Effect of rock fracture toughness and mineralogy on cutting performance of surface miner - some investigations

Cuttability of rocks in intimately related to the variation in fracture and micro-petrographic properties of the rocks. An understanding of fracture mechanism and fracture toughness (FT) of rocks is useful to evaluate production performance of rock cutting machines. A study was conducted on rock samples collected from two limestone mines located in India where surface miner (SM), a popular drum type cutting machine, was used for excavation of rock. FT in Mode I was measured by Chevron edge notched round bas (CENRB) method. A simple and accurate procedure of sample preparation of specified dimension, and experimental approach for determining the FT has been discussed in this paper. The study also covers the relation between fracture toughness and mineralogy of limestone as well as their role in estimating production performance by SM. FT was found to be strongly related to uniaxial compressive strength (σc) point load strength index (Is) and Young’s modulus (E). The study show that the fracture toughness of the rock is governed by the configuration of carbonate grains, grain texture and gain matrix. FT was also found to decrease with increase in marl content resulting in increase of production performance of SM. Principal component analysis (PCA) was also conducted to develop a correlation matrix for FT and its inter-relationships with other influencing parameters. Critical strain energy release rate (GIC) was also found to be related with production performance of SM.