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By I. R. Muirhead

"One approach to making new technology available is to demonstrate its value under full-scale operating conditions. Studies were undertaken to assess the feasibility of this approach to introducing a longwall mining system to the western Canadian coalfields.The longwall method of mining coal is described, world and Canadian usage is reviewed, and the merits of the system in comparison 10 other coal mining methods are discussed.The rationale for a longwall demonstration in western Canada is presented, along with a proposed organization for the design, operation and dissemination of the findings from such a trial. The factors which must be considered in the design of the demonstration, and in the assessment of a potential site are highlighted. It is concluded that a demonstration of this technology is both timely and essential to prepare the way for the western Canadian coal industry of future prospects for coal.IntroductionFor many years CANMET has encouraged research work organized on a cooperative basis. This requires that a working consensus must be negotiated by researchers and operators at the beginning of the project and continuously refined as work proceeds. The result is usually a more relevant selection of research problems, improved direct ion and con duct of experiment al work and often a validation phase in which research concepts are tested in an opera ting environment. All this tends to narrow the gap between obtaining research results and applying them.Even under the best of circumstances cooperative projects require a good deal of coordination and enthusiasm to maintain focus and the pace of work. The working perspective of a research scientist in a government laboratory is substantially different from that of a mine operator at a producing mine, and a common ground must be found. This is difficult to do and cooperative projects typically evolve over several years as experimental results progressively define the potential solutions to mining problems."

Jan 1, 1985

By Peter N. Calder, Louise H. Michaud

"An interactive mine planning package has been developed to aid with the tasks involved in generating dragline mine plans. This package employs recent advances in PC-based,3D computer graphics and 3D geologic modelling. A Gridded Seam Model (GSM), capable of modelling rugged topography and multiple coal seams, including folding and faulting, is used to generate the geologic database This model is then integrated with an interactive graphics mine planning system in order to develop one model and one database for the generation of the mine design, the depletion of the coal reserves and the removal of waste material.As well as offering large potential saving in the time required to carry out the planning tasks, the system offers immediate visual feedback to the planning engineer. This can greatly aid in the conceptual understanding of complex geology and mine plans and can allow for the evaluation of a number of mining options within a reasonable time frame.IntroductionThere are a large number of variables that must be taken into account during the development of a dragline mine plan. This is especially true when developing a mine in mountainous terrain, where there is a lack of continuity of the geology and topography over the mine site. Until recently, the complexity of dragline mine plans has prohibited the development of a universal mine planning package that is applicable to all geologic and topographic situations. The majority of the commercial programs that are presently available to facilitate dragline mine planning have been developed for specific mine properties or are limited in the coal geology and mining methods that they can simulate (Brown and Clifford, 1983; White 1983; White and Jones, 1984; Sadri and Lee, 1982; Dagdelen, 1979)."

Jan 1, 1993

By Deni Pageau, Deni Caron

"This paper describes the operations of the open pit and emphasizes particular aspects of Les Mines Selbaie. The open pit as well as its related services were incorporated into a complex which includes an underground mine and a concentrator. The equipment was chosen with the objective of auto-sufficiency during each phase of mining. The paper outlines the organization and the methods used in each step of mining, notably: drilling, blasting, loading, transporting and crushing. The responsibilities of the Engineering Department are also outlined from the conception of the open pit to the latest follow-up methods. A short resume of the results which have been obtained as well as suggestions for improvement are provided.Layout in Consideration of Main SiteThe A-I zone deposit is located I km from 8 zone. Open pit mining of A-I zone required the regrouping of different services to those already existing.I. The crusher was placed in an area close to the concentrator in order to minimize the length of the conveyors and to provide space for the crushed ore reserves (50000 tonnes).2. The location of the service building (warehouses, mine offices, maintenance, engineering and geology) raised a few problems. Because of the multiple services provided therein , it was impossible to fulfill all the requirements, and the garage in itself is located a fair distance from the pit. Added to this inconvenience is the fact that heavy equipment regularly travels throughout the main yard.3. The storage of explosive magazines has been changed to obtain more surface space and meet government regulations.4. A space has been provided for minor repairs in the garage used during exploration. A trailer was installed next to the garage to provide a lunch room for the employees working at the open pit."

