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The far reaching consequences of designing pillars for coal mines, while retaining concern for safety and economics, are cause for the search for refinement of the existing engineering methods to continue. Coal pillars, while having various functions within the overall mine plan, are the basic structural elements that assure the stability of a mine. Reliable coal pillar design methods take into account criteria which the pillars should meet in specific applications. These applications include typical mining situations such as the partial extraction room and pillar method with and without subsidence considerations, high extraction rate room and pillar, longwall mining chain pillars, and barrier pillars. However coal pillars are onlyu one element of a three element roof-pillar-floor system, weakest element of which system usually determines the stability of the excavations; however, the mining engineer can ony change dimensions of a pillar, properties of the surrounding strata remain beyond his control. The state of the art approach in pillar design places emphasis on recent developments in research. A widely encountered problem in certain coal fields is where pillars are underlain by weak floor strata. The resultant pillar design constantly maintains the perspective of the reliability of the design.

Jan 1, 1991

UNLIKE coal mines, in which some form of artificial ventilation is rendered necessary by gases given off by the material mined and is also enforced by the mining laws of all countries, metalliferous mines have almost entirely relied on natural ventilation, viz., that due to the difference in temperature between the outside atmosphere and the mine air. In small mines natural ventilation has proved sufficient, but as mining proceeds at a greater depth, and where large ore bodies arebeing attacked the writer is of opinion that some means of artificial ventilation will be rendered necessary if only from an economic standpoint.The Broken Hill Proprietary Mine was one of the first metal mines to introduce a scheme of artificial ventilation on a large scale. In order to render the working conditions of the semi-friable stopes of Block 12 and the lower levels of Block 11 morecomfortable for the men at work in these places, in 1903 it was decided to install a fan to thoroughly ventilate these stopes. The fan chosen was a Capell double-inlet fan beltdriven from a steam engine: this engine was later on replacedby an electric motor. The fan was put in commission at the latter end of 1904; its principal dimensions are as follows: Length 6 ft. 6 in., diam. 7 ft., diam. of inlet 4 ft. 7i in. The fan is reversible, though this is a rather misleading term, asthe direction in which the fan blades revolve is not reversed...

Jan 1, 1921

The subject of octanes and knock in petrol engines is of general interest, not only to the engineers and chemists in the petroleum and automotive industries, but also to the motorist who wishes to see some light through the haze of propaganda regarding "super" petrols. A mixture of petrol vapour and air will explode when a spark is passed through it if it contains more than one and a half per cent. or less than six per cent. of petrol vapour by volume. In a petrol engine the mixture has to be within the explosive range before it will operate. When the spark is passed it 'ignites the petrol vapour-air mixture which burns with rapid but finite progress of the flame front 'through the unburnt gases in much the same manner that a charge of dynamite is consumed. The turbulence of the gases in the cylinder under normal operating conditions more than doubles the velocity of the flame front and enables the combustion to be completed by the end of the working (expansion) stroke:KNOCKIf the cylinder head 'is poorly designed or is covered with a deposit of carbon, it is possible for "hot spots" to develop, and these can ignite the mixture before the spark is passed. This pre-ignition gives rise to an engine knock but is accompanied by a dull thud rather than the ringing knock associated with the true "knocking" found in a petrol engine and attributed to the detonation of the mixture. Until a few years ago it was thought that this detonation was due to a shock wave produced by the rapid combustion of the mixture, and sufficiently intense to cause ignition of...

Jan 1, 1951

By Bell LC

Overburden removal, mining and reclamation are now accepted as the basic operational steps involved in the winning of coal by open cut methods. To attain the lowest operational cost, the recontouring and revegetation of spoilpiles must be planned concurrently with the planning of overburden removal and mining. The earthworks associated with reclamation work on spoilpiles often account for 75 - 90 per cent of total reclamation costs. Experience at Callide Mine has shown that the way that spoilpiles are contoured does influence water retention and can reduce erosion from rainfall run-off. However, provided the recontoured slopes meet'Mines Department specifications, the quality of reclamation work is judged not by the quality of the earthworks but by the plant regrowth on the reshaped surface. Thus it is the quality of the revegetation which is of prime importance. For vegetation to be successful, time must be spent on planned research into methods of overcoming plant nutrient deficiencies and selection of suitable grass and tree species. The research programme undertaken at Callide Mine consists of three stages :- laboratory studies glasshouse trials field trials

Jan 1, 1978

By Hall T. P, Taylor R. N

Fluid flow in a 1:14 scale water model of the shaft and settler of the Kalgoorlie Nickel flash smelter has been investigated by flow visualisation and numerical modelling. Detailed flow fields through the reaction shaft, settling chamber and uptake are presented for flow rates up to 800 Vm and a number of burner configurations. The predicted flow fields were compared with experimental data obtained from streak photographs and video recordings. The effects of cessation of flow through individual burners and changes in shaft dimensions were also Investigated.

