Influence of moisture content on the LCPC test results and its implications on tool wear in mechanized tunneling

Abstract

Various testing methods have been proposed to measure rock abrasiveness as an input into the prediction models for estimating the tool wear in mechanized tunneling and mining. Among the proposed tests, LCPC test has been used by many researchers for assessment of rock abrasivity. In this study, 20 rock samples from various locations in Pakistan were subjected to comprehensive testing of various properties. The tests included LCPC (Laboratorie Central des Ponts et Chaussees) rock abrasivity tests as well as a complete suite of standard rock physical and mechanical property tests. Whilst the standard LCPC test is run in dry samples, this study compared the results of the LCPC method in dry and saturated conditions, performed at water contents of 15, 30, 45 and 60%. Overall abrasivity [measured as ABR (g/t)] decreased with the increase in water content with peak values of ABR (g/t) attained at 15% water contents for low porosity rocks and 30% water content for high porosity rocks when compared to dry tests. Similarly, a gradual decrease in the LCPC Breakability Index (BR%) was noted in the case of low porosity rocks with the corresponding increase in water content. However, for high porosity rocks there was a cyclic fall and rise in breakability (BR%) at 15% and 30% moisture levels, respectively. This was in contrast to dry tests. A steady drop in BR% was also observed at higher water contents. This paper discusses the result of the testing as well as practical implications of these measurements on predicted wear of cutting tools used in mechanized excavation in mining and tunneling applications. Preliminary statistical analysis of the data and correlations between ABR, water contents, and petrographic and engineering rock properties are also included in this paper.