Indicator kriging applied to RMR geomechanical modelling in a Pb-Zn deposit case study

Luciana Arnt Abichequer,Juliana Fernandes Fabrício,Luis Eduardo De Souza,Mariane Cristina Trombetta

doi:10.1590/0370-44672020740071

Luciana Arnt Abichequer, Juliana Fernandes Fabrício + Show 2 more

Open Access

https://doi.org/10.1590/0370-44672020740071

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Abstract

Abstract The opening of a mining enterprise requires knowledge of the geomechanical characteristics of the mineral deposit, which will be worked according to the use of parameters of stability and/or resistance of the material, as well as the discontinuities present in the rock. In this study, the Rock Mass Rating methodology was used to propose a geomechanical model in a lead and zinc deposit hosted in the sedimentary rocks of Camaqua Basin, Brazil. A geological model was created using the analysis of 50 drill holes with their geological descriptions, grouped into five lithological units, from base to top: rhythmite, lower sandstone, conglomerate, upper sandstone, and ore. The samples were regularized in composites of three meters in length, and then categorized into the five classes of the RMR system. Classes were estimated for each lithological unit using indicator kriging to obtain a model with the probability of each estimated block belonging to each RMR class, and thus the predominant class probabilities of each block. While it was possible to observe a predominance of class II (good rock) in the conglomerate, lower sandstone and ore, in the upper sandstone and rhythmite class III predominates (fair rock), and a few blocks were classified in class IV (poor rock) and V (very poor rock). Although the geomechanical model demonstrates the quality of the rock mass in general, being indispensable to more detailed studies, it is believed that the model allows greater safety in the classification of the rock mass and later use for slope stability and pit design.

Highlights

Mineral deposits are characterized by complexity, uncertainty and heterogeneity resulting from the complex geological processes that acted during its formation and evolution (Chen et al, 2017)
The spatial distribution of these data becomes a useful tool in the reproduction of the variability of ore grades, lithologies and geomechanics quality in order to assist the decision-making process
The Rock Mass Rating (Bienas rock discontinuities characteristics. iawski, 1973; Bieniawski, 1989) is one of the most widely used systems to estimate the quality of rock masses in mining projects

Summary

Introduction

Mineral deposits are characterized by complexity, uncertainty and heterogeneity resulting from the complex geological processes that acted during its formation and evolution (Chen et al, 2017). In the early stages of a mining project, sometimes even before proving the project pre-feasibility, it is necessary to make decisions, such as the mining method to be used for ore extraction. The spatial distribution of these data becomes a useful tool in the reproduction of the variability of ore grades, lithologies and geomechanics quality in order to assist the decision-making process. Iawski, 1973; Bieniawski, 1989) is one of the most widely used systems to estimate the quality of rock masses in mining projects. Since the project is still in pre-feasibility phase, with only drill hole database information; the version suggested by Bieniawski (1989) was used in the present study. The classification is based on the attribution of weights to the six key parameters that the author considered most important for the behavior of rock masses: (i) uniaxial compressive strength of rocks; (ii)

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