Jan 1, 1992

By P Grouhel

In the recent years several new blasting technologies have come into use in surface mines. Electronic initiation, low-density emulsion explosives and modelling software are in regular use throughout the world. In Australia, these new technologies have achieved significant application, largely in open cut coal mines where more than 20 per cent of blasting is now conducted with electronic initiation systems. These new techniques have contributed to the vast improvement in blasting outcomes evidenced by increased recovery of saleable product and faster excavation rates. In large surface mines, OricaÆs unique combination of electronic initiation systems, bulk emulsion explosives and modelling software can be harnessed to target critical value outcomes. This includes targeting better fragmentation, increased ore uncovery rates and better wall stability û all adding to improved mining operation profitability. Orica Mining Services have combined these technologies into a set of offerings called Blast Based Services (BBSÖ). The paper describes applications of these new technologies and possible benefits in large surface mines.

Jan 1, 2007

By Amer S, Novais A. Q, Limpo Gil J

A proprietary hydrometallurgical ammonium chloride process for the recovery of not only zinc, but also copper, lead and silver from sulphidic zinc-rich concentrates has been developed at bench scale by CENIM and INETI (ex-LNET) as part of a research project supported by the Commission of the European Community (DGXII). This paper deals with the innovative chemical aspects applied to this chloride process and also with the more relevant data relating to mass balance, heat balance and process economics. Under mild temperature and oxygen pressure leaching conditions it is possible to extract practically all the zinc together with the other metals of interest and to precipitate simultaneously the solubilised iron fraction as goethite. The pH is kept close to neutrality in spite of the ammonia released in the leaching of the non-ferrous sulphides. A buffer effect is observed mostly due to the formation of zinc ammines which are very soluble in this medium. The zinc is further extracted by D2EHPA, the acidity being neutralised by the ammonia. Most of the ammonium chloride is naturally regenerated in this step. The zinc is recovered as zinc cathodes in a conventional sulphate electrowinning circuit. All the main raw material consumptions excluding the concentrate, such as oxygen, lime and ammonium chloride are linked to the sulphate formation in the leaching step which must be kept as low as possible by decreasing the reaction time under neutral conditions. The process analysis is complemented by the economic evaluation of a reference case. Difficulties encountered in finding a more convenient method of assessing the economics of the process in the absence of a reference price for a complex sulphide concentrate are examined and discussed. The reason why this analysis was performed with a much more optimistic metal prices scenario is also highlighted. The process economics are primarily dependent on the zinc market quotations and of course on the concentrate cost. Around 70 per cent of the total revenue is due to zinc sales. Assuming an internal rate of return of 17 per cent, the price of the concentrate can be as high as 255 $US/t for a plant capacity of 320 000 t/y (90 000 t/y of zinc).

Jan 1, 1993

By Yao S, Wang P, Zhang C

The Zhilingtou Au-Ag deposit is situated in the eastern part of the complexly deformed and metamorphosed South China Caledonian Fold Belt. It consists of seven orebodies that are almost exclusively hosted by biotite plagioclase gneiss of the Precambrian Chencai Group. They form an apparent en echelon pattern in both cross-section and level plan. Three different ore types, based on mineralization textures, have been recognized within the Zhilingtou lode. These are Au-Ag-rich quartz veins, Au and Ag-bearing silicified rocks and Au-Ag-containing altered rocks with quartz stockworks. The mineralization is principally composed of electrum, argentite, pyrite and minor sphalerite, galena as well as traces of hessite and chalcopyrite plus a gangue assemblage of quartz, rhodonite, sericite and chlorite. Fluid inclusions related to Au-Ag mineralization yield a wide range of homogenization temperatures from 110 to 447¦C, with two distinctive peak values at 250-300¦C and 350-400¦C respectively. S30Si values of quartz veins and silicification from the three stages of mineralization range from -0.1 to -0.4%o. The mineralization at Zhilingtou is interpreted as forming by recirculated meteoric water extracting ore-forming elements from metamorphic rocks due to Mesozoic volcano-magmatic activity.

