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By J. -P. Tshibangu, M. Ramos da Silva, F. Descamps, C. Schroeder, J. -C. Verbrugge

"The mechanical behaviour of rock materials is largely influenced by the stress state and pore pressure; this needs to be considered in many applications, such as petroleum engineering, tunnelling or stability of underground excavations.Conventional triaxial tests (d2 = d 3) are generally used to assess the influence of confining and pore pressure. In this work, those tests are performed on a porous rock named Sorcy limestone, along with more advanced stress paths like triaxial extension (d 2 = d 1) and purely deviatoric tests with independent pore pressure control. Those tests are combined to a true triaxial study on the dry rock in order to investigate the effect of true triaxial stresses and, hence, build three-dimensional limiting envelopes accounting for the influence of pore pressure.Three-dimensional limiting envelopes of dry Sorcy limestone are built in meridian and octahedral planes. The shape of the octahedral sections changes with the mean stress from triangular to hexagonal and then quasi circular. At even higher mean stresses, the evolution continues towards a triangle with apexes oriented in the direction of triaxial extension stress states. In meridian sections, the deviatoric stress first increases with the mean stress. The transition between this deviatoric mechanism and the cap surface occurs at different mean pressures depending on the Lode angle.Terzaghi’s effective stress is found to govern the yield and plastic behaviour of saturated Sorcy limestone. Triaxial tests show that the limiting envelope does not depend on the loading path (conventional compression and purely deviatoric stress paths). In triaxial extension, the brittle-ductile transition is observed for a higher mean pressure than in triaxial compression, as previously found for true triaxial tests on the dry rock.Finally, it is shown that upon appropriate normalisation, the dry and saturated yield envelopes come very close one to each other. This suggests that only the size of the yield envelope changes between dry and saturated state (pore pressure = 5 MPa); its shape does not seem to evolve."

Jan 1, 2015

By Claudio Rocha Rosales

"Peñoles is a mining group with integrated operations for the smelting and refining of non-ferrous metals, and it is also a chemicals producer. Peñoles is the world’s foremost producer of refined silver, metallic bismuth and sodium sulphate. It is also the leading Latin American producer of refined gold, lead and zinc. The Met-Mex Peñoles Zinc Plant commenced operations in 1973 with an annual production capacity of 105,000 t/y zinc. Since then, production capacity has increased, and at present, it stands at 240,000 t/y zinc. In this paper, the leaching process and particularly the operation of the jarosite circuit is reviewed, specifying process improvements to treat high iron calcines.INTRODUCTIONTwenty years ago the Electrolytic Zinc Plant in Peñoles was treating high quality zinc concentrates with low concentrations of iron (~7.5 wt.%) and silica (1.8 wt.%). Nowadays the quality of zinc concentrates is poor with a typical iron content of around 11 wt.% and silica at 2.0 wt.%. This has created numerous processing problems in our roast-leach-purification- electrolysis sections. In order to meet customer requirements it is necessary to find processing solutions to assure the operational continuity of the plant. These processing solutions are the focal point of this paper.REVIEW OF THE LEACHING PROCESSThe purpose of the leaching process is to recover the metals, mainly zinc, through a series of extraction stages with sulphuric acid solutions, which progressively increases the zinc dissolution. After the series of acidification stages, the solution, which is rich in iron, is sent to the jarosite circuit to separate zinc from iron (Garcia & Valdez, 1996). The first step of the leaching process is the neutral leach circuit which produces a zinc sulphate solution that is sent to the purification section for the removal of impurities such as cadmium, cobalt and copper. Then this solution is sent to the tank house to feed the electrolytic cells."

Jan 1, 2016

By N. Hwang

There has been increasing interest in the use of robotic machines, and several prototype robotic machines have been developed to automate the grit-blasting process for the purpose of steel bridge maintenance. To utilize such a robotic grit-blast machine effectively, the first consideration is automating the determination of the rust surface area to blast, on the basis of standards of practice, in a rapid manner. This study aims to propose a method to rapidly and accurately determine the rust surface area on steel bridges to blast, with consideration for the standards of practice, from images acquired via a blasting machine. The first step is to perform a color space conversion to transform the input image from a red/green/blue (RGB) color space to a hue/saturation/intensity (HSI) color space. The next step is to detect the presence of rust, using pixel-level classification via the C4.5 decision tree algorithm. Then it is necessary to confirm the blasting area by verifying whether the rust detection result satisfies the specified criteria on the basis of standards of practice. The proposed method was validated on 39 test images with various characteristics with respect to the degree of rusting and rust distribution type. The experimental results showed that the average accuracy rate of rust area classification was about 97.63%, and the success rate of the final decision of blasting area determination was 100.00% for 39 test examples. The whole processing time took an average of only 0.86 seconds per image. The preliminary results demonstrated that the proposed method not only determined whether rust was present in an image and the amount of rust but also indicated whether blasting was necessary, and, if necessary, it rapidly specified the rust surface area that should be blasted on the basis of standards of practice. The proposed method could be successfully incorporated into a robotic grit-blast machine.

