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By S. Murdock, R. L. Fleischer, H. W. Alter, J. E. Gingrich

The use of solid state track deters allows totally passive, integrating measurements of 222Rn (radon) or of 220Rn (thoron) plus radon. A track-detecting solid is placed in a holder that is closed by a selective membrane and exposed to the atmosphere of interest to produce an accurately time-averaged record over times of interest that range typically from a week to a year. By selection of the proper membranes, dosimetry can be done for radon or for the sum of radon and thoron. A different membrane is appropriate for measuring radon under humid conditions such as are found in the ground. Large numbers of measurements have been made with these systems both in the ground, where radon levels are high, and in indoor environments, where levels are orders of magnitude less. Calibrations have been carried out at both high and low concentrations of radon. New results in the air at the site of the Shirley Basin mine and mill give reproducible results with month-long integrating periods. The off-site background levels are in the range 0.7 to 1.0 pCi/l (26-37 Bq/m3). The average yearlong on-site level is 1.5 pCi/l (56 Bq/m3); at the mill it is 2.6 pCi/l (96 Bq/m3); and the level measured at the backhoe in the open pit mine is 3.9 pCi/l (144 Bq/m3). The region of significantly elevated radon levels is confined to a radius of 1.6 km of the mine and mill. All of the on-site radon concentrations are less than but comparable to the typical values found in the living areas of modern energy-efficient homes.

Jan 1, 1981

By Juhani Pulkkinen, Pekka Lappalainen

Preplaced cable bolts - fully grouted old hoisting cables or stress relieved steel strands - have been used succesfully to pre- reinforce ore contact zones and pillars in sublevel stoping at Outo- kumpu Oy mines for ten years. The purpose is to make open stoping methods possible even in "poor'' conditions and to decrease waste rock dilution. Since 1971 more than 120 km cable bolting has been done, and plans for this year in five mines amount to 33 km. In order to understand the function of cable bolt, pull-out tests have been done both in the laboratory and in situ. Bond strength between cable and cement is highly dependent on cable structure and cable surface dirtiness. Steel cables with steel core and rough surface structure have highest bond strength ( 6 MP~). A cable bolt is a friction bolt. After losing its peak bond strength - after starting to move - a cable bolt still has a high loading capacity due to the friction caused by the uneven surface of the cable. Cable bolting is done before actual stoping from existing drifts, sublevel drifts, e.g. or from special bolting drifts. In general stress relieved steel strands are used; 2 x 15.2 mm dia per hole. FEM or BEM calculation is utilized in cable bolting design. Bolts 2 are in fan shape, 10 m ... 50 m long and are spaced 1/20 m ... 1/50 m2 at stope walls. Pretensioning of cable is not needed, when bolting is done before rock deformations. Bolting costs vary between 0.3 USD ... 1.0 USD/ore ton. In the beginning only manual cable installing technique bras used. Now bolting can be done as fully mechanized with the developed cable bolting machine; i.e. drilling of the hole, installing and cutting of cables and grouting of hole.

Jan 1, 1983

By T. F. Witherbee

ON the 22d of November, „1879, white iron unexpectedly appeared while working the Cedar Point Furnace, Port Henry, N Y., on the following burden, calculated to turn out mill and foundry iron: Anthracite coal, - 3000 pounds. Connellsville coke, - 1500 pounds. Total, - 4500 pounds. Old Bed ore, - 3750 pounds. New Bed fine ore, - 2000 pounds. New Bed chunk ore, - 1000 pounds. Kearnev hematite ore, - 750 pounds. Total, - 7500 pounds. Magnesian limestone, - 1865 pounds. Common limestone, - 885 pounds. Total, - 2500 pounds. The production per week since making mill iron-from September 1st, 1879, to date, seven weeks-was 412 gross tons. Ore was not immediately taken off, as nothing serious was looked for. The iron for the next week graded from No. 4 to white, and in. six days the make was 274 1/2 tons. At 10 P.M., Friday, the 28th, a slip of-..4 feet occurred, and on Saturday, at 5 A.M., another of 3 feet on the south side and. 7- feet on the north side took place. At this time it was found that the south side had been hanging for over a week--a fact which had not been reported. Throwing off the wind, to produce slips. and reduce pressure, had been tried with no effect. The stock, as seen through the tuyeres, seemed to consist almost entirely of coal, with just enough infusible cinder to cement it into a mass through which the blast could not be forced. At 3.50 A.M., Sunday, the 30th, the first cinder seen in seventeen hours came into tuyeres Nos. 1, 2, 3, and 6, At 9.30 A.M. No. 3 was taken out to see if the stock

