Abstract:
Soil bioengineering combines plants' root systems to prevent erosion and stabilise slopes,
offering sustainable, nature-based solutions for environmental restoration. Shear strength
evaluation of soil bioengineering is discussed under mechanical and hydrological aspects but
remains unimproved, highlighting a significant research gap. This research presents a
comprehensive investigation on the shear strength improvement of soil through soil
reinforcement, focusing on the use of vegetation roots as a reinforcement material. The study
combines experimental testing and numerical modelling using Abaqus software to assess the
effectiveness of root reinforcement in enhancing soil stability. The experimental phase
involved conducting tensile strength tests on natural Alstonia Macrophylla roots. Performing
large-scale direct shear tests with roots can be a challenging endeavour. Roots have a
significant impact on the mechanical behaviour of soil and introduce complexities into the
testing process. In this research, Finite Element Analysis (FEA) was implemented in Abaqus
to model large-scale direct shear tests involving soils with roots. This approach offered a
versatile and powerful means to simulate the complex interplay between roots and soil
behaviour. Obtained experimental data, including the Young's modulus value of the root, were
utilized for the numerical model calibration. In the experimental phase of the study, a practical
approach to quantify the tensile strength of roots was employed. This was achieved using a
Universal Testing Machine (UTM), a widely used apparatus for measuring the mechanical
properties of materials. However, certain properties such as Poisson's ratio and density for the
root were obtained from relevant literature due to the unavailability of specific data. For
validation purposes recently conducted direct shear tests results on Alstonia Macrophylla root
permeated soil were adopted. The numerical model was established using a solid model
approach, simulating the actual size of the soil samples, and employing appropriate material
properties. The simulation accounted for soil-soil and soil-root contacts using appropriate
contact models. In simulating the direct shear test, a "Surface-to-Surface contact" approach
modelled soil and root interactions. Soil surfaces were defined as "Master" and "Slave," using
a "Penalty formula" for tangential friction and a "hard" contact type for normal behaviour.
Roots were treated as embedded bodies with ABAQUS constraints, ensuring realistic contact
representation. The results of the numerical simulation demonstrated the stress concentration
within the soil, particularly in regions in contact with the root, indicating significant shear
strength improvement due to root reinforcement. The obtained shear stress-displacement
relationship allowed for the determination of the shear strength of the system. Simulation and
experiments showed root-soil shear strength enhancement. Accurate parameters and 3D
modelling were vital for reliability. This study's findings provide guidance for root growth
regulation and slope protection research. Overall, this research contributes to the understanding
of soil reinforcement mechanisms and provides valuable insights into the use of Soil bio
engineering as an effective means of enhancing soil stability.