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By E S. Souza, H Delboni Jr, M F. Calixto

This paper aims at presenting the results of laboratory, pilot plant and simulation studies for the design of the grinding circuit for the beneficiation of compact itabirites from the Conceitpo mine. Two alternatives were investigated, both utilising the current crushing circuit up to tertiary crushing. Under alternative #1, quaternary crushing was considered to produce the feed of the ball mill; under alternative #2, high pressure grinding rolls were selected to prepare the ball mill circuit feed. Pilot scale studies pointed towards the use of high pressure grinding rolls (HPGR). The circuit design was based on a throughput of 720 t/h, representing a nominal solids flow rate of 600 t/h, considering a design factor of 1.2, and P80 of 95 ¦m.

Jan 1, 2007

By P Jones

Fosterville Gold Mine is an underground operation located approximately 20 km northeast of Bendigo and 170 km north of Melbourne. Fosterville is the most productive gold mine in Victoria, producing over 100 000 ounces of gold annually. Access to the underground is via two portals cut into previously mined open pits. Fosterville is 100 per cent owned and operated by Northgate Minerals, a gold and copper producer with mining operations, development projects and exploration properties in Canada and Australia. (Northgate Minerals Corporation, 2010).Underground operations commenced in 2006 with ore production focused on three orebodies – Phoenix, Ellesmere and Falcon. Primary ventilation to the existing operation is provided by wall mounted exhaust fans located underground. This system provides approximately 220 m3/s of primary ventilation to the operations with intake achieved through the portals. Exploration drilling during recent times has uncovered another lode, the Harrier orebody, located 2.2 km to the south of the existing workings. Due to the location of the new Harrier orebody, vent analysis revealed the requirement for a separate source of primary ventilation to service Harrier. Figure 1 shows a current underground long section and the location of Harrier in relation to the existing workings. A number of options were considered, including a parallel decline from one of the existing two portals, however, a 4 m diameter, 350 m deep surface ventilation shaft was selected as the most suitable and feasible option for the mine.In December 2009, geotechnical drilling commenced to determine the most suitable location for the shaft. Site locations were constrained by a number of factors including interaction with current and planned surface infrastructure as well as proximity to nearby community members at the southern end of the mining lease. Results from the geotechnical drilling indicated that the majority of the proposed shaft would be suitable for a 4 m raise bored shaft. However, the top 40 m of the proposed shaft were deemed unsuitable for raiseboring due to zones of weakness that would likely influence the stability of a 4 m diameter shaft (Robinson, 2010). Following independent geotechnical advice and input from experienced raiseboring contractors, it was decided to construct a 40 m presink prior to raiseboring activities.A crane mounted auger was chosen as the preferred method to construct the presink. This method differs substantially from traditional blind sinking methods which are highly labour intensive. The auger, or drill, is designed and built to be attached to a crane base using engineered pivoting cradles. The auger is suspended from the crane jib by pennant ropes attached to hydraulic rams. The auger applies rotation and axial loads to the drilling tools via a telescopic steel bar (Kelly Bar). Drill tools are attached to the bottom of the Kelly Bar and comprise an assortment of drilling buckets and reaming barrels. Drilling buckets cut in situ material and collect the spoil for removal and are used for the excavation of the ‘pilot hole’. Reaming barrels are used to expand the diameter of the excavation by directing cuttings into the pilot hole which are then removed by the drilling bucket. In June 2010, the presink was constructed utilising a crane mounted auger with support to the shaft walls applied via a remote fibrecrete unit. The excavation method involved cutting a series of smaller diameter holes (2.4 m wide) before reaming out to the final diameter (4.7 m wide) in 4 - 5 m vertical increments. Fibrecreting activities were carried out on the backshifts, to ensure the stability of the excavation and minimise interaction between the two units. The presink was completed on time and offered many advantages compared to traditional blind sinking methods, including safety, costs and timing. This paper will examine the benefits of this method as well as lessons learnt and future applications in the mining industry.