Jan 1, 1881

By L. A. Tarshis, H. E. Cline

A stability criterion for a lamellar eutectic interface was derived previously1 assuming that the wavelength, A,. of the perturbation which grows most rapidly is much larger than the lamellar spacing. A. This assumption was required to permit averaging of both the interface temperature and composition over the complicated geometry of a lamellae. If this assumption is invalid, as has been suggested.2,3 then the problem becomes too complicated to solve completely. The first of these analyses1 did not calculate the wavelength. A,. of the initially unstable perturbation. whereas the more recent analysis.' which led to a contradiction of this assumption. did not include one of the key factors for determining this wavelength. To rigorously determine the wavelength, the effect of the curvature of the perturbed interface (not considered by either of the above treatments) must be included. By omitting this term, one would be led to an incorrect conclusion regarding the magnitude of A,. but to an accurate criterion for stability as evidenced by the excellent agreement with experimental observations.' In the case of single-phase alloys. the critical wavelength. A,. for instability can be calculated from the Mullins and Sekerka4 (M.S.) analysis which includes the effects of capillarity. In the following discussion, the M.S. analysis is applied to lamellar eutectics and the critical wavelengths calculated for reasonable growth conditions in Pb-Sn eutectic alloys. In order to apply the M.S. analysis to eutectics. one may substitute i) the effective liquidus slope.1 m*. for the single-phase liquidus slope and ii) the ratio of the bulk alloy composition. C,. to the average interface composition in the liquid (Ci = CE where CE is the equilibrium eutectic composition) for the distribution coefficient to give:

Jan 1, 1970

By Jeff Hussey

Since 1955, Gaspe Mines has produced 150 Mt (165 million st) of ore averaging 0.9% copper. The ore was mined from two open pits and from underground workings. In 1994, four exploration drill holes discovered a buried porphyry/skarn copper-molybdenum (Cu-Mo) deposit at depths of between 1,000 and 1,700 m (3,280 and 5,580 ft) below the top of Porphyry Mountain. The mineralization and alteration associated with the Porphyry Mountain quartz monzonite does not outcrop. Prior to 1997, about 19,500 m (64,000 ft) of drilling in 12 drill holes had outlined 200 Mt (220 million st) grading 0.73% Cu and 0.08% Mo. Mineralization occurs as veins and disseminations of chalcopyrite and molybdenite.

Jan 1, 1998

By Clay Haynes, Tim Pearia, Robert Robinson, Judy Cochran

A 1.89 km-long, 4.5 m-I.D. tunnel was successfully constructed through saturated hard clay, and highly abrasive dense sand and gravel, with groundwater heads ranging from 10 to 20 m. In order to address these conditions, a Lovat earth pressure balance TBM was used, with soil conditioning by foam, water and various polymers. Support was provided by a single-pass segmented concrete lining. Groundwater inflows of 400to 1,600 lpm at times created challenges for changing cutting tools. Surface settlements were generally less than measurement thresholds, except under very low cover at startup. This project provides a pivotal case study of the successful application of EPBM technology in saturated, abrasive glacial soils and the successful application of soil conditioners.

Jan 1, 2003

By Cheryl M. McInnes, Graham J. Sparrow, James T. Woodcock

Three composites, assaying about 3 g/t Au and 0.75% Cu, were investigated. Each contained oxide copper minerals, iron oxides, and silicates. One composite also contained copper and iron sulphides. Maximum gold extractions by thiourea leaching were obtained after copper removal by acid pre¬leaching at pH 1.5 and redox potentials of 400 mV (Pt versus SCE). Best thiourea leaching conditions were pH 1.5, redox potentials over 200 mV, and 0.4% thiourea. This gave 90% gold extraction in 2 h with thiourea consumptions of 25 kg/t. Lower potentials gave poorer extractions. Ferrous iron additions before leaching halved thiourea consumptions. Longer leach times and the presence of sulphide minerals sometimes resulted in reprecipitation of gold.

