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By H. D. Stolovitch, M. L. Lavallée

"An engineering system used to analyze and improve the performance of industrial grinding circuits has been adapted into a training program. The systematic approach to the design of training was applied in order to:Determine if training was an appropriate and effective tool for the transfer of this new technology;Define the technical content of the program;Establish program specifications based on learner and context characteristics;Design and test prototypes of the instructional modules; and,Establish a strategy for plant implementation and maintenance of the training program.This paper thus describes how a engineering system is transferred to the workplace through the use of designed instruction.INTRODUCTIONTraining can change human performance in a permanent way. It can improve productivity for the overall benefit of an operation. Organizations can therefore use training as a mean to achieve their specific goals. Training is not the solution to every performance problem. However, in many cases, it can be a very effective way to attain desired performance.The benefits of training are often difficult to assess. However, to remain competitive, organizations must introduce new products and innovative technologies. Often, they can do both most effectively through suitable training interventions.In order for the effort and investment of training to provide optimal results, two points of view should be adopted.• An overall view of the system in which training is to be applied.• A systematic approach to the design of training (Stolovitch and Keeps, 1989)."

Jan 1, 1992

By P. R. Richardson

"Milling is the weak link in the process chain of many mineral operations. While this activity accounts for only a relatively small proportion of the direct costs of most mineral processing complexes, there are intangible and indirect costs associated with milling which are extremely large. For example, significant opportunity costs are associated with the relatively low yields which characterize this stage of the process.There are changes abroad in the world which I believe are going to cause us to reformulate the whole concept of milling. Increased competition in mineral markets are going to force managers to look anew at the high mineral values reporting to tailings which are a high opportunity cost for many operations. Tailings recovery plants are not the ultimate solution to this problem. Greater environmental concerns are going to increase the costs associated with tailings disposal and force the mining industry to look for other ways to dispose of waste products. Technology changes currently underway in manufacturing and other process industries, such as the automated 'lights-out' plant are going to be brought into this industry, and the changes will be dramatic.These are major long term changes which probably seem rather remote to many managers and professionals in existing operations which are faced with much more mundane challenges arising from day-to-day operations. However, I believe that milling is increasingly a 'lean and keen' operation involving fewer and fewer people, but who are increasingly skilled and professional. Traditional cost management approaches are no longer adequate and the industry has to take a new look at the nature of cost reduction in this core activity. This stage in the mineral process provides opportunities for value creation leading to a significant unit cost advantage for the corporations willing to adopt a total cost approach."

Jan 1, 1988

By C. Veloo

"Westmin Resources operates a mine/mill complex at Myra Falls and produces copper and zinc concentrates with minor associations of gold, silver, and lead from a polymetallic, massive sulphide orebody. Mill flotation performance has historically been plagued by periods of uncontrollably high circulating loads leading to low concentrate grades and below optimal tails. This led to a detailed examination of the flotation process. Locked cycle, and pilot plant data are presented. In addition, plant design and commissioning as well as column cell details are discussed. A comparison between actual and predicted performance is also presented. Benefits realized are higher copper and zinc concentrate grades and improved zinc recovery.PrologueMyra Falls Operations is located at the south end of Suttle Lake in Strathcona Provincial Park. Access to the mine site is provided by a 90km paved highway from Campbell River, British Columbia.The mine and facilities are nestled in the narrow Myra Valley between Mount Phillips and Mount Myra. These steep, rugged mountains rise from the valley floor at an elevation of 900 feet to summits of almost 6000 feet. The steep slopes are heavily wooded with fir, hemlock, and cedar up to an elevation of 4000 feet where a transition to alpine meadows occurs. The summits are craggy rock faces, some capped with glacial ice. Myra Creek winds its way through the valley dropping several hundred feet into Suttle Lake. Precipitation is high at over 100 inches per year, which may include up to 10 feet of snow in winter. The temperature may range from 32° C in summer to -18° C in winter.Myra Falls began production in 1965 with the Lynx Mine, supplemented by the Myra and Price Mines in subsequent years, feeding a 950 stpd mill up until the middle of 1985 when the H-W mine was brought into production. The original mill was replaced with a modern 2700 mtpd facility and in 1988 production was increased to 4000 mtpd.Both Lynx and H-W mines are currently in production producing an average of 3650 mtpd. The ore minerals are primarily sphalerite and chalcopyrite, with subordinate galena, bornite, tetrahedrite, and electrum."

