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Utilization factors help estimate diggability of excavators
173A
Blasting 913346 Drill/blast methods King, T Woeld Tannlg V3, N6, Nov 1990. P421-429 Drill and blast is still used in the majority of rock tunnels and in mineral extraction. Its advantages are described at scales from hand-held to the largest drilling jumbo. Automated, computer controlled drilling machines are now available. Geological factors to be considered, principal types of round, explosives (including permitted explosives), smooth blasting, and detonation practices are outlined. Some examples of practices and equipment used in major projects are briefly presented.
913347 Open-pit blasting practice in the U.S.S.R. Efremov, E I Minerals, Materials and Industry, Proc 14th Congress of the Council of Mining and Metallurgical Institutions, Edinburgh, 2-6 July 1990 P439-448. Publ IMM: London, 1990 Optimising blasts and blasting techniques has potential for cost savings and environmental protection. The achievement of optimum firing conditions with respect to the detonation efficiency and gas factor is known to minimize the consumption of explosives, increase the quantity of fractured rock mass, and give rise to environmentally acceptable conditions. Theoretical, explosives, practical, and economic considerations are examined.
913350 Effect of cutter pick rake angle on the failure pattern of highstrength rocks Goktan, R M Min Sci Teelmol VII, N3, Nov 1990, P281-285 When cutting high strength rocks, low or negative cutter rake angles are adopted to minimise cutter pick damage. The fundamental rock cutting theory of Evans, based on assumption of tensile failure, is examined within the confines of this geometry. Analysis indicates that rock failure is here more likely to occur as a consequence of compressive stress created by the geometry of the pick. Some available laboratory data are presented to support this proposal of shear failure. 913351 Recent advances in mechanical excavation Whittaker, B N World Tunnlg V3, N6, Nov 1990, P403-410 Major improvements have been achieved in penetration rates in both full face (TBM) and selective cut (roadheader) tunnelling in recent years. Roadheader uprating results primarily from improved cutterhead design. Radial, forward attack, semi-forward attack, and point attack picks are used as appropriate. Water jets also increase cutting rate while lowering specific energy and dust make. Hard rock tunnelling with the TBM has been improved by application of disk cutters, although drag picks are still preferred for softer rocks. Advantages of both excavation methods are examined and expected performance in a variety of conditions discussed.
Rock and Soil Reinforcement and Support
Machine excavation 913348 Utilization factors help estimate diggability of excavators Chironis, N P Coal V95, NiO, Oct 1990, t)58-59 The seldom used Maximum Utilization Factor (MUF), developed for large stripping shovels and draglines, has been extended to apply to backhoes and crawler driven draglines. M U Fs are calculated for a variety of machines and normalised against machine weight. Heavier machines or those with shorter booms can apply more traction and thus have higher diggability coefficients. Data are presented in graphical form for ease of machine evaluation.
913349 Advances in hardrock mining Schmidt. R L Engng g i n J VI91, NIO, Oct 1990. P36-38 Drill-blast-muck has been successfully used in hard rock mining over many decades, and will no-doubt continue in use. Two alternative approaches towards more continuous production are described. The radial-axial splitter, developed from the hydraulic splitter used for secondary breakage, has been brought to prototype stage, and its capabilities evaluated, although it has yet to mine a heading. The ripper-cutter attacks rock at a shallow angle with a broad, slow moving bit, causing rock ahead of the bit to spall, breaking to the surface as a conchoidal fracture. Laboratory tests have demonstrated its ability in medium strength rock.
Bolts and anchors 913352 Design and load-displacement behaviour of anchorages in weathered sandstone and shale. Technical note Yue, C K inst Civ Engrs Proc V89. Pt 2, Dec 1990, P565-571 When a 5 storey building was to be constructed next to an existing 3 storey car park in Singapore, the new footings were set back and cantilevered to support the exterior columns of the new structure and avoid interference with the existing footing. Six permanent anchors in weak to moderately weak steeply dipping rocks were installed to tie down the new footings. Design data were obtained from loading of a test anchor. Two permanent anchors were then installed and tested satisfactorily at working loads to 1000KN. Creep was seen to be insignificant. 913353 Action of fully-grouted bolts in jointed rock and factors of influence Spang, K; Egger, P Rock Mech Rock Engng V23, N3. Jub'-Sept 1990, P201-229 About 70 field and laboratory tests were carried out to clarify the action of fully bonded, non-tensioned rock bolts in stratified or jointed rock. Three dimensional finite element analysis was used to check test results and provide information at all stages of the shear test. Principal bolting parameters were systematically varied. Contributions to shear resistance from friction along the joint, dilatancy, bolt inclination, and
1991 Pergamon Press plc. Reproduction not permitted
Blasting 913346 Drill/blast methods King, T Woeld Tannlg V3, N6, Nov 1990. P421-429 Drill and blast is still used in the majority of rock tunnels and in mineral extraction. Its advantages are described at scales from hand-held to the largest drilling jumbo. Automated, computer controlled drilling machines are now available. Geological factors to be considered, principal types of round, explosives (including permitted explosives), smooth blasting, and detonation practices are outlined. Some examples of practices and equipment used in major projects are briefly presented.