Jan 1, 1989

By B. Yarar

Samples of coal from an adit in the Fording River District of British Columbia showed hydrophilic properties between depths of 0-24.5 m (0-80 ft) and was naturally hydrophobic at greater depths. Laboratory experiments indicated that weathered samples (i.e., those mined at 0-24.5 m) could be upgraded by froth flotation at pH32 following slimes removal. The i.e.p. of samples varied regularly between pH = 1.6-4.1, the weathered fractions being at the lower end of the pH scale. These values followed a pattern comparable with the flotation behavior of samples. A patchwise structure for coal surfaces determining the resultant disjoining pressure which in turn determines flotation-non-flotation relationships is postulated.

Jan 1, 1983

By Stephan Iversan, Janae Singer

High resolution seismic refraction tomography has proved to be a useful tool to effectively estimate depth of blast induced damage in rock. Excavation blast damage can be as shallow as 1 to 2m (3 to 7ft) and requires resolution at a fraction of a meter for effective imaging. We used an accelerometer with flat frequency response to 1000Hz to record data at spacings of approximately 0.25 to 0.5m (0.8 to 1.6ft) along mine walls. The resulting tomograms of P-wave velocity show low velocity zones which we interpret as residual fracturing from blasting. Experiments on a concrete test block and at two underground mine locations give results that are consistent with fractured rock transitioning to competent rock.

Jan 1, 2009

By Wojciech Klecan

Cobb County, located on the northwest side of Atlanta, GA, is continually growing and, like many other metropolitan areas, it needs to increase the capacity of its waste water system to meet future demand. The Cobb County Water System (CCWS) is the responsible agency for water distribution, waste water collection and treatment in most areas of the county. CCWS, one of the most progressive agencies in the metro-Atlanta area, is addressing its future waste water capacity needs in the southern part of the county with the construction of the South Cobb Tunnel and Pump Station. This project consists of an 8.8-km- (5.5-mile-) long, 8.2-m- (27-ft-) diameter, tunnel boring machine (TBM) excavated waste water storage and conveyance tunnel; six tangential vortex-flow intakes ranging from 1,533 to 5,700 L/s (35 to 130 mgd) peak flow capacity, two construction shafts, six 1.8-m (6-ft) finished diameter connecting tunnels ranging in length from 6 to 975 m (20 to 3,200 ft) and a 5,700-L/s (130-mgd) wet/dry pit pump station. The pump station will have a semi-circular wet well with a dividing wall that extends almost to the top of the shaft and a spilt dry well for reliable operation. Roller gates will control the flow to the wet well from the tunnel. The pump station will have six 1,420 L/s (32.5 mgd) pumps and two sets of stair wells and elevators. With a finished diameter of 32 m (104 ft) and a depth of 62 m (204 ft), this is the largest pump station shaft constructed so far in Georgia for the dewatering of a waste water tunnel. The pump station shaft was also the highlight of the well attended and successful 2009 Shaft Design and Construction Short Course held in Atlanta, Sept. 10-11. The two-day course was sponsored by the Underground Construction Association of SME and Pennsylvania State University and concluded with a field trip to the pump station shaft. The tunnel starts south of the city of Austell and finishes at the South Cobb Water Reclamation Facility (WRF), located on the banks of the [ ] Chattahoochee River just north of Interstate 20 (Fig. 1). The South Cobb Tunnel will run 30 to 137 m (100 to 450 ft) below the surface, with an average depth of about 91 m (300 ft), through metamorphic rocks (Fig 2). The construction contract was awarded to Shea-Traylor JV with the lowest bid price of $305 million and notice-to-proceed was given on July 14, 2008. Jordan Jones & Goulding, Inc. (JJG) is the project designer and performed the geotechnical investigations. Parsons/Jacobs Associates is the construction manager. The South Cobb Tunnel is CCWS?s second deep hard rock tunnel. The 15.3-km- (9.5-mile-) long, 5.5-m- (18-ft-) diameter TBM excavated the Chattahoochee Tunnel was the first deep tunnel to be construced in Cobb County. Construction began in 2000 and the project was completed four years later. It is located about 16 km (10 miles) northeast of the South Cobb Tunnel in similar geology. It was designed by JJG to meet east Cobb?s long-term waste water capacity needs and provide flow equalization to the R.L. Sutton WRF. The Chattahoochee Tunnel was named ?Outstanding Civil Engineering Project of the Year? by the Georgia Sec-tion of the American Society of Civil Engineers in 2006.