Jan 1, 1992

By Eugen Gluck, Gus Van Weert, Peter Kondos

"Microwaves have the capability to heat up sulphides, especially clusters of particles of approx. 1 mm. Some sulphides absorb microwaves more readily than others. Molybdenite is especially effective in this regard, possibly due to its flaky nature and/or electrical conductivity. Even where it occurs in low concentrations in a deposit, individual rocks may be ore grade due to the high monetary value of MoS2. Such rocks often result from crushing mined veinlets or stockwork, or are contained in the cutoff grade fraction of ROM. Machine segregation of rocks high in MoS2 by infrared sensors after microwaving could therefore advantageously be used to upgrade lower grade ore between Mine and Mill. This would reduce the size of the latter, and thus its CAPEX and OPEX. Such upgrading could also yield shipping ore for a distant Mill, or extend ore reserves.Barrick Gold Corp. has been supporting the development of MW/IR sulphide sorting for the past three years. The results of MW/IR sorting work on molybdenite and other (pyritic) ore samples from a variety of sources are being presented here.INTRODUCTIONThis paper looks at mechanized, i.e. machine ore sorting technologies currently available and under development, and what conditions would be needed for the potential application of such ore sorting to sulphide mining and milling. Current machine sorting involves no-contact sensing technology for rocks, and signal processing after sensing to activate airblast segregation of certain rocks, normally the smallest mass to keep compressed air costs down.The forerunner of modern sorting is probably magnetic separation, which utilizes an inherent property of certain ores to divert it into mag and non-mags fractions. Radiometric ore sorters, which have been applied successfully for decades in the pre-concentration of uranium ores (Wotruba and Riedel, 2006) initiated modern sorting. In the 90’s, sensor-based machine sorting became a viable means of increasing the overall economic recovery of a resource. This technology became driven by the availability of low cost computing equipment and the concurrent development of algorithms, and by the availability of extremely fast response sensors and air actuators, allowing the sorting equipment to run faster, dropping the cost per tonne. It has been in industrial minerals processing that rock sorting has been most widely adopted, not really surprising. Liberation occurs on a different scale than in the base metal industry. Most industrial minerals are mined from massive deposits, requiring (in the past) no upgrading. Many of these operations now run into product contamination problems, which ore sorting can solve. One illustration: in Finland, a quarry is separating limestone from dolomite at 500 tonnes / hour, with individual rocks weighing up to 15 kg. Many of these industrial minerals operations have stockpiles of earlier discarded below-quality rocks, now being reprocessed with the help of ore sorting. The economics of this are very favourable, going from zero or negative value (stockpiles can not be left when closing the mine) to full product value for at least a portion of the stockpile. This suggests that in the future the economics of overburden sorting could become attractive under the right circumstances and such treatment could well become an integral part of open pit mine development."

Jan 1, 2009

By A. C. T. Bigg

"The mineral potential of the Nanisivik area was discovered as far back as 1910 when a prospector of the Geological Survey of Canada, on an expedition under Captain J. G.Bernier, recorded a deposit of pyrite with minor sphalerite and galena. An outcrop of the present orebody was discovered by Texas Gulf Company in 1957. Subsequent drilling outlined the orebody consisting of 6,000,000 tonnes of ore containing 13 % Zinc and 1.5 % Lead. The orebody appears to have been formed by the filling of a limestone cavern with sulphides. The sulphide minerals consist of pyrite, sphalerite and galena. The limestone bedrock is mostly dolomite with some calcite and magnesite. A cutoff grade of about 6% Zinc has been calculated.In 1972 Mineral Resources International Limited took an option on the property. Upon completion of the feasibility study by Watts, Griffiths and McOuat, the then new independent project management group of Strathcona Mineral Services Ltd. were engaged to develop the project through the financing, construction and operating phases. Strathcona Mineral Services still manage the project from their head office in Toronto and through the Mine Manager and Department Superintendents at the Mine site. The interest for the project is presently split five ways: Mineral Resources International Ltd. 53.5 %, Government of Canada 18 %, Metallgesellschaft A.G. of Germany 11.25 %, Billiton B. V. of Holland 11.25 % and Texas Gulf Co. 6 %."