Jan 1, 1995

By King D, Dickinson S. B, Matheson R. S

Graham Hall and V. M. Cottle (Rosebery, Tas.) : In their paper on "The Mineralized Rift Valleys of Tasmania", Campana, Dickinson, King and Matheson have summarized a wealth of data from many sources. In proposing the new concept of a rift valley structure, they claim to have found a new guide to regional ore control and distribution in North-west Tasmania.Although the authors acknowledge suggestions made by us prior to publication of the pa:per, we are still at variance with their conclusions. We are not convinced that a rift valley structure exist~d when the Ordovician conglomerate was deposited. We are unable to find evidence for Cambrian deposition in a rift valley or reason to project the structure to embrace Hercules, Rosebery, and "possibly" Mt Bischoff.That the Great Lyell Fault (the authors' Owen Rift Fault) is a promising place to look for ore is not a new idea, but the existence of important ore deposits away from the structure reveals its inability to provide an adequate explanation of regional mineral distribution. A well-known structure that does have an influence on ore deposition is not discussed by the authors.STRUCTURAL CONSIDERATIONSThe great thickness of coarse unsorted Ordovician conglomerate lying in an elongate but narrow belt of country is presented as evidence of its deposition centrally within a rift valley, the position-of which is now said to be outlined by resistant slabs of the conglomerate. The marginal shears of the rift are said to show up well along the edges of the conglomerate.

Jan 1, 1959

By A Xenidis, N Papassiopi, I Paspaliari

Acid generating sulfidic tailings covering a surface area of approximately ten hectares have been deposited in the historic mining area of Lavrion in Greece. For the development of a remediation strategy, the performance of three alternative acid generation control techniques was assessed under actual field conditions. The techniques involved the application of dry covers, including a synthetic HDPE liner and a compacted clay layer with capillary barriers. Furthermore, the potential formation of a low permeability hardpan layer at the sulfidic tailings surface by limestone addition was investigated. The field tests covered an area of 2500 m2, which was divided in equal quadrants, corresponding to the control plot and the three alternative remedial options. To monitor the amount and quality of percolated water, lysimeters were installed beneath the four plot areas. Based on the monitoring results over a period of six years, due to the dry climate encountered in the Lavrion area, a low amount of water percolates through the pyrites if no action is taken (control area), corresponding to 20 - 25 mm per year. This water is highly acidic, pH = 1.2, and contains a heavy load of contaminants, eg Fe 40 g/L, Zn 15 g/L, and As 1.5 g/L. The HDPE cover eliminated the percolation of water into the material for a period of five years, whereas thereafter the volume of leachates increased to values similar to those recorded in the control plot. The water collected in the lysimeter of the clay cover has been minimal corresponding to approximately five per cent of the drainage volume produced in the control area. In the fourth plot, which involved limestone addition to sulfidic tailings, the volume of drainage initially collected was almost double compared to the control area. After three years of monitoring, significant reduction in the amount of percolated water was observed, attributed to the formation of a cemented layer (hardpan), at a depth of 40-80 cm from the testpad surface.

Jan 1, 2003

By Stein A

The general mechanism of recrystallisation for cold worked metal is well established, and need be only briefly summarised with a few references to recent articles which clarify minor points. The types of extension, whether by stretching, drawing, hammering, rolling, etc., do not alter the general principles (1), although quantitative results may differ somewhat, particularly with regard to differences between the surface and interior of samples.These principles can be summarised as follows: The first stage in annealing is a recovery (sometimes known as relaxation) of physical properties such as hardness, elongation, etc., without any appearance of recrystallisation; the second stage involves a further alteration in physical properties, accompanying the formation of new recrystallised grains which replace the original structure; a possible third stage involves an increase in the grain size of the completely recrystallised structure by absorption of smaller grains by larger ones. These three stages will be referred to as recovery, recrystallisation, and grain growth. Depending on conditions, the three stages may be clearly marked or may occur more or less simultaneously.For a given annealing temperature, cold deformations below a certain amount fail to give recrystallisation, and the final structure consists of the original grains which have recovered and possibly become more equiaxed. When a certain deformation, critical for that annealing temperature, is given, recrystallisation can occur, and will give the maximum recrystallised grain size.Increasing deformations beyond this give progressively smaller grain sizes.For each material there is a minimum recrystallisation temperature, below which recrystallisation will not occur whatever the deformation or time of annealing. For a given deformation there is a temperature, critical for that deformation, below which recrystallisation will not occur, and above which it will take place with increasing rapidity.