Jan 1, 1990

By C. Mattich, Å. Holmström, L. Hedström

"The fluidized bed at Division Ministro Hales (DMH) division of Codelco in Calama, Chile is currently the largest operating roaster for partial roasting of arsenic rich copper concentrates. The roaster converts the Mina Ministro Hales (MMH) enargite rich (Cu3AsS4) copper concentrates into calcine with a low arsenic content that is suitable for mixing with other copper concentrates feeding a flash furnace. The plant sets a new standard for the processing of arsenic rich concentrates, both from the quality of the calcine as well as the environmental performances. The process technology and expertise are based on the solid practical experience of treating arsenic rich concentrates from both the Boliden smelter and Outotec.The partial roasting process is located next to the mine and concentrator and includes a sulphuric acid plant with auxiliary equipment. The produced calcine has an arsenic content significantly below target and the residual sulphur meets the requirement of the flash furnace. The plant operates with high efficiency cyclones resulting in a low amount of calcine passing to the hot electrostatic precipitator (HESP). The small flow of HESP calcine dust can be combined with the low arsenic calcine and still meet the flash furnace feed arsenic requirements.SO2 formed during roasting is converted into sulphuric acid, while volatized arsenic is recovered in the wet gas cleaning section of the acid plant along with a large proportion of antimony present in the MMH concentrate. Arsenic is stabilized as calcium arsenate and sent to disposal at a specially prepared site.The present production rate (September/October 2015) is close to or higher than the original maximum design capacity of the plant.INTRODUCTIONMineralogyThe mineralogy of an ore and concentrate is important, since there is a direct link between roasting performance and concentrate mineralogy. The MMH concentrate has a good combination of minerals that makes the roasting process efficient and flexible. The main minerals are pyrite, enargite and chalcocite (Figure 1). The inert content is about 15% and consists mainly of silicate and alumina based minerals. The lead content is very low and this is desirable, since the presence of even a small amount of lead will cause a substantial increase of sintering during roasting."

Jan 1, 2016

By Alan F. Stewart, Frederic B. Claridge, Robert S. Nichols

"In recent years, an increasing number of mines in mountainous terrain have examined the possibility of placing mine waste rock into stream valleys. Pressure to utilize stream valleys as a primary location for waste disposal has increased at many of the mines currently under development or expansion. As the number of environmentally and economically ideal wastedumping sites is limited, consideration must be given to utilization of stream valleys. This raises concerns about maintaining water quality in streams passing through or beneath the dumps and potential detrimental effects to dump stability. Commonly, the flows in the streams tend to be flashy, reflecting localized intense storms and rapid runoff in steep-sided slopes within the watershed. These conditions pertain particularly to British Columbia, which is characterized by mountainous terrain and periodically intense precipitation events.The method of conveying flow through a waste dump depends on a number of geotechnical and hydrological factors, including the size, durability and transmissivity of the rock and the design stream flood flow. This paper describes the approach to the design of waste dumps in stream valfeys developed at several mines in British Columbia."

Jan 1, 1986

By R. A. Walker, G. Scheltgen, T. Javorsky, G. Blackwell

"Recent engineering advances in open pit rock mechanics have resulted in improved pit wall slope design and improved operating procedures in the event of a major wall instability. At the other end of the spectrum, on the scale of single bench failures, considerable discretion is left to the mine operators as to how potential problems are handled. The usual alternatives are either to operate with caution beneath potential hazards, or try to bring the unstable rock down. In specific cases it may be advantageous to attempt to stabilize rock structures for reasons of access and operating safety.A t the Brenda Mines open pit a prominent structure on the north wall had caused recurring bench-scale wedge failures when exposed on each mining level. In spite of operating precautions a shovel was hit by a rockfall causing significant damage. The first section of this paper describes the investigative, design, and stabilization methods which permitted subsequent mining beneath the structure to proceed without incident. Emphasis is placed on the personnel and equipment resources available at the mine site which were used to minimize costs and which would be available at most operating mines.The second section describes an ongoing research project that utilizes radio telemetry to transmit slope monitoring data. As part of this project the wedge structure was instrumented so that it could be continuously monitored with the aid of a computer. The application demonstrated the potential of 'micro- chip' technology to remote data collection and processing as related to rock structure monitoring, slope stability and safety."