Jan 1, 1980

By Randy Clarkson

"Free gold particles occur in many base metal and precious metal mines throughout the world. Occasionally mine operators are unaware of the presence of free gold particles in their ores because they have not seen free gold hand specimens or at the working face of the mine.Due to the high density and malleability of gold, large circulating loads of free gold particles can build up over time in grinding circuits. This gold is often deposited in unintended traps throughout the mineral processing system.These unidentified free gold deposits represent a serious security risk as well as inaccessible inventory of gold. Deposits of free gold particles often remain undetected by mine management until they are accidentally discovered while repairing mill equipment. The trapping and subsequent release of gold particles can frustrate attempts to calculate accurate metallurgical balances.Nuclear tracers have been used to determine the free gold recovery efficiency of gravity recovery equipment, drills, and sampling equipment (Clarkson, 1994, 1997, 1998, 1999 and Walsh, 1986, 1992). In 1995, the author used radiotracers to locate and eliminate gold traps at La Mine Doyon (Clarkson, 1997). In 1998 and 2001, the author also salted mineral processing circuits at Royal Oak's Pamour Mine in Timmins (Clarkson, 1999) and at Gold Corp’s Red Lake Mine in Ontario with radioactive gold particles.The gamma and X-ray radiation from gold's nuclear isotope (Au198) were detected through steel, in pipes, and in moving equipment with scintillometers. The radiotracers proved to be a safe, rapid and accurate method of identifying gold traps, improving security, determining the recovery efficiency of Knelson gold concentrators and estimating retention times of gold particles in various processes."

Jan 1, 2003

By Martin Stoklossa

Surface mining operations typically require run-of-mine material to be sized for further processing. In-pit crushing facilities serve this need, as stationary, semi-mobile or fully mobile units. Although in particular fully mobile crushing facilities have been in use for over half of a century, other surface mining techniques have typically been implemented. However, with increasing operating costs in truck and shovel operations, and other economic considerations, mobile crushing plants are increasingly a viable option. The operational and economical parameters in relation to the optimal surface mining equipment selection will be reviewed. The role of the mobile crushing technology within the continuous vs. noncontinuous surface mining operation and basis for mine planning are also discussed. Current applications and respective case studies will be reviewed. Key performance indicators will be presented. These performance parameters can be viewed as a tool to aid in the equipment selection process. The future direction for further research and development in mobile crushing facilities will also be presented.

May 1, 2008

By Christopher W. Corti

A major aim of the GOLD 2003 conference, is to promote new gold related science and technology with a view to developing new useful industrial applications for gold. Current industrial uses have provided a steady annual industrial demand for gold of around 350-400 tonnes in recent years, the bulk of which is centred on electronics applications, with dental uses constituting the second largest application. However, there is good reason to believe that whilst gold will continue to play a major role in these sectors in the future, substantial growth of demand is not anticipated. Increased industrial demand for gold is only likely to come through the emergence of new applications, probably most significantly in five broad market sectors: ? Pollution and emission control technologies, including fuel cells. ? New uses for gold in advanced electronics, electrical systems and devices. ? Chemical processing of a range of bulk and speciality chemicals, using gold based catalysts ? Advanced coatings exploiting the novel properties of gold, particularly in nanoparticulate form. ? New biomedical uses for gold including medical treatments, drugs, implants, sensors and devices. There is cause for optimism that many new applications for gold could emerge in these sectors over the next decade and that this will lead to a substantial growth in demand for gold. It is clear that many of these new opportunities will be based on a chemical approach to synthesis of useful products rather than what has historically been a materials or mechanical approach. To turn this expectation into reality requires sustained support of R & D and a determination to exploit this new science and technology into viable commercial applications.

Oct 1, 2003

By P. K. Naik, B. Das

Flotation studies were carried out to recover carbon values from blast furnace flue dust containing ~30.34% carbon, 4.6% volatile matter (VM), and 65.03% ash. The variables chosen for the experiments were dispersant (sodium hexametaphosphate), pH, collector (diesel oil), and frother (MIBC). The experiments were designed according to a 24 full factorial design method and regression equations for the recovery of carbon and product grade were determined from the data. Experiments were performed to optimize recovery and grade using the steepest ascent method. The maximum recovery of carbon was 90.0% with a concentration of 56.5%, whereas the maximum obtainable grade of carbon was 66.35% with 50.45% recovery.