913347 Open-pit blasting practice in the U.S.S.R. Efremov, E I Minerals, Materials and Industry, Proc 14th Congress of the Council of Mining and Metallurgical Institutions, Edinburgh, 2-6 July 1990 P439-448. Publ IMM: London, 1990 Optimising blasts and blasting techniques has potential for cost savings and environmental protection. The achievement of optimum firing conditions with respect to the detonation efficiency and gas factor is known to minimize the consumption of explosives, increase the quantity of fractured rock mass, and give rise to environmentally acceptable conditions. Theoretical, explosives, practical, and economic considerations are examined.
913350 Effect of cutter pick rake angle on the failure pattern of highstrength rocks Goktan, R M Min Sci Teelmol VII, N3, Nov 1990, P281-285 When cutting high strength rocks, low or negative cutter rake angles are adopted to minimise cutter pick damage. The fundamental rock cutting theory of Evans, based on assumption of tensile failure, is examined within the confines of this geometry. Analysis indicates that rock failure is here more likely to occur as a consequence of compressive stress created by the geometry of the pick. Some available laboratory data are presented to support this proposal of shear failure. 913351 Recent advances in mechanical excavation Whittaker, B N World Tunnlg V3, N6, Nov 1990, P403-410 Major improvements have been achieved in penetration rates in both full face (TBM) and selective cut (roadheader) tunnelling in recent years. Roadheader uprating results primarily from improved cutterhead design. Radial, forward attack, semi-forward attack, and point attack picks are used as appropriate. Water jets also increase cutting rate while lowering specific energy and dust make. Hard rock tunnelling with the TBM has been improved by application of disk cutters, although drag picks are still preferred for softer rocks. Advantages of both excavation methods are examined and expected performance in a variety of conditions discussed.
Rock and Soil Reinforcement and Support
Machine excavation 913348 Utilization factors help estimate diggability of excavators Chironis, N P Coal V95, NiO, Oct 1990, t)58-59 The seldom used Maximum Utilization Factor (MUF), developed for large stripping shovels and draglines, has been extended to apply to backhoes and crawler driven draglines. M U Fs are calculated for a variety of machines and normalised against machine weight. Heavier machines or those with shorter booms can apply more traction and thus have higher diggability coefficients. Data are presented in graphical form for ease of machine evaluation.
913349 Advances in hardrock mining Schmidt. R L Engng g i n J VI91, NIO, Oct 1990. P36-38 Drill-blast-muck has been successfully used in hard rock mining over many decades, and will no-doubt continue in use. Two alternative approaches towards more continuous production are described. The radial-axial splitter, developed from the hydraulic splitter used for secondary breakage, has been brought to prototype stage, and its capabilities evaluated, although it has yet to mine a heading. The ripper-cutter attacks rock at a shallow angle with a broad, slow moving bit, causing rock ahead of the bit to spall, breaking to the surface as a conchoidal fracture. Laboratory tests have demonstrated its ability in medium strength rock.
Bolts and anchors 913352 Design and load-displacement behaviour of anchorages in weathered sandstone and shale. Technical note Yue, C K inst Civ Engrs Proc V89. Pt 2, Dec 1990, P565-571 When a 5 storey building was to be constructed next to an existing 3 storey car park in Singapore, the new footings were set back and cantilevered to support the exterior columns of the new structure and avoid interference with the existing footing. Six permanent anchors in weak to moderately weak steeply dipping rocks were installed to tie down the new footings. Design data were obtained from loading of a test anchor. Two permanent anchors were then installed and tested satisfactorily at working loads to 1000KN. Creep was seen to be insignificant. 913353 Action of fully-grouted bolts in jointed rock and factors of influence Spang, K; Egger, P Rock Mech Rock Engng V23, N3. Jub'-Sept 1990, P201-229 About 70 field and laboratory tests were carried out to clarify the action of fully bonded, non-tensioned rock bolts in stratified or jointed rock. Three dimensional finite element analysis was used to check test results and provide information at all stages of the shear test. Principal bolting parameters were systematically varied. Contributions to shear resistance from friction along the joint, dilatancy, bolt inclination, and
1991 Pergamon Press plc. Reproduction not permitted