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By Sengstock G. W, Spathis A. T

Benchmarks of mine equipment involved in the excavation process of coal mines would suggest that such equipment is not always operating at an optimum level. Dragline operations and truck/shovel operations rely on efficient use of their plant in order to maintain high mine throughput. The first process which affects the material to be excavated is the drilling and blasting process. Drilling and blasting delivers a fragmented material with a given disposition ready for excavation by mine equipment. As mine operators demand more productivity from their major excavating equipment, many sites are considering the use of productivity monitors to measure their outputs. Some of these productivity improvements will be directly related to the drilling and blasting process, so that as the monitoring systems improve, the opportunities to evaluate all drilling and blasting variables will also improve. This paper reviews current and newer methods for monitoring equipment productivity in mines. These include simple time and motion studies obtained by either manual timing of processes or by automated data collection equipment being adopted by the industry. Case studies for truck/shovel operations are discussed and the productivity improvements are compared with typical industry standards. These improvements relate specifically to parts of the load, haul and dump cycle and the potential for significant improvements are identified. Particular opportunities for drilling and blasting improvements are also presented.

Jan 1, 1995

By Hoppe AJ

Drilling and shooting techniques at Moura open-cut have evolved over a period of 16 years and are the result of hard earned experience combined with established practices and consul- tation with professional services. The wide range of overburden types encoun- ted in the field requires varying methods to achieve the best results at all times. Safe working conditions for the employees and protection of mining equipment is of para- mount importance and close liaison is maintain- ed with the Department of Mines Queensland to keep abreast with changing legislation. Drill patterns, charging profiles, types of explosives and ultimate results are des- cribed in detail along with a resume of equip- ment. Costs of drilling, labour and explosives are also analysed with a total of approximately 20c per cubic metre of shot ground. Future developments and improvements to facilities are also outlined.

Jan 1, 1978

This paper gives a first-hand account of what a graduate mining engineer can learn by visiting Atlas Copco in Sweden and gives reasons why all mining engineering students should apply for this excellent scholarship. It will also (attempt to) refute the authorÆs mine managerÆs claim that the trip was a huge junket.

Jan 1, 2006

By Just G. D

The results of a geostatistical analysis of geochemical data obtained from field measurements are described in the paper. Q values derived from seismic signal rise times for different travel paths in the rock masses were used in the study. Cross-hole seismic measurements made at surface and underground sites formed the basis for the work. Geostatistical estimation of average l/Q values for area of the rock were compared with geological interpretions of rock type distributions. Reasonable correlations were obtained between the two methods of rock quality estimation.

Jan 1, 1988

Resource rent tax is a form of taxation or royalty, which only become effective at such a time as a pre-determined rate of return has been achieved by an operation. The offshore petroleum industry in Australia is already subject to RRT as is the Roxby Downs (Olympic Dam) Mine in South Australia. Both the mining and petroleum taxation regimes in Papua New Guinea include a resource rent tax component called Additional Profits Tax (APT). The implications of the current form of Additional Profits Tax for shareholder cash returns are that the tax burden on the operation may suddenly increase at some stage in the life of the mine, if and when the threshold level of profitability for the tax to be triggered is exceeded. From that point in time onwards the cash return to the shareholders on the capital invested is greatly diminished. For mining companies in Papua New Guinea, the effective tax rate increases from 35% to 57.75% as a result of the onset of Additional Profits Tax. This tax rate penalty is so severe that there appears to be merit in considering the concept of managing profitability through time rather than purely maximising annual pre-tax profits as is currently the case in most mining operations. This would have the benefit of deferring or perhaps preventing altogether the onset of the tax. One possible method for the effective management of profitability is through the control of average mining grade by cutoff grade manipulation. Traditional cutoff grade theory has usually considered taxation as a direct cost at a fixed or variable percentage of annual profits. As a result of this most analyses are conducted on a pre-tax basis. If tax is included in analyses it is usually present as a time independent function of gross profit. Additional Profits Tax is both time and rate of return dependent and therefore not adequately accommodated by currently accepted cutoff grade theory. A review has been made of the effects of resource rent taxes on both the investment decision-making process as well as possible development and mining strategies which may be employed by mining companies faced with Additional Profits Tax. The review includes examples based on the structure of Additional Profits Tax which is levied in Papua New Guinea.

