Influence of propeller material hardness, testing time, rock properties, and conditioning on LCPC rock abrasiveness test
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ORIGINAL PAPER
Influence of propeller material hardness, testing time, rock properties, and conditioning on LCPC rock abrasiveness test M. Z. Abu Bakar 1
&
Y. Majeed 2 & M. A. Rashid 1
Received: 31 May 2020 / Accepted: 30 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
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. Keywords Wear . Soft steel propeller . Hard steel propeller . Mass loss (%) . Test time . Schimazek’s F value . RAI value
Introduction In the tunneling industry as well as other geotechnical construction projects, rock and soil abrasiveness are frequently determined parameters used to estimate wear of excavation tools. The word abrasiveness describes the intrinsic quality of a rock or soil to cause tool wear (Plinninger and Restner 2008), while wear is the slow damage at the cutting edge of a tool during its interaction with the rock (Zum Gahr 1987). The harder the rock’s constituent minerals, the higher the possibility that rock will be abrasive to certain tool materials. For example, quartz is abrasive to steel but not to tungsten carbide (Verhoef 1997). Nilsen et al. (2006, 2007) described two major types of wear in mechanized tunneling, namely primary
* M. Z. Abu Bakar [email protected] 1
Department of Geological Engineering, University of Engineering and Technology, Lahore, Pakistan
2
Department of Mining Engineering, University of Engineering and Technology, Lahore, Pakistan
and secondary wear. Primary wear refers to the anticipated wear on rock cutting tools including drag-bits, disc cutters, scrapers, and buckets which require replacement at suitable intermissions. Contrary to that, secondary wear occurs randomly as a result of excessive pri
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