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By J S. Kuszmaul, T O. Aspinall

The applicability of environmental geotechnics for erosion management is increasing in importance worldwide. The environmental impact of mining and evolving environmental legislation has been receiving increased attention worldwide in the last two decades (Bradfield, Shultz and Stone, 1996). The potential impacts associated with unstable spoil dumps from mine operations is the focus of concern both by the mining industry, environmental legislative agencies and members of the public. This is because of the need to increase the reliability of erosion prediction and in the minimisation of costs for spoil dump design. Engineered slopes of mine spoils may be stable at the end of construction, but they can deteriorate over time. Engineering design of mine spoil dumps seeks to reduce the potential for such erosion damage through correct selection of an initial stable landform scheme (Goh, 1997). The design of mine spoil dumps must also conform to the specifications of evolving legislation. The Queensland Environmental Management Overview Strategy (EMOS) states that, for minimised degradation of the surface area due to erosion during the development of a project, the erosion rates should be between 12 - 40 tonnes/hectare/year and that the depths of rills and gullies be limited to less than 30 cm (QDPI, 1988). The aim of engineering design is to ensure the long-term stability of the spoil dumps. The implementation of effective planning and operating procedures through recontouring and grading assists in the reshaping of spoil dumps to a safe, stable and non-erodible environment.

Jan 1, 1998

By D Craw

Quaternary warping and uplift of antiformal schist ranges in Central Otago, New Zealand, has resulted in recycling of alluvial gold from widespread, generally weakly auriferous, Miocene fluvial gravels that unconformably overlie the schist, into aprons of fan sediments along the range margins. Basement erosion during uplift has been limited and so gold input from sparse gold-bearing quartz veins in the schist has been relatively minor. In an eluvial cycle on the slopes of the ranges, chemical remobilization of gold occurs during oxidation and erosion of the Miocene sediments. The typically fine-grained (300 - 400 ¦m) gold undergoes chemical modification and grain size enhancement of up to two orders of magnitude, and much of it is redeposited in a large number of relatively small alluvial fans along the range margins. Groundwater mobility within the fans results in minor additional gold mobility and grain size enhancement. During range uplift, a small number of relatively large axial streams and rivers have developed in structural lows between growing antiformal folds. Axial streams 'gather' their flow from consequent streams draining the folds, and flow parallel to a range axis for some distance before cutting across it in an antecedent gorge. The axial streams rework alluvial fan sediments along the range margins, and transport mainly fine-grained gold from the fans along the ranges. This gold is redeposited where the axial streams emerge from a range in the neighbouring structural basin. Axial streams drain relatively large areas of range surface, and thus reconcentrate significant quantities of gold in a small number of relatively large fans and fluvial deposits. The processes of gold collection and re-deposition by axial streams are essentially the same, regardless of stream size. Coarse-grained gold produced by chemical remobilization, is more difficult to transport in fluvial systems, and thus remains in close proximity to eluvial environment where it was formed.

Jan 1, 1995

Integrated geological interpretation of aerial photographs and Landsat images revealed that the gold mineralisation at Kyauk Pahto took place in a narrow zone of tension fractures within part of a previously unrecognised dextral wrench fault system. The latter is the wider manifestation of the well known Sagaing (right-lateral) strike-slip fault which has a length of more than 1 000 km, and it demarcates the boundary between the Indo-Australian and Asian plates. A subtle, right-handed kink affects the full width of the Sagaing Wrench-fault System at about the latitude of Kyauk pahto, and the extra dilatancy imposed on the tension fracture zone facilitated episodic ingress of mineralising hydrothermal fluids by "seismic pumping".

Jan 1, 1987

By Szwedzicki T

In recent years substantial advances have been made in the field of geomechanics. Staff at the Western Australian School of Mines (WASM) are keen to see that such advances continue and that the mining industry in Australia can take full advantage of such developments in a timely manner. WASM views mining geomechanics in its broadest sense, as being concerned with the characterisation of the physical properties and the behaviour of earth materials (soil, rock and water) and openings as mining proceeds. Aspects such as, soil and rock improvement techniques for difficult site conditions and the rock breaking processes, are also considered to be an integral part of mining geomechanics. This paper indicates the inter-relationships between the various areas within the field of geomechanics and the strong reliance of all of these areas on site specific engineering geology.

