Effects of mechanical and mineralogical properties on CERCHAR abrasivity index and specific energy of some Thai rocks

Abstract

The objective of this study is to determine the correlations between CERCHAR abrasivity index (CAI) and mechanical and mineralogical properties of twenty rock types encountered in mining and construction industry in Thailand. These rocks represent soft to medium strong rocks on which their CAI properties have rarely been investigated elsewhere. Results indicate that fair correlation is obtained between CAI and rock strength. CAI’s increase linearly with friction angle, they however show no correlation with the cohesion. Minerals composing each rock type obtained from XRD analysis are used with their corresponding Moh’s scale hardness to determine volumetric hardness (HV) of the specimens. HV’s can correlate with rock abrasivity better than the widely used equivalent quartz contents. Both parameters give better correlations with CAI when clastic and crystalline rocks are analyzed separately. Scratching groove volume reduces exponentially with increasing rock abrasiveness. CERCHAR specific energy (CSE) correlates well with all rock groups, providing that only hardness of soft minerals in clastic rock group is used in the regression. CSE also increases with CAI’s, suggesting that rocks with high abrasivity require higher energy to cut, and yield lower excavated volume than those with lower abrasivity. The research findings can be used to predict the wear of excavation tools in soft to medium strong rocks using the correlations between CAI test results and their mechanical and mineralogical properties.

Keywords

• abrasiveness
• rock strength
• friction angle
• rock hardness
• mohs scale