Mar 21, 2011

By C Nucifora, M Landers, J Jones, G Maddocks, K Mandaran, A Forbes, W Wilson, S Newman

Glencore’s Mount Isa Mines Limited (MIM) operates the Mount Isa open cut and underground copper (Cu) and zinc-lead (Zn/Pb) mines near Mount Isa in Queensland, Australia. Tailings from processed Cu and Zn-Pb ore is contained in a 1,315 ha shallow (< 35 m deep) multi-cell valley fill tailings storage facility (TSF). Static geochemical testing conducted by MIM over the life of mine (LoM) verifies that the Cu, and Zn-Pb tailings has a wide range in sulfide content and diverse mineralogy with significant acid neutralising capacity (ANC) in some samples. The tailings are predominantly classified as potentially acid forming (PAF) using static analytical methods. Kinetic leach testing using free draining columns and humidity cell tests simulating tailings placed on the surface of the TSF suggest that the tailings samples are likely to remain non-acid forming (NAF) for 10 to 40 years under aerial exposure, and much longer than this under saturated conditions within the TSF. During this period of weathering, as ANC is depleted, the neutral pH drainage may contain elevated concentrations of some elements including sulfate, manganese and zinc. Only when the ANC is depleted would the tailings then begin to produce acid drainage. CITATION:Mandaran, K, Jones, J, Nucifora, C, Maddocks, G, Landers, M, Forbes, A, Wilson, W and Newman, S, 2018. Mount Isa Mines Rehabilitation Materials Sampling and Analysis program for closure planning, in Proceedings Life-of-Mine 2018, pp 138–140 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

Controlled Source Audio Magnetotelluric (CSAMT) surveys were carried out by Glass Earth (New Zealand) Limited (Glass Earth) in 2006 - 2007 to investigate epithermal gold targets in the central North Island of New Zealand. The surveys were conducted using a Zonge GDP 32 8-channels receiver and a Zonge XMT 32 transmitter powered by a 16 KW generator. The electric field dipole was maintained at 20 m length (five dipoles per 100 m spread) and the frequency ranged from 4 KHz to 4 Hz. Only scalar (TM mode) signals were recorded, using one magnetic coil per spread. The transmitter bipoles were 1 - 4 km in length and located about 5 to 10 km from each survey area.   Sixteen individual target areas were surveyed by June 2007. The CSAMT survey lines (100 - 400 m spacing) were determined mainly on results from previous ultra-detailed airborne magnetic and gravity surveys conducted by Glass Earth in 2005. The data from each CSAMT line was carefully examined to remove any spurious signals and processed using Zonge SCS2D software, which can produce smooth 2D resistivity inversions of the field data. The results were presented as resistivity sections and maps to help the identification of exploratory drilling targets, mainly from the existence of subsurface high resistivity zones (resistors) that can be interpreted as caused by silicification associated with epithermal mineralization.   An example of processing and interpretation of the CSAMT data is presented in this paper on results from Glass EarthÆs Tahunaatara target, where CSAMT surveys have identified zones of epithermal mineralization confirmed by exploratory drilling.

Jan 1, 2007

By Hermulheim W

In the Federal Republic of Germany hard coal is mined underground only. The coal mines reach down to 1 500 m deep, recently having an average depth of 900 m. The commonly used winning system is long- wall mining with face lengths up to 250 in. The gate roads, which separate the seam into single panels, have an average length of one kilometre with a cross- section up to 20 m2. These single entries are usually supported by yielding steel arches. The installation of steel arches can hardly be mechanized. The choice of heavier support, caused by increasing depth and roadway cross-section, results in high cost for labour and material in gate roads. Furthermore, the heavy steel arch is acci- dent-prone, not only during installation but also during transportation and ship- ment. Rock bolts combined with a suitable lagging offer a way of mechanizing support work in headings. The aim is to decrease cost and to increase mine safety and pro- ductivity. Over the last ten years, 50 km of gate roads have been reinforced by a combination of rock bolts and weld mesh. Nevertheless, there are still differing opinions on the feasibility of rock bolting in gate roads. In Germany a long tradition and experience with steel arch support exists, whereas the function of an anchorage is a closed book to miners, preventing this new technique from spreading more quickly. Advantages and shortcomings of both steel arch support and rock bolting are compared. The experience with rock bolting up to now is reported. Possible improve- monts arm discussed.

