) as the spacing between plants decreased, the effect of vegetation on the slope increased. (2) Slope angle modification with a combination of plant roots had a significant impact on slope stabilization. Of the five-selected plant species, Salix subserrata was the promising plant species for slope stabilization as it exhibited better root mechanical properties among selected plant species.

Growth Characteristics and Anti-Wind Erosion Ability of Three Tropical Foredune Pioneer Species for Sand Dune Stabilization

“…Root tensile strength significantly affect the magnitude of root reinforcement in bioengineering [31,[58][59][60]. Our analyses show that root tensile resistance and tensile strength are significantly different among species.…”

Mechanical Characteristics of the Fine Roots of Two Broadleaved Tree Species from the Temperate Caspian Hyrcanian Ecoregion

“…Deciduous broadleaf species characterized by an intensive development of fine roots in the upper soil layer instantly linked to different factors such as climate, age, DBH, and stand composition [47]. Root reinforcement has been noticed as one of the key factors when dealing with slope stability issues and landslides safety, thereby becoming one of the criteria in managing forests against natural hazards [10,11]. Large roots anchor the soil, especially across planes of weakness, and fine roots provide an extensive network that increases soil shear strength [6,48,49].…”

“…Commonly, it is believed that no general rule exists to explain the differences in root growth and mechanical properties on the slope, similar to our results. Although earlier studies examined a variety of parameters on root tensile force (e.g., slope position, species, soil types) [9,10,42,51,53,56,58,62]; to the best of our knowledge, we are the first to attempt to examine the interactions of these parameters. Our finding of an interaction between species and slope positions on two of three sites (i.e., Chelir and Patom) suggests that the effective parameters on root tensile force are various and complex.…”

“…Particularly for trees, roots are known to reinforce soil through three mechanisms [4][5][6][7]: basal root reinforcement, lateral root reinforcement, and increasing the stiffness of the root-soil composite material. In all of these mechanisms, the contribution of roots is defined by their mechanical properties (strength and elasticity) [4,5,[8][9][10] and their density and spatial distribution [4,6,9,11], although species, environment, root diameter, root branching order, age of the trees, root architecture, and forest structure are known to influence root reinforcement variability [12][13][14].…”

Assessment of stability of a Himalayan road cut slope with varying degrees of weathering: A finite-element-model-based approach

“…The findings of their research were in line with other research studies ( Digvijay et al., 2017 ; Griffiths and Lane, 1999 ), revealing that FEM–SRF is capable of simulating a slope more accurately and automatically provides the FoS for the critical slip surface without any assumptions. In the SRF method, the shear strength parameters (cohesion and friction angle) of the materials forming the slope are progressively reduced until the instability state of the slope is reached and the SRF is calculated, which is equivalent to the FoS ( Bushira et al., 2018 ; Siddique and Pradhan, 2018 ; Tsige et al., 2020 ; Yang et al., 2010 ; Zienkiewicz et al., 1977 ). In this work, a road cut slope near Shivpuri is demarcated, and FEM–SRF is used to evaluate the stability of the slope from different sections.…”