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By Yoshii Y

Many kinds of shield machines are being driven in the soft ground of Tokyo metropolitan area. Tunnel alignments for underground power transmission lines are generally planned to pass under public roads where facilities, especially life-line facilities, are densely located. Therefore, it is frequently required to drive the shield machines along very sharply curving routes. This paper reports on the performance of the new shield machine - the Sharp Curve Excavation Shield Machine - developed by Tokyo Electric Power Co., Inc., which can freely drive along a much sharper curve than conventional machines. Some of features of the developed devices of this machine are, maximum flexing angle of 6.5 degree in all deirection at the middle of shield body, maximum bending angle of 3.5 degree in all direction at the cutter disc, and so on. This shield machine can there- fore drive along curve of minimum radius 15m. The machine was confidently applied to the const- ruction of tunnel in soft clay strata at N values 2 to 5. Outer diameter 3.7m. Length 202m. Horizontal curve; radius 15m, length 20m x 2. Vertical curve; radius 30 m, inclined driven up 29%. The behaviors of the shield machine, segments and surrounding ground were monitored during construction for safety and efficiency check of this machine.

Jan 1, 1987

By Hoban M, Smith CJ

Norwich Park Mine commenced production of export coking coal in November 1979. Attention to consumables control was limited during the early running of the plant. Once higher than anticipated magnetite consumption levels were confirmed, efforts were directed at determining the causes. Extensive plant sampling, monitor- ing of operational procedures and plant modif- ications have led to a significant reduction in magnetite usage.

Jan 1, 1978

By Oliver R

The Hamersley Iron ore resources are geologically complex with fluctuations in mineral chemistry. From this resource Hamersley Iron must produce consistently high quality direct shipping products and have the ability to evaluate the effects of changes in demand. In order to achieve these objectives an incremental long term planning technique has been developed. This method reduces the total geological resource statement into a simple, logical sequence of events. A logical sequence of mining increments is defined within individual areas based on a final pit and access system. Increment characteristics are derived manually and from a computer based orebody model. The end product of the technique, an optimum mining schedule, is readily developed from the incremental information. Among its many benefits, this simple technique rapidly provides management with information for policy formulation.

Jan 1, 1979

Many of the large refrigeration plants used in, the cooling systems on deep South African gold mines are situated on surface where they are exposed to seasonally and diurnally varying climatic conditions, and to a diurnally varying demand for cooling made by the mine. It has been traditional to accommodate the seasonal variation in climate by manual control applied to the plants at appropriate times of the year, and the plants have normally been specified to conform passively to the diurnal variations. This paper introduces new strategies for the active automatic control of the plants on a diurnal cycle, and shows that attractive benefits in energy and chilled water resource management can be accrued through the use of these strategies. The results have been derived through the modelling and simulation of a representative refrigeration plant.

Jan 1, 1985

By Watkins JR

Movements in the mineral trade cycle are almost invariably out of phase with the gradua- tion rate of mining engineers, metallurgists and geologists. This commonly leads to situations where graduates are scarce in "boom" periods and in free supply when the trade cycle is depressed. This problem reflects the difference in elasticity and flexibility between the educational and industrial environments. In the educational system the decision that brings students to graduation is made three to five years prior to the event. This is quite a lengthy period of time in terms of mineral trade cycles. By contrast, the mineral industry has far more elasticity in responding to short term fluctuations in mineral trade. The authors do not believe that the mis- match between the availability of skilled personnel and the manpower requirements of industry in the short term is intractable. Much is to be gained by more realistic and rational manpower forecasting combined with greater flexibility in the educational realm.

Jan 1, 1982

By Quast K. B

The ore used in this test program was a composite sample from Waihi, New Zealand containing 2.7 g/t gold and 36 g/t silver. From the testwork it was found that a high concentration of sodium cyanide (0.1 per cent) was necessary to ensure a high recovery of both gold and silver. There appeared little chance for either differential leaching or adsorption of gold and silver. The addition of bentonite clay decreased the rates of gold and silver dissolution. The addition of 50 g/1 NaCI had little influence on the rate of silver extraction. The addition of 5 g/l carbon gave adsorptions of 70 per cent of the gold and 35 per cent of the silver, indicating the possible presence of base metal cyanides in solution. The addition of excess sodium sulphide only precipitated 70 per cent of the silver in solution, adding further evidence to the presence of base metal sulphides. The production of separate silver and gold products was not possible by either preferential leaching, preferential adsorption of gold on carbon or preferential precipitation of silver.