Jan 1, 1992

Cominco Ltd's Polaris Mine in Canada's High Arctic has been successfully mining zinc ore in permafrost since 1981. Mining methods using frozen backfill have been the key to success. The mine is now producing about 60 per cent of the ore from pillars while maintaining high productivities. Annual ore production is just over one million tonnes providing more than 200 000 tonnes of zinc concentrate each year. Cominco Ltd has adapted management and operating practices to suit the harsh environment and the isolated site, and has shown that a profitable development can be carried out in the tough Arctic conditions, with minimum impact on the environment.

Jan 1, 1993

By Leigh J. H

A history is given of the dust control techniques developed and applied by the mining companies at Broken Hill. A history of the regeneration works undertaken since 1936 is out- lined. Particular emphasis is placed on the stabilization of mine residue dumps which are located throughout a belt of mining leases in the middle of the city and which began in 1937. The establishment of vegetation for dust control techniques is discussed in detail and a case study is given of the successful revegetation of the sides of a 650 metre long, 350 metre wide and 35 metre high residue dump.

Jan 1, 1976

By Membrey W. B, Partridge A. C

Lower transportation costs, improved handling and better utilization efficiency are some of the reasons that make low moisture coal product desirable. There has been considerable interest in the development of effective coal dewatering techniques to achieve this result. One avenue of considerable merit for enhancing dewatering processes is by modification of the surface chemistry of the coalwater slurry system by chemical means, resulting in better performance of existing equipment. This paper reports the results of an investigation of the utility of surface active agents in the enhancement of fine coal dewatering. A large variety of proprietary dewatering agents have been studied in relation to their efficiency in enhancing the dewatering of a number of Australian coals. Properties of particular coals that make them amenable to improved dewatering by particular chemical agents have been identified. Surface studies, including surface tension and zeta potential measurements as a function of surfactant concentration, as well as dewatering assessments, were used. Particular attention was paid to filtration, but the results could be applied to other dewatering systems.

Jan 1, 1989

The gas drainage characteristics of two seams, the Bowen at Bowen No. 2 Colliery, Collinsville, and the Gemini at Leichhardt Colliery, Blackwater, are assessed. Single borehole tests and drainage panels were studied by underground monitoring of pressures and gas flows. Permeability was found to be effected by cleat to an order of magnitude. Other structural features are shown to be important. In this context, the need for delineation of no-flow zone locations in boreholes is shown to be of great importance where in-seam pre-drainage is being used for outburst control. Water in the seams strongly influences permeability causing gas flows to fluctuate with time. Use is made of modified reservoir engineering techniques to analyse the drainage characteristics of seams.

Jan 1, 1982

By Takagi T, Seetharam R, Sie SH, Naito K

Tin-polymetallic vein type deposits are one of the major source of metal producers in the Circum Pacific Belt. This type of deposit is of great importance for the modem electronics and medical industries because of their high content of rare metals (especially indium and bismuth). We have studied two representatives, Tosham of India (Cu-In-Bi-Sn-W-Ag-Au), and Mount Pleasant of Canada (Zn-Cu-In-Bi-Sn-W), using proton and electron microprobes in order to delineate the distribution of medical/high-tech rare metals. The electron microprobe study showed that major indium carrier in such type of deposit are roquesite (CulnSZ), sphalerite, stannite and a Cu-Zn-Fe-In-Sn-S mineral; and that indium is incorporated in sulfides by coupled substitution like Cu + In = 2(Zn + Fe). The proton microprobe showed that indium at trace levels is also present in chalcopyrite and pyrite. In addition, zinc, copper, arsenic, antimony, selenium, tin, and bismuth are common in chalcopyrite and pyrite. Arsenopyrite contains nickel, copper, zinc, silver, tin, antimony and bismuth. In chalcopyrite and pyrite, zinc, arsenic, indium, bismuth and lead are higher in Mount Pleasant ore, but silver is higher at Tosham. Also thallium and gold were found only in Tosham pyrite. The Tosham deposit is genetically related to S-type magma, while the Mount Pleasant deposit is related to A-type granite. Tosham ore contains zinc-bearing biotites that coexist with chalcopyrite in ore bodies but Mount Pleasant ore lacks such biotite. We propose that the difference in elemental abundance between the two deposits are caused by the different character of source magma and different mineral associations of the ore body.

