A Closer Look into Chip Shape/Size and Efficiency of Rock Cutting with a Simple Chisel Pick: A Laboratory Scale Investigation

Abstract

Chip geometry can play a crucial role in understanding the rock cutting efficiency in mechanical excavation. In this study, the shape and size distribution of chips produced in laboratory scale rock cutting tests and their relationship with cutting geometry and rock cuttability were analyzed. For this purpose, a series of small-scale linear rock cutting tests (SSLRCT) were carried out with a simple chisel tool in unrelieved mode at cutting depth of 1, 2, 3, and 4 mm to determine the cuttability of four rock types (sandstone, marl, salt, and coal) and two synthetic (dental plaster and concrete) specimens. The size distribution of all cuttings collected from the grooves in different samples was determined by sieve analysis. The results were used to create a comprehensive particle size analysis, including a Rosin–Rammler plot (d′), coarseness index (CI), median (d50) and Krumbein mean particle size (dMPS). Also, the chips remained on the 4-mesh sieve and greater were chosen for chip shape analysis. The results obtained from chip analysis indicated that 85.6% of selected chips were fragmented in very platy and very bladed shape. Also, the analysis results showed that an inverse exponential correlation exists between specific energy and particle size indicators including CI, dMPS, d50, and d′ as anticipated based on rock fragmentation and grinding theories. Furthermore, a strong inverse correlation was found between specific energy and representative chip volume. The findings highlight the relationship of rock cutting efficiency with chip shape and size.