Jan 1, 1991

Rare-earth permanent magnetic roll separators, pioneered by our group a few years ago, have distinctly different operation characteristics compared to prior art electromagnetic separators of various types. Many new applications for dry high-intensity (or better: high-force) magnetic separation have been developed in a short time period. It has also been found that the new generation of separators generally are more efficient with regards to removal of weakly magnetic contaminants in glass and ceramic raw materials with minimum loss of valuable product compared to induced magnetic roll (IMR) separators.The latest development is in the area of production of clean magnetic concentrates at high recoveries. It is likely that the PERMROLLR magnetic separator will replace cross-belt and lift-type magnetic separators as a result of this most recent advance.The paper will review the features of the PERMROLLR magnetic separator in comparison with other types of magnetic separators on the market and give examples on applications.

Jan 1, 1990

The heavy media cyclones at Argyle Diamonds are subjected to extremely abrasive service conditions and have been the subject of a development program from the time the first ore was treated in the AKl processing plant. In the past ten years the cyclones have been re-engineered from a standard DSM design, in which some components would only last four days, to the current Argyle design in which the minimum component life is 175 days. Development has focused upon the elimination of turbulence in the cyclone and combating unavoidable abrasion through the use of appropriate wear materials.

Jan 1, 1996

By Blair J. R

In the Bayer process, bauxite is leached with caustic soda, forming a solution of sodium aluminate, from which hydrated alumina is precipitated. The efficient operation of the continuous form of this process requires that the concentration of caustic soda be controlled. A computer simulation of the concentration of caustic soda has been conducted to provide information, regarding the dynamic behaviour of caustic concentration, which is not available from normal plant data. The basis of the simulation is a state- space model of an alumina refinery, linearized about the normal operating condition. The formulation of the model, with the relevant approximations and assumptions, is outlined. The simulation of the mudwash section of the. plant is described in detail. A continuous model of the mudwash, having time-varying coefficients, was driven using operating data from an alumina refinery. The modelled response showed reasonable agreement with the recorded plant response.

Jan 1, 1977

By Davey FJ

The Hikurangi Margin of eastern North Island New Zealand represents the feather edge of the over-riding Indo-Australian Plate at its convergent boundary with the subducting Pacific Plate. Towards the south, convergence becomes slower and increasingly oblique, and sediment supply from the Southern Alps becomes increasingly rapid. In this environment a 150 km wide, imbricate thrust, accretionary prism has grown since the Miocene, uplifting slope ridges and basins and a range of coastal hills. Offscraping of thick, axially transported, trench-fill turbidites begins in a zone of proto- thrusts, which extends up to 25 km beyond the principle, slope-toe, deformation front. On the slope, landward tilted, trench-slope basins are separated by ridges. The ridges ride up on thrusts that sole out at a major decollement. The decollement dips landwards at 3 degrees to a depth of 14 km at the coast, where it coincides with an onshore zone of high seismicity. Beneath the decollement, about 1 km of consolidated, oceanic sediment is going under the margin with the underlying oceanic basement. Some of these sediments may underplate the frontal ranges to the west and geochemical evidence of subducted sediment is found in the volcanic zone beyond. A rapid decrease in the width of the accretionary prism to the north is associated with a decrease in sediment supply and perhaps with a dislocation in the downgoing plate. To the south, the accretionary prism narrows, swings westward, and merges into the zone of very oblique collision that marks the transform between mirror image subduction to north and south of New Zealand.

Jan 1, 1987

By Thatcher R

In areas where land suitable for development is a scarce resource, an upgraded post-mining land use can result in economic benefits to both the mining company and to the community.A study undertaken at Aberdare Colliery near Ipswich during 198611987 assessed the costs and benefits of developing the site following mining for grazing, forestry and residential uses. The proposed fmal land use plan comprised a combination of these uses that can be upgraded to higher valued uses once subsidence monitoring of backfilled open-cut areas and dumps indicates that total settlement has reached acceptable levels for development to proceed.The study involved the documentation of existing site environmental parameters and the delineation of site opportunities and constraints. The unpredictable nature of settlement over backfilled open-cuts and overburden dumps represents the major constraint to urban development on mined areas.