Jan 1, 1997

By D Feng, G C. Lukey, J S. J, R R. Dagastine

An ongoing challenge in the coal industry is pyrite removal using the flotation method for fine particles. The use of a æseparation in frothÆ (SIF) technique to recover coarse particles of up to a few millimetres in size has presented a potential solution. However the commercial success of SIF is still limited due to the poor understanding of the separation mechanism. The particle floatability in SIF is determined by the constructive or destructive stresses resulting from the forces exerted by the particle on the bubble films. Hence, the surfactant properties and the mineral characteristics (eg hydrophobicity, shape, etc) are the key factors that control the interaction between the particle and froth. In the present work, the interaction forces between different particles (ie crushed glass, pyrite and coal) and a single air bubble are measured in a non-ionic surfactant solution (pentaethylene glycol mono n-dodecyl ether, C12E5) using an atomic force microscope (AFM). Experimental results show that the interaction is primarily dependent on the contact angle (ie the degree of hydrophobicity of the minerals). For crushed glass, the transition from repulsion to attraction was observed as the contact angle increased. As the concentration of C12E5 increased, the adhesion force was suppressed due to wrapping effect. For coal and pyrite with much higher hydrophobicity, long-range attraction was observed. The effect of shape factor was only visible at high surfactant coverage where sign of destabilisation became noticeable on the retracting force curve. These results provide a fundamental understanding of the direct interaction forces of a complex real system between an irregular particle of either crushed glass, pyrite or coal and a single air bubble. Theories developed for interpretation and modelling are thus far based upon the study of ideal systems of glass or polystyrene spheres and an air bubble and were incapable of explaining the interactions in complex real systems. The presented measurements were a first approach to the problem of real mineral-bubble interaction in flotation systems. Thus, the results can only best be interpreted semi-quantitatively.

Jan 1, 2005

By G Cormack

By designing comminution circuits for mineral liberation rather than the final recovery process and by using high mass pull gravity recovery, the concept of underground processing has become a reality. Gekko has found that many ores respond favourably to fine crushing with either high pressure grinding rolls or vertical shaft impactors which when combined with the InLine Pressure Jig gravity separator and coarse flotation results in a narrow, low-head, compact processing plant that can be sensibly fitted in existing underground openings. The focus on fine crushing reduces the power requirements of the plant to approximately 5 kWh/t for a capacity of up to 20 t/h run of mine ore feed. The use of water recycle systems places no extra load on the mineÆs normal water handling system. GekkoÆs underground processing plant, the æPythonÆ, has been designed to be towed down the decline or lowered down a shaft and is capable of being installed in sloping, non-linear drives for placement close to the working face. The overall benefit to mining companies of this concept has been estimated to be a significant operating cost-saving, lower cut-off grade and a significantly smaller environmental footprint.

Jan 1, 2008

Coal losses and dilution are among a coal mine operators everyday problems. These losses and unwelcome additions are generated primar- ily by the stripping operation and secondly by the coal mining opera- tion. Losses in yield due to preparation plant efficiency are a separate issue although they may be related to the coal mining operation. The losses and dilution can be traced to the following operations: (A) Overburden or Interburden Removal (1) Removal of coal edge by blasting operations. (2) Removal of top of seam by drilling/blasting. (3) Removal of top of seam by stripping equipment. (4) Removal of coal edges by stripping equipment. (5) Dilution due to stripping equipment. (B) Coal Mining (for the case where seams are ripped rather than shot) (1) Coal rib losses. (2) Coal rib dilution. (3) Coal left in floor. (4) Coal left in fault areas. (5) Floor material picked up whilst loading. (6) Spoil material picked up. (7) Spoil material from poor surface clean up. (8) Top of coal losses from final clean up. (9) Dilution from ripping too deep, i.e. into floor below seam. (10) Dilution from interseam parting. The losses apply to both the single seam and multi seam oper- ations although they are more pronounced in the multi seam mines than in a single seam mine due to the position of the coal which is lost. For example in the multi seam case the top seam coal edge loss is final. There is little chance of recovery with the subsequent pass even if the extra rehandle is done. However conversely the lower seam is relatively easy to locate as it has nowhere to go being contained by the lowwall bench.

Jan 1, 1988

The implementation, during recent years, of the concept of distributing chilled water to improve cooling at the working faces represents a very important innovation for the mining world. In a logical extension to that concept it has been recognized that distribution of the cooling water at high pressure would provide a potential source of energy for driving water powered hydraulic machinery such as rockdrills, water jets for moving rock, and support props, in the workings. With this in mind, the Research Organization of the Chamber of Mines of South Africa is pursuing the development of such a dual system that will provide cooling in a deep mine and, at the same time, drive hydraulic machinery. A comprehensive design of such a system has been completed and has shown the concept to be entirely feasible technically using technologies currently available. A pilot system is working in a mine shaft 2000 m deep giving a pressure of 20 MPa at the bottom of the shaft and distributing the cold water into the workings at a pressure of 17 MPa. The system shows considerable potential for improving existing mining methods and will open the way for the development of new mining methods for deep mining operations.