Aug 1, 2013

By J. A. MacLellan

"CONSTRUCI'ION OF SHERRITT'S CONCENTRATORSSherritt Gordon is operating two mills north of the 56th parallel, and is presently engaged in building a third. The author was closely involved in the design and construction of all three of these concentrators.The Lynn mill is the oldest of these three concentrators-it is a 4,000 ton per day nickel-copper plant built in 1953. The Fox mill is a 3,000 ton per day copper-zinc concentrator built in 1970. The Ruttan mill will be a 10,000 ton per day copper-zinc plant scheduled to go on line in July 1973.LYNN MILL The Lynn mill including the crushing, concentrating, drying and load out plant is about 69,700 square feet or 17.4 square feet per ton per day. '!his plant was originally built in 1927 at Sherridon, 150 miles south of Lynn Lake, as a 2,000 ton per day copper-zinc plant. In 1952 the plant was moved by tractor train to Lynn Lake. The whole plant was re-oriented within the original perimeter walls as a 2,000 ton per day nickel-copper plant. This plant was expanded to 4,000 tons per day by the addition of t1-Jo rod mills and a 5-1/2 short head crusher in 1959.The Sherridon mill processed its last ore in Sherridon in September 1951 and the first load of nickel concentrate was loaded at Lynn Lake on November 9, 1953 when the railroad arrived at Lynn Lake.The site for the Lynn Lake mill was cleared of overburden in the summer of 1952 and foundations for structural steel and SO!l8 equipment foundations were poured the late summer and fall of 1952 • Steel was erected from January to June 1953. Most of the equipment came in from January to March of 1953 by tractor sleighs. Sane sleighs upset but no equipment was lest through the ice."

Jan 1, 1972

By J. Bouchard, R. del Villar, A. Vazirizadeh

"Industrial flotation is a continuous and often multistage process, where particles of a given mineral species (usually the targeted one), present in different sizes, encounter a large amount of gas bubbles (normally air) to produce mineral–bubble aggregates, which are removed from the flotation device (cell or column) as a valuable product (concentrate). The bubble content inside the cell is characterized by the prevailing hydrodynamic conditions (known as gas dispersion variables), which in turn are known to influence the flotation performance. Although most researchers and practitioners agree that the relationship between the hydrodynamic variables and flotation performance exists, the lack of an adequate method foronline measuring the average bubble diameter has prevented such studies.The aim of this study is to apply appropriate hydrodynamic variables for flotation kinetic modeling (as a key feature of flotation performance) for a given introduced particle size distribution (PSD). In this regard, experiments were conducted in a laboratory flotation column (5.6 cm internal diameter for a total height of 650 cm), and mixtures of quartz (hydrophilic gangue) and talc (naturally hydrophobic mineral), classified in four different size fractions. The correlation between the flotation rate constant and given hydrodynamic variables were analyzed. Results suggest that the relative importance of hydrodynamic variables for flotation rate modeling depends on the PSD. Finally the suggested hydrodynamic variables for each of the various particle size-classes considered were used to produce single variable models for the flotation rate constant. INTRODUCTIONIndependently of the prevailing flotation conditions, the mechanisms for bubble-particle aggregation and the residence time of the phases inside the device must also be considered. In this regard, one of the most used approaches to represent the overall flotation process is as a pseudo-chemical reaction between a particle and a bubble, whose rate (at a given time) is proportional to the amount of remaining floatable species. The proportionating constant is called the kinetic constant or the flotation rate constant."

