Natural Caves Empirical Stability Assessments - Application of Laubscher’s Diagram and Barton’s Support Graph

In Brazil, due to the environmental legislation restrictions and the mining industry importance, geotechnical approaches to natural caves issues are becoming increasingly common. Stability or support charts, such as Laubscher's and Barton's, are very popular in stability assessment and this study's goal was to compare these techniques application to ferriferous caves. The methodology consisted in rock mass classification in five caves inserted in iron-rich lithologies, using MRMR and Q index, and dividing them into spans to assess their stability. The values were, then, plotted in both system's charts and the results were compared. Barton's support graph was simulated with three ESR values: 1,0; 1,3 and 1,6. Considering the expected stability assessment, Laubscher's diagram presented satisfactory outputs. Barton's support graph seems to be more applicable to ferriferous caves with the increase of the ESR values, being the most suitable value for the considered sample 2,5. The hypothesis that the support graph's output is less accurate when the ratio W/L is closer to 1,0 could not be conclusively tested due to the small sample of 12 spans.