Jan 1, 1989

By D. F. VanDine, H. George

"The possibility of spoil pile failure at the Kara Kara bauxite strip mine, Guyana, South America, is of major concern to the mine operators. The current mining technique requires the continuous operation of an 11 ms bucket capacity walking dragline on top of 18 metres of freshly spoiled uncompacted overburden material consisting of varying mixtures of kaolinitic clay and quartzitic sand. A field biased geotechnical study of undisturbed overburden and corresponding spoiled material has identified site-specific, non-linear correlations between vane shear strength, standard penetration resistance and spoil pile composition. Readily available geological exploration borehole logs has enabled a composite clay isopach map of the entire mining property to be drawn and critical areas to be zoned according to expected slope stability. Stability has been assessed using simple hand calculation techniques. Use of the resulting stability map provides the mine operators with a means of forecasting the need for appropriate preventative measures at varying stages of mine development, throughout the life of the mine.A similar investigation procedure could be employed at many presently operating and future strip mines.IntroductionThe Kara Kara bauxite stripe mine is located at Linden within the bauxite belt of Guyana in South America. The mining property covers a total area of 88 hectares of flat to gently sloping ground of which some forty per cent is being actively mined or being preparatorily stripped of overburden, prior to eventual mining (George and Gordon, 1979). The regional climate is tropic and humid. Temperatures vary from 16°C to 38°C and yearly rainfall averages 2600 mm, with at least 55 per cent of this precipitation occurring during the 'wet season' months of May to July and December to January."

Jan 1, 1983

By M. P. Filion, K. Ferguson, L. L. Sirois

Acidic drainage is the largest single environmental problem facing the Canadian mining industry today. Technologies to prevent acidic drainage from occurring in wasterock piles and tailings sites, and on the walls of open pits and underground mines, need to be developed and demonstrated. There are two groups in Canada which have accepted this challenge: the national Mine Environment Neutral Drainage (MEND) program and the British Columbia Acid Mine Drainage (BCAMD) Task Force. This paper summarizes the activities of these two organizations.

Jan 1, 1990

By Roger C. Parsons

"The problems presented by ice formation and interference with processes, structures and mechanical operations in the mining industry can be expected to increase sharply as more of our mineraI needs are supplied from the far north. A process of rapid ice destruction is presented which lends itself to the effective removal or penetration of ice. Suggestions are offered for applying the system to problems related to mining activity in cold environments. The system can be readily adapted to large-scale operation, the reactant components being transported in crystalline form and volatilized on site.IntroductionThe number of operational mines in northern environments, relative to the number of mines in the temperate zone, will increase in the years ahead. This is not surprising, because:(a) in the past, those mines closest to centres of commerce had minimum transport charges and hence were more economic to develop;(b) great centres of commerce were far removed from northern environments;(c) the exhaustion of ores and lowering of grades in temperate zones now offset to some degree the extra transport costs applied to northern ores;(d) the abundance of excess energy in the north in the form of oil, gas and hydropower attracts mining as a means to justify its development; (e) assuming that the frequency of mineral occurrence north of the 52° N latitude is no different than south of it, there are many deposits waiting to be developed.As a result of current and projected activity in northern environments, we are faced today, and will be increasingly so in the future, with mining problems rarely encountered before-problems related to below-freezing temperatures. Engineering activity in permafrost regions will increase as new mining ventures are developed north of the 52° N latitude, roughly coinciding with the -1.1 ° C isotherm in Labrador, the upper temperature boundary for permafrost."

Jan 1, 1982

By Eric D. Marks

Fatalities resulting from ground workers colliding with objects and construction equipment accounted for approximately 18% of the total construction fatalities experienced in 2010. Current injury and fatality measuring methods have proven to be inadequate due to their use of passive measures of safety rather than a more active approach, such as the use of leading indicator data (also called near misses) of hazardous proximity situations between ground workers and heavy equipment on construction sites. The objectives are to create and evaluate the effectiveness of a reliable algorithm for collecting and analyzing the resulting leading indicator data from hazardous proximity situations. Numerous experiments emulating typical interactions between workers-on-foot and heavy equipment are used to evaluate the proximity sensing and detection technology. Safety leading indicator data (also called near misses) generated by the proximity sensing and detection technology during the experimental trials are used to create and assess the resulting algorithm. Results from the experiments indicate that leading indicator data generated from these systems can be processed and analyzed to identify hazardous proximity situations and incidents on construction sites.