Jan 1, 2016

By Adam Jordens

Along with gravity separation and froth flotation, magnetic separation is one of the most common techniques for separating minerals. Minerals are separated by a magnetic force that is dependent on a combination of the applied magnetic field, the magnetic field gradient and the magnetic properties of the minerals themselves. Minerals may be classified as diamagnetic, paramagnetic or ferromagnetic based on the way they interact in a magnetic field. The magnetic susceptibility of a material may be determined by using a vibrating sample magnetometer to determine the magnetic moment of the material in an applied magnetic field and then converting this measured moment into the material?s magnetic susceptibility. In the case of rare earth minerals, magnetic separation is commonly used to remove ferromagnetic iron-bearing gangue minerals and to concentrate paramagnetic valuable minerals such as monazite and xenotime. These magnetic separation steps are frequently preceded by a gravity separation step as many iron oxides and rare earth minerals have specific gravities that are much larger than those of typical gangue minerals. By varying the magnetic field intensity it may be possible to use magnetic separation to selectively separate the paramagnetic and ferromagnetic minerals that report to the concentrate after gravity separation. Test work on a Canadian rare earth ore has shown that a gravity concentration step using a Knelson concentrator was able to selectively concentrate heavy magnetic minerals as evidenced by increased recoveries, relative to the Knelson tailings and fresh feed, after processing through a wet variable intensity magnetic separator. Mass pull to the Knelson concentrate was 4.5 % and the magnetic recovery of this concentrate, at 0.94 T, was approximately 40 % higher than the magnetic recovery from the Knelson tailings (70 % versus 30 %). The products of the wet high intensity magnetic separation were also analysed using a vibrating sample magnetometer to determine the magnetic susceptibilities of the various concentrate and tailings products.

Aug 1, 2013

By C. R. Edwards

"Equity Silver Mines Limited owns and operates an open pit silver 111ine located 37 km southeast of Houston in the Omineca District of British Columbia, Figure l. The property is approximately 300 km west of Prince George and 417 km east of the Port of Prince Rupert. This is the largest silver mine in Canada and one of the five largest silver producers in the western world.Equity is a subsidiary of Placer Development Limited, which owns 70 of Equity's issued and outstanding Common Shares. Placer was responsible for financing and developing the property and now provides general management and administrative services.All mining is by open pit methods, using three 1600 P&H shovels, eight 45 t Caterpillar and three 77 t Wabco trucks, three 40R rotary drills, two D8 dozers, one 9888 front-end loader and other ancillary equipment. We are now phasing out the Southern Tail pit and bringing the Main Zone into productior; see Figure 2.Comminution in the concentrator is achieved via primary, secondary, and tertiary crushers followed by rod and ball mills. The flotation circuit, with Southern Tail ore, produces a concentrate containing between 3 000 and 6 500 g of silver per tonne, 201 copper, and 25 g of gold per tonne. Running Main Zone ore, concentrate grades will decrease to about 4 500 g of silver per tonne, 17% copper, and 18 g of gold per tonne. Design milling capacity is 5 300 tpd, which is often exceeded.The flotation concentrate contains relatively high levels of antimony and arsenic. Because of these impurities Equity was unable to obtain economically acceptable long-term sales contracts for flotation concentrate. For this reason a leaching process was developed, and a plant designed, built and placed in operation. Due to the complex and unique technology involved, many start-up problems were encountered but by March 1983 the leach plant was considered ""fully operational."" This paper describes some of our progress and problems in bringing the Equity leach plant through its start-up period."

Jan 1, 1984

By L. C. Hsu, M. O. Desilets, P. J. Lechler, Jr. Bonham, J. G. Price, L. J. Garside

Geochemical background levels have been established for unmineralized sedimentary rocks that are elsewhere the hosts of Carlin-type gold deposits in the Getchell Trend. The Paleozoic rocks in the Winnemucca Quadrangle consist predominantly of the lower Paleozoicsiliceous and clastic sequences that were carried eastward along the Roberts Mountains thrust during the Late Devonian and Early Mississippian Antler Orogeny and the late Paleozoic Havallah and Pumpernickel sequences brought along the Golconda thrust eastward during early Mesozoic Sonoma Orogeny. Over 260 rock samples were collected from the Paleozoic sequences. Major and trace elements were determined by instrumental methods best suited for the specific elements. The general geochemical features of the Paleozoic sedimentary rocks are discussed in detail with reference to the data of average abundances of elements in sedimentary rocks. The background and threshold values of certain trace elements in sandstone, shale, and carbonate rock of one formation, as well as back-ground levels for the entire sequence were obtained. The characteristic geochemical features of the Paleozoic rocks in this area include: consistently high Ba and low Au contents (1.1 ppb, 1.5 ppb, 1.1ppb Au for average sandstone, shale and carbonate, respectively); generally low contents of those elements which may be of environmental concern such as As, Cd, Hg and Pb. Plots of major and trace elements suggest that the majority of the Paleozoic clastic rocks are related to a passive-margin tectonic setting. Samples with gold values higher than threshold are considered to have been affected by hydrothermal alteration related to gold mineralization. Most of these samples generally also have higher values of Sb, Hg, V and/or As. These observations support the use of such elements as pathfinders for gold, although V has not been identified as such before. Ba is not effective for gold exploration in this area due to the generally high background value of Ba, even though it may be an important pathfinder elsewhere.

