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By N. A. Warner, R. K. Manna

Physical modelling of liquid-phase oxygen mass transfer in a water model of part of a proposed new polymetallic smelter has been achieved. A study of solute mass transfer caused by multiple, subsonic air jets contacting superoxygenated water flowing in a channel model of the smelter converting hearth has been carried out. For a wide range of channel flow rates the rate of mass transfer was found to be independent of water velocity. The water model has been used to compare mass transfer for both open-packed and close-packed multiple-lance arrays with circular nozzles of diameters 2.26, 4.95, 10.95 and 24.40 mm. It was found that with fewer of the larger-diameter nozzles a reduction of up to 58% in liquid-phase mass transfer occurred, especially for the close-packed lance configurations. This restriction of liquid-phase mass transfer would result in reduced metal losses in the analogous smelting situation. The larger nozzles, however, exhibited more jet-jet and jet-channel wall interference effects than their smaller counterparts, resulting in an effective reduction in the momentum fluxes of the impinging jets

Jul 1, 1991

By T. Banerjee, D. Felsher, G. Leavoy

"Lake Shore Gold is engaged in commercial gold production at both the Timmins West and Bell Creek mines, located in Timmins, Ontario. Run of mine ore is processed at the Bell Creek mill which consists of a conventional gold mill flow sheet involving crushing, grinding, gravity concentration and carbon-in-leach (CIL) for gold recovery. Since 2009, the operating capacity of the mill has been upgraded from 2000 tpd tonnes per day (tpd) to over 3,000 tpd. The most recent expansion involved the installation of a low aspect ratio SAG mill to replace the secondary crusher. Without operational data on the low aspect mill, combined with a site team that was new to SAG milling, there were many challenges in achieving the target throughput from the circuit. Through the implementation of AwaRE advanced controllers, running in closed loop with PRC fragmentation cameras as well as embedded PARC modules within the Allen Bradley PLC, the site was able to rapidly develop a best operating practise and has been successful in creating a stable and consistent operational environment. The process, lessons learned and eventual solution will be reviewed in this paper.INTRODUCTIONLake Shore Gold is engaged in commercial gold production at both the Timmins West and Bell Creek mines, located in Timmins, Ontario. Run of mine ore is processed at the Bell Creek mill which consists of a conventional gold mill flow sheet involving crushing, grinding, gravity concentration and carbon-in-leach (CIL) for gold recovery. Since 2009, the operating capacity of the mill has been upgraded from 2,000 tpd tonnes per day (tpd) to 3,150 tpd. The most recent expansion involved the installation of a low aspect ratio SAG mill to replace the secondary crusher. This endeavor was split into two phases: the expansion of the back-end (Phase 1) and the front-end (Phase 2) of the mill. Phase 1 of the expansion was completed at the end of 2012 and involved enhancements and capacity addition to the leaching and adsorption circuits, which increased the mill’s capacity to 2,500 tpd. Phase 2 of the expansion commenced at the end of July 2013 and involved the expansion of the crushing and grinding circuits. The expanded front-end of the mill now has a capacity of 5,500 tpd, and processes ore from both Bell Creek and Timmins West mines. The updated flow-sheet, as shown in Figure 1, illustrates the replacement of the two-stage crushing and ball milling circuit with a single stage crusher and a low aspect ratio SAG mill."

Jan 1, 2015

By M. K. G. Whateley, W. Hatton

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 20pp., 31 refs. Estimates of coal tonnage on UK open cast mining sites often vary from the recoverable tonnage. This is because the estimates depend on the geological variability of the coal measures. Geological parameters, such as thickness, quality and disturbance of the seam, have a direct control upon this variance. Risk analysis techniques have been applied using commercially available software to combine each parameter's variability into a cumulative variance, resulting in a tonnage distribution. Sensitivity modelling has also been used to identify the geological parameters which have the largest influence on the variance of the simulated tonnage distribution. An understanding of the relationship between the tonnage and geological variability has helped to focus exploration more efficiently. A cost to risk relationship can now be monitored, helping management to avoid negative consequences on site

Aug 1, 1995

By Matthew Janes

Statnamic load testing is becoming widely accepted as a method to quickly and economically determine the load-deflection behaviour and ultimate static resistance of high capacity deep foundations. Strain instrumented large diameter bored shafts were tested at four locations for the federal and state Departments of Transportation in the United States. Tests were conducted vertically (to 30 MN) and laterally on the shafts and, in some cases, testing was completed over water. Instrumented shaft test results provided shaft load distribution with depth and shaft shear transfer stress throughout the soil stratum. Shaft end bearing and ultimate end bearing stress values were provided. On two projects, Osterberg load cells provided comparative static data for skin friction and end bearing. Correlations between Statnamic derived static load-displacement results and Osterberg load-deflection results are very good. Statnamic lateral load test results were correlated with static lateral results in addition to providing useful dynamic response and damping data.