Jan 1, 1986

By K Guilfoyle, A Robertson

In the mid-1970s, trucking ore from 400 m depth to the surface was perceived to be the practical and economic limit for metalliferous underground mines. Improvements in truck design and decline development resulted in the economic depth of haul exceeding 600 m by the mid-1990s. Today, mine operators and contractors are planning to use trucks for ore haulage from depths in excess of 1000 m. The authors of this paper estimate that there are in excess of 300 diesel-powered trucks operating in mines in Australia, and that by the year 2005 more than five per cent of these trucks will be æroad trainsÆ (ie trucks towing powered trailers or truck-trailer combinations). This paper examines the road train concept, presents cost and performance data and describes the advantages and disadvantages of the road train system as well as proposing the types of applications for use of road trains in Australian metalliferous underground mines. Truck performance is based on payload and average speed (expressed as tonnes x kilometres per engine hour (t km/h)). A road train with a powered trailer has a large payload capacity and two engines to provide a high ratio of power to gross weight. Thus it is possible to exceed 300 t km/h per cycle for an average haulage gradient of 1:9 compared to 250 t km/h for conventional articulated dump trucks (ADTs). It is likely that road trains in excess of 100 t capacity will have application for level ore haulage at large mines in Australia.

Jan 1, 2002

By R Jacobs, J Yeates

"The Stockman base metals project is situated in State Forest in the alpine area of East Gippsland, Victoria, adjacent to a National Park and within the headwaters of a major Ramsar-listed wetland catchment and the Murray-Darling River system. Site topography is steep, and elevated (650 m – 1200 m above sea level), and subject to circa 1 m annual rainfall, with occasional winter snowfall. The project consists of two volcanogenic massive sulfide (VMS) deposits to be mined by underground methods and treated in a 1.0 Mt/a central concentrator to produce copper and zinc concentrates for export over a ten year operational life. New resource projects are rare in Victoria. Recognising the sensitive setting, planning for the Stockman Project, which is now in the advanced permitting stage, has focused on balancing economic, environmental and social outcomes to ensure social licence to operate is secured and can be maintained. This has involved close attention to triple bottom line (TBL) risks and outcomes. Stockman has successfully gained State and Federal approvals via the Environmental Effects Statement process. The process of obtaining these approvals has required close attention to effective stakeholder involvement, and management of a lengthy and difficult approvals process, which is still to be finally concluded. This paper is a case study of the process of that permitting and the issues encountered to date. Key learnings from the experience have included: successful approvals require close attention to much more than just the project and its technical aspects and physical setting – effective stakeholder involvement and endorsement is critical the differing consultation requirements for local, regional and government stakeholders, to design and plan implementation of a project to meet TBL objectives, and to gain social licence to operate within the Victorian approvals process, the need for an effective lead government agency with policy authority dealing with material policy change requiring post-closure financial sureties estimating realistic permitting time and cost during the project evaluation phase. CITATION: Jacobs, R and Yeates, J, 2016. Stockman base metals project – sustainability, social licence to operate and permitting lessons learnt, in Proceedings Project Evaluation 2016, pp 98–110 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By Johnson I. R, Muir M. D