Jan 1, 1995

By Terry J. Briggs, Ian J. Kelso

"Abstract- The Century mine in northwest Queensland,Australia, is a major sediment-hosted zinclead- silver orebody, located within the western Mount Isa Basin. Stratiform, carbonaceous shalehosted mineralization is developed within Proterozoic shale and siltstone sequences of the Lawn Hill Formation. CRA Exploration Pty Ltd (CRAE) discovered the Century deposit in 1990 and open pit mine development commenced in 1998 under the ownership of Pasminco Century Mine Limited (PCML). The deposit contains an identified mineral resource of 105 Mt @ 12.1% Zn + 1.7% Pb + 46 g/t Ag (Broadbent and Waltho, 1998) which is currently being mined at a rate of 5 Mt/y.In December 1998, an exothermic reaction was observed between explosives spilt onto shale drill cuttings from a blasthole. This reaction is referred to as ‘reactive ground’ and has the potential to cause premature detonation of explosives in a charged blasthole with catastrophic consequences. The incident led to a subsequent geological and geochemical assessment of the different rock types at the Century deposit and their potential reactivity with ammonium nitrate-based (AN) explosive products. This assessment was conducted in an attempt to characterize zones safe for blasting with uninhibited AN-based explosive products. A direct result of this study is a set of procedures outlining the use of different AN-based explosives in areas defined as potentially reactive or non-reactive for the different lithologies present. Black shales contained in both the waste and mineralized sequences contain the sulfide mineral pyrite (FeS2), which is thermodynamically unstable with AN contained in commonly used explosives. The potential reactivity of partially weathered pyrite can ultimately result in the decomposition of an AN-based explosive. It was determined that only pyritic black shales showed any potential to react with AN, irrespective of their position in the stratigraphic sequence. Other lithologies present at Century, including Proterozoic sandstone and Cambrian limestone, are classified as non-reactive with AN. This is a geological risk management situation present at the Century mine."

Jan 1, 2001

By L. C. Hsu, H. F. Jr. Bonham, M. O. Desilets, P. J. Lechler, J. G. Price, L. J. Garside

Abstract-Geochemical background levels have been established for unmineralized sedimentary rocks that are elsewhere the hosts of Carlin-type gold deposits in the Getchell Trend. The Paleozoic rocks in the Winnemucca Quadrangle consist predominantly of the lower Paleozoic siliceous and clastic sequences that were carried eastward along the Roberts Mountains thrust during the Late Devonian and Early Mississippian Antler Orogeny and the late Paleozoic Havallah and Pumpernickel sequences brought along the Golconda thrust eastward during early Mesozoic Sonoma Orogeny. Over 260 rock samples were collected from the Paleozoic sequences. Major and trace elements were determined by instrumental methods best suited for the specific elements. The general geochemical features of the Paleozoic sedimentary rocks are discussed in detail with reference to the data of average abundances of elements in sedimentary rocks. The background and threshold values of certain trace elements in sandstone, shale, and carbonate rock of one formation, as well as back- ground levels for the entire sequence were obtained. The characteristic geochemical features of the Paleozoic rocks in this area include: consistently high Ba and low Au contents (1.1 ppb, 1.5 ppb, 1.1 ppb Au for average sandstone, shale and carbonate, respectively); generally low contents of those elements which may be of environmental concern such as As, Cd, Hg and Pb. Plots of major and trace elements suggest that the majority of the Paleozoic clastic rocks are related to a passive- margin tectonic setting. Samples with gold values higher than threshold are considered to have been affected by hydrothermal alteration related to gold mineralization. Most of these samples generally also have higher values of Sb, Hg, V and/or As. These observations support the use of such elements as pathfinders for gold, although V has not been identified as such before. Ba is not effective for gold exploration in this area due to the generally high background value of Ba, even though it may be an important pathfinder elsewhere.