Jan 1, 1996

By E. D. Gardner

This is one of a series of papers describing mining and related subjects affecting mining in western mining districts and mineralized areas. The parts of this paper pertaining to current production, mining and milling methods and practices, and general conditions affecting mining were collected principally during a field survey made in May 1935. Some original data obtained on previous visits to the area are also included. The history, geological background, and past production of the mines and district are largely abstracted from previous publications, for which due credit is given later in the test. The principal districts in the Black Mountains are the Oatman or San Francisco and the Union Pass or Katherine. This range contains the principal producing mines of the State, in which gold is the only important metal. Although the total production of gold is relatively small as compared to other districts where the precious metals are obtained as a by-product in copper min¬ing, the area is one of considerable economic importance to the State.

Jan 1, 1936

By Corby G. Anderson

Since 1985, the Sunshine Mining Company has used a patented nitric-sulfuric acid pressure leaching system for production of silver and copper from a refractory sulfide ore body. To better understand this novel process, a program of lab scale testing was undertaken to quantify the effect of system variables on silver recovery. Some of the factors studied include temperature, agitation, acidity, vessel pressure, particle size, percent solids and oxidizer amount. In turn, this knowledge will be applied in actual plant practice to upgrade reaction time, increase concentrate throughput, raise silver recovery and lower reagent costs. A discussion of plant process changes resulting from lab scale testing is included.

Jan 1, 1991

By P. Campbell, E. M. Gardy, L. Hachkowski

Introduction The efficient process control of a uranium mill and its associated mining operation requires a nearly continuous knowledge of the uranium concentration in the ore. Generally, the approach is to use laboratory assays of grab samples from the mill feed belt. In some cases, elaborate and expensive systems have been used to ensure random sampling, but even with these systems, mass-balance discrepancies still exist. There is a requirement for an on-line instrument that can give a prompt, accurate analysis of a large portion of the feed stock. The authors have recently evaluated a laboratory system that achieves these goals using neutron activation and delayed neutron counting. The development of the on-line uranium ore analyzer is a consequence of previous work done at the Whiteshell Nuclear Research Establishment (WNRE) (Campbell et al., 1978 and 1981), and is based on the emission of delayed neutrons after the neutron irradiation of fissionable materials. The mechanism of delayed neutron emission has been described (Keepin, 1965), but briefly is as follows. The fission fragments resulting from irradiation are in an excited state. Certain of these delayed fission products, precursors, decay to a more stable state by the emission of a delayed neutron. The delayed neutrons can be divided into six groups with effective half-lives ranging from 0.2-55 sec. It is important to note that more than 50% of the delayed neutrons are emitted within the first 6 sec after irradiation; this has an influence on the design of the analysis instrument. Measurement Cycle The measurement cycle involves a neutron irradiation, a delay time, and a counting period. The laboratory demonstration model of the ore analyzer comprises a californium-252 neutron source, a source chamber, a pneumatic transfer facility, and a neutron irradiation and counting module (Fig. 1). The ore sample is placed in the irradiation chamber. The neutron source is transferred to the center of the chamber for a 5-sec irradiation while the helium-3 thermal neutron detectors are switched off. As the source returns to the storage chamber, the detectors are switched on and the delayed neutrons counted. The total assay cycle is 16 sec. The current instrument design calls for the ore to be cut from the main belt every 16 sec by a mechanical arm and dropped into the analyzer directly, or via another belt. The cycle starts when there is a sufficient mass of ore in the irradiation chamber to depress a switch and stops when the delayed neutron count is finished. The ore is then dropped through the bottom of the analyzer chamber and returned to the main belt. The counts from each cycle are accumulated and the data reduced to give the desired information. Key for Fig. 1 A-Helium-3 neutron detector B-Wax moderator for neutrons C-Irradiation chamber D-Funnel for receiving ore E-Gate F-Transducers G-Biological shield for neutron source H-Transfer tube for neutron source I-Neutron source J- Microprocessor K-Accumulator for hydraulics L-Control panel M-Electro-hydraulic servo valve to control movement of the source N-Electro-hydraulic proportional valve to control movement of the gate O-Hydraulic power unit Irradiation and Counting Equipment Irradiation of the ore is achieved using a 1 X 10 7 neutron*s-1 californium-252 neutron source. The source is contained in an iron capsule and pneumatically transferred between the irradiation/counting and storage chambers. The irradiation/counting chamber possesses 12, 600-mm (24-in.) long helium-3 thermal neutron detectors embedded in an annulus of wax (Fig. 1). Two sets of six detectors are each interfaced to a preamplifier, amplifier and single-channel pulseheight analyzer system, and the two systems are connected to a scaler. A special timing unit controls the transfer of the source and the on and off switching of the detector assembly, in sequence with the movement of the source. Results and Discussion In the experimental demonstration, using the 107 neutron.s-1 source, a 10% uranium ore was measured to ± 10% (2o total error) in 10 cycles and ±6% (2o) in 100 cycles. Since a larger source was not available, it can be statistically predicted that a 109 neutron-s-1 source could be used to measure a 0.1% ore to ± 10% (20) in 10 cycles. The uranium can occur as discrete nonhomogeneous particles in the ore, and the error caused by such a distribution of particles is ± 4% (2o), as determined by