The Dugald River zinc-lead deposit is located 60 km northwest of Cloncurry. It was discovered prior to 1881, and since 1937, has been the subject of several drilling programmcs which have outlined a resource potential of 60 million tonnes grading 10 per cent zinc, 1 per cent lead, and 30 g/t silver.The deposit is a classical example of stratiform zinc lead mineralization in a black shale host. It occurs within a restricted clastic sedimentary basin within the Corella Formation of Carpentarian (Middle Proterozoic) age. Sabkha, lacustrine and fluvial sedimentary environments have been recognized within this basin. Each environment is characterized by suites of evaporite mineral pseudomorphs, after both shortite and gypsum, indicating that both alkaline and hypersaline environments prevailed at different times during basin evolution. The Dugald Slates which host the zinc-·lead mineralization are lacustrine in origin. Thin Mount Isa-type K-rich tuffite beds occur in the Dugald Slates and in the sabkha sequences.The basin as a whole appears not 10 have been marine, and 10 have had strong tectonic controls on its depositional history.The mineral deposit itself is conformable within the Dugald Slates and many primary sedimentary and soft-sediment deformation structures are preserved. It has a strike length of 2 km, average width of 10 m, and a westerly dip of 50-80 . Drilling suggests continuity to 1000 m vertical depth. The predominant sulphides are pyrrhotite, pyrite, sphalerite and galena in graphitic slate and quartz-carbonate ganguc. Anomalous concentrations of barium, manganese, cadmium, mercury and antimony are present in the ore.The deposit crops out over a distance of 2 km as a gossan ranging from 5-15 m in width. There is a striking vegetation anomaly over the gossanous outcrops. The gossan is enriched in lead, silver, antimony, barium, titaniulll, silica and iron, with respect to the primary mineralization. The depth of total oxidation reaches about 20 m.Cieochemical and geophysical test surveys over the deposit give pronounced anomalies.

Jan 1, 1982

By M Chiquito, R Castedo, P Segarra, L M. López, J A. Sanchidrián, J Navarro

The aim of this work is to assess the performance of different constructive solutions against explosions on the strength of masonry walls. The solutions tested, namely an external metal mesh, a glass fibre film on the external face of the wall and a basalt fibre film located on the inner face of the wall, have low to medium cost and are originally designed for other purposes, like seismic protection. Four cubic boxes 3 × 3 × 3 m were built using each of the solutions and typical masonry blocks. In the tests, a spherical plastic explosive initiated in the centre was placed at scaled distance of 2.9 m/kg1/3, so that moderate damage would be caused on the wall. In order to assess the performance of the explosive, pressure gauges were placed at the wall and at different distances from the explosion. Additionally, vibrations were monitored with seismographs in the far field and a high-speed camera was used to estimate the shock wave velocity during the tests. The resulting damage has been evaluated on 13 points of the external wall of each box using a rebound hammer. Damage maps have been drawn for each wall based on these measurements and damage has been assessed inside the box considering the fragments mass launched during the test. The use of external metal mess leads to a decrease of 34 per cent on damage of the external wall and 38 per cent reduction of spalling. The use of a film in the inner wall provides a strong reduction on spalling.CITATION:López, L M, Segarra, P, Castedo, R, Sanchidrián, J A, Navarro, J, Santos, A P and Chiquito, M, 2015. Performance of different constructive solutions against explosions in full-scale masonry walls, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 819–824 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By A Fareth