Jan 1, 1995

By D. Atkinson

"Porphyry molybdenum-tungsten mineralization on the east flank of Hudson Bay Mountain crops out over 5 km2 and is intersected to depths of 2 km. Features such as a hornblende-biotite aureole, mineralogical zoning and dike, vein and fracture geometries within lithologies of the Middle to Lower Jurassic Hazelton Group and Cretaceous Skeena Group reflect an intrusive complex, the Upper Cretaceous to Early Tertiary Hudson Bay Mountain stock which has been intersected by drill holes. The stock is believed to be the mineralizing agent. A southeast-dipping granodiorite sill has been outlined by drilling within the Hazelton Group. Molybdenite and scheelite veins cut all rock types; however, the granodiorite sill hosts a higher density of fine-grained, banded, quartz-molybdenite and pegmatitic quartz-molybdenite veins reflecting a competency contrast between the intrusive sill and other country rock. Due to the relative abundance of these veins, grade is higher within areas of the sill. Above the 15000£ cross-cut 20.6 million tonnes grading 0.401% MoS2 and 0.041% W03 have been defined. During exploration of the deposit sampling procedures had to be adjusted because of the nugget effect attributed to drill intersections of banded and pegmatitic veins.IntroductionMolybdenite was discovered in outcrop at the foot of Kathlyn Glacier on Hudson Bay Mountain and first reported by the Geological Survey of Canada in 1944. The deposit has several names: Hudson Bay Mountain or Glacier Gulch, both after its location, and Yorke-Hardy after the original staker.The deposit is on the east flank of Hudson Bay Mountain, 9 km northwest of Smithers, west-central British Columbia, within NTS area 93L/14 (54° 49' North, 127° 18' West, Fig. 1). Hudson Bay Mountain, on the southern edge of the Bulkley Valley, is a dominant topographical feature reaching 2590 m elevation. Mineralization is partly overlain by the Kathyln Glacier which is visible from Highway 16. Access to the 3100 m of underground development is from a portal at 1066 m elevation on the east slope of Hudson Bay Mountain."

Jan 1, 1995

By J. Keith Haddock

"IntroductionThe Bienfait Mine is operated by Bienfait Coal Company Ltd., one of the Luscar Limited group of companies. Situated 5 km southeast of the town of Bienfait, Saskatchewan, it can produce 2.0 million tonnes of lignite annually in addition to 158,000 tonnes of char from a carbonization plant located on the property. Geology The economically mineable coal seams of the Estevan area are found in the Ravenscrag Formation. The lignite-bearing sands, silts and clays were deposited in Early Tertiary age, in an inland sea centred in the Williston Basin of North Dakota. The top of the Ravenscrag is an erosional surface, overlain by Tertiary or Quarternary sands and gravels or glacial till. The regional structure is a gently plunging syncline which dips to the southeast at about 0.3 degrees. There are minor undulations in the Bienfait area which are due to differential subsidence during deposition. Sporadic faulting is probably a result of glacial pressures, and preglacial and glacial channels are responsible for washout zones and the abrupt irregular subcrop found in the area. There are two economic coal seams in the Bienfait area, an uppe; seam locally known as the Roche Percee, and a lower seam, the Estevan. Both seams have been extensively mined since lignite mining began in the area in the late 1800s. The Roche Percee remains only in a small portion of the Bienfait Mine and comprises a very minor portion of the reserves. It averages 1.74 m thick under 8.1 m of overburden. The till rests on top of the Roche Percee and due to weathering the seam is generally of poorer quality. The Estevan seam comprises the majority of reserves at Bienfait. The main seam which is being worked on consists of an upper bench averaging 2.75 m, a carbonaceous parting of 0.21 m, and a lower bench of 0.92 m. Overburden depth above this seam varies from 21.0 m to 38.0 m."

Jan 1, 1985

By E. Barnard, J. Tero, J. Rajala, N. Avenido, M. Fullam, A. Nashitati, S. Mbalamba

"The Otjikoto mining and milling complex is 90% owned by B2Gold Corporation, and began commercial operation on February 28, 2015. The milling circuit operates at a throughput 3.3 million tonnes per annum, with an average reserve gold grade of 1.28 g/t. The ore is high in Gravity Recoverable Gold (GRG), which varies between 73-91%, depending on ore type. Overall gold recovery since start-up is 98.2%, with about 63.5 % coming from the gravity circuit as doré. 2016 cash operating costs, and all in sustaining cost (“AISC”) were $361 and $604 per ounce, respectively.During design, three ore types were tested for GRG content, and based on the high GRG value of all three ore types, the decision was made to treat the full ball mill circulating load by gravity. Once operating, the gravity circuit performance was characterized by performing a detailed gravity audit, which included the ore, cyclone classification, Knelson concentrators, and the Consep Acacia intensive leach system. The deeper ores contain significant pyrrhotite, and this created some unusual challenges that had to be overcome. This paper presents the gravity circuit design process, the circuit commissioning, and the audit results and ongoing improvements.IntroductionHeadquartered in Vancouver, Canada, B2Gold Corp. was founded in 2007. Currently, B2Gold has five operating mines, and numerous exploration projects in various countries, including Nicaragua, the Philippines, Namibia, Mali and Burkina Faso. The Otjikoto Mine is located in the north-central part of the Republic of Namibia. It is situated approximately 300 kilometers north of Windhoek, the country’s capital, within the Province of Otjozondjupa. The Otjikoto mining and milling complex is 90% owned by B2Gold Corporation, and began commercial operation on February 28, 2015. The milling circuit operates at a throughput 3.3 million tonnes per annum. During design, a large emphasis was placed on gravity recovery, as the Otjikoto ores are unusually high in Gravity Recoverable Gold (GRG)."

