Influence of plant root reinforcement on 3D geosynthetic slopes

Abstract

Plant roots serve as a natural reinforcement method with the potential to significantly enhance slope stability. In engineering practice, roots can function synergistically with geosynthetics, reducing the reliance on artificial materials. Based on a three-dimensional (3D) rotational failure mechanism, this study proposes a novel framework to evaluate the influence of plant roots on the stability of geosynthetic-reinforced slopes. By integrating the hydrological effects of transpiration and the mechanical composite action of root–soil interaction, the reinforcing capacity of uniform root systems is comprehensively assessed. The required dimensionless reinforcement strength at the limit failure state is derived using the functional balance equation. The validity of the proposed method is confirmed through comparisons with existing two-dimensional (2D) solutions for vegetated slopes and 3D solutions for non-vegetated reinforced slopes. Furthermore, various parameter plots are provided to facilitate design analysis. The results indicate that accounting for 3D spatial effects and plant root reinforcement significantly reduces the required reinforcement strength, thereby lowering construction costs and enhancing overall slope safety.

1. Introduction

Slope stability is a key concept in geotechnical engineering, referring to the ability of a slope or hillside to resist the downward sliding or collapse of soil and rock materials. For natural slopes with good soil conditions, their stability typically meets design requirements. However, many slopes are at risk of instability due to poor soil conditions or external disturbances. For slopes at risk of instability, the use of geosynthetics is an effective reinforcement measure. Various methods have been developed to assess the reinforcing effects of geosynthetics on slopes [1–4]. With the increasing pursuit of environmental protection and sustainable living, urban greening has been gradually improving, and many reinforced slopes in cities are now covered with abundant plant. Research indicates that plant roots not only effectively reinforce slopes but also create a synergistic effect with geosynthetics [5, 6]. As a natural reinforcement material, plant root and geosynthetics work together to further enhance slope stability and provide more significant reinforcement effects. From an environmental perspective, combining plant roots with geosynthetics for slope reinforcement can reduce negative impacts on the environment, such as damage to soil and ecosystems, while also lowering energy consumption and costs in construction. It can increase the ecological restoration capacity of the slope and has significant sustainable advantages, making this reinforcement method highly promising for practical application.

In recent years, a large number of studies have been devoted to evaluating the stability of slopes under three-dimensional (3D) failure modes. Common methods primarily include limit analysis, limit equilibrium, and numerical analysis. The limit equilibrium method [7–9] is based on the critical equilibrium assumption of the slope and assesses stability by analyzing the force and moment equilibrium along potential slip surfaces. This method is intuitive and relatively simple theoretically, but it requires simplifying assumptions about the stress distribution along the slip surface, and it has certain limitations when dealing with complex terrain. Numerical analysis methods [10–12], such as finite element and discrete element methods, construct mechanical models of the slope and solve stress and displacement fields, allowing for precise simulation of complex slope geometry, nonlinear material properties, and various external conditions. However, numerical analysis methods are computationally expensive, highly sensitive to input parameters, and the initialization of the model and selection of parameters significantly affect the reliability of the results. In contrast, the limit analysis method [13–16] utilizes plastic limit theory, avoiding complex parameter settings and lengthy computations. It does not rely on complex stress distribution assumptions and can efficiently assess slope stability and provide a safety factor. Over the years, the limit analysis method, with its theoretical rigor and computational efficiency, has gradually become an important and powerful tool for 3D slope stability analysis.

In nature, due to factors such as rainfall, human activities, and underground seepage, the soil in actual slope engineering is often unsaturated [17]. In recent years, plant root reinforcement of slopes has received widespread attention be...