Jan 1, 2009

By Vince Luongo

PROJECT DESCRIPTION The York Durham Sanitary System (YDSS) Interceptor in the Town of Richmond Hill located just north of Toronto, Ontario, Canada will see the construction of a tunnel extending along 19th Avenue for a length of approximately 3.8 Km from Yonge Street, east to Leslie Street and will have a minimum internal diameter of 2.1 m. t to Leslie Street and will have a minimum internal diameter of 2.1 m. The tunnel will connect into four shafts, for which two of the shafts will be constructed using the slurry wall construction method given the high water table and difficult ground conditions encountered at these locations. The two shafts noted as Access Shaft No. 2 and No. 3 were designed and constructed to meet regulatory conditions, which required a sealed shaft construction method. GEOGRAPHICAL PROFILE The ground conditions in the Toronto region consist predominately of glacial till, glaciolacustrine and glaciofluvial sand, silt and clay deposits, and beach sands and gravels. The shallow geological formation found in the project area consists of four types of deposits: Oak Ridge Morain deposits, Halton Till, Glacial lake deposits and Organic soils. The Oak Ridge Morain is the dominant deposit encountered along the tunnel alignment. This formation consists of three deposits: The Upper Till, Middle Sand and the Lower Till. Standard penetration tests (SPT) carried out in these deposits measured N-values ranging from 2 to more than 100 blows/300mm which indicate very loose to very dense soil conditions. The Middle Sand deposit will be the dominant feature within the slurry wall construction at access shafts 2 and 3. Access Shaft 3 The base of the slurry wall will be 20.5 M below the ground surface. Slurry wall excavation will be within peat and organic soils found at the upper 3 M, followed by 5 M of the Upper Till. The remainder of the excavation will be within the Middle Sand. The piezometric head elevation is found at the ground surface. Access Shaft 2 The base of the slurry wall will be 22.5 M below the ground surface. Slurry wall excavation will be entirely within the Middle Sand 2.The piezometric head elevation is found at 7 M below the ground surface.

Jan 1, 2007

By A. H. Onur, S. Ural

"The Afsin-Elbistan coal deposit with its 3.4 billion metric tons of reserve is the biggest coal basin and one of the most important resources for electrical energy production in Turkey. The coal deposit is located north of Elbistan, Kahramanmaras Province, in southeast Turkey (Fig. 1).The Kislakoy sub-basin of the Afsin-Elbistan basin was selected as the first open cast mine to feed four power station blocks of 340 MW each. The mine is equipped with six identical bucket wheel excavators of the type Sch Rs (2300/5) 32. The annual coal demand of the power station is 18.5 million metric tons. The Elbistan basin encompasses an area of 900 km2, and its centre lies about 1150 m above mean sea level. The sedimentation took place mainly in the upper Pliocene period. The thickness of the coal bed varies from 20 m to 60 m, respectively. The basal part of the coal beds consists of clay, marl and sandy clay. These formations are overlain by gyttja, which may also occur in the form of calcareous ooze, enveloping coal beds. The thickness of the gyttja is up to 35 m (Otto-Gold, 1969). The coal of Afsin-Elbistan is soft coal and the quality has been found to vary considerably throughout the deposit. The thicknesses of the sterile intercalations vary from 0.50 m to 2.2 m and average 1 m in thickness. From the quality control point of view, the coal seam is regarded as upper seam where the gyttja formation occurs as sterile intercalations, and lower seam where the clay formation occurs instead of the gyttja (Fig. 2). The CaO content of upper Kislakoy coal is very high, grinding resistance is low and base to acid ratio of ash, that is, the ratio of acid oxides of metals to base, is greater than one (Ural and Onur, 2001). Contrary to upper Kislakoy coal, CaO content of lower Kislakoy coal is very low, grinding resistance is high and base:acid ratio of ash is smaller than one. Modified Impact Strength Index (MISI) tests are used to determine the grindability of the Elbistan coals (Ural, 1999)."

