UNDERGROUND EXCAVATIONS:MINES

villages. "II~e Mount Gilo tunnels will measure 265m long by 7.6m diameter, and 930m long by 7.6m diameter. Drill and blast excavation is being used. The predominant rock is limestone~ but soft chalky marl is encountered in the southern tunnels. Tunnelling equipment is in short supply in Israel. Support structures on the southern tunnel are steel arches with mesh and shotcrete. The northern tunnel incorporates rock boit.~ and shotcrete. (J.M.McLaughlin)

954328 Lesotho Highlands water project: excavation of the transfer tunnel A. Boniface, E. A. Schutz & A. J. H. Speirs, International Water Power & Dam Construction, 46(10), 1994, pp 48-50.

Excavation of the 45kin long, 5m diameter transfer tunnel for Phase 1 of the Lesotho Highlands water project in South Africa is described. This required the simultaneous use of three hard rock tunnel boring machines (TBMs). Topography and geology, tunnel layout, TBM operation and performance, tunnel support methods, probe drilling and grouting, services, and project organisation are described. (J.M.McLaughlin)

954329 High speed tunnelling through TBM (a case study of Dulhasti project of NHPC) A. L. Jaggi & R. Saxena, Irrigation & Power Journal, 51(2), 1994, pp 7-11.

The Tunnel Boring Machine (TBM) has revolutionized tunnelling operations in comparison to the conventional technique. It has successfully completed a number of tunnels in western Countries and is now being tried in Himalayan geology for the first time in India. NHPC has recently introduced a Tunnel Boring Machine [8.3 m din] in its Dulhasti Hydroelectric Project. This paper reviews the performance of TBM in general and its application in Dulbasti Project in particular. (Authors)

Mines

954330 Managing risks in New South Wales coal mining J. Joy, in: Managing risk. Proc. 4th open pit conference, Perth, 1994, (AIMM), 1994, pp 265-268.

This paper discusses the evolution of the risk assessment approach in equipment design and mine operations, as well as the specific risk assessment methodology. The paper also presents the reactive side of risk management, the method of investigating failures in the management system, usually referred to as incidents or accidents. (Author)

954331 Analysis of key block in the structure of voussoir beam in longwall mining (in Chinese) Qian Minggao, Miao Xiexing & He Fulian, Journal - China Coal Society, 19(6), 1994, pp 557-563.

Based on analysis of the complete structure of a voussoir beam in longwall mining, the key block, which affects safety of production at work face, is simplified into an arch with three articulations. Basically, there are two modes of instability, namely instability due to sliding(S), and instability due to rotation(R). The major factors that affect the stability of the structure are rotational angle of the voussoir beam, ratio of length and height, rock type and height of carrying rock strata. Based on detailed analysis of these factors and their range, the theory of 'S-R' stability for rock structure in mine workings is preliminary established. (English summary)

191A

954332 Three models of technology for mining gently inclined thick coal seam with sub-level caving mining method (in Chinese) Wu Jian, Yu Haiyong & Zhang HaJge, Journal - China Coal Society, 19(6), 1994, pp 612-619.

Based on experiences of applying the sub-level caving method to gently inclined medium hard seams, unstable soft thick seams with soft roof and floor, and inclined thick seams the authors propose three models to suite the above-mentioned conditions. The Yangquan model, Mieun model and Wulan model. It is proved that the measures taken are feasible, e.g. simultaneous operation, control of top coal at the face end, anti-skew and anti-toppling, etc. In addition, the recovery of coal, prevention and control of spontaneous combustion, gas and dust are also analyzed. (English summary)

954333 Mining zinc and lead at the top of the world J. Chadwick, Mining Magazine, 171(4), 1994, pp 205-212.

Polaris is the world's most northerly metal mine, located over 1100 km inside the Arctic Circle. Development, excavation and production at the lead and zinc mine, erupted by Conijco (77.5%) and Pine Point Mines (22.5%), is described. Safety and ground control is discussed together with maintanance and backfill techniques used to maintain the integrity of the permafrost. Milling and tailings disposal is also outlined. (P.M.Taylor)

954334 Surface mining of Canadian coal R. Singhal, J. L. Collins & K. Fytas, Coal International, 242(6), 1994, pp 212-218.

Canada's coal production is approximately 65.4 million tonnes of which 95% is produced by surface mining methods, mostly from the three Western provinces (British Columbia, Alberta and Saskatchewan). The mines are highly mechanised; productivity gains during the past few years have ranged from 60-80%. Truck/shovel methods are common, although Saskatchewan lignite is almost exclusively mined by draglines. This paper provides an overview of the Canadian coal mining industry v'is avis surface mining. Emphasis is on application and utilisation of mining equipment and asso- ciated mining methods. (Authors)

954335 American Barrick L. White & S. Kral, Mining Engineering, 46(11), 1994, pp 1231-1242.

The largest gold producer in the world outside South Africa, Barrick, has developed the Betze-Post mine and plant on the Goldstrike property into one of the most technologically advanced gold mining and processing facilities in the world. The Meikle underground mine is being developed 1.6 km (1 mile) north of the Betze-Post pit. When it starts up in 1996, Meikle will contribute 1.8 kt/d of high grade ore to existing plant feed. Three other exploration targets are being drilled on the Goldstrike property - the Screamer, Rodeo and Griffin deposits. None of these is yet counted as contributing to reserves. The company have put in place a waste rock management plan that addresses the potential for acid mine drainage. Areas with the potential to generate acid are identified before mining takes place, and a system is implemented to route it to areas where it will be isolated and contained. Barrick has also allocated funds to create suitable wildlife habitats and is working with Bureau of Land Management in several long-term projects to enhance riparian areas and provide supplemental water sources for wildlife. (Authors)