Constructed between 1885 and 1891, the New Croton Aqueduct (NCA) in New York State is a 50 km long (31 mi) brick-lined tunnel conveying water from the Croton watershed north of New York City to distribution systems in the Bronx and Manhattan. Except at two siphons, the aqueduct operates as an open channel conduit from the New Croton Reservoir downstream 39 km (25 mi) to the Jerome Park Reservoir in the Bronx. The remaining 11 km (6 mi) is operated as a pressurised conduit and includes a major siphon, of circular cross-section, under the Harlem River. The aqueduct has a flow capacity of approximately 1100 million litres of water per day (13 m3/s or 290 million gallons per day) and supplies on average ten per cent of New York CityÆs drinking water. The CityÆs water supply system is operated and maintained by the New York City Department of Environmental Protection (NYCDEP). This paper covers the work done during the three main stages of the program to rehabilitate the entire NCA: inspections, design and rehabilitation. It also includes some of the more interesting structural findings of the original construction as well as documents and drawings from the NYCDEP archives. The rehabilitation program has been underway in phases since 1993, with inspections scheduled to minimise outages, allowing this strategic aqueduct to remain in service during critical seasonal periods. The open channel flow section of the aqueduct in the north is horseshoe shaped, with inside dimensions of 4.1 m (13.6 ft) in width and 4 m (13.5 ft) in height. The pressurised section is 3.7 m (12.3 ft) in diameter, and includes a 90 m (330 ft) deep siphon under the Harlem River. A total of 163 million bricks were used in the construction, enough to build a 48 km (30 mi) wall around Manhattan Island, 3 m (10 ft) thick and 15 m (50 ft) high.Between 1993 and 1997 a series of in-tunnel investigations were performed in the open channel portion of the NCA, consisting of field inspection, non-destructive geophysical testing, and coring of the brick liner. Between November 2004 and September 2005, a major inspection program was conducted to assess the condition of the 11 km (6 mi) long pressurised section and all shafts, headhouses and blow-off structures along the entire 50 km (31 mi) alignment. Inspection methods included using an underwater remote operated vehicle (ROV) equipped with sonar and cameras to inspect the deep siphon, fibre optics examinations of probe holes drilled through and beyond the brick lining, and core holes and geophysical inspections to assess properties of the liner and behind-the-liner materials. A water pressure and test grouting program was conducted to assess methods and expected grout takes for the rehabilitation work in the pressurised sections. The rehabilitation program is anticipated to be completed in 2010.

Jan 1, 2008

By P Licence, M Stevens, P Atkinson, J L. Mauk

The Rahu and Ascot epithermal Au-Ag prospects are two km north of the Karangahake deposit in the Hauraki Goldfield, and all occur in an approximately 6 km2 north-south elongated magnetic æquietÆ zone. The prospects are hosted by andesitic flows, lithic-crystal tuffs and local sedimentary rocks; local silica sinter occurs at Ascot. These host rocks are intensely altered by quartz, adularia, albite, chlorite, pyrite, illite, interstratified illite-smectite and calcite. Several minerals show zoned distributions, such as widespread adularia that overlies more localised and deeper albite. Illite is the only dioctahedral phyllosilicate in several drill holes, but elsewhere it forms a shallow carapace underlain by interstratified illite-smectite with 50 to 90 percent illite. Veins are common with quartz dominating near the surface and calcite becoming more abundant at depth. Local laumontite-calcite veins also occur. Pseudosecondary and secondary fluid inclusions in quartz and calcite at Rahu and Ascot have homogenisation temperatures (Th) that range from 162¦ to 268¦C and 128¦ to 243¦C, respectively. Most inclusions have trapped dilute fluids with salinities of less than 1.9 weight percent NaCl equivalent, but 20 percent of the inclusions have salinities of 2.0 to 10.5 weight percent NaCl equivalent. Calculated paleowater table elevations suggest that the water table at Rahu occurred at 440 m above sea level (asl). At Ascot, silica sinter formed from discharging geothermal fluids (=100¦C) at the paleosurface at ~135 m asl. However the sinter also contains comb quartz with pseudosecondary inclusions that have a Th average of 229¦C, corresponding to a paleowater table at ~430 m asl during inclusion entrapment. Taken together, these results suggest that the Ascot sinter was buried by approximately 300 m of cover material during a major volcanic or tectonic event, and that subsequent hydrothermal fluids formed veins and alteration at Rahu and deposited comb quartz at Ascot.

Jan 1, 2007

By Graylin R. K, dea T. R, O&apos

The Wolgan Seam of the Upper Permian IlIawarra Coal Measures of the Western Coalfield of New South Wales consists of high volatile, low sulphur, medium hard coking coal with high fluidity. This seam, 1·8-2·4m thick, in the Wolgan area, dips gently at 1°_20 ENE and lies at 160-440m below the deeply dissected surface of the western margin of the Blue Mountains plateau.A detailed study of the deposit has revealed that the Wolgan Seam consists of four main coal plies separated by three distinct stone bands. Each of these subunits is lenticular and displays individual physical, chemical and mineralogical characteristics which exhibit distinct spatial distribution patterns across the area. Most noticeable is the presence of long linear ESE-trending zones of low ash - high volatiles - high fixed carbon - high fluidity which delineate the major distributary pattern within the deltaic environment of coal formation.This seam contains some of the highest fluidity coal in the world.The Wolgan area, close to the western margin of the Sydney Basin, is characterized by:I. a regional, closely spaced, homogenous joint fracture pattern dominated by an orthogonal pair set trending 3400 and 0700, to which the face- and butt-cleat directions respectively of the Wolgan Seam are sub-parallel, and2. a more widely spaced, heterogenous, cross-cutting pattern of regional structural fractures. Zones of bad roof conditions are probably associated with these lineaments which are subvertical and trend in three majordirections, viz., 005°,035° and 115°.

