Spatially Variable Coal Slope Stability Analysis using Image-Based Scaled Boundary Finite Element Method

Abstract

Slope stability analysis is a challenging task when complex stratigraphies, complex geometries and spatially variably soil parameters are considered. Numerical methods, such as the finite element method are commonly used in slope stability analyses, however, these methods require significant user input when meshing geometries consisting of heterogeneous and spatially variable materials. This paper presents a numerical technique combining the scaled boundary finite element method and image-based meshing for slope stability analysis. The inputs for the analyses require images detailing the stratigraphy and the spatial variation of the material properties. Quadtree decomposition is applied to simultaneously generate meshes and consider the spatial variation of material properties directly from the images through a mapping technique. The stability of slopes is analysed assuming an elastoplastic Mohr-Coulomb constitutive model for the soil. The shear strength reduction technique is applied to evaluate the shear reduction factor iteratively to define the factor of safety of the slope. Coal slopes at Yallourn open-pit mine, Victoria, Australia was considered, forming the basis of a case study to demonstrate the applicability of the presented method. 1 INTRODUCTION Slope instability in open-pit mining is a critical problem as it can cause fatal disasters, impacting human life and the economy. Hence, considerable attention has been given to slope stability analysis, with various methods often categorised into numerical methods [1-3] and Limit Equilibrium (LE) methods [4-6]. Numerical methods such as the finite element method have become commonplace in slope stability analysis as numerical methods do not require assumptions such as material isotropy, linear elastic perfectly plastic materials, and quasi-static loading regimes compared to LE. The stability of a slope can be affected by the factors such as groundwater conditions, soil properties and their variation, slope geometry and distribution of discontinuities. However, traditional slope stability analysis is performed on a homogeneous slope [1]. In reality, soil and rock properties are spatially variable and are often reflected in more conservative factors of safety [7]. Slope stability analysis integrating real conditions is still a challenge due to complex

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