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Measurement of the fragmentation efficiency of rock mass blasting and its mining applications
ROCK BREAKAGE:MACHINE This paper presents the global status of the blast casting technique. A critical analysis of the existing ideas and blasting theories on the subject, coupled with experiences gathered in mines and rock excavation projects, enables the authors to propose a generalized design for blast casting. It also discusses the associated environmental problems and their mitigation. (Authors) 967193 Trouble shooting problem blasts C. J. Konya, Coal, 101(2), 1996, pp 30-31. In the past few years, there have been many occasions to find out why explosives were not functioning properly at surface coal mining operations. It is not uncommon to find water-gel or emulsion explosives or heavy Anfo’s (ammonium nitrate and fuel oil) either not detonating in some blastholes or producing yellow- or reddish-brown fumes upon reaction. Under tough blasting conditions, with long blastholes and high heads of water, the method of gassing or putting entrapped air into the explosive can be extremely critical. For best results, it is desirable to use positive methods of gassing where the gas bubbles will be retained in the explosives regardless of the environmental conditions, timing, or the delays in adjacent holes or adjacent decks. Under the most severe of blasting conditions, best results can be obtained using microspheres rather than chemical gassing. For conditions that are not extreme, chemical gassing may work equally as well as microspheres. (from Author) 967194 Measurement of the fragmentation efficiency of rock mass blasting and its mining applications J. Aler, J. Du Mouza & M. Arnould, International Journal of Rock Mechanics & Mining Sciences, 33(2), 1996, pp 125-139. This new approach differs from most methods as it is predicated on a pre-existing in situ block size distribution in the rock mass as defined by the natural discontinuity network. Blasting therefore accomplishes the supplementary fragmentation of the already fragmented rock mass, the efficiency of which depends on the blasting parameters emuloved. The blasting efficiencv is evaluated throueh comp&ison of the blockYsize distributions of the rock m&s and the corresponding muck pile. (from Authors) I
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3E5A
proposed and the factors responsible for the inconsistency in results identified. (from Author)
967197 Innovative cautious blasting technique to a running hydro-electric powerhous A. K. Chakraborty, V. M. S. R. Murthy & J. L. Jethwa,
Proceedings - ICE: Geotechnical Engineering, 119(l), 1996,
pp 57-63. The paper reports a case where blasting was conducted to remove 10 000 m3 of granite without causing any damage to a nearby powerhouse complex. A muffle bucket, designed on the basis of dynamic load concept was used both for the muffling and loading operations. The ucket displacement due to throw of rock fragments and the average fragment size were found to be directly dependent on the specific charge. Analysing the results of more than 300 blasting events suggests a new approach for very accurate prediction of peak particle velocity. (from Authors)
Machine excavatio
967198 Economic mining of thin seams in surface miners B. Schimm, Mining Technology, 78(895), 1996, pp 89-92. Simplifying the mining process and increasing the product quality under working conditions is becoming ever more difficult; for such tasks surface miners are very often the most economical alternative. Surface miners loosen, cr and load material in one pass with only one machine. e cutting depth can be regulated exactly so that thin, flat seams and partings can be mined separately. These ~~araeteristics are discussed. (from Author)
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967195 Evaluation of blast fragmentation efficiency and its prediction by multivariate analysis procedures J. Aler, J. Du Mouza & M. Arnould, International Journal of Rock Mechanics & Mining Sciences, 33(2), 1996, pp 189-196. Presents the application of multivariate statistical methods in analysing the results of blast fragmentation. Results indicate that geometrical parameters exercise the most direct influence on the resulting fragmentation, specifically the spacing-toburden ratio and the size of the blast. Furthermore, the influence of these parameters can be considered independent of those associated with explosive energy. As to the in situ block size as determined by the natural fracturing of the rock mass, the results indicated that better fragmentation results are achieved when the rock mass is more massive. (from Authors) 967196 Mechanism of tracer blasting s. P. Singh, Geotechnical & oGeological Engineering, 14(l), 1996, pp 41-50. Tracer blasting involves placing a low-strength detonating cord along the length of a blast hole prior to charging with ANFO. A series of bench blasts and pipe tests were carried out to investigate the mechanism of tracer blasting. The evidence indicated partial deflagration and desensitization of ANFO, thus reducing the total available explosive energy. The rock mass surrounding the traced blasthole experienced a low level of ground vibrations. As a result of the continuous side initiation of ANFO, energy partitioning was more in favour of gas energy. A mechanism of tracer blasting is