Jan 1, 1995

The Gympie Province is a unique tectono-stratigraphic unit which does not fit into the overall palaeogeographic pattern of the New England Fold Belt (NEFB), and part of it has been proposed as an exotic terrane more closely linked to New Zealand. From E to W the Gympie Province comprises 6 distinct units which can be evaluated as suspect or exotic terranes.

Jan 1, 1990

By KenGemar P, Perembo R. C B, Winn R. D

The New Guinea orogen comprises terranes that have accreted to the northern margin of the Australian craton. The history of the accretion of terranes begins earlier (in the Late Cretaceous) and is more complex than has been suggested previously. There was a collision in the central highlands in the Late Paleocene or Early Eocene, and a Finisterre collision that precedes and is distinct from the later (Pliocene) Bismarck volcanic arc collision.

Jan 1, 1997

By Cuff C, Taylor RG, Georgees C

Mineralisation adjacent to Herberton occurs within three main subcentres. The Her- berton Hill subcentre is characterised by the association of Sn,W the Herberton Dividing Range South subcentre by Sn, and the Herberton Dividing Range North by Cu, As. The relation- ships between the subcentres are discussed in terms of metal distribution, production, deposit types, wall rock alteration and re- lationships with granitoid intrusives. The temporal and three dimensional spatial re- lationships between the centres are uncertain.

Jan 1, 1978

By Breen AM, Phelan JM, Doherty RJ

Early in 1990, Pancontinental Resources (Base Metals) Pty Ltd commenced flotation treatment of ore from the complex copper-lead-zinc sulphide orebody at Thalanga, 65 km west of Charters Towers in North Queensland. The orebody consists mainly of primary sulphide ore but also contains a substantial proportion of supergene ores which are being processed during the first year of operations. The supergene ores are of three main types, designated as A, B, and C. Supergene A ores are essentially copper ores, containing little lead and zinc, while B and C ores are copper-lead-zinc ores with different degrees of alteration of the original chalcopyrite and different ratios of copper to zinc content. Copper is present in the supergene ores mainly as chalcocite, digenite and covellite. Lead and zinc occur mainly as galena and sphalerite respectively. This paper describes the development of flotation plant practice, aided by laboratory testing, to process the supergene ores. The major challenge in treating these ores is that a varying proportion of the sphalerite is naturally activated and is not easily depressed in flotation by the conventional zinc depressants.

Jan 1, 1991

By Smitham J. B

A selection of Australian washed coal samples was examined to determine the effect of sample hydrophobicity (rank) and particle size on froth stability in the flotation process. The results indicate distinct rank-based variations in froth volume and stability for flotation tests conducted without the use of collector, over a series of particle size distributions.High-rank coals showed a greater tendency to generate stable, high-volume froths than coals of lower rank. Implications for circuit design and operation are outlined.

Jan 1, 1988

This paper describes preliminary research on the application of Markov Decision Processes (MDP) to Real Option Valuation (ROV) and the optimisation of mine scheduling. The MDP framework is a novel approach to option valuation and scheduling in mining operations. A learning agent is introduced into the valuation process of an open pit, where prices and block ore grades have probabilistic values. The prices are modelled using a mean reverting diffusion process and the block grades using sequential Gaussian simulation. The agent is asked to learn which production parameters should be used in order to maximise the overall value of the project. The introduction of the agent permits a real option approach to mine valuation, such that the value associated with the robustness of a design to uncertainty can be measured. A simulated example is used in which there are ten blocks to be extracted under conditions of grade and price uncertainty. Using policy iteration, an optimal policy is generated and the value of production options is found. The potential financial gains from applying MDPs to mine valuation and optimisation are substantial and warrant further investigation.

Jan 1, 2007

By A K. Bayer

When the human eye fails in the evaluation of quality parameters in the extraction of minerals the use of laser-induced fluorescence analysis (LIF) can supply more detailed information on the composition of rocks. On the basis of measurements of selected raw materials engineering concepts for the use of this method in the mining industry as an innovative system for horizon control of mining machines will be described and the most important analysis parameters, influencing factors and interference variables are presented.

Jan 1, 2003

A review of all major TBM projects from 1974 to 1990 has been undertaken and the results entered into a database. A similar database was prepared from information obtained from a principal TBM manufacturer covering the period 1952 to 1990. The database includes information such as machine specifications, machine performance data, tunnel specifications and ground characteristics. The database can be used as a guide to gauge potential machine performance in a range of ground conditions and tunnel geometries. The review also indicates that current TBM technology is limited to certain ground strength conditions.