Jan 1, 2018

By Jacob Wood, Robert Matusewicz

The Outotec® Ausmelt Top Submerged Lance (TSL) Process has achieved widespread commercial acceptance over the past 40 years for the processing of copper, nickel, lead, tin, zinc and precious metal bearing feeds. The continual development and evolution of the technology during this period has resulted in a more intense smelting process with higher energy efficiency and lower operating costs. More recently, considerable effort has been invested in decarbonisation of the process through improvements such as increased oxygen usage, dry feed injection and use of low-carbon auxiliary fuels. This paper covers a number of these recent advances to the technology and highlights their impacts on energy consumption and CO2 emissions for a range of non-ferrous smelting flowsheets. INTRODUCTION Relentless demand for improvements in the profitability, safety and environmental performance of non-ferrous smelting plants has driven a continual development and evolution of processing technologies in this industry. In response to these demands, a number of bath smelting technologies have emerged over the past 40 years and have been implemented for the treatment of primary and secondary feedstocks. The Outotec® Ausmelt Top Submerged Lance (TSL) Process (henceforth Ausmelt Process) is one such bath smelting technology which has been widely adopted in a large number of greenfield projects and brownfield plant modernisations (Wood & Hughes, 2016). Emissions of CO2 from the production of non-ferrous metals represent approximately 4-5% of global totals (Rankin, 2012), comparable with the almost 10% attributed to iron and steel production. Despite significant improvements in the energy efficiency of modern smelting technologies (Coursol, Mackey, Kapusta & Cardona Valencia, 2015), primarily through increased oxygen usage, further innovation and development is still required to address their reliance on fossil fuels such as coke and coal. Transformation of the non-ferrous smelting industry to low-carbon technologies and process flowsheets is lagging behind the power and transport sectors, which have witnessed significant growth in clean/renewable energy technologies to reduce CO2 emissions and address the issue of anthropogenic climate change (IRENA, 2018; IEA, 2018).

Jan 1, 2019

By Caitlyn J. McKinley, Ahmad Ghahreman, Maziar E. Sauber

Ever-growing global needs for critical metals, such as rare earth elements (REE), and base metals, such as copper and nickel, and their environmental impact motivated the pursuit of sustainable flowsheets. Regeneration of hydrochloric acid in chloride-based leaching flowsheets as a critical unit operation is an example of such endeavours. This study presents an efficient hydrochloric acid regeneration method from a magnesium chloride solution waste by addition of sulphuric acid in relatively low temperatures. The effects of temperature, initial magnesium chloride concentration, amount of sulphuric acid added, and airflow are examined. Experimental work are focused on temperatures between 80 and 95°C, initial magnesium chloride concentrations of 2 to 5 M, 100% to 220% stoichiometric sulphuric acid additions, and airflows between 200 to 600 mL/min. The developed technology recovers hydrochloric acid at a high rate and concentration with a relatively small environmental footprint. INTRODUCTION The mining and metals sector is under increasing environmental and economic pressure to make more efficient use of chemical reagents and energy in the production process. This affects several areas of process and flowsheet design such as the selection of the most appropriate unit operations and the overall design of the process steps paying heed to sustainability. Owing to the inherent inefficiencies of physical and chemical processes used in the mining industry, there will be materials and streams generated that are not a desirable part of the envisaged flowsheet. Thus, methods are implemented to recover and recycle such effluents. If the recovery and recycling are not economical, then procedures are followed to neutralize and dispose these effluents. In many cases, these effluents are potential contaminants or hazardous materials, and their disposal should be looked at in a much larger context. The safe management of the contaminants and hazardous effluents is a daunting problem in the mining industry and is fraught with technological, economic, social, and political challenges.