Jan 1, 1980

By M Chaudhari, G Manekar, D Shome

MOIL Limited is operating 7 underground and 3 opencast mines in central India and producing annually more than 1.2 million tonnes of various grades of manganese ore. The underground mines are operating at shallow - 90 m at Munsar mine to moderate - 353 m at Balaghat mine below the surface with horizontal cut and fill (HCF) or its variant method of stoping with post filling by hydraulic sand stowing. The Munsar mine is being worked underground since 1903. The opencast mining is presently stopped. The ore body below the opencast quarry is geological continuity of the area excavated in past by opencast method of mining. The underground mining is done through the adit in three levels i.e. 270’L, 220’L, 170’L and by incline in western part of the property at 70’L. The horizontal drift development has been developed in the manganese ore body with sill drive of 5 m above the sill pillar in lower level at 70’L and barrier pillar of 5 m thickness is left for protection of upper level at 170’L. Valuable mineral has been locked in sill pillar and therefore rock mechanics investigations have been carried out. On the basis of study now the drift development has been carried out in footwall rock at 70’L, (-) 30’L and below levels and it has improved the mineable manganese ore by about 20%. In this modified HCF stope design, an alternative fill material in place of sand, which has been developed in house by use of overburden (OB) material after treatment, has been used for hydraulic stowing. The experimental trials find out that the alternative fill material of OB is more compact and forming a non expansion floor for the men and machines in the stope. This will certainly help in the introduction of mobile underground mining equipment for drilling in the stopes and mechanical mucking, transportation and loading of the ROM. The paper presents rock mechanics investigations and future use of alternative fill material of OB for better safety and productivity at Munsar Mine of MOIL. CITATION:Manekar, G, Shome, D and Chaudhari, M, 2018. Modified ground support with alternative fill material for ground control at Munsar underground manganese mine of MOIL Limited, India, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 58–65 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

The purpose of the Lower Lea Valley Cable Tunnel project is to relocate the overhead power lines circuits, which currently cross the proposed site for the 2012 London Olympics in East London. This was the first contract to be awarded as an Olympic project and is on the critical path for the proposed Olympic Park as the construction of the Olympic village, stadium and other venues cannot begin until the tunnels are complete, the cables installed and the overhead power lines removed. The tunnelling works for the scheme include two parallel tunnels between Hackney and West Ham. Each tunnel is approximately 6 km in length. One tunnel is 4.15 m ID and connects the National Grid substations. The other is 2.82 m ID and connects the EDF Energy substations. The tunnels were constructed through mixed ground using four earth pressure balance tunnel boring machines. These were driven simultaneously from two drive shafts within a single site. The 12 km of main tunnels were constructed within a year from start to finish, with completion in June 2007. The shafts range between 6 m and 15 m ID. These were constructed using a combination of caisson sinking and underpinning techniques. Dewatering was adopted to suit the groundwater conditions.Other works include the design and construction of the head house buildings, cable and ventilation culverts, mechanical and electrical (M&E) installations and all associated works. In addition to the above, a further 1 km of tunnel and two shafts were added to the project scope connecting the EDF Energy tunnel to the substation at Bow. These additional works provided further challenges to the project to ensure that these works were constructed within the program constraints for the 2012 London Olympics. This involved refurbishing one of the tunnel boring machines from the main EDF Energy tunnel drives and relaunching the machine to construct the Bow tunnel. The Bow tunnel was constructed within two and a half months, with the tunnel boring machine breaking through in August, ahead of schedule. The main challenge presented by this project is the program constraints. This project outlines the requirement for team work between the client, stakeholders, contractor and designer in order to provide program certainty. A close working relationship between the contractor and the designer is required to provide value engineered, time-saving solutions to mitigate the risks associated with the design and construction program.