Jan 1, 2003

By Reza Kamali, Mohsen Bashiri, Hadi Fanisalek

"Nomenclature: A: area (m2), C: heat capacity (WIK), cp: specific heat (J/Kg K), d: internal tube diameter (in), F: correction factor for multi-pass and crossflow heat exchanger, h: convective heat transfer coefficient (W/m2K), k: thermal conductivity (W/mK), L: length (m), m: mass flow rate (Kg/s), W: flow rate, N: number, Q: heat rate (W), R: thermal resistance, T: temperature (°C), U: overall heat transfer coefficient (W/m2K), ;1,,P: pressure drop (Pa), ;1,,T: temperature difference (°C), p: density (lb/ft3), N: number of tube passes, U,: velocity in tubes, iJh: head loss in feet of flowing fluid, Up: velocity in the pipe leading to and from the heat exchanger (ft/sec), µ: viscosity ( cp ), Llpf frictional pressure loss (psi/l 00 equivalent ft of pipe) Subscripts: b: baffle, c: cold, cf counter flow, ex: exchanger, f: fouling, h: hot, i: inlet-inner, ib: inlet baffle, lm: logarithmic mean, m: mean, o: outlet-outer, s: shell, t: tube, w: wall AbstractThe main bottleneck for primary aluminum production industry is dealing with a huge amount of input energy. The fact is that part of provided energy to aluminum production smelters will be lost as waste heat and it never used for aluminum production. One part of waste heat is escaping from the potroom exhaust gases, which was studied for possible recovery in a desalination plant to produce distilled water and the paper was presented in 2011 TMS Annual Meeting. However, it was shown that waste heat recovery plant to produce distilled water is highly profitable but the main fact is that the exhaust gases from potroom are highly corrosive, abrasive and dusty. The main challenge for desalination plant construction, which is using aluminum smelter exhaust gases as the main heat source, is the highly corrosive environment that makes the situation difficult and complicated for equipments design and plant construction. In this paper, we are trying to study a detailed investigation regarding the heat exchangers fouling, corrosion in heat exchangers including heat exchangers' material, how often we need to shut down the plant for maintenance or cleaning, and plant thermal efficiency with considering fouling."

Jan 1, 2012

"The Metropolitan St. Louis Sewer District (MSD) in Missouri, the country’s fourth largest sewer system, is upgrading its storm and wastewater infrastructure in a 23-yearlong, $4.7 billion initiative called “Project Clear.” Historically, during times of intense precipitation, the current sewer system becomes overwhelmed. The primary goals of this project are to improve water quality and to alleviate many wastewater concerns in the St. Louis region by planning, designing and building community rainscaping, system improvements and an ambitious program of maintenance and repair.Part of the system renovation has focused on constructing underground tunnels for storm water storage, permitting controlled drainage of runoff, and preventing overflows into rivers and streams. Construction plans for these storage tunnels called for eight vertical intake and ventilation shafts to be bored from the ground surface. These shafts will then be intercepted in the bedrock at a depth of about 150 ft (45.7 m) during the excavation of the 3,000 ft (915 m) long underground tunnel that will be about 28 ft (8.5 m) in diameter. According to John Deeken , a geotechnical engineer with Black & Veatch Corp. and construction manager for the Maline Creek project, the drilling and blasting technique for creating the shafts was ruled out because the project was located in a residential neighborhood. “We could have used rock coring or a cutter head, but the drop shaft for this project is constructed within 10 ft (3.05 m) of an existing 108 in (274 cm) diameter sewer main,” Deeken said. “We had to take precautions to avoid damage to it.”A primary planning mandate of all MSD Project Clear phases requires minimized impact on traffic and residents. The canister drilling method enabled work to be confined to the median of a residential boulevard running perpendicular to the side street without detouring traffic. In addition, canister drilling offered a highly-precise means to create the shafts, leaving a smooth-sided borehole, right on target. Ground conditions in this 132 in (3.35 m) diameter intake shaft were wet due to the high groundwater levels and close proximity to the Mississippi River. “They’ve been finding shale in 2 to 6 ft (0.6 to 1.8 m) layers between weathered layers of Mississippian limestone,” said Dan Spiecher, technician at Center Rock (CRI). “The 2 ft (0.6 m) layers we can punch through. The 6 ft (1.8 m) layers slow us down.”"