Jan 1, 1984

ALTHOUGH the development of the various flotation processes during the last 8 years has been so revolutionary, this development has been, until recently, entirely confined to the separation of the gangue from the mixed metalliferous sulphides.The desirability of finding some method of separating the independent sulphides from such a miXture, by means of flotation, has long been recognized. ThIS need was emphasized when the slimes resulting from the grinding of Broken Hill sulphide ores were for the first time successfully dealt with by the Mineral Separation Company's process on the Central mine. This process proved the practicability of separating the sulphides of lead and zinc as a mixed concentrate from the gangue present in slime. Although this was a very notable achievement, the process has not been generally used, owing to the mixed lead and zinc concentrates resulting from the treatment being acceptable neither to the zinc nor the lead smelters.Although the introduction of eucalyptus oil in minute quantities as an emulsifying agent has simplified the work of the subsequent tabling of mixed sulphide concentrates, rendering unnecessary the burning off or removal of the oil, there will always be a considerable quantity of slimy product too fine to settle on the moving surface of the concentrating machines, and therefore requiring other means for its division into lead and zinc concentrates.

Jan 1, 1912

By R. G. Reddy

Reduction of different chromite ores with carbon was studied as a function of C/FeO ratio and temperature in the range 700 °C to 1100 °C by thermogravimetry (TGA) analysis. Powders of chromite ore(-150 mesh) and carbon(-150 mesh) were thoroughly mixed in a desired proportions and were placed in the reaction crucible. The reduction rates of reactions were determined by continuously monitoring the weight loss as a function of time at constant temperature using TGA set up. The analysis of results suggest that FeO present in the chromite ores is reduced to Fe involving gaseous intermediates CO and CO2. The overall rate of FeO reduction is controlled by the oxidation of carbon. A kinetic equation, that of random nucleation, was proposed. The activation energies for the reduction of FeO, present in Roast Movat and Transvaal ores, with carbon were determined to be 55800 and 23000 J/mole, respectively. The results of the present study are compared with the data available in literature. The low activation energy values as determined in this study suggest that the carbon oxidation reaction is catalyzed. It is concluded from the present investigation that the low grade chromite ores can be significantly upgraded to higher value added chromite that can be used as a feed source for economical smelting.