Jan 1, 1990

The uptake of nickel into the lattice of pyrrhotite,Fel_oS has been studied experimentally in the temperaturerange 200 DC to 760 DC. Nickel from both aqueous solutionsand salt melts diffuses rapidly into the sulphide latticewith ,an accompanying rel~ase of iron into the solution ormelt. The rate of uptake of nickel and its diffusion intothe sulphide lattice have been followed ,by opticalmicroscopy and by analysis with an electron probe microanalyser.Some geological consequences of this phenomenonaffecting the distribution of nickel in rocks associatedwith nickel-iron sulphide ores are discussed.

Jan 1, 1980

By Stitt P. H

This paper provides a brief historical review of the invention of the spiral separator and its adoption into Australian metallurgical practice. The purpose of the review is to demonstrate that spiral development to date appears to have been a largely empirical process, and that the cur- rent resurgence of interest in the spiral, especially in the coal industry, warrants an increased fundamental research effort. Current research work concentrating on empirical modelling is outlined, while some preliminary experimental results of a more fundamental nature are presented and some research of other disciplines interested in particle transport introduced in order to stimulate further work and discussion.

Jan 1, 1988

By S Gannon, J Abols, T Hughes

In the past year, two very innovative gold ore processing plants have been designed, built and commissioned by Gekko Systems Pty Ltd. The first plant in Vietnam utilises conventional crushing and ball milling followed by gravity concentration (Inline Pressure Jig (IPJ) and Falcon concentrator), flotation, intensive leaching (GFIL), the first industrial scale use of AuRIX«100å ion exchange resin and a cyanide destruction circuit. The second plant, in Australia, uses a three-stage crushing circuit to crush the gold ore to minus 1 mm, followed by gravity concentration utilising a rougher, scavenger, cleaner circuit of IPJs and a Falcon concentrator. A direct smeltable gold concentrate is produced as well as a lower grade concentrate for future intensive leaching or sale. Both plants were designed and built within very tight time frames and budgetary constraints. The experience gained during the plantsÆ design, commissioning and operation are discussed.

Jan 1, 2006

This paper discusses design concepts in planning a large modern bulk terminal. The need is emphasised for a studied master plan, in-built materials handling flexibility and staged development. An integrated approach is advocated, combining functional purpose designed foundations and structures to serve their mechanical, electrical and environmental functions. Dry bulk and slurry handling are also compared in perspective.

Jan 1, 1983

The Quioma Mine is located along the axis of the Cordillera Oriental, 130 km southeast of Cochabamba, South Central Bolivia. Silver, lead, zinc, antimony, and gold have been intermittently produced from veins in the Quioma area since Colonial times. Mineralization occurs within steeply dipping fissure veins transecting moderately folded Lower Ordovician sediments. Tectonic activity is early to mid-Tertiary and the vein system parallels the fold axis of a major northwest-southeast striking, doubly plunging anticline. Vein sets occur within a 2 km wide band over a strike distance of 13 km along the northeast limb of the anticline. Economic mineralization occupies syntectonic pre-mineral fault zones developed in more competent stratigraphis units of Lower Ordovician clastic sediments. Veins average 55 cm in width, although mineralized structures up to 3 m wide with a known strike length of several hundred meters have been mined. Mineralization consists of siderite, argentifferous galena, sphalerite, and quartz, with minor amounts of chalcopyrite, barite, and bournonite. Pyrite is rare except at the Boston vein where it occurs with stibnite that contains trace amounts of gold. A marked characteristic of veins in the district is evidence of repeated stages of movement during mineralization. Intrusive rocks are rare in the Quioma area. Narrow porphyritic dikes of Andesitic composition averaging 1 m in thickness have been observed. These dikes occasionally show a close spatial relationship to the veins and are often kaolinized and carbonitized. Vein and dike contacts are sharp and alteration does not appear to extend into the wall rock. Mineral zoning is suggested by antimony mineralization observed in peripheral areas of the anticline.