Jan 1, 2005

By Gregory A. Johnson

Operations and Maintenance departments have long had an adversarial relationship. The widespread evolution and adoption of modern management techniques such as Reliability Centered Maintenance (RCM) and Lean Production however has driven interest in working co-operatively to optimize overall plant performance. Mining and minerals operations have long adopted RCM in maintenance, and are now adopting Lean throughout the organization. Modern management initiatives like these explicitly call for co-operation between the two disciplines of maintenance and production and many advances have been made in the realms of people and methodology. One area that has lagged behind in supporting these developments however is information systems. Enterprise Asset Management (EAM) systems in maintenance and newer Manufacturing Execution Systems (MES) in operations have not been truly integrated in the way needed. Complicated plants, different software architectures, continually changing conditions and many variables have lead to systems problems which have contributed to the maintenance/operations divide. Master data synchronization (the ?plant tree?) and integrated reporting of real-time data with transactional data are just two of the issues that are being solved by new approaches in information technology including web services and service orientated architectures. New technologies are coming on-stream to enable the final ?bridging of the gap?.

Feb 1, 2008

By S. Pinard, J. MacLellan, G. Ehlert

"The Kidd Creek concentrator is looking actively for alternative technology as means of reducing operating costs in their concentrate handling section. The use of pressure and vacuum filters to eliminate the multiple hearth dryers would have the most beneficial effect. The dryers which constitute the greater portion of concentrate drying costs consume about 35,000 m3 per day of natural gas.After the evaluation of various filters by Kidd's technology group, it was clear that, because of the low final moisture requirements of 5.5 to 6% H20, few filters were able to achieve this target economically. Lately attention has focused on the Andritz hyperbaric filter. Testwork has shown that target moistures can be achieved with an appreciable reduction in operating cost.1.0 INTRODUCTIONThe Kidd Creek Concentrator is located 28 kilometers east of Timmins, Ontario. The ore is hauled by the Kidd Creek Railroad to the concentrator where it is milled to produce separate copper and zinc concentrates.Projected concentrator feed for 1991 is 3,750,000 tonnes of ore grading 3.3 % Cu and 4.7 % Zn. The concentrate production is expected to be 458,080 dry tonnes of copper concentrate at a grade of 25.7 % Cu and 265,020 dry tonnes of zinc concentrate at a grade of 54 % Zn.Currently, there is active investigation toward cost reduction through implementation of new technologies. One area which has been extensively evaluated is the concentrate dewatering and drying section. In that section, the multiple hearth concentrate dryers represent the largest source of operating costs, mainly through maintenance and energy costs (electricity and natural gas). The replacement of these dryers with filtration technology that could produce the required concentrate dryness would represent substantial savings.In September of 1990 filtration testwork carried out by Andritz Ruthner showed that Kidd Creek copper and zinc concentrates could be filtered to below 6 and 8 % moisture respectively. In late May 1991 the laboratory testwork was duplicated on siteand one month later a 5 m2 pilot filter was tested on site. Based on the pilot test results, an economic evaluation was performed. It indicated that a reasonable payback could be realized if hyperbaric filters were to replace the existing concentrate drying section."

Jan 1, 1992

By G. Barbery

"Particle composition distribution is an essential feature of materials processed by physical separation methods. The amenability to segregate a feed material in a concentrate and a tailings stream depends to a large extent on what is called usually the ""liberation"" of the various mineral phases that are present in an ore. In fact the energy consumed in crushing and grinding has the major justification of producing particles that are as close as possible to monominerallic. Monophasic particles are able to reveal physical differences in mineral properties that make their separation possible. For many years, various authors have insisted on the concept of liberation, without noting that, in practice, it can be a pure concept which does not lead to measurements or predictions. The present paper insists on the concept of particle composition distribution, in which the complete distribution is the information to be obtained, and not the ""liberation·· of various phases, just like for particle size distribution, the complete distribution is an objective commonly desired, and not one or two values representing the coarse or fine fraction.2. NOTATIONS-EQUATIONSFor the purpose of the paper, a particle will be characterized by its volume Vp, and its volumetric composition with respect to a mineral of interest, which will be given the notation ""O"". All the other minerals present will be called ""1"". This notation does not imply that the particles are biphasic, but that we are interested in the composition of particles with respect to one phase only. The volumetric composition will be given the sybol m:"