Jan 1, 1986

By J McQuie

The concentrator at WMCÆs Leinster Nickel Operation has operated with flash flotation in the grinding circuit since the early 1990s. There has always been a positive correlation between flash flotation Ni recovery and overall Ni recovery û however this relationship could be explained by differences in the ore, rather than by the action of the Flash flotation cell in reducing overgrinding of Ni. In July 2003, refurbishment within the plant made it necessary to operate the concentrator for a period with the flash flotation cells off. The resulting data set provided evidence that flash flotation in the grinding circuit changes the size distribution of Ni to reduce the amount of slow-floating fine (-7 ¦m) Ni produced. Ni recoveries in the finer size fractions were similar with flash flotation on or off û but because less fine Ni is produced when the flash flotation cells are operated, overall Ni recovery improved.

Jan 1, 2005

The grinding of ore to a size that is conducive to the extraction of minerals by leaching or flotation is an essential and expensive component of most mineral-processing operations. Overgrinding results in reduced flotability of the minerals, as well as problems in the filtration and thickening processes, while undergrinding leads to a product in which the minerals have not been exposed, and cannot be leached or floated effectively. Furthermore, coarse material causes settling in thickeners and agitator tanks. It is therefore essential, from the perspective of both operational and extraction efficiency, to grind the ore to an optimum size fraction. A well-run milling circuit will yield a product within a narrow size band and at a high throughput. Although the effective operation and control of milling circuits with their many operating parameters is widely acknowledged as a complex as well as a critically important operation, the benefits of such control are difficult to quantify. This is due to the difficulties in relating more stable operation to increased recovery of the valuable components in downstream processes.

Jan 1, 1993

The St George orebodies are situated within the tectonically disrupted eastern limb of the Boogardie Syncline.Highly disturbed rafts of banded chert formations occur within a sequence of felsic volcanic tuffs. The chert forms the hostrock for the gold mineralization.The gold distribution within the irregular and narrow banded chert formations is erratic and patchy. The average gold content of the two orebodies is between 3 - 4 g/t Au.Economic mining of these relative small, irregular and low grade St. George orebodies can be carried out by using a highly selective mining method.The highly selective mining method uses an excavator as the principle mining tool. Blasting, breaking and loading of the rocks is done in a different way than by using a front-end loader as with the conventional mining method. Simple, and therefore cheaper, blasting breaks the rocks and lifts them up without major displacements.

Jan 1, 1984

Conditional simulation is a branch of geo- statistics which allows the simulation of a mineral deposit so that predictions can be made about the variability of some particular parameter of the deposit. A summary of the general principles, advantages and limitations of conditional simulation is presented together with an example based on coal seam thickness.

Jan 1, 1981

By D S. Clarke, K B. Sporli

Structure is an important control in the localisation of gold mineralisation in epithermal systems. There has been, however, only limited investigation of the structural elements involved; such a study is currently directed at the gold deposits of the Coromandel Volcanic Zone (CVZ). Here, mineralised veining and brecciation ranges up to tens of metres in thickness. Dips of veins are mostly steep, but not vertical, and there is a significant number of low angle veins. The structural control of epithermal deposits may be considered on four scales. At the mega-tectonic scale, pre-volcanism fault patterns mostly relate to separation of the New Zealand micro-continent from Gondwana. The major structural controls on mineralisation at this scale, however, are associated with the volcanic arc processes responsible for the CVZ. Post-mineralisation faulting are linked to the Hauraki Rift and the Colville Ridge-Havre Trough system. Regional scale faults controlling the distribution of gold deposits are the product of these tectonic events; much of the faulting may relate to rifting and calderas, but further work is required to demonstrate this. Detailed study is also needed on vein systems at the prospect scale to validate models of brittle deformation responsible for such systems. Evidence that a variety of structural mechanisms dominated in different deposits is found at the vein scale, with Coromandel gold deposits being classified according to their different styles of vein-fill texture.

Jan 1, 1990

By Zhao JC, Chen JJJ

A water/air model was developed to simulate the refining of molten aluminium by the sparging of gas through an impeller. The optimal gas dispersion depends upon selecting the correct gas rate for a given impeller rotational velocity to prevent flooding or channelling. Correlations illustrating this flooding behaviour exist for standard impellers within standard tank geometries. However the validity of these correlations has not been substantiated for gas dispersion in high temperature molten metals with non-standard tank and impeller dimensions.