Jan 1, 1947

By M Csar

The Nicolsons Find gold project is located 35 km southwest of Halls Creek in the east Kimberley. It was discovered in the late 1980s by John Nicolson and Stuart Skoglund, when high grade gold mineralisation within outcropping gossanous quartz reefs was found. The area has produced a modest 28 150 ounces of gold over two brief mining periods in 1996 and 2002 - 2003. Indicated and inferred resources as of September 2011 stand at 1 384 000 t at 5.58 g/t Au for 248 500 ounces of gold.The project is situated within the Halls Creek Orogen. Principal host units are metasediments and volcaniclastic sediments of the Koongie Park Formation. Minor mafic units are also recognised. Immediately east of these units, emplacement of the loadstone granite is believed to have provided the structural setting for the later gold mineralising event.Mineralisation is hosted within a broad, brittle-ductile arcuate shear zone about the western contact of the Loadstone granite. In the Nicolsons Find area, the shear zone strikes north-northeast and within the shear zone, gold is hosted in a series of narrow, quartz rich veins up to 200 m in strike length, plunging moderately to the north-northeast. To date, mineralisation has been drilled to a depth of 360 m below the surface. The veins are stepped or en-echelon in nature with low gold values towards the quartz vein limits where compression is inferred and higher grades present in the dilational body of the quartz veins. Gold is fine grained and can be present with or without associated sulfides. Sulfides are generally minor and consist mainly of arsenopyrite with traces of chalcopyrite, pyrite and sphalerite. Where present, sulfides are generally indicative of higher gold values.CITATION:Csar, M, 2012. NicolsonÆs Find gold project, East Kimberley, Western Australia, in Proceedings Narrow Vein Mining 2012 , pp 31-36 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By Johnson D. P, Beamish B. B

The northern Bowen Basin has a very large resource of coalseam methane gas-in-place - 136 TCF(7ohnson and White, 1988). The gas is pipeline quality, being 98-99 per cent methane with traces of carbon dioxide and higher hydrocarbons. The largest resource of natural gas within the coalseams of the northern Bowen Basin is contained in the Moranbah Coal Measures (75 per cent). The next most important resource is in the combined upper Fort Cooper (16 per cent) and Rangal (nine per cent) Coal Measures. The far northern parts of the basin have low gas contents due to the combined effects of limited extent of the coal measures, shallow depth and low rank. Reserves per well are more than double that of the best coalseam methane wells in any basin in the United States. In some areas of the Moranbah Coal Measures, the gas-in-place estimates exceed 225 million cubic metres per well (80-acre spacing). A distinction is made between resource base, as determined from this basin assessment, and the deliverability potential. Parameters used to estimate gas-in-place (coal area, thickness, density, rank and depth) can be adequately extrapolated from areas of high- to low- data density. Parameters affecting methane production (permeability, gas depletion factor and critical desorption pressure) cannot be generalised. Exploration and development programs must rapidly develop a predictive capability for these factors, on a local scale, through geological modelling and confirmation drilling.

Jan 1, 1991

By Bruce P, Luyendyk

The South Island of New Zealand comprises a collage of distinct tectonostratigraphic terranes. Some tectonic models predict that these terranes formed on or near the margin of Gondwanaland. However, geologic evidence suggests that some of these terranes may be exotic. Over 400 samples from 30 sites were collected from the Brookstreet terrane within the Takitimu Mountains. The section includes the early Permian Takitimu Group and the late Permian White Hill Intrusive Suite. Over 80% of the rocks show a partial or complete regnetization in the present field due to recent acquistion of VRM. Although some remagnetization of the Takitimu Group occurred during the emplacement of the White Hill Intrusives, both early and late Permian direction have been isolated. These directions indicate a mid-latitude origin for the Brookstreet terrane, and suggest a strong clockwise rotation between early and late Permian time. A published paleomagnetic result from the younger, but related, Murihiku terrane suggests that the Brookstreet terrane was sutured to the margin of Gondwanaland by the late Triassic, or that the Brookstreet and Murihiku are two distinct terranes.

Jan 1, 1987

By M A. Gontalves, A F. D C Varajpo

The Rio Capim kaolin district, located in the north-east of Parß State, Brazil, constitutes one of the worldÆs largest high-whiteness kaolin reserves for the paper coating industry. It contains, at the base of the main ore, a soft kaolin that gradually changes at the top into a ferruginous duricrust followed by a flint kaolin. The flint kaolin is completely discarded during the exploitation of the soft kaolin. With the view of a more complete beneficiation, aiming at a sustainable development of the minerals industry, the use of this residual flint kaolin has been considered for the manufacturing of zeolites. Zeolites were synthesised from the flint kaolin through a reaction between metakaolinite with soda at 80¦C, for durations of 24 to 144 hours. The transformation into metakaolinite was carried out at 800¦C and was not affected by the titanium oxides. For a synthesis time of only 24 hours, a zeolite 4A very close to its theoretical definition was obtained, whereas for synthesis times longer than 96 hours, a slight formation of hydro-sodalite was also observed. The synthesised zeolites were tested as cationic adsorbents on 0.5 molar solutions of Cu, Pb, Cd and Zn. The adsorption was measured for contact durations of one and three days. It was noted that the exchange kinetics were slow and that the retention was significantly greater after three days than after one day. The retention was greater than 50 per cent of the theoretical exchange capacity for Pb, Cd and Zn, which was different to Cu, where the retention exceeded its theoretical exchange capacity.

