Browsing by Author "V.R. Sastry"

Now showing 1 - 5 of 5

An investigation into the effect of blast geometry on rock fragmentation
(International Society for Rock Mechanics and Rock Engineering, 1987) D.P. Singh; V.R. Sastry
S Reck fragmentation due to blasting is dependent on geomechanical, explosive and blast geometry parameters. A laboratory scale study was made to evaluate the effect of some blast geometry parameters (burden, spacing and bench height) on rock blasting. Experiments were divided into two groups-single hole tests to evaluate the effect of burden and bench height, and double hole tests to find out the effect of spacing and bench height. Optimum fragmentation burden was found to be 51 per cent of bench height. Significant increase in optimum breakage and fragmentation burdens vas observed with increase in the bench height. The rate of fall in fragmentation with increase in burden was greater in smaller benches because of increased stiffness of burden rock. Spacing to burden ratio of 3.0 to 4.0 gave optimum fragmentation. Fragmentation at less than optimum fragmentation burden even at a spacing to burden ratio of 5.0 was finer compared to the values obtained at optimum and greater than optimum fragmentation burdens for all spacing to burden ratios, suggesting smaller burdens even with larger spacings for finer fragmentation. Considerable improvement in fragmentation was achieved both qualitatively and quantitatively with increase in bench height. © 6th ISRM Congress 1987. All rights reserved.
Effect of controllable blast design factors on rock fragmentation
(1988) D.P. Singh; V.R. Sastry
Rock blasting results are influenced by a host of factors, which can be categorised into explosive, rock and blast design parameters. An attempt is made in this paper to discuss the role played by different blast design parameters, e.g. blasthole diameter, length and alignment, burden, spacing, sub-drilling, stemming, etc. in the
Effect of strain rate on mechanical behaviour of rocks
(International Society for Rock Mechanics and Rock Engineering, 1990) D.P. Singh; V.R. Sastry; P. Srinivas
In recent rock mechanics studies, more attention is being focussed on the behaviour of rocks under varying straining conditions, as it is a vital factor in the design of rock structures as well as various mining operations like drilling, blasting and crushing. Many researchers have been investigating into the effects of strain rate on strength, Young's modulus, ultimate strain and also the failure behaviour of the rocks. However, conflicting results have been obtained by various investigators. An investigation, therefore, was carried out by the authors to study the effect of strain rate on mechanical behaviour of some Indian rocks. A third degree polyncmial has been found to give the best fit to the plot between ultimate strength and strain rate, and oung's modulus and strain rate of rock samples. The failure strength was found to increase wijth increase in strain rate and an abrupt increase was observed at strain rates of 101/sec and 102/sec. The Young's modulus also increased with increase in strain rate. However, the ultimate strain was found to be independent of the strain rate. © 1989 Balkema, Rotterdam.
Investigation into the effect of blast geometry on rock fragmentation
(1987) D.P. Singh; V.R. Sastry
Rock blasting is dependent on explosive, blast geometry and geomechanical parameters. A small-scale study was conducted to evaluate the effect of some blast geometry parameters on fragmentation results (burden, spacing and bench height). Three bench heights of 35 mm, 50 mm and 65 mm were taken with different burdens and spacings. Significant increase in optimum breakage and fragmentation burdens was noticed with increase in bench height. The rate of fall in fragmentation with increase in burden was greater in smaller benches due to the increased stiffness of rock. Spacing to burden ratio of 3.0-4.0 gave better fragmentation results. Considerable improvement in fragmentation was achieved both qualitatively and quantitatively with increase in bench height.
ROCK FRAGMENTATION BY BLASTING - INFLUENCE OF JOINT FILLING MATERIAL.
(1986) D.P. Singh; V.R. Sastry
The orientation, spacing and filling material of joints influence blasting results. Therefore, a laboratory scale investigation was carried out to evaluate the effect of joint filling material on rock fragmentation. Bench shaped models (700mm multiplied by 400mm multiplied by 150mm) of Chunar sandstone, which is known for its homogenity, elastic nature and high blastability ratio were used incorporating a joint of 3mm width running parallel to the face. Four filling materials, (limestone representing calcareous material, quartz representing siliceous material, water and air) were used and for each filling material, investigations were carried out with three burdens (30mm, 40mm, and 50mm) and two rib thicknesses (20mm and 15mm). Detonating cord representing cylindrical charge was used for blasting the models. Mass of fragments, mass-surface area, average fragment size, fine fragmentation index, coarse fragmentation index and fragmentation gradients were used as the criteria for evaluating the fragmentation.