Jan 1, 1995

By Lauricella P. F, Hendri D

In the Mesel sediment-hosted disseminated gold deposit, the spatial distribution of hydrothermal alteration is controlled by steeply dipping faults and shallowly dipping lithologies. Hydrothermal alteration of carbonate rock is characterised by decalcification, dolomitisation and silicification. Intense argillic alteration occurs in a laccolithic andesite intrusion adjacent to decalcified and silicified carbonate units. Sulphide minerals (pyrite, realgar, orpiment, stibnite and cinnabar) accompany hydrothermal alteration and precious metal mineralisation. The trace elements Ag, As, Sb and Hg are zoned spatially throughout the deposit. Mesel contains a mineable gold reserve of 7.8 million tonnes at 7.3 g/t Au. Gold mineralisation is preferentially localised in carbonate rocks adjacent to and beneath the andesite intrusion. The ore body consists of a central, near-vertical, high grade "feeder" system flanked by tabular, inward dipping, moderate grade "ouflow" zones. Mineralisation is controlled predominantly by two steeply dipping faults with high grade (>10 g/t) gold zones centred about structural intersections and fault splays. Gold is submicron size and locked in very fine grained (

Jan 1, 1995

By Kurihara M

In Japan, shield tunneling method is generally used to drive a tunnel in sand layers around the urban area. In this report, appli- cability of NATM (New Austrian Tunnelling Method), which uses rock bolts and shotcrete as support, to water-bearing sand layers is studied aiming at establishing more economical tunnel driving technique. After the geological exploration, the conditions (i.e. pitch of steel supports, water content, cohesion, and fine content of ground,)necessary to ensure the face stability were investigated by using centrifuge loading tests. Concerning measures to manage ground water, an air permiability test was carried out to investigate the effect of the compressed air to cut-off inflow, and pumping test to study the applicability of dewatering. Furthermore, two dimensional elastic FEM analysis consider- ing progress of the excavation face was perform- ed to analyze stresses in the support system and deformation of the ground, and to investi- gate safety of the support and the ground. From these prior investigations, possibility of the applicability of NATM to the present pro- ject was predicted. Finally, based on these results, a real scale field application test was put into practice to confirm the prediction, and to pursue construction efficiency and phenomena which could not have been predicted Beforehand.

Jan 1, 1987

By M J. Sale

The Epithermal and Mesothermal Gold Prospectivity Modelling Projects recently completed by Crown Minerals provided explorers in New Zealand with a new compilation of historical exploration data combined with new geological information from the GNS QMap 1:250 000 scale mapping project. These data were used to produce predictive mineral potential maps for gold mineralisation in New Zealand. The aim of these projects, which was to stimulate mineral exploration and investment in exploration, has been successful with new companies acquiring new tenements and committing significant exploration expenditure to exploring in New Zealand in the coming years. The projects were undertaken at a national scale and consequently not all exploration data were compiled into the prospectivity models. HPD New Zealand Ltd recognised the value of the prospectivity modeling work and committed exploration funds to continue the modelling process started by the projects. They recognised the need to compile the remaining data and run the models again to allow detailed exploration targeting.

Jan 1, 2004

Diamond drilling is a relatively new commodity in terms of drilling. The first known diamond drilling activities were carried out in the Swiss Alps around 1863 when the Swiss engineer M Leschot designed and made a tube with a diamond set face which was used in probing ahead drilling for the Mont Cenis tunnel (Figure 1). Craelius AB which today is a part of the Atlas Copco Group was formed in 1886. The name Craelius is a family name and the founder of the company was Per Anton Craelius (Figure 2). He went to the United States to study this new technology using diamonds to extract core samples and when he returned to Sweden designed his first diamond drilling machine. It was a man-powered drill needing a crew of six men, two to crank the unit, one to feed, two to power the flush pump and a foreman (Figure 3). As time passed through research and development, the original design was improved and manpower was substituted for steam engines and later combustion engines or electric motors (Figure 4). During the 1930s the drills radically changed designs and took the form of the short stroke drills which to a certain extent are still in use today. The original design of these drills have been refined during the years, hydraulic chucks, gear boxes and other improvements have been added.

Jan 1, 1995

By A Tomsett, R Kidd, Z Casley

Bivariate recoverable resource estimation aims at predicting the recovered metal for a secondary variable when a cut-off is applied to a primary variable. The choice of a consistent geostatistical model is advisable to allow a robust estimation from exploration data of the primary and secondary metal recovery functions on a generic selection block (selective mining unit û SMU) within large panels. Ore processing decisions at Lihir Gold LimitedÆs Lihir Gold Mine are based on the gold and sulfur estimates of SMUs from production (grade control) data. The predictive model from exploration data at Lihir is based on the estimation of a recoverable resource for gold by Uniform Conditioning (UC), with an estimate of the sulfur grade being provided by Ordinary Kriging of panels. While univariate UC is adapted to the diffusive nature of the gold mineralisation (Ladolam orebody) at Lihir, the independent estimation of sulfur, through ordinary kriging, fails to capture the potential spatial correlation that exists between gold and sulfur mineralisation. This paper presents a practical implementation of bivariate UC, which better represents in the resource model the spatial correlation between gold and sulfur. Incremental economic gains through improved definition of material categories and scheduling are investigated, and the particular impact on the process of geological interpretation and domaining is emphasised.

Jan 1, 2009