Jan 1, 2008

It is now 32 years since Walsh's classic publication (1) heralded the beginning of atomic absorption spectrophotometry (AA) as we know it today. During this time, AA has developed into the most widely used analytical techniques for the determination of the metallic elements. The years have seen progressive changes in instrumentation so that today it is a highly sophisticated technique. One area of development in AA that is experiencing renewed attention is in the area of electrothermal excitation. In this technique a flame is not used by the analyte solution is atomised by an electrically heated graphite furnace. For a large number of elements the graphite furnace atomic absorption spectrophotometer (GFAA) is considerably more sensitive than flame work. It is common to be able to detect concentrations one hundred times smaller than those possible by flame. Today's geochemists are finding that they can gain valuable information out of very low limits of detection. Electrothermal atomic absorption spectrophotometry (or GFAA) allows for low limits of detection and can be seen to be a valuable aid to geochemical prospecting Analysis.

Jan 1, 1987

By N Harries

The management of risks associated with slope instability is an essential process in the safe and economic operation of open cut mines. The æslope stability radarÆ (SSR) has been developed to better manage those risks. The SSR can remotely scan a rock slope to continuously measure any movement of the face. The system can detect and alert users of wall movements with submillimetre precision. The high level of movement precision and broad area coverage of the rock face can allow for a better understanding of the geomechanics of slope deformation, including magnitude of potential failures and additional warning time of impending instability. Additionally, radar waves adequately penetrate through rain, dust and smoke to give reliable measurements, 24 hours a day. SSR systems have been deployed in many mines in Australia, Indonesia, Africa, Chile and the United States. Greater than 100 rock falls and waste dump failures (from several tonnes to millions of tonnes) have been monitored, and on every occasion precursor æwarningÆ movements were recorded by the SSR. This technology enables a radical change in the management of risks in open cut mining. This paper presents recent case studies of how the SSR technology has provided safety and productivity benefits to large open cut metalliferous mines.

Jan 1, 2007

The Electricity Generating Authority of Thailand own and operate an opencut mine supplying coal to on-site power stations at Mae Moh, 600 km North of Bangkok. The mine is being expanded from an annual production of 1.5 million tonnes per year in 1982 to over 9.5 million tonnes per year by 1991. The mine will be amongst the largest open pit operations in the world. It is technically difficult to operate and plan due to complex geology, weak strata and surface constraints including reservoirs, forests and traditional villages. This paper presents a case study of mine planning for the above project including associated collection and processing of geological and geotechnical information. The existing operation is described, as well as the strategy adopted for the mine at expanded production. The planning covers various phases of mine planning including a Conceptual Study, a Definitive Study and detailed short term planning. Each stage incorporated new information and reflected a higher level of confidence in the data and resulting plan. Sophisticated computer techniques were required including geological modelling, calculation of volumes, geotechnical analysis, scheduling and costing. The planning was undertaken on site by a team of Australian and Thai Engineers as part of the Thailand-Australia Lignite Mines Development Project which is a four year programme of assistance funded by the Australian Government.

Jan 1, 1986

Material hardness and environmental factors can limit or restrict conventional blasting techniques and this has led to advancements in the performance and efficiency of ripping. Not all materials can be ripped, however today's technology and experience can help make a reasonable prediction. A ripping versus blasting decision will depend on the total volume of material to be moved, the production capabilities and costs of the ripping tractor(s) and on the size and relative efficiency of drilling and Blasting.

Jan 1, 1995

By Yusuf R

Many heap and dump leaching processes involve competitive, complementary and sequential reactions between multiple minerals and reagents. A comprehensive model has been developed to deal with these complex chemical interactions which is based on diffusion control of the reaction rates. All of the mineralogical and chemical data are obtained from representative samples of the ore or the chemical literature. These properties have been incorporated in a general way, making the model applicable to a range of ore-process systems. The simulation is used to predict the absolute reaction rates and can be used before any leach tests are carried out on the ore itself. The applicability of the model and some tests of its validity are presented.

Jan 1, 1984