Jan 1, 1986

By K. S. Kalenchuk

Massive landslides display complex deformation processes. For instance, slope movements of the Downie Slide, monitored using borehole inclinometers, extensometers, and survey monuments, show considerable spatial and temporal inconsistencies in the displacement rates. This study assesses the influence that inferred shear surface geometry, as a key factor contributing to variable slope movements, has on resolving spatially discriminated slope deformations in three-dimensions. Borehole data defines the shear surface location at discrete points within the slide and therefore, the shear surface geometry for the extent of the slide must be largely inferred. A series of three-dimensional numerical simulations have been run to assess the effect of different interpretations of the shear surface geometry. This investigation illustrates the importance of rigorous geospatial definition of slip surface geometry and the value of three dimensional modelling.

May 1, 2009

"It is projected that the reactivity of acid generating tailings and waste rock can be minimized by reducing the access of oxygen by placing these materials under water in natural or manmade lakes. A project under the MEND and B.C. AMO Task Forces has been in progress for four years to evaluate active and historic tailing sites in B.C. and Manitoba. The sophisticated geochemistry studies conducted on the interstitial pore water has illustrated encouraging results which are discussed. The additional studies which are needed to complete the scientific database for the study sites, for achieving regulatory and public approval and for the engineering of application of this method of control are outlined.IntroductionWorld wide research effort is in progress to find the solution to the acid mine drainage problem. A great deal is known about acid mine drainage but much work is required to find economic and effective approaches to the problem. Two coordinated programs have been initiated recently in Canada: the National Mine Environment Neutral Drainage (MEND) program and the British Columbia Acid Drainage Task Force.Disposal of tailings materials under a water barrier such as a natural lake, is thought to be one solution to prevent acid generation by preventing oxygen and bacterial action on the sulphide surfaces. The deposition of reactive tailings materials under water in natural lakes has been used historically at various mines in Canada. However, there has never been a thorough review of the long and short term impacts of historic sites which may provide crucial information to understand the physical, chemical and biological processes which are taking place.This paper provides a general overview of a series of studies which examine the general biophysical characteristics and the sediment geochemistry of four lakes where subaqueous disposal has been or is currently being used for acid generating tailings. The subaqueous disposal studies have been conducted from 1989 through 1991 and were initiated and supported by both research task forces. The objectives of this paper are to summarize the history and the background information of the studies conducted, the general results obtained from each lake, an overview of the major collective results and the additional work which is required to achieve the final objective of developing criteria for applying this technology in the industry."

Jan 1, 1992

By James A. Finch, Stéphanie Gélinas

"A colorimetric technique, originally developed for methyl iso butyl carbinol (MIBC) based on the Komarowsky reaction, has been extended to a wide range of common mineral flotation frothers. The procedure, which is briefly described, is shown suited to on-site determination in a series of industrial campaigns. Some frother observations are described, including: concentration evolution down a bank, distribution between pulp and froth phases, and a mass balance around a circuit. Minute amounts of frother in recycle water were also measured.The contribution of frother and alcohol by-products in the analysis was generally additive for plants using aliphatic alcohol type frothers and decoupled for systems using glycols. Typically, U250C (polyglycol) was used at higher concentration (>10 ppm) than MIBC (aliphatic alcohol) (<10 ppm) or F-150 (polyglycol) (<3ppm).The ability to monitor frother easily will help interpret gas dispersion behaviour and should permit further optimization of flotation cell hydrodynamics and chemistry. The capability to directly measure should help optimize the type, amount and location of frother addition, and to assess frother recycled with reclaim process water.INTRODUCTIONOwing to the lack of analytical methods, the task of determining frother concentration in plant flotation circuits is not routinely performed. Industrial sites seldom outsource analyses that are both costly and inconvenient, due to the necessity of shipping freeze-dried samples to remote testing facilities. A more direct colorimetric method has recently been demonstrated for the laboratory characterization of common industrial frothers (Gélinas and Finch, 2004). The approach, based on the Komarowsky reaction (Penniman et al., 1936; Coles et al., 1942; Duke, 1947), was previously described by Parkhomovski et al. (1976) for methyl iso butyl carbinol (MIBC). The reaction involves the interaction of the OH group of a higher alcohol, concentrated sulphuric acid, and salicylaldehyde, to yield coloured solutions with intensities that can be analyzed by UV-visible spectrophotometry."

