The role of numerical analysis in the study of the behaviour of hard-rock pillars

Abstract

Rock pillars can be defined as the in-situ rock between two or more underground openings. However, one aspect that is seldom considered in analysis of hard rock pillars, and indirectly in synthetic rock mass models to determine rock mass strength, is the actual stress level and stress path imposed on the pillar due to the excavation sequence and the location of the pillars within the mine lay out. In this paper we propose to use numerical stress analysis to determine how stresses vary across the excavated pillars in a typical room-and-pillar mine lay out, and thus generate a spatially variable determination of pillar stability. Because of the computational difficulty associated with hybrid modelling of realistic discrete fracture networks, synthetic rock mass modelling is commonly carried out using a 2D approach. By comparing 3D and 2D results for selected cross-sections across, we believe the results of the analysis will provide the opportunity to better constrain the stability implications of a 2D approach to pillar design and synthetic rock mass modelling.

Stochastic Continuous Modeling for Pillar Stress Estimation and Comparison with 2D Numerical, and Analytical Solutions in an Underground Stone Mine

“…These assumptions cause 2D numerical solutions to underestimate stress concentration on pillars. Similar observations have been done by Elmo et al [10] when assessing the role of 2D and 3D numerical simulation in pillar stress estimation. Not only, are these results valid in underground pillar design, but also, they are applicable to the analysis of rock slope stability in surface operations.…”

“…Uncertainty is a term that reflects the degree of knowledge an observer has with regard to certain parameter or process. Some authors have discussed that even though variability and uncertainty are two different concepts, in the context of rock engineering, both terms define intertwined processes [10]. This means that characterizing the variability of a measurable parameter (e.g., intact rock strengths, discontinuities orientation, rock density) helps to reduce uncertainty (or increase our degree of knowledge).…”

Cave mine pillar stability analysis using machine learning

“…While these approaches could oversimplify the stability assessment problem, they can be reliable provided they are calibrated using sufficiently large case databases, accounting for site variability by applying appropriate Factors of Safety. An advantage is that they do not require an understanding of failure mechanisms (Stacey and Wesseloo, 2022;Elmo, et al, 2021), although the factors incorporated in the formulae should be directly related to (or be proxies for) the most important elements controlling the failure process, which in this framework are based on experience and insight.…”

Analysis of stability law and optimization of slope angle during excavation of deep concave mine slope

“…From the perspective of geotechnical engineering, rock pillars can be defined as in-situ rock between two or more underground openings. However, in the analysis of hard rock pillars and in rock mass models to determine rock mass strength, it is very important to consider the actual stress level and stress path imposed on the pillars due to the excavation sequence of the pillars [ 9 ]. From the perspective of excavation stability, the complex nonlinear mechanical behavior of the combined system of rock and coal that surrounds mine openings is a major obstacle in the excavation, stability, and support design of mining thin coal seams [ 10 – 15 ].…”