Root biomechanical properties of Chrysopogon zizanioides and Chrysopogon nemoralis for soil reinforcement and slope stabilisation

Abstract

Plant root reinforcement in soil bioengineering has gained increasing interest as a means of sustainable and environmentally friendly soil reinforcement and stabilisation. While Chrysopogon zizanioides is widely distributed in tropical regions worldwide and has been advocated for use in slope stabilisation and soil erosion control, C. nemoralis is normally distributed in mountainous areas in Southeast Asian countries, and its potential to reinforce soil has rarely been explored in the soil bioengineering literature. With the importance of root properties in soil bioengineering, this study was carried out to provide a comprehensive dataset of root biomechanical properties, morphological traits, and root reinforcement of these two contrasting vetiver species. A series of experiments, including root observation with a rhizobox system, uniaxial tensile test, and direct shear test, was performed. Results showed that Young's modulus and diameter of C. nemoralis roots were almost 1.4‐ and 1.3‐times greater than those of C. zizanioides roots (p < 0.05). By contrast, no significant difference between the two vetiver species was observed in terms of tensile strength, 'side' root area ratio (RARS), and root orientation (p > 0.05). The diameter–strength (R2 = 0.55–0.56, p < 0.05) and diameter–modulus relationships (R2 = 0.51–0.6, p < 0.05) of both species were consistent with negative power‐law models. Conversely, their diameter–orientation relationship followed a linear model (R2 = 0.85–0.89; p > 0.05). The soil shear strength in terms of cohesion greatly increased in the presence of the roots of C. nemoralis (Δc = 4.9 kPa) and C. zizanioides (Δc = 4.4 kPa). Therefore, C. nemoralis could be an alternative to C. zizanioides in soil bioengineering applications.

Use of Microbially Induced Calcite Precipitation for Soil Improvement in Compacted Clays

“…The current research trend in ground improvement technology focuses on biological approaches that are sustainable, environmentally friendly, and energy efficient. One such approach, called soil-bioengineering, is the use of vegetative root systems to stabilise soil structures against erosion [28][29][30]. Although the utilisation of natural vegetation provides many benefits for improving soil stability, its performance consistency and maintenance schedules are adversely affected by growing seasons and climate changes that introduces variability in the growth and propagation of plant roots within the soil [31][32][33].…”

Reinforcement losses in soil stabilisation due to decomposing roots of Chrysopogon zizanioides and Chrysopogon nemoralis

“…We found negative power correlations between T r and d f as well as between E s and d f for both C. nemoralis and C. zizanioides at all decomposition durations (Figures 1 and 2; p ‐value < 0.05). These correlations have been commonly proposed for several species (i.e., woody species, grass species) (Liu et al, 2022; Phan et al, 2021; Pollen & Simon, 2005; Wu et al, 2021). The modulus and tensile strength of roots were found to increase with cellulose content (Genet et al, 2005) and root moisture (Mahannopkul & Jotisankasa, 2019a; Phan et al, 2021).…”

“…Two vetiver species, C. nemoralis and C. zizanioides , were tested. Despite of their contrasting growth habitat, geographical distribution and root morphology, these two vetiver species have been considered effective for a oil stabilisation because of their fast‐growing traits and impressive biomechanical properties (Phan et al, 2021; Truong et al, 2008). These two species were grown in rice husk ash (i.e., power plant by‐product) for measuring the root biomechanical properties and also in lateritic soil (i.e., construction material) for determining the root reinforcement.…”

“…In this study, we measured the variations of the biomechanical properties of decomposing roots of two contrasting vetiver species, including C. nemoralis and C. zizanioides , following herbicide application, and the changes of their ability to provide mechanical reinforcement to the soil. Both C. nemoralis and C. zizanioides species are widely distributed in Southeast Asian countries and have been extensively studied and recognised to be used for eco‐friendly slope stabilisation (Amiri et al, 2017; Donjadee et al, 2010; Eab et al, 2015; Fahlen, 2002; Gao et al, 2020; Kavian et al, 2018; Leknoi & Likitlersuang, 2020; Mahannopkul & Jotisankasa, 2019b; Phan et al, 2021; Wasino et al, 2019). The objectives were: to (i) quantify the evolution of the root biomechanical properties (in terms of tensile strength, Young's modulus, secant modulus, breakage strain) of the two species with increasing duration of decomposition by using uniaxial tensile strength combined with an image processing; and (ii) measured the variations of root reinforcement (in terms of cohesion increment) and maximum dilatancy due to decomposition by using direct shear tests.…”

Experimental investigation on water release and gas emission of evapotranspirative capillary barrier landfill covers

“…Landfilling has been used as a strategy to store municipal solid waste in many parts of the world (Z. Chen, Chen, et al., 2020; Ng, Liu, Chen, & Xu, 2015; Phan et al., 2021). Rainfall infiltration into the waste increases the amount of poisonous leachate, which could contaminate the surrounding soil and groundwater (Mu et al., 2020; Zhou & Chen, 2021).…”