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Cuttability of rocks is 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 bar (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 shows that the fracture toughnessof the rock is governed by the configuration of carbonate grains, grain texture and grain 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. [ABSTRACT FROM AUTHOR]

Steel fibre reinforced cementitious composite (SFRCC) panels are numerically investigated for their performances under high velocity impact of short projectiles. Numerical responses are obtained using advanced constitutive material model of Riedel-Hiermaier-Thoma (RHT) for cementitious materials and adopting appropriate modelling techniques. Effects of steel fibre volume and the thickness of panels on the impact performance are mainly highlighted in this paper. Various characteristics phenomenon during impact on cementitious composite panels namely, spalling, cracking, scabbing and perforation, are captured which is a difficult task. Scabbing is likely to occur when tensile stresses at the back face of the panel exceed dynamic tensile strength of the material. Various critical aspects in numerical modelling like boundary conditions, material input parameters, and handling severe distortion of the Lagrangian based finite elements are appropriately explained. Design chart is also developed to determine optimum fibre volume and thickness for an impact energy level up to 2.2 kJ. The numerically predicted impact responses are found to corroborate well with experimental results. [ABSTRACT FROM AUTHOR]

High-wall mining, an extension to open cut mining, commonly use auger and continuous highwall mining system. Rock properties and structural geology' of rock are the vital parameters for designing highwall mining. The limitations of basic equations/models developed for computing web and barrier pillar strength, geological conditions and improper execution of highwall mining are the key causes for instability of highwall. Meticulous monitoring of displacement rates is imperative to evaluate the stability of the highwall and, in turn, safety of men, material and machinery. There are several land based, airborne and satellite based techniques of highwall movement monitoring systems. Frequency of measurement depends on the rate of ground movement. Total station can be used for daily monitoring whereas slope stability radar can be adopted for continuous monitoring if required. A study was conducted at OC-II of Singerani Collieries Company Ltd. by Total Station. The safe limits of highwall stability in terms of strain are discussed in the paper. [ABSTRACT FROM AUTHOR]