Jan 1, 1987

By McCarthy PL

Widespread interest in reopening Victorian gold mines, regenerated by increased gold prices, has highlighted the technical problems prevailing. A combination of historical lease legislation, minimal recent mining activity, forms of mineralisation, high insurance rates and tortuous approval requirements for mining mean the potential investor assessing an old mine must address a wide range of technical problems. The requirements for establishment of ore reserves and attraction of capital for mine development are fundamental. Underground reef mining was historically generally on a small scale, and as mining on many fields ceased about the turn of the century, past geological and production records cannot be correlated to personal experience and comment. The impact of modern mining technology on future reef mining will be to reduce operating costs and significantly improve historic metallurgical recovery. Roth these are commensurate with increased capital costs. Workers compensation rates currently applicable in Victoria are many times higher than in other states, adding significantly to operating costs. Establishment of a pilot plant testing facility in central Victoria would provide an invaluable service in treating bulk samples essential for grade and recovery assessments of Victorian ores.

Jan 1, 1982

Effective pre-splitting is a key feature of wall control blasting. Most mining operations use historical designs or rules-of-thumb for designing pre-split blasts. If productivity and safety benefits are to be gained, these methods need to be improved in order to accurately predict pre-split performance. This will become more pertinent as overburden depths increase, placing more demands on the pre-split operation. A classical qualitative quasi-static description of pre-splitting (Kutter and Fairhurst, 1968) is presented and it is shown to give some useful insights into the pre-splitting process. In particular, it is clear that the time interval between the initiation of adjacent pre-split holes is a very important factor. In terms of this analysis, it is shown that current techniques which employ detonating cord as the surface initiation system are not optimal. A static quantitative model for pre-split design which has been widely reported is then discussed and its simplifying assumptions and their implications are examined. It is shown that several of the assumptions may be reasonably justified in the light of real pre-split results. It is concluded that the model should yield conservative designs. For this model, the key calculation of the blasthole pressure that is needed to determine the required explosive charge is highlighted. Popular methods employed in the literature for describing the expansion of real detonation products are shown to be inappropriate and an alternative method using the non-ideal detonation code, CPeX, is proposed.

Jan 1, 1995

By Sen G

An amount of explosives, whether it be cylindrical, spherical, etc in configuration, with a hollow cavity in one face or end is known as a hollow or shaped charge. When this charge is initiated, a focussing of explosive energy will occur within this cavity. This focussing, or concentration of detonation products creates an intense localised force greater than just the simple detonation of a conventional explosive, (without a hollow cavity). If this hollow cavity explosive is directed against a target material this concentrated force is capable of creating a deeper penetration than the same amount of explosive without the hollow cavity. If a metallic liner material is used in the hollow cavity, upon detonation of the explosive this liner will form into a high velocity penetrating jet. Depending on the explosive type and the liner material's configuration the jet tip can travel up to 10 km/s. Linear shaped charges were developed using the abovementioned shaped charge concept but instead of being formed about an axis, they are elongated and constructed along the principal axis. Therefore instead of creating a narrow circular penetration jet, it forms a thicker planar cutting jet ideal for linear cutting purposes. Using Linear Shaped Charges (LSC) for pre-splitting is expected to result in more accurate directional fracture propagation, while minimising lateral micro fractures in the surrounding rock mass which is required to remain undamaged.

Jan 1, 1995

The South Ghorveh Batholith (SGB) and the Almoughlagh Batholith (AB) intruded the volcanosedimentary sequence of Songhor Series (Triassic-Jurassic), during the Oligo-Miocene orogenic phase. The granitoids of the AB belong chiefly to the quartz-syenite and syenogranite clans while those constituting the SGB can be generally characterised as quartz monzonite varying towards quartz monzodiorite, and diorite. Granitoids constituting both the batholiths are low in free quartz, and possess characteristics of the æmagnetite seriesÆ, mostly of I-type, metaluminous to marginally peraluminous and calk-alkaline type. Adjacent to them are located the magnetite skarn deposits of Baba Ali and Gelali. In the light of petrography, geochemistry, mineralogy and field geology investigations they could be classified as Fe-skarn and mainly bear characteristics of calcic skarn deposits.

Jan 1, 2005