Jan 1, 2007

By Dave Bulled, Khiratt Husain

"The use of High Pressure Grinding Rolls is gaining significant interest as a replacement for SAG milling in the comminution of hard rock ores because of the potential for reduced costs in terms of energy and grinding ball consumption. Estimation of expected energy consumption for fullscale operations has conventionally involved the testing of a few fairly large samples in pilot scale HPGRs. This paper describes the development of a small-scale batch test method for determining a work index for HPGR of a large number of samples that can be used to show the variability of the ore as an integral part of a geometallurgical approach to circuit design and production forecasting.The test equipment that was developed comprises a hydraulic press with adjustable pressure operating on small batches of ore in a locked cycle test procedure. A work index measurement was determined that links the specific energy consumed in the test to the breakage achieved such that the index can be used to predict comminution energy requirements.The measurements were calibrated against laboratory scale HPGR equipment to develop a model for design and forecasting that includes crushers, HPGRs and ball mills in a complete comminution circuit.INTRODUCTIONEstimation of the expected energy consumption for full-scale HPGR operations has conventionally involved the testing of a few fairly large samples in laboratory and pilot scale machines (Danilkewich, 2006). With the financial input of five mining corporations, SGS Lakefield Research has developed a small scale test capable of providing relevant information on the variability of energy consumption and size reduction from drill core samples. It is our intention that the values measured in the test will be scaled up, through benchmark comparison with pilot sized and full sized HPGR units, to allow plant design and throughput forecast on a block by block basis of the mine plan using a new CEET program. CEET® (an acronym for Comminution Economic Evaluation Tool) is an advanced grinding design and performance predicting tool that uses energy relationships to model the performance of SAG / Ball mill circuits."

Jan 1, 2008

By Graham A. Karklin

"The Echo Bay Mines silver property is located 875 air miles north of Edmonton, Alberta. The mine is on the east shore of Great Bear Lake at Port Radium which is twenty six miles south of the artic circle, in the North West Territories.HISTORYThe area was first surveyed by J. Mackintosh Bell of the Geological Survey of Canada in the early nineteen hundreds. In May 1930, Gilbert LaBine staked claims at Port Radium called ""Cobalt"" and ""Cobalt I"". What he had discovered was an extremely rich vein of pitch-blend. These claims were the birth of mining in this area. The first ore shipment of pitch-blend was hand-picked and flown out of Port Radium in 1931. LaBine's discovery of pitch-blend became of world-wide importance with the outbreak of World War II. In 1939 the splitting of the uranium atom brought this area into world focus. It is generally believed that it was ore from this area that was used in the production of the devastating bombs which were dropped on Japan.It was at Port Radium that the leaching process for uranium extraction was pioneered. The resultant methods have been modified and adopted for use around the world. The mine was originally owned by Eldorado Gold Mines Limited. Echo Bay Mines leased the property in 1964, subsequently purchased it, and have been producing silver and copper every since."

