A statistical approach for the correlation between Cerchar Abrasivity Index and Uniaxial Compressive Strength of rocks

In any underground excavation project, choosing the best excavation technique and careful preliminary assessments of wear costs and production rates are crucial aspects to consider. The production rate and costs of tools, as well as the frequency of tool replacement, deeply affect the duration and cost-effectiveness of the whole project. Among the rock-specific characteristics affecting tool wear, Cerchar abrasivity index (CAI) and uniaxial compressive strength (UCS) play an important role. In this article, the relationship between these two parameters was examined by regression analyses for 237 different rocks with the aim to define a preliminary and expected wear potential of three groups of rocks: sedimentary, metamorphic and igneous rocks. The analysis of the results showed that 86 % of the igneous rocks analysed have a CAI > 2, which is a medium or high level of abrasiveness. In sedimentary rocks, over 70 % of the samples are characterised by low abrasiveness behaviour (CAI < 2). Results obtained for these rocks can represent an instrument for predicting the abrasiveness potential of a rock when the UCS is known associating it with an expected range value of CAI. Metamorphic rocks, on the other hand, cannot be classified in specific ranges of UCS and CAI. For this rock group, therefore, a univocal tool for forecasting could not have been obtained, but analyses of rock type and quartz content show that the mineralogical content cannot be considered the only parameter for a wear analysis.