Jan 1, 1993

By B Arthur, K Sexsmith, D Hockley, S D

At the proposed Crandon Project, mill tailings would be depyritised for upland disposal. The resulting pyrite concentrate would be disposed of in the underground workings as a cement-amended paste backfill. In the long term, the underground workings would be flooded and the potential for the paste backfill to generate acid would be limited. However, while the mine is operational, there is potential for oxygen ingress to the backfill that may lead to sulfide mineral oxidation and acid generation. A series of humidity cell tests were completed to assess the potential for groundwater contamination. To assess effects of surface area on oxidation, the humidity cell tests were conducted on moulded cubes of paste backfill. The tests were terminated at different intervals, and the cubes were dissected and examined mineralogically. Various leach extraction procedures were also used to assess the progress of oxidation and secondary mineralisation within the paste backfill. The test results showed that: the cement amendment significantly contributes to acid neutralisation and results in a lag in excess of one year before the onset of acidic conditions (in comparison to less than three weeks for the pyrite concentrate); the depth of oxidation in the paste backfill is restricted to about 1 mm after 107 weeks of testing; and secondary minerals form a distinct ærindÆ at the surface of the paste backfill. The results indicate that acid generation in the backfilled stopes would be minimal. The importance of including the surface area effect in the testing (ie using moulded cubes) is clearly demonstrated.

Jan 1, 2003

By Thompson IR

This paper describes a Client Consultant Relationship and shows how an engineering team created an environ- ment which fosters the development of good, economical and sometimes unique solutions. A major factor in establish- ing this environment was the Client's instruction to the Consultant to "propose solutions which, in the Consultant's considered opinion, best satisfy the needs of the project - not necessarily solutions which reproduce methods adopted elsewhere in the past." The Consultant's experience in other projects and disciplines outside mining has contributed by providing a cross- fertilisation of ideas. The team approach also allows the Client's expertise to be applied positively throughout the design process. These factors and the Client's foresight in providing adequate time for planning, allow the Client-Consultant Team to apply sound fundamental engineering in developing effective solutions.

Jan 1, 1975

By D H. Bell

Slab-buckle failures in coal sequences involve thin slab deformation in strata dipping parallel to the footwall, and are a consequence of both unloading and the weak nature of the thinly bedded rock mass. Methods of modelling and predicting such occurrences include: +        a conceptual model using a base friction table, +        a mathematical model using the Euler solution for column and beam bending (after Goodman, 1980), and +        computer analysis techniques such as UDEC (Universal Distinct Element Code after Cundall and Hart, 1993).   Slab-buckle failures have the potential to seriously disrupt production because of their volume and rapidity, and to endanger both equipment and personnel working on the pit floor.   In July 2004 a large slab-buckle failure occurred overnight after a new batter and bench had been formed at the Malvern Hills Opencast Mine in inland Canterbury. This involved the entire length of the pit (85m along strike) when a 2m thick intact slab with a total volume of ~3500m3 translated down dip 6.2m on the base of a thin coal seam to form a pronounced buckle at the toe. The coal measures consist of finely laminated mudrocks with multiple coal seams of varying thickness dipping ~45¦ to the southeast, and the opencast mine had been designed with footwall batters formed parallel to bedding with a vertical bench separation of 15m.   Back analysis of the Malvern Hills failure was necessary to investigate the controls on footwall instability, and for future mine design. An engineering geological model was created and samples of the slab material and failure surface were collected and tested to establish the required parameters for use in the Euler solution for column and beam bending. Back analysis using the Euler solution provided unrealistic results that overestimated the overall length of a stable slope by more than 10 times.   No further large scale slab-buckle failures have developed at the mine site, in part because of the slow rate of coal extraction, but precautionary drainage of the footwall slopes has been undertaken to improve overall batter stability. The location of the slab-buckle failure on a critically positioned pre-sheared thin coal seam with full hydrostatic head is considered the most probable cause of the July 2004 failure, rather than inherent instability of the generic bench and batter arrangement adopted. The use of a precedent-based engineering geology approach to future mine design is considered the most appropriate solution in the circumstances.

Jan 1, 2007