Abstract
Usually the study of the strength and stability of pillars in cave mining is performed through empirical, analytical and numerical modeling methods. A comparative assessment of two empirical methods used to estimate the stability of hard rock pillars was conducted. Considering different pillar geometries, and specially an abutment stress model, the induced vertical stress in a rib pillar type were evaluated. To demonstrate the application and variability of the outcomes, the factors of safety was calculated taking as input variables the vertical stress over the pillars and the strength values obtained from the empirical methods mentioned. For the simple example of rock pillar stability analysis chosen, it has been demonstrated that a significant range in potential outcomes are possible, based on the natural variability (known and/or unknown) of the rock materials, pillar geometry and induced stress state. The empirical pillar design methods cannot be directly used for the design of pillars loaded in both compression and shear. The improve of rock mass characterization methods, in combination with probabilistic analysis and numerical modeling, may provide a means to incorporate natural variability in modeling parameters into the design of hard rock pillars in deep cave mining.
1. INTRODUCTION
In cave mining projects, the pillars are the main support system for the production and undercut levels. The mining operations must be safe and with a minimum cost of reinforcement and/or repair, so the pillars must be and remain stable.
Empirical methods provide an attractive rock pillars design option for geotechnical engineers. These provide an effective means of analyzing the geometry, strength, and pillar stresses, as well as the properties of the rock mass. This paper makes a comparative assessment of two empirical methodologies available to design rock pillars, also the scenarios where these are applicable, and in addition the critical parameters required for a complete analysis are studied.
A comparative assessment of two largely empirical methodologies used to estimate the stability of hard rock pillars was carried out. Considering different pillar geometries, and specially an abutment stress model, the induced vertical stress in a rib pillar type were evaluated by Stacey and Paige [1], and Lunder and Pakalnis [2] methodologies.