Jan 1, 1998

By J. A. Elliot

Deep Mix-in-Place soil stabilisation is achieved by forming columns of soil/cement arranged to overlap by secant intersection. Alternate columns are constructed initially and infilled. The cementitious material injected is designed to retard the strength of the resulting mix thereby allowing satisfactory overlapping. Columns are constructed using a designed large diameter mixing auger mounted on a smaller diameter auger stem. This is firstly screwed to the design depth removing only such spoil as to enable penetration of the auger, and subsequently counter rotated and extracted in a predetermined mixing pattern and grout injection rate to ensure continuous and homogeneous treatment through each successive level. The process is performed whilst monitoring auger depth, grout flow and pressure. Cementation Piling and Foundations Limited used this technique to stabilise allu­vium and to facilitate the construction, by conventional techniques, of a circular pumping station pit of 10M diameter to 10M below ground level. The work was carried out within 3M of adjacent domestic properties, and on a very restricted site in Elland, West Yorkshire. Ground conditions consist of 2M of cohesive alluvium becoming water bearing and increasingly sandy and gravelly with cobbles which overlies the mudstones at 10.0m depth. Sandstones beneath formed an aquiclude to artesian ground water with the underside of the open excavation approxi­mately 1.0M from the top of this material. Peripheral treatment into the mudstone, coupled with pressure relief wells, proved successful and final excavation depth was achieved in "the dry".

Jan 1, 1989

A series of stemming confinement tests were conducted at a test site near Vernal, Utah. The purpose of the study was to determine the relative performance of various stemming enhancement “plugs”, stem types and loading configurations. The stemming performance was quantified in terms of: . Stem confinement time . Stem ejection velocity . Ground swell velocity . Ground vibration . Air blast . Crater formation Of primary interest was the performance of a new spherical stemming enhancement plug. The initial findings indicate that the hard plastic spheres improved blast performance when used appropriately. Their ability to improve blast performance is reduced when used in over confined or severely underconfined conditions. The study also evaluated the effects of air decking on stemming confinement and explosive performance.

Jan 1, 2000

By H. F. Zurbrigg

Introdduction The main line of ascent in the development of the nickel industry may be traced back through the International Nickel Company of Canada, Limited, to its earliest antecedents, the Canadian Copper Company and the Orford Copper Company. Mining geology is but one aspect of the overall development of this organization, and the stress it has placed on geology grew according to the need. In the early days, intensive geology was not required because ore supply was not one of the main problems of this or any of the pioneer companies. The difficulty then was to find economic methods for reducing the ores to nickel and copper, and markets for absorbing nickel in the face of a limited demand from consumers heavily prejudiced in favour of the New Caledonia product. "Very early in the history of the region it was patent to everyone that to share in the full benefits of the industry the same individuals or company must control the whole of the operation necessary to manufacture the finished product' (1, p. 45). These conditions were fulfilled for the International Nickel Company in 1902 when the Canadian Copper Company (incorporated 1886), with its ample ore supply, took the initiative to merge its interests with those of the Orford Copper (Refining) Company (incorporated 1887) to form the new company which, with reorganizational changes, emerged as the producer of the overwhelming bulk of the world's nickel. The Mond Nickel Company, Limited, entered the field in 1899 with a refining process, and over a period of years acquired ore through purchase of mining properties. This Company operated successfully and independently until 1929 when its assets were joined with those of the International Nickel Company in order to permit the most economic exploitation of the Frood-Stobie orebody in which both Companies were interested.

Jan 1, 1948

Drilling and blasting are an essential part of most mining operations, and are commonly major operating cost centres. The effectiveness of blasting can have a significant influence on all subsequent activities, and hence overall operating costs. Drilling and blasting systems must be compatible with the overall mining method, to minimise total costs and ensure operational efficiency. Selection of suitable equipment and techniques requires an understanding of the total operation, plus current skills in specialised technologies. This paper examines the contribution of drilling and blasting to total costs, including the balance between capital and operating costs. The use of computer modelling is discussed, to demonstrate how blast performance and costs can be predicted and alternatives analysed. Case studies illustrate how cost savings can be made in operating mines, and alternative systems evaluated to optimise new projects.