Aug 1, 2013

By K. J. Brouwer, J. P. Haile

"Construction of the first stage of the tailings disposal facility for the Montana Tunnels Project was completed in October 1986. The project is located 37 km south of Helena, Montana, and involves mining of42 million tons of weathered diatreme are at a rate or 13 500 tpd to produce a gold/silver dore, as well as lead and zinc concentrates. The tailings disposal facility for the project includes a fully drained tailings impoundment for storage of the tailings solids, and a process waterpond for storage of all decanted water prior to recyling to the mill. The over-all facility is designed to achieve the basic objectives ofminimizing seepage to the environment in the short- and longterm, and achieving a fully drained stable tailings mass suitable for immediate reclamation on completion of mining. Specific features of the design include a soil bentonite seal and drainage system within the tailings basin, a free draining embankment with a design flow-through capacity of 4000 US gpm and an ultimate height of 230 ft (70 m), and a soil bentonite lined make-up water pond with a capacity of 420 acre-feet (530 000 m'). The tailings will be discharged in a rotational sequence through multiple spigot offtakes to achieve a thin-layer low energy laminar flow. This 'sub-aerial' deposition results in higher stored densities and maximizes liquid-solid separation on the tailings beaches. The over-all design played a major role in the successful permitting of the project, and was significantly cheaper than a conventional wet disposal system, with overall unit costs for tailings disposal of less than US$0.36 per ton.This paper outlines the site characteristics and the tailings material properties and their influence on the design. Extensive use was made of naturally occurring free draining materials as well as bentonite modified soil liners within the tailings basin, embankment and retention ponds. General construction procedures for the various components are described, as well as on-going construction requirements utilizing materials from the open pit. Finally, the over-all costs and unit costs for tailings disposal are presented."

Jan 1, 1988

By Neal Harries

Ground movement is normal in open cut mining operations, mainly caused by excavation response and blasting. Movement of the ground can be acceptable provided it is not unexpected and catastrophic. However, in steep mine walls and the very large open pits being developed today the consequence of slope collapse can be catastrophic. Such risks can be minimized at the planning stage by reducing slope angles, but this carries a very high cost. Also, instabilities which develop whilst mining can lead to ore reserves being quarantined, which represent a high cost to the mining operation. In spite of such safety measures, unexpected failures have occurred in the past. These issues motivated the development and production of the slope stability radar (SSR). There are currently over 80 GroundProbe SSR systems deployed in metalliferous and coal mines in 17 countries. The unexpected failure of rock walls at mining sites is a major cause of death and serious injury. Slope failure is also one of the major causes of economic and production losses. An unexpected wall failure can bury critical equipment. It also disrupts the mine plan. It is common to cease mining for several days or weeks following a wall collapse due to uncertainty over stability. Direct economic losses in remediation alone can easily exceed $1,000,000 per incident. The economic costs of injury or fatality are much higher including closure of mines during the incident investigation process. Massive wall failure can result in direct and indirect costs measured in millions of dollars. This paper will present some recent case studies of the SSR operation in open cut mines in North America, including Thompson Creek Mining Company (Idaho), Smoky Canyon Mine (Idaho), and a general case study on extreme cold weather use of the SSR.

May 1, 2009

By J. Bigu, M. G. Grenier

"Dust size distribution and aerosol size distribution measurements have been carried out in several Canadian underground uranium mines. In addition, dust samples have been analyzed for long-lived radioactive products of the U-238 and Th-232 natural decay chains using ex-spectroscopy and -y-spectroscopy techniques.From the data collected one may summarize: (a) most airborne particulates are of size below I u-m and 50% by mass are found above 1 u-m; (b) dust clouds are bimodal; (c) preferential deposition of radon (thoron) daughters takes place on airborne particulates in the sub -micron range at about 0.1 u-m; (d) deposition of radon (thoron) daughters is proportional to particle surface area; and (e) ex-spectroscopy and -y-spectroscopy of dust samples reveals the presence of U-238, Ra-226 and some of their short-lived and long-lived decay products.IntroductionExtended inhalation of airborne radioisotopes poses a potential health problem to occupational workers. Because of this, monitoring of radiation and dust levels for dose exposure calculation purposes is not only recommended but in most cases mandatory.CANMET (Energy, Mines a nd Resources Canada) has long since been engaged in a comprehensive monitoring program aimed at determining dust concentrations in the respirable size range, aerosol concentration in the sub-micron range, and in the radioactivity associated with these particulates in underground uranium mines. Measurements have been carried-out with gravimetric dust samplers, dust size selectors (including a horizontal elutriator , a fineparticle spectrometer and Nuclepore* filters of different pore sizes) and a condensation nucleus counter(1 – 6). Inactive and active working sites have been monitored according to some typical mining operations. A summary of these data has been given elsewhere(3- 5)."