Jan 1, 1981

By Y. Shu, A. R. Laplante

"A laboratory Knelson Concentrator (LKC), 7.5 cm in diameter, was used to study the performance of a similar unit at plant scale, 76 cm in diameter, This paper reports on sampling and assaying procedures and problems, and discusses the performance of the plant unit.The sampling procedure was based on the extraction of large samples, 5-15 kg, and their complete processing with a LKC, to characterize size-by-size performance. The procedure yielded reliable estimates of overall gold assays, after blatant assaying errors were corrected. The plant centrifugal unit concentrate was sampled in situ, which yielded very erratic grades, with a large overall negative bias. Due to the very heterogeneous nature of the concentrate, which can be linked to flow patterns in the riffles of the unit, it is recommended that for future testwork, the concentrate be recovered separately, blended and then sampled.The plant centrifugal separator, when operated at a feed rate of 25 t/h, yielded total and free gold recoveries of 41 % and 62%, respectively. This is much lower than previously reported data, and suggest that at 25 t/h, the unit is overloaded. However, recovery did not decrease with time over a loading cycle of 2 hours, which suggests that present loading cycles, generally 1 hour, can be significantly increased. INTRODUCTIONThe study of gold gravity circuits is plagued with the statistical problem of determining the behaviour of particles occurring with a very low frequency. This problem becomes particularly acute with increasing particle size. For example, considering the average weight of a gold flake in the 840-1200 µm (20/28 mesh) to be about 5 mg (Banisi et al, 1991), a reasonably high grade feed of 10 git would require, for a relative error (standard deviation) of 10% on grade, 100 particles, that is 0.5 g of gold, or 50 kg of 840-1200 µm material (a Poisson distribution is assumed). Gy's formula, for the same data, yields a weight of 33 kg, with a shape factor of 0.1 and a size distribution factor of 0.5. Both results are comparable; to obtain the suggested weight of material, a stream containing 5% weight in the 840-1200 µm would require 1 tonne samples (of unsized material). The problem rapidly disappears with decreasing particle size. Still with Banisi et al's data, a gold flake in the 300-420 µm range averages 0.5 mg in weight; the same 10% error on grade corresponds to a weight of 5 kg. Gy's formula for the same size distribution and particle shape factors as above predicts a required mass of 1.4 kg. This would correspond to an unsized sample weight of 10 kg with 14% weight in the 300-420 µm, for example."

Jan 1, 1992

By M. Helinski

In the authors? experience inappropriate water management in hydraulic fill masses has been the root cause of most barricade failures. Inappropriate water management can lead to high water pressures, reduced effective stresses and increased barricade stresses (Kuganathan 2002). In addition the high hydraulic conductivity and non-plastic nature of most hydraulic fills makes susceptibility to piping failure (Cowling et al. 1987) a high possibility in many hydraulic backfills where a static water head is available. In order to avert both of these failure mechanisms it is essential to control the elevation of the phreatic surface within the fill mass. This is usually achieved through campaigned filling and resting periods. The duration of filling and resting periods are often estimated using some form of stope drainage simulator. Due to the random nature of many characteristics that influence the fill mass hydraulic conductivity, simulation of hydraulic fill drainage can be difficult. The high consequences of inaccurate phreatic surface estimates combined with the high variability in drainage properties often results in operators taking a conservative approach to this modelling. This conservative approach can lead to significant delays in the filling cycle which can have a major impact on the productivity of many hydraulic fill operations and can often results in an unnecessary movement towards capital intensive paste fill systems. This paper presents a water management technique which combines a simplified drainage model with in-situ monitoring to provide a rational approach to water management. With an accurate drainage model filling operations can be carried out at optimum efficiency without compromising safety. The implementation of this strategy has lead to a significant increase in filling rates at a number of Australian filling operations. A brief case study from one of these sites has been presented.

May 1, 2007

By M. Cai

A practical simple method is proposed to estimate the tensile strength (st) of strong brittle rocks from the strength ratio of R= sc/st = 8 sc/sci, where sc is the uniaxial compressive strength and sci is the crack initiation stress in an uniaxial compression test. 8 is the Griffith strength ratio and the term sc/sci accounts for the difference of crack growth or propagation in tension and compression in uniaxial compression tests. sci can be reliably obtained from volumetric strain measurement or acoustic emission (AE) monitoring. With the strength ratio R determined, the tensile strength can be indirectly obtained from the result of uniaxial compression tests. In addition, a practical estimate of the Hoek-Brown strength parameter mi is presented and it is suggested that mi = 12 sc/sci can be applied to strong, brittle rocks in high confinement zone and mi = 8 sc/sci can be applied to low confinement to tension zones. It is found that the predicted tensile strengths and Hoek-Brown strength parameter mi using this method are in good agreement with test data. The rock strength parameters like st and mi, which require specialty tests such as direct tensile (or Brazilian) and triaxial compression tests for their determination, can be reasonably estimated from uniaxial compression tests.

May 1, 2009