A Brief Description About all the Steps Related to the Development of Lattice-Spring-Based Synthetic Rock Mass (LS-SRM) for Slope Stability Analysis

Abstract

ABSTRACT: Geotechnical design criteria and geotechnical risk management processes are related to the representativeness and reliability of the geotechnical model. Developments in continuum and discontinuum approaches allowed a better representation of discontinuities, intact rock and failure mechanisms. A greater portion of the continuum methods cannot simulate crack development, large deformations and rotation of pre-existing discontinuities. Besides that, for a portion of the discontinuum methods, the discrete approaches, such as the DFN (Discrete Fracture Network) and DEM (Discrete Element Method), are now combined with the development of synthetic rock masses (SRM). When considering DEM, better efficiency and results for large scale problems can be obtained for brittle rock using the Lattice approach. The computational demand is small when compared with other approaches. The lattice-spring-based synthetic rock mass (LS-SRM) modeling approach is not trivial. It involves the development of at least three different models and rigorous calibration and validation processes. The intact rock model, based on the lattice model (LM), requires the definition of microscale and macroscale properties. The DFN model is based on assumptions about geometrical, geomechanical and statistical properties of the discontinuities. Lastly, LM and DFN models are combined to develop LS-SRM. A brief description of all these steps is proposed. 1. INTRODUCTION Geotechnical design criteria and open pit geometries are strongly related to safety indexes, obtained from slope stability methods, as well as risk management processes. Both are dependent on the reliability of the geotechnical model, characterized by several sources of uncertainties associated to geotechnical, geological and hydro-geological properties, geological structures, environmental conditions, analytical and numerical models. For the rock mass, composed of intact rock, the discontinuities and groundwater, are also naturally complex. This mass should inherently be considered as being environmentally heterogeneous and anisotropic, with significant variability possessing mechanical behavior. In fact, even intact rock presents compositional and textural variation and could be considered a heterogeneous and anisotropic material and therefore mechanical behavior. On the other hand, discontinuities may present systematic patterns, but these produce regions with an anisotropic response (Mars et al. 2011). While determining the mechanical behavior of a sample of intact rock and discontinuities in the laboratory is relatively simple, determining the mechanical behavior of the rock mass presents several challenges. Given the difficulties of performing large-scale rock mass mechanical behavior tests, empirical methods of rock mass classification, such as the Geological Strength Index (GSI) (Hoek et al. 2018), Rock Mass Rating (RMR) (Bieniawski 1989) and Q-system (Barton 1977) are often used to extrapolate the mechanical behavior of rock masses. Despite the widespread use of empirical methods for classifying rock masses in engineering, their ability to consider heterogeneity, anisotropy and the scale effect remains limited (Mars et al. 2011). The idea of characterizing rock masses from a single value within an index is also controversial.