Jan 1, 1984

By James E. Fisher, Roger Cotton

"The legal background f or environmental issues, and the growing emphasis both from government and private concerns of corporate and management liability for environmental problems provides one of the driving forces behind the growing concern with environmental law for the future. One prime objective must be the identification and minimization of potential liability, both for the corporation and its officers, directors and employees.This paper will identify the basis for liability of individuals and corporations for environmental matters, focussing on current legal requirements, and the appropriate legal response to events of such potential liability. It will also consider the reduction of liability through the implementation of management systems and environmental policies in order to ensure due diligence both with respect to corporate responsibility and the responsibility of the individuals within the corporation.IntroductionConsolidated Professor Mines Ltd . and its predecessor have been exploring in northwestern Ontario for about sixty years . During the last twenty years, the company has been interested in developing a gold mine, the Duport Project, on Stevens Island in Shoal Lake . The lake straddles the border between Ontario and Manitoba and is a drinking water supply for Winnipeg and environs.The Duport Project involves the mining of 450 t/day grading an average of 0.35 oz Ault of ore . At the minesite, located on Steven s Island in Shoal Lake, only preliminary processing of the ore will take place, to produce gravity and flotation concentrates for final gold recover y at a mainland plant well removed from the Shoal Lake watershed. No hazardous chemicals will be used at the island site."

Jan 1, 1991

By David Christensen

The long-term performance of dry covers is being examined in a research study funded by the International Network for Acid Prevention (INAP). The study was separated into two phases. The two main components of Phase 1 of the study were the identification and research of the processes affecting the long-term performance of dry cover systems and an examination of available numerical models for simulation of long-term cover performance. Identification and research of the physical, chemical, and biological processes affecting long-term performance showed that cover performance could be related to the change in the saturated hydraulic conductivity of cover material, the change in the soil-water characteristic curve, and the physical integrity of the cover system. Seven numerical models were examined to evaluate their effectiveness in predicting the long-term performance of cover systems. VADOSE/W (Online Help v1.01, 2002) was selected for use in cover system modeling in Phase 2 of the project. Phase 2 of the research study is currently in progress and involved the selection of five mine sites with a minimum of three years of performance monitoring data for analysis of cover performance. Two of the mine sites will be analyzed with the two-dimensional VADOSE/W numerical model. In addition, field saturated hydraulic conductivity tests were completed at three mine sites to investigate the change in field hydraulic conductivity of the cover system materials. The objective of the field testing program was to evaluate changes in hydraulic conductivity of cover material with time. Measurements of field hydraulic conductivity were completed with a Guelph permeameter and a pressure infiltrometer at three sites. The field hydraulic conductivity data was used to evaluate whether a change in this key material property had occurred over time. Field observations and the historic performance monitoring data provided the necessary information to develop hypotheses as to the likely processes that led to any change in field hydraulic conductivity. This paper will briefly summarize the research completed in Phase 1. The remainder of the paper will focus on the field testing program completed to measure the field hydraulic conductivity of constructed cover systems.

Nov 1, 2002

By J. Bigu, M. G. Grenier, S. Hardcastle

"This study was undertaken in a belt conveyor drift of an underground hard rock mine. The conveyor transported ore or waste from a crushing operation located upwind from the drift sampling locations. A 250 m section of this drift was selected and several types of measurements were taken. Average respirable concentrations in the drift were 0.43 mg/m3 and 0.19 mg/m3 for total and silica dust, respectively. From the respirable dust concentration profile along the drift, it may be possible to estimate the contribution from extended sources such as dust produced by the belt and return idlers.The airborne dust in the drift had an average mass-median aerodynamic diameter of 4.2 micron. A continuous dust monitor showed that the crushing operation produced fairly high dust concentrations (sometimes greater than 4 mg/m3) over short periods of time.IntroductionAirborne dust in the respirable range is known to be the cause of various forms of lung ailments . In underground mines, respirable dust sources are created at many stages of production. All mining operators are responsible for de signing and establishing means of reducing airborne dust. In some cases, sources of dust are well defined and suppression methods are standard.In the case of interest here, the airborne dust cloud was formed from the contribution from many sources, which may be either discrete or extended. At the experimental site, the discrete or point sources were the crushing operation and the belt conveyor transfer point (tail pulley). These sources may be controlled by proper dust capture and scrubbing systems as well as dilution ventilation. Examples of extended dust sources in the area include dust produced by the re-entrainment of settled particles along the drift. Ventilation air movement and vehicular traffic both contribute to this phenomenon. Dust produced by the conveyor is another example of an extended dust source. Caked deposits on the return strand and idlers as well as the transportation of dry material on the belt, can be major contributors. Proper wetting of roadways and muck as well as proper belt cleaning techniques can help reduce these emissions. The cleaning apparatus, used on the belt where these experiments were conducted, is shown in Figure I. These and other belt cleaning techniques are described in more detail elsewhere."