Jan 1, 2019

By D. J. Bowen

"The Great Dyke extends for 540 krn along strike, to unknown depth, and varies in width from 3 krn to 11 krn. Rb/Sr age determinations gives values of approximately 2470 Ma.The Dyke consists of a variety of mafic and ultramafic rocks, many altered to serpentinites. These include, from top to bottom, successions of gabbro/norites, pyroxenites, peridotiteslharzburgites, and dunites/picrites.The layers dip in from either margin, steepest at the edges (20°) and flattening toward the central sections. Four separate complexes are present. From north to south these are termed the Musengezi, Hartley, Selukwe and Wedza Complexes, and are described as 'boat-shaped' or 'pig-troughed'. All are similar in petrological sequences. Physiographically, the Dyke is spectacular in the north, where as a mountain range it meets the Zarnbezi Escarpment. Elsewhere in the central parts there is little surface expression and wide open treeless vleis. Dyke rocks cut through granite and schist belt terrain and are termed 'The Magnesia Belt'.Vast mineral resources exist. These include chrome, asbestos, platinoids, nickel, copper and gold. Up to eleven chrome seams numbered from top to bottom occur in the lower ultramafic sequences. Seams are narrow at 10 em to 30 em but of high grade. The platinum occurs 10 m to 40 m below the norite/pyroxenite contact.A 60 m wide zone of Light Sulfide Mineralization (LSM) of less than 1070 sulfides extends from the lower gabbronorites into the upper pyroxenites. In this LSM, four enriched zones carry up to 5% sulfides. The most widespread is termed the Main Sulfide Zone (MSZ), below which is No. 2, No.3 and No.4 Sulfide Zones. The MSZ carrying pyrite, pyrrhotite and chalcopyrite is a multielement ore with components of PGE (pt-Pd-Rh), nickel, copper and cobalt, and gold and silver.Extensive exploration programs have been carried out and the intention is to begin large-scale mining. However, with Russia supplying metals to the western markets, South Africa's cutback on production, and an end to the Cold War, delays have arisen."

Jan 1, 1994

By Jian-bin Xie, Lin-fang Shen, Zhi-liang Wang

"In order to research temperature field for construction of connecting passage in Metro using artificial freezing method, the finite difference software FLAC3D is employed to numerically simulate construction process of connecting passage. During construction, the overall distribution of temperature field around connecting passage, the relationship between soil temperature and freezing time, the distribution and variation for the thickness of freezing wall are studied from the perspective of numerical analysis. The results show as follows: after 55 days’ freezing, the soil temperature surrounding connecting passage is about -24 oC ~ -28 oC, and the minimum thickness of freezing wall is about 4.0m, which is larger than the design value 3.1m. So construction conditions have satisfied to the excavation of connecting passage and pumping station. During the excavation of connecting passage, soil temperature has almost no obvious change and the thickness of freezing wall remains constant mainly. After 45 days’ normal thawing, the temperature of freezing wall rises 12 oC approximately. And the soil temperature rises faster at the beginning of the normal thawing stage. In the whole process of construction, the frozen area is about 5m outside the edge of connecting passage, and the cooling area is about 10m outside the edge of connecting passage. INTRODUCTIONThe first recorded application of the artificial freezing method is on a mineshaft project in 1862, and it has been widely used in foundation pit engineering, subway tunnels, mine shaft engineering and so on (Wang Zhiliang, 2010; Zhang Juanxia, 2012; Qiu Fan, 2007; Zhou Xiaomin, 1999). This method has many advantages of enhancing soil strength; decreasing permeability and adopting various unstable soils (silt clay, sand, gravel, etc.). It has been applied successfully in metro engineering construction in Beijing, Shanghai and Nanjing. According to incomplete statistics, the construction of connecting passage using artificial freezing method accounted for 98% in Shanghai metro (Qiu Fan, 2007)."

