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A 3D numerical model was presented to investigate the blast-induced damage characteristics of highly stressed rock mass. The RHT (Riedel, Hiermaier, and Thoma) model in LS-DYNA was used to simulate the blast-induced damage and its parameters were calibrated by a physical model test. Based on the calibrated numerical model, the influences of confining pressure and free surface span on the blast-induced damage characteristics were investigated. The results show that under uniaxial loading, the crater volume increases with confining pressure increases. The uniaxial static load can change the optimal burden and the critical embedding depth of charge. In stressed rock, the variation law of the crater shape affected by radial tensile fractures is opposite to that affected by reflected tensile fractures. Under the biaxial static load, the crater volume of the borehole placed on the side of the max static load is greater than the other side. The explosion crater can be improved by increasing the free surface span on the same side. Finally, it is suggested that the blasting efficiency can be improved by preferentially detonating the charge on the side of the max static load, and then the charge on the other side can be detonated with a wider free surface span.

With the increase in automation and use of computer control in machine tools, the number of cutting tools per machining setup is on the increase. On one hand, such multi-tool setups offer the advantages of reduced down-time and cost of production and require less space and in-process inventory, and on the other hand, require proper tool management for economic operations. A number of strategies have been devised to solve the tool selection problems and a number of tool replacement policies have been proposed in the past. These strategies have been solved in isolation, whereas, a comprehensive algorithm for proper selection of tools out of those available in the tool magazine for performing operation and for replacement of tools on failure/wear is necessary. In this paper, taking cue from the computer memory management policies, four tool selection strategies have been presented and their performance in tandem with various tool replacement policies has been studied. The effect of important parameters such as reduction of tool life due to regrinding, limited number of regrindings, catastrophic failures etc. have been considered. Cost has been computed for each combination of tool selection and replacement policy. Also, the number of machine stoppages has been worked out in each case. The results indicate that the combination of various selection strategies with suitable replacement policies affects the overall cost