An alternative pillar design methodology

Abstract

The aim was to investigate stable pillar design procedures currently in use on chrome and platinum mines, subject them to a critical appraisal, and review some of the alternatives proposed in the literature. It is concluded that these pillar design methodologies suffer from drawbacks that can be detrimental to the mining industry and that an improvement is essential. It was decided that the increased availability of analytical models and failure criteria could be exploited to update the empirical to an analytical/empirical method. The proposed methodology adopted FLAC2D simulations using the Hoek-Brown failure criterion to calculate full stress-deformation curves for typical pillars. The mine stiffness concept was introduced to determine the pillar load, integrating the influence of the pillar and strata stiffness and mining geometry. The proposed methodology was calibrated by comparing experimental and predicted deformations and failure depth of pillars in one hard-rock mine. The conclusion was that the methodology is an improvement over the one currently in use. An improved factor of safety is given by the intersection point of curves for the stiffness of the system and the pillar strength.

Cave mine pillar stability analysis using machine learning

“…Pillar stability can be assessed using a variety of methods, among which empirical formulae and numerical modelling are the most frequently employed (Zhou, et al, 2015). The simplest approaches are empirical strength formulae (Salamon and Munro, 1967;Obert and Duvall, 1967;Lunder and Pakalnis, 1997;Martin and Maybee, 2000;Esterhuizen, et al, 2011) that use simple parameters such as width, height, strength, plus calibration constants, and which are still widely used in early stages of design (Sinha and Walton, 2019;Kersten, 2019). 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.…”

Using Rock Mechanics Concepts in Tectonic settings

“…A reduction in resistance after peak strength has been reached is termed brittle behaviour while for plastic response the plastic yield strength is maintained with increase in displacement. Yield in terms of the stress only does not describe the full process since the load line of the system has to be included, Kersten [1]. Figure 1 depicts the concept of brittle, plastic and stick slip mechanisms in terms of yield strength and the load line of the system.…”