Influence of propeller material hardness, testing time, rock properties, and conditioning on LCPC rock abrasiveness test

Abstract

LCPC rock abrasiveness test is gaining popularity for quick estimation of rock and soil abrasiveness in the preliminary site exploration stage of tunneling projects. However, there are parameters such as test propeller hardness and testing time, which may affect the test results thereby influencing the tool wear rate estimates of the tunneling machines employed in those projects. This study evaluates LCPC rock abrasiveness test by using both the standard (grade XC 12; 60-75 HRB) steel and hard cold work tool (54-56 HRC) steel propellers. It is found that the wear in the case of hard steel propellers, ABRh (g/t), is almost 70% less than that in the ABRs (g/t) of standard/soft steel propellers. It is established that 40–60% of the propeller wear occurs during the first 2 min of testing. Moreover, bentonite slurry as a conditioning agent produced promising results in the reduction of ABRh (g/t) values in contrast to the unconditioned test results. The correlation of LCPC test parameters ABRh (g/t) and BRh (%) with the geomechanical rock properties and rock wear indices especially Schimazek’s F value and rock abrasiveness index (RAI) show similar trends to the ones obtained using soft steel propellers in the previous studies. However, breakability BR (%) is found to have no appreciable difference once measured using both the soft and hard steel propellers.