Jan 1, 2008

The company was formed in 1926 to exploit tin bearing veins adjacent to Aberfoyle Creek in north-east Tasmania. In 1928 a 923ft tunnel was driven to explore and develop the mine 150ft below surface. This put the company on a path to become Australia's second largest tin producer by the late 1960's. Recently, Aberfoyle Resources Limited completed a 1.1km tunnel to access the major Hellyer zinc, silver, lead orebody at 300m depth. Production at 1 million tonnes a year is likely, and will make the company a significant world supplier of zinc by the late 1980's. The intervening 20 year history of survival and diversification illustrates principles of mineral exploration which proved valid in the Australian context. The objective of exploration should be to develop mines which can survive rigorous competition and downturns in commodity prices. Such mines will be based on orebodies with many of the following characteristics described by Richards (1986).

Jan 1, 1987

By I P. W Chau

Construction of twin stacked railway tunnels through mixed ground conditions in the heavily populated urban environment of Hong Kong, including tunnelling in poor ground conditions, with low cover and under or adjacent to sensitive structures with minimal impact was the challenge presented by the tunnelling section of the Kowloon Southern Link project. This paper details how twin 1.1 km tunnels of 7.0 m internal diameter were driven by Mixshield tunnel boring machine (TBM) in mixed ground through one of the exclusive shopping and hotel districts in Kowloon. The paper addresses the challenges required to be considered and managed for the success of the project, including ground conditions, TBM selection, Mixshield TBM operation, settlement monitoring and control, ground- borne noise and vibration, proximity to utilities, buildings, roads and operating railways.

Jan 1, 2008

A summary of a proposal to develop a 20 000 tpa underground gold operation in a Forest Park. The environmental constraints are severe and affected the mine development planning and choice of mining method. The mine will use trackless methods to access the narrow 1.5 m ore shoots, and to mine ore by cut and fill methods. The use of Microscoop and CT 1700 HE electric LHDs for mucking, together with special drilling attachments for drilling, is central to efficiency and small Kubota diesel haulers will be used for carrying ore to surface.

Jan 1, 1986

By Zeni J. T

Gold was mined from quartz bodies at Ballarat East from the 1850s until closure of the last mine in 1917. The average depth of mines was about 350 m.Ballarat Goldfields Limited (BGL) carried out diamond drilling from surface between 1985 and 1987 which proved the continuation of gold-quartz mineralisation beneath the old mines.During 1989 an underground development program was commenced to access the mineralisation for detailed exploration. The program included two simultaneous shaft developments. These were known as B2 shaft and Llanberris No.1 shaft.

Jan 1, 1992

By Hansmire WH

The 14.7 km Mt. MacDonald Tunnel beneath Rogers Pass in Canada used both drill-and-blast and machine boring methods. A unique ventilation system provides for diesel operations. The design featured minimum construction support and an unrei.nforced poured concrete lining. The west heading was excavated in a single-stage drill-and-blast operation. The east heading used a TBM top heading with a drill-and-blast keyhole bench. The choice of methods was controlled by varying geology, with up to 1,700 m rock cover. Construction performance and progress are evaluated.

Jan 1, 1987

Samples weighing O·25 g are fused with 1 g potassium hydrogen sulphate, leached with 5 ml. of hydrochloric acid, and then diluted with another 5 ml. of acid. After settling, an aliquot of the clear solution is reduced with stannous chloride, and then a zinc dithiol solution is added to form a coloured tungsten complex which is extracted with petroleum spirit for comparison with standards.Concentrations down to 4 p.p.m. may be analysed at a rate of 100 determinations per man-day of 8 hr.

Jan 1, 1970