Jan 1, 2015

By Nobuyoshi Yabuki

Building Information Modeling is a prevailing methodology in the building industry and half (by length) of the world's shield tunnels are in Japan. Accordingly, for shield tunnels from 2005 to 2007, we developed a product model called IFC-ShieldTunnel, which is based on Industry Foundation Classes (IFC), in order to meet the future demand for such a product model. IFC-ShieldTunnel was developed by adding new elements that are specific to shield tunnels and that are not included in the original IFC. The added elements include shafts, segments (A, B, and K types), waterproofing elements, segment joint elements, and ring joint elements. Furthermore, soil layers and void elements were created. Recently, we updated the product model by re-organizing the entities and correcting errors. We deployed the updated IFCShieldTunnel model in the construction of an actual shield tunnel in Tokyo for about a year from August 2010 in order to check its feasibility. In the verification process, first, segments were modeled using Autodesk Revit Structure 2011 and property data were assigned to each segment element. Next, a mapping between the original attributes of the entities of IFC and properties of IFC-ShieldTunnel segments was developed. Using this mapping and IFC?s IfcBuildingElementProxy function, we were able to convert the IFC data from Revit Structure 2011 to IFC-ShieldTunnel automatically. Segment data were also converted from Revit Structure to Google SketchUp by IFC-ShieldTunnel. Furthermore, the construction scheduling and cost data were converted from Revit Structure to EXCEL for 4D and 5D analyses of construction. We interviewed engineers who used IFC-ShieldTunnel and received positive comments about the utilization of the product model. Overall, our test demonstrated the feasibility of IFC-ShieldTunnel. In future work, we plan to apply IFC-ShieldTunnel to more projects and test its practicality.

Aug 1, 2013

By A. C. Gagnon, H. Saroglou

"The focus of this paper is on the analysis of geometrical discontinuity properties for the rock mass located within an open pit mine located in Western Africa. Discontinuity data were collected using various techniques including oriented core logging, borehole televiewer surveys, surface pit wall mapping and photogrammetry. The geological setting was initially studied prior to the data analysis to produce threedimensional ground models of the regional and mine site geology along with block diagrams illustrating predicted fracture patterns. Stereographic and statistical discontinuity data analysis of the geometrical properties of the rock mass was subsequently performed to identify unique structural domains throughout the open pit area. The discontinuity data collected throughout the studied open pit area were primarily discontinuity orientation, frequency and spacing and the investigation focused on the reasons for observed differences between the various data collection techniques. Stereographic analysis was used to assess the preferred geometry of discontinuities filtered by lithology, data collection technique, borehole, discontinuity type and pit wall (footwall or hanging wall). The observed fracture pattern is explained adequately by the geological setting. The need for accurate ground models for the design of open pit slopes is highlighted.INTRODUCTIONThe Tasiast Mine is an open pit operation located in north-western Mauritania, approximately 300 kilometres north of the capital Nouakchott. The Tasiast mine, which is owned and operated by Kinross Gold Corporation (Kinross), began commercial operations in 2008. The Tasiast mine is located in an area characterized by flat desert terrain within the western reaches of the Sahara Desert region. The current mine site includes mill buildings, shop facilities, waste dumps, tailings facilities and two main open pit operations (Piment and West Branch). The West Branch pit is the focus of this paper. The current open pit plan for West Branch indicates a final pit measuring approximately 2.5 km long by 1.4 km wide and 510 m deep."

Jan 1, 2015

By Victor Dolmage

"The localization of orebodies by geological structures is well demonstrated at the Copper Mountain mine of southwestern British Columbia. These extensive deposits; owned and workd by the Granby Consolidated Mining; Smelting and Power Company; are at Princeton; abo!lt 150 miles east of Vancouver and 40 miles north of the International boundary. The geology of the deposits and the surrounding district is described by the present writer in Memoir 171 of the Geological Survey of Canada; pub1ished in 1934.The main geological feature is a gabbro stock, elliptical in plan, with a major axis about 5 miles in length extending in a northwest-southeast direction. The stock varies in composition from syeno-gabbro (gabbro plus orthoclase) through diorite and syenite to a core of syenite pegmatite. All the members contain orthoclase, which ·increases greatly in amount toward the centre, but all are devoid of quartz. The stock has been injected into a steeply folded series of volcanic flows, breccias, and tuffs that strike more or less parallel with the major axis of the stock. On its northeast side the stock is flanked by a band of fairly coarse volcanic breccia of andesitic composition and ·having fragments up to several inches in length. Where this breccia is tangential to the stock it is both dynamically and chemically metamorphosed to a marked degree, and within the zone of this metamorphism are enclosed the copper deposit~. The ore consists of bornite, chalcopyrite, and a little magnetite occurring as disseminated grains and small veinlets in the metamorphosed breccias. The only gangue minerals are orthoclase, albite, oligoclase, and biotite. The two most common vein minerals, quartz and pyrite, are conspicuously rare or absent. The dynamic metamorphism has produced two well-defined structures, namely, a strong schistosity parallel with the curved vertical contact of the stock and a very striking set of small, straight, nearly parallel open fractures that stand nearly vertical and at right angles to both the schistosity and the stock contact. These are called the ore fractures."

Jan 1, 1954