Observations on the Bond standard grindability test, and a proposal for a standard grindability test for fine materials

254A and enable computer blast simulation programs to be developed. Important information on the structural dynamics of the orebody during blasting was obtained, and improved blast design with lower surface vibration has followed. 895202 Cost-benefit analysis of applied blasting research programmes May, J R; Hail, S J Proc 8th AMIRA Technical Meeting, Advances in Blasting and Ground Support,Sydney, 8th October 1987 P8.1-8.9. Publ Melbourne: AMIRA, 1987 The AMIRA project at the Julius Kruttschnitt Mineral Research Centre, designed to optimise blasting, is reviewed. Six case studies from underground and open pit mines are presented. Blast vibration, fragmentation and damage were monitored. Direct cost savings (drilling and explosives) from improved blast design are discussed. Other savings related to damage control, and improved fragmentation and muckpile diggability are less easy to quantify, but may be equally important.

and operating conditions, parameters such as bit penetration, penetration resistance and acoustic emission in coal blocks were monitored. After testing, the fracture surface was photographed and a sonic velocity survey carded out. Results show that fragmentation is highly complex and is affected by characteristics of the coal, such as compressive strength and grindability, and machine-coal interaction. Size distribution of fragments is affected by depth of cut, bit spacing, speed of cutting head,type of bit and bit attack angle. 895206 Boring long tunnels in rock subject to high ground pressures requirements to be met by the TBM of the future (In German and English) Lauffer, H Worm Tannlg Special Edition, P9-13. (paper to the 2nd International Tunnelling Symposium, Munich, 12 April 1989)

895203 A55 North Wales Trunk Road Penmaenbach Tunnel: use of NONEL blasting techniques Watts, R Proc Tunnelling '88, London, 18-21 April 1988 P389-399. Publ London: IMM, 1988

The TBM of the future will have to bore large cross-sections in rock subject to high ground pressures, so design aim should be guaranteed high advance rate regardless of rock properties. Some problems with current TBMs and solutions for future design are presented. These include variable diameter to protect the cutting head from deforming rock, reduction of the unsupported span and provision of continuous support from the face, new support types and continuous deformation measurement.

Driving of a 660m long tunnel, of which 90m is in soft glacial material and the remainder in intrusive rhyolite rock, is described. Because of fears of damage and safety problems for nearby roads and railway lines, peak particle velocity was limited to 50mm/s in rock, 25mm/s in the softer material. Geophones within the tunnel were used to monitor blast effects. The NONEL detonation system was used. Blast design is illustrated and monitoring results presented.

895207 Design and execution of the shield drive for the Nurnberg subway using the improved design mix shield for the first time in rock and loose soil (In German and English) Bauernfeind, P; Frolich, H World Tunnig Special Edition, P21-23. (paper to the 2nd International Tunnelling Symposium, Munich, 12 April 1989)

Crushing and grinding 895204 Observations on the Bond standard grindability test, and a proposal for a standard grindability test for fine materials Levin, J J S Aft lnst Min Metall II89, NI. Jan 1989, P13-21 q'he Bond standard grindability test can be used to estimate energy required for grinding. It cannot be used for fine materials, where a comparative test is used, in which reference material is ground to determine the equivalent energy consumption per revolution of the laboratory mill. This equivalent energy consumption should be a constant, and once determined, the mill can be used to determine grindability of fine materials without the need for reference materials. Some problems with the Bond grindability test, such as variation in work index, slip of grinding load and influence of coarse mica and minor hard constituents, are described.

To drive a tunnel under buildings, where low settlement was essential, through Keuper marl and Quaternary sands mainly under the water table, a mix shield machine was used. The machine was designed to bore through sand and rock equally well. The shield design and design of the shield gap grouting are described. 895208 Recent developments in assessing rock cuttability and boreability Howarth, D F Proc 6th Australian Tunnelling Conference, Melbourne, March 1987 VI. P143-148. Publ Parkville: AuslMM. 1987 Two models of assessing TBM borability, Farmer and Glossop (1980) and Lislerud (1988), are outlined, and predictions of instantaneous penetration rates derived compared with data from 20 case histories. The effect of rock texture on drillability is discussed, and a method to quantify rock texture outlined. 895209 Considerations for mechanised excavation of rock tunnels McFeat-Smith, I Proc 6th Australian Tunnelling Conference, Melbourne, March 1987 VI, P149-157. Publ Parkville: AuslMM, 1987

Machine excavation See also: 895425 895205 Mechanisms of coal fragmentation by a continuous miner Wahab Khair, A; geddy, N P; Quinn, M K Min Sci Technol 118, N2, March 1989, P189.214 An automated rotary coal cutting simulator was designed to study different machine and in situ parameters influencing the fragmentation of coal. During tests under a given set of in situ

A guide to programming, costing and selection of machines for tunnel excavation is presented. Key geological features affecting performance of tunnelling machines are outlined, and penetration ability of roadheader and TBM considered. Factors affecting machine progress, such as adverse ground, machine utilisation and advance probing, are discussed with reference to a number of case studies.

~ 1989 Pergamon Press pie. Reproduction not permitted