Correlations of rock mass classifications applied to ferruginous caves

Abstract

For the Brazilian iron ore mines, the presence of caves presents a challenge, since most of them are located within the ore deposit. The National Environment Commis- sion (CONAMA 347 Resolution/2004) establishes that the speleological heritage, as well as its area of influence, cannot sustain irreversible environmental impacts. The physical integrity of caves adjacent to mining operations is an issue of pivotal impor- tance to be scrutinised in studies towards the delimitation of the cave’s protection ra- dius. This article presents the study of various models of correlation between the RMR and Q systems used for the stability assessment of natural iron ore caves. In order to study a correlation between the RMR and Q systems, the most popular rock mass clas- sifications, and their application as a validation tool, a selection of measurements of Q and RMR, organized in a database from seven natural caves of ferruginous lithology, are submitted to a study and statistical analysis. An empirical equation was obtained from the data, using a simple linear regression. The result of the regression was com- pared with selected correlation equations and the best fit for the data was chosen. The best fit was the Rutledge & Pearson correlation equation, which presented the best combination of R² and S, after the equation created on basis of the real values for RMR, though the other equations have results similar to it. As the results were quite similar, the recommendation still is that correlations should be used with caution, and associ- ated to other methods and field analysis.