967199 The power loader - the third element in the ion L. R. State, Coal International, 244(l), 1996, pp 20-28. The author discusses advances in the design of power loaders in use on longwall coal faces over the last 30 years, culminating in the advanced double-ended ranging drum all-electric shearer. (from Author)
967200
O&K continues a successful tradition P. N. Grimshaw, Goad Znternationai, 244(l), 1996, pp 18-19. This feature shows how a German manufacturer of hydraulic excavators has found UK opencast sites an ideal proving ground for new models. An example is the use of the O&K RI-I170 at Llanilid in South Wales. (Authors
Machine abrasion
967201 Numerical analysis of rotary cutting ANON, Tunnels & Tunnelling, 28(3), 1996, pp 40-41. Describes the development of a mathematical model to predict roadheader performance from lab testing of rock samples. This short article describes the methodology behind the model, the data required for operation and describes the results which can be expected. (C.Paice)
AB
3E5A
proposed and the factors responsible for the inconsistency in results identified. (from Author)
967197 Innovative cautious blasting technique to a running hydro-electric powerhous A. K. Chakraborty, V. M. S. R. Murthy & J. L. Jethwa,
Proceedings - ICE: Geotechnical Engineering, 119(l), 1996,
pp 57-63. The paper reports a case where blasting was conducted to remove 10 000 m3 of granite without causing any damage to a nearby powerhouse complex. A muffle bucket, designed on the basis of dynamic load concept was used both for the muffling and loading operations. The ucket displacement due to throw of rock fragments and the average fragment size were found to be directly dependent on the specific charge. Analysing the results of more than 300 blasting events suggests a new approach for very accurate prediction of peak particle velocity. (from Authors)
Machine excavatio
967198 Economic mining of thin seams in surface miners B. Schimm, Mining Technology, 78(895), 1996, pp 89-92. Simplifying the mining process and increasing the product quality under working conditions is becoming ever more difficult; for such tasks surface miners are very often the most economical alternative. Surface miners loosen, cr and load material in one pass with only one machine. e cutting depth can be regulated exactly so that thin, flat seams and partings can be mined separately. These ~~araeteristics are discussed. (from Author)
d
967195 Evaluation of blast fragmentation efficiency and its prediction by multivariate analysis procedures J. Aler, J. Du Mouza & M. Arnould, International Journal of Rock Mechanics & Mining Sciences, 33(2), 1996, pp 189-196. Presents the application of multivariate statistical methods in analysing the results of blast fragmentation. Results indicate that geometrical parameters exercise the most direct influence on the resulting fragmentation, specifically the spacing-toburden ratio and the size of the blast. Furthermore, the influence of these parameters can be considered independent of those associated with explosive energy. As to the in situ block size as determined by the natural fracturing of the rock mass, the results indicated that better fragmentation results are achieved when the rock mass is more massive. (from Authors) 967196 Mechanism of tracer blasting s. P. Singh, Geotechnical & oGeological Engineering, 14(l), 1996, pp 41-50. Tracer blasting involves placing a low-strength detonating cord along the length of a blast hole prior to charging with ANFO. A series of bench blasts and pipe tests were carried out to investigate the mechanism of tracer blasting. The evidence indicated partial deflagration and desensitization of ANFO, thus reducing the total available explosive energy. The rock mass surrounding the traced blasthole experienced a low level of ground vibrations. As a result of the continuous side initiation of ANFO, energy partitioning was more in favour of gas energy. A mechanism of tracer blasting is
967199 The power loader - the third element in the ion L. R. State, Coal International, 244(l), 1996, pp 20-28. The author discusses advances in the design of power loaders in use on longwall coal faces over the last 30 years, culminating in the advanced double-ended ranging drum all-electric shearer. (from Author)
967200
O&K continues a successful tradition P. N. Grimshaw, Goad Znternationai, 244(l), 1996, pp 18-19. This feature shows how a German manufacturer of hydraulic excavators has found UK opencast sites an ideal proving ground for new models. An example is the use of the O&K RI-I170 at Llanilid in South Wales. (Authors
Machine abrasion
967201 Numerical analysis of rotary cutting ANON, Tunnels & Tunnelling, 28(3), 1996, pp 40-41. Describes the development of a mathematical model to predict roadheader performance from lab testing of rock samples. This short article describes the methodology behind the model, the data required for operation and describes the results which can be expected. (C.Paice)