Jan 1, 1987

By P. R. G. Brandão, E. E. Ferreira

The presence of metallic cations in solution will affect the aggregation or dispersion of the fine hematite particles, depending on the type of cation adsorption: either specific or non specific adsorption. In this work, the zeta potential measurements were carried out on a sample of pure hematite as a function of pH and metallic cations concentration (Ca2, Mg2+, Mn2+, K+, Na+ and Al3+). The objective of these studies was to clarify the effect of these metallic cations on the surface chemical properties of pure hematite. The cations K+ and Na+ adsorbed as non-specific species and caused only the reduction on the values of zeta potential (in terms of absolute value) over the entire range of pH values tested. For the Al3+ cation, in the acidic pH range it adsorbed as a specific species and increased the zeta potential values. The cations Ca2+, Mg2+ and Mn2+, adsorbed as a non specific species at pH levels less than 6.0 and caused the reduction of zeta potential due to the compression of the electrical double layer. However, for pH values greater than 6.0, these cations adsorbed as a specific species causing the zeta potential to increase and became more positive as the pH value increased (alkaline). This effect could be due to the adsorption of some hidroxy complex species of these cations, which contributed to the positive charge. The effect of metallic cations (Ca2+, Mg2+ and Al3+ concentration, at pH 4.0, 7.0 and 10, showed the following results: a) at pH 4.0, increasing the concentrations of Ca2+ and Mg2+ resulted in on a small reduction in the value of the zeta potential. At this pH, increasing the concentration of A131 cations caused the zeta potential to increase due to specific adsorption of a negatively charged Al3+ hydroxy complex b) at pH 7 and 10, increasing the concentrations of Ca2+ and Mg2+ caused the zeta potential to change its charge from negative to positive.

Jan 1, 2004

By R. G. L. McCready, R. O. van Everdingen, M. Kalin, R. van Everdingen

"This paper is based on data generated between October, 1986 and October, 1989, during the implementation of an Ecological Engineering close-out for a zinc mine in Northern Ontario, where 690000 tonnes of tailings contain 41.1% pyrite and 4.1% pyrrhotite. The objective was to determine rates of sulphide oxidation and iron precipitation in the tailings. Those rates are relevant for the assessment of the long-term effectiveness of biological systems employed in the removal of heavy metals from contaminated drainage issuing from tailings.Data were collected on the topography and stratigraphy of the tailings basin, subsurface temperatures and groundwater levels, and chemical analyses were made of water samples collected from a number of piezometers. The thickness of unsaturated tailings varied widely between individual piezometer locations; annual maxima ranged from 0.67 m to 3.55 m, and annual minima from 0 to 2.68 m. Sulphate concentrations ranged from 36 mg/L to 20180 mg/L; iron concentrations from 0.36 mg/L to 9938 mg/L; and zinc concentrations from 0.33 mg/L to 1123 mg/L.The geochemistry of the piezometer samples suggests that some of the initial Fe content, resulting from metal sulphide oxidation, is subsequently precipitated in the tailings pile and, possibly, in the underlying unconsolidated sediments, probably in the form of iron-hydroxide and Na-jarosite. Other metals such as Zn may be co-precipitated with Fe. The discharge of a portion of these metals to the environment would be delayed by this process. Some of the initial sulphate may also be lost from solution, probably by precipitation of gypsum; approximate saturation degrees for gypsum ranged from -3.27 to +0.47. The precipitated minerals will somewhat decrease the porosity and permeability of the tailings.Sulphide-oxidation rates, calculated using the analytical results and the estimated amount of annual recharge at the tailings site, average 0.0057 mol/kg/yr. Calculated iron-precipitation rates average 0.000386 mol/kg/yr. It is concluded that the characteristics of seepage from mining wastes may change with time, reflecting the solubilization of precipitated secondary minerals."