Jan 1, 1990

By Martin van Staveren

In today's rapid changing construction world, the business pressures on piling and deep foundations reach sky-high levels. Ever increasing complexity of construction projects do severely contribute to these business pressures. Projects are often constructed in densely populated areas and located close to vulnerable buildings and infrastructure. The inherent uncertainty of ground conditions plays a dominating role in these foundation projects. Effective risk management is a key success factor for profitable and sustainable operations of piling and deep foundations. It starts with a fundamental requirement to be aware of risks. Next the different risk perspectives of all stakeholders in any foundation project have to be acknowledged. A simple and structured risk management approach is introduced, to demonstrate that effective risk management is not necessarily that complicated. A major element is the contractual allocation of risks, as a result from differing ground conditions. It is based on the so-called Geotechnical Baseline Report (GBR). The main objective of the GBR is to provide a clear contractual arrangement for the allocation of risks, arising from differing site conditions. The benefits of explicit risk management in general and contractual risk allocation in particular are illustrated with an example and experiences. The presented structured risk management approach, including contractual risk allocation, is still rather new. It proves to be promising for cost-effective risk control of piling and deep foundation projects, anywhere in the world.

Jan 1, 2006

Major Francis Hamilton Buchanan coined the term `laterite' (Latin; brick-rock) in 1807 for the red earths used for building blocks in southern India. Although these earths were actually weathered basalts, the term is now applied to weathering profiles developed upon a wide range of bedrocks. The Ni-laterites are a special class within the broad laterite family.

Jan 1, 1996

By K. Thuro, R. J. Plinninger

ABSTRACT: Determining tunnel stability is a key issue during preliminary site investigation. In contrast, problems of excavatability have been largely ignored. While the choice of an economic tunnelling method is admittedly a clear priority in the planning stage, special investigations focus-sing on rock fragmentation (e.g. drilling or cutting performance, rock mass blastability or tool wear) are rarely carried out. This paper explores possibilities to quantify key parameters for rock mass excavatability in drilling, blasting and cutting by TBMs and roadheaders. RÉSUMÉE: La détermination de la stabilité du tunnel est une question clé lors des études prélimi-naires. En revanche, les problèmes d'excavabilité sont souvent en grande partie ignorés. Tandis que le choix d'une méthode de percement économique est évidemment une priorité claire dans l'étape de planification, des investigations spéciales se concentrant sur la fragmentation de la roche (par exemple le comportement de la roche au forage, à l’excavation ou au dynamitage et l’usure des outil) sont rarement effectuées. Cet article explore les possibilités pour quantifier les paramè-tres clé de la roche lors d’excavation par forage, dynamitage, au tunnelier (TBMs) ou à l’excavatrice. ZUSAMMENFASSUNG: Beim Tunnelbau wir meist die Vorhersage der Stabilität des ausgebrochenen Hohlraums als Schlüsselfragestellung betrachtet. Im Gegensatz dazu werden Probleme der Gebirgslösung weitgehend ignoriert. Während der Wahl einer wirtschaftlichen Vortriebsmethode während der Planungsphase meist noch eine gewisse Priorität beigemessen wird, werden spezielle Untersuchungen zur Gebirgslösung (Bohr- oder Schneidbarkeit, Sprengbarkeit oder Werkzeugverbrauch) nur sehr selten durchgeführt. Diese Publikation zeigt Möglichkeiten der Quantifizierung von Schlüsselparametern für die Gebirgslösbarkeit auf, also der Bohr- und Sprengbarkeit, der Fräsbarkeit mit Teilschnittmaschinen und der Schneidbarkeit mit TBMs.

Jan 1, 2003

By W. Pariseau, S. Puri, S. Schmelter

Introduction Joints often have profound effects on elastic properties and strength of rock masses and therefore on rock slope stability. In surface mine slopes, joints are usually too numerous to be taken into account individually, so an equivalent properties approach is necessary. Previous work that treats a jointed rock mass as an equivalent composite material of joints and intact rock between resulted in excellent agreement between estimated and true rock mass elastic moduli in case of fully persistent joints (e.g., Pariseau, 1999) Rock mass failure mechanisms on joints and through intact rock were retained obviating the need for an equivalent rock mass strength. Impersistent joints, which are not continuous on a joint plane, can be accommodated (Pariseau, 2003). However, slope stability analysis of a large, deep copper mine indicated a need for computational efficiency even in two-dimensional analysis of vertical sections through pit walls (Puri, 2006). The analyses by the popular finite element method used small elements of bench size near the pit slopes and much larger elements away from the pit walls. The reasons for the graded meshes were numerical quality (small elements) and computational economy (large elements). Small elements contained only a few joints, while the larger elements contained hundreds of joints and led to impractical computation run times (days!). A new modeling procedure that recognizes sufficiently large elements as representative volume elements (REV’s) overcomes this obstacle. A companion improvement recognizes the concept of a representative area element (RAE) in association with joint impersistence and the probability that joint material occupies a considered site. Both are steps towards greater model realism and a practical slope stability analysis procedure. Consider the open pit mine photo shown in Figure 1(a), a companion plan view in Figure 1(b), and the problem of slope stability where high slope angles favor economics but low slope angles favor safety. These competing factors in surface mining generally result in some sections of the mine that have unstable slopes that require monitoring and perhaps mitigating action to improve stability. Although stability of a given section may not be easy to quantify with a single number, useful design guidance can be obtained from a finite element analysis of a proposed mining sequence leading to future pit slopes and profiles. The presence of water from rain and snow melt indicates a need for a coupled analysis that links water pressure, effective stress and total stress (Schmelter, 2001).