Jan 1, 1992

By Bhawani Singh, Mahendra Singh, N. K. C Samadhiya

"Inherently anisotropic rocks occur in abundance at many rock engineering project sites in Himalayan region. These rocks pose difficulty in analysis and design due to their direction dependent strength behaviour. Moreover the strength varies in a non-linear manner with confining pressure. Mohr- Coulomb strength criterion is widely used by geotechnical engineers for defining strength of rocks subjected to given confining pressure. However, the conventional Mohr-Coulomb (MC) criterion suffers from the limitation that the strength is treated to be linearly dependent on confining pressure. In the present article, the MC criterion has been modified by incorporating non-linear term while retaining the original parameters c and ?. The non-linearity with confining stress level has been imbibed through critical state concept (Barton, 1976). The criterion has been applied to a triaxial test data base comprising of more than 1140 triaxial tests conducted world-wide on anisotropic rocks. Statistical evaluation of the goodness of fit of the proposed criterion to the data-base has been carried out. Further the predictive capabilities have been evaluated by determining the error in estimation of triaxial strength if only few triaxial test data are available for determining the criterion parameters. The data base has also been back-analysed to assess the critical confining pressure for anisotropic rocks. Statistically the critical confining pressure, for the present criterion, may be taken nearly equal to 1.25?cmax, where ?cmax is the maximum value of the UCS out of all orientations of planes of anisotropy. It is concluded that reasonably good estimates of the anisotropic strength are possible through the proposed criterion.INTRODUCTIONMany rocks encountered in Himalayan region like shale, slate, schist and phyllite are inherently anisotropic and exhibit direction dependency in their strength behaviour. In addition, the strength of the rock also depends on the confining pressure and, the strength response is non-linear especially when the confining pressure may vary over large range. Conventionally, Mohr-Coulomb criterion is the most widely used criterion for rocks. However, the limitation of this criterion in its present form is that the strength is treated to be linearly dependent on the confining pressure. The present study attempts to address the following two main objectives: i) Include nonlinear response in the Mohr-Coulomb criterion while retaining parameters c and In their original form; and ii) consider anisotropic response of the rock for a given confining pressure. A nonlinear strength criterion, which uses shear strength parameters c and as per Mohr-Coulomb criterion, has been suggested based on critical state concept for rocks."

Jan 1, 2015

By J. M. Skeaff

"The main solution, ore and residue pulp streams in the Rio Algom Quirke I uranium mill at Elliot Lake have been sampled and analyzed for radium-226. Analysis of the ore and leached residues indicates that Ra-226 dissolves and precipitates within the first pachuca tank. A maximum of approximately 0.2% of the Ra-226 in the ore remains in solution during leaching.IntroductionConcern over the acid drainage and radionuclide dissolution problems associated with uranium tailings disposal sites in Canada has prompted investigation into methods for improving current uranium processing practice.Present commercial practice usually involves leaching of the uranium ore with sulphuric acid, ion-exchange separation of the uranyl sulphate complex from the leach liquor and"" precipitation of the uranium as yellowcake. Daughter products of U-238, such as Th-230, Pb-21O and Ra-226 remain with the tailings and undergo long-term dissolution.Table I summarizes the probable behaviour of the radionuclides during milling. The concern here is with Ra-226, because it will deposit in the bones if ingested and is ""thus considered a serious health hazard(1), Similarly, Po-218 and Bi-214, which are daughter products of Rn-222, can be retained in the lungs and are considered to be the principal sources of radiation dosage(2) arising from the inhalation of Rn-222. Previous investigations(3-9l indicate or imply that Ra-226 undergoes redistribution during milling. However, detailed published information on the behaviour of Ra-226 in the uranium milling process appears to be lacking. A knowledge of the behaviour of Ra-226 in uranium mills, particularly during leaching, could lead to improved methods for its control.This paper reports the occurrence of Ra-226 in the Rio Algom mill. The main objectives of the study were to determine (1) the distribution of Ra-226 within the solids, (2) at what point, and how rapidly, redistribution occurs and (3) whether there are high concentrations of Ra-226 in solution."

Jan 1, 1981