Jan 1, 2007

By Lewis Robert M.

The importance of phosphate in feeding the people of the world has been recognized by mining companies as they continue their search for new ore deposits and ways of improving phosphate production. An extensive phosphate-recovery research project involving investigation of beneficiation variables by batch testing, flotation pilot-plant processing of the major portion of the ore, gravity separation of the coarse fraction, and recovery of byproduct heavy minerals of a North Carolina phosphate deposit has been completed. Data obtained through batch tests enabled the development of an economical flowsheet which proved successful for the efficient recovery of a good quality phosphate concentrate in a pilot plant.

Jan 1, 1975

By Mark M. Petersen

As part of the addition of eight new combined cycle generating units at the Florida Power & Light Sanford Plant, 2,129 piles were to be installed. The existing plant elements were supported on driven piles, and the variation in pile lengths during previous work, as well as available subsurface information, indicated a complex stratigraphy. At the request of the owner, the designer/construction manager developed a program to evaluate the use of pressure-grouted displacement piles. A pre-design load test program in areas that represented the apparent extremes in subsurface conditions indicated that the system was feasible; however, the presence of existing features that were to be demolished later precluded the clear delineation of subsurface conditions in advance of construction. A contract was negotiated with the pile installer based on the best estimate of potential pile lengths, with modifications to pile lengths to be set based on additional exploration. A total of 52 cone penetration soundings and five load tests were performed immediately prior to and during pile installation to establish correlations between the CPT data and pile performance. Pile depths were set based on these correlations. Pile installation was completed 6 weeks ahead of schedule and 15 percent under the original budget estimate. This paper documents the evaluation of pressure-grouted displacement piles as an emerging technology, and illustrates the benefits of a close working relationship between the owner, designer, and pile contractor at a site with variable subsurface conditions.

Jan 1, 2002

By Ernie Holden, Chris Ringas

In the last 20 years, In Line Inspection (ILI) using intelligent pigs has become the principal tool used by pipeline operators to assess the condition of their pipelines. New pipelines are normally designed to take intelligent pigs, but many older pipelines require some modifications and special procedures for their inspection. This paper is aimed at practicing engineers and managers of pipelines, or people aspiring to those positions. The paper describes the benefits of ILI and some of the practical issues regarding pipeline preparation and cleaning, choice of inspection tool, running pigs in pipelines, and what to do with the data collected. What are the responsibilities of the Pipeline Engineer ? ? Maintain reliable and acceptable performance of the pipeline in terms of safety and product delivery at economical cost. ? Provide a defined margin of safety for operating the pipeline at its designated pressure. ? Provide timely information on all pipeline defects such that repairs can be carried out according to a managed schedule. What Defects does the Pipeline Operator have to cope with ? A useful record of actual incidents seen in pipelines can be obtained from the web site of the US Office of Pipeline Safety (OPS) - http://ops.dot.gov/stats/stats.htm. US pipeline Operators are obliged by Law to report all pipeline incidents exceeding certain threshold criteria (e.g loss of life, escape of product, cost of incident etc). These OPS statistics show that corrosion and third party damage have remained consistently the prime causes of reportable incidents in the US, with similar experience elsewhere. There are several kinds of flaws and defects in pipelines that can lead to failure, the main families being :- ? Metal loss ? Cracks or crack-like defects ? Laminations and other mid-wall defects ? Geometric anomalies

Jan 1, 2006