Jan 1, 2017

By R. J. Davidson, W. D. Douglas, J. A. Tumilty

SYNOPSIS Two pilot plants operating on different types of carbon were used to generate steady-state adsorption data in the treatment of gold-plant solutions of high and low tenor. A pilot plant comprising three 4 m long columns and using 3 mm extruded activated carbon was used to treat pregnant solutions with a gold concentration of 5 to 8 g/t at pH 10 to 11,5. Column influent was pumped at a super¬ficial flow velocity of 0,5 m/min while the carbon was moved daily so as to effect gold loadings on the carbon of 5 to 10 k /t. With a carbon-bed depth of 12 m, an adsorption efficiency of 99,9 per cent was obtained in a bed depth of 9 m, which was subsequently reduced to 8 m when the depth of the carbon bed was reduced to 8 m. This improvement in efficiency was attributed to the reduced residence time of the carbon from 12 to 8 days. A corresponding decrease in adsorbed silica indicated that some silica fouling of the carbon had occurred. A second pilot plant, comprising a single column 6 m in length and using coconut-shell carbon of 1,0 to 2,4 mm, treated a solution with a gold concentration of 0,7 g/t at pH 8,0. Feed solution was pumped at a superficial flow velocity of 1,0 m/min while carbon was moved every 8 hours to give gold loadings of more than 5 kg/t. An adsorp¬tion efficiency of 99,5 per cent was indicated at steady state. Intermittent washing of the column with dilute hydrochloric acid was shown to have a beneficial effect on the gold adsorption and to reduce the pressure drop across the column. Intermittent washing with dilute sulphuric acid indicated that there had been some passivation of the car¬bon during the treatment of a solution with a gold concentration of only 0,2 g/t. Compared with other adsorption systems, the countercurrent moving bed appears to offer significant advantages in terms of metallurgical efficiency and capital investment. The inability normally associated with moving-bed systems to treat solutions containing suspended solids may be overcome to a degree by the use of relatively coarse extrud¬ed carbon.

Jan 1, 1985

1. New Publications Tin and its uses no. 140. Greenford (England), International Tin Research Institute, 1984. Catalogue. English translations of German standards 1984. Berlin, Beuth Verlag GmbH, 1984. Mining and mineral processing operations in Canada 1983. Ottawa, Canadian Government Publishing Centre, 1984. $6.00. Canadian mineral deposits not being mined in 1983. Ottawa, Canadian Government Publishing Centre, 1984. $6.00. 2. Mintek Publications Report M42D The recovery of tantalite and cassiterite from a bulk sample of pegmatite supplied by Falconbridge Explorations Limited. (First issued 1982.) Report M46D Tests on the nature and reduction of the chlorine in fluorspar concentrate from the western Transvaal. (First issued 1982.) Report M58D An electrochemical process for the recycling of tungsten carbide scrap. (First issued 1982.) Report M59D Testwork on samples of oxidized ore from the Potgietersrus Prospect. (First issued 1982.) Report M60D The production of electrolytic manganese dioxide from furnace sludge. (First issued 1983.) Report M64D Isotope-source neutron-activation analysis for the determination of manganese in bulk samples. (First issued 1982.) Report M128 The determination of cyanide in hydrometallurgical process solutions and effluents by ion chromatography. Report M132 Mineralogical parameters influencing the acid-bacterial leachability of low-grade nickel ores. Report Ml34 The NIMROC reference materials: revised values for thorium, yttrium, lanthanum, and the rare-earth elements. ReportM140 The effect of physical and chemical factors on the corrosivity of a synthetic mine water. Report Ml44 The development of standard procedures for the evaluation of magnetite for use in heavy-medium separation. Report M145 A preliminary study of the mineralogy of the nickel occurrence at Mabilikwe Hill, northern Transvaal.

Jan 1, 1984

By B. P. Watson

Uniaxial tests performed on core from instrumented sites at Amandelbult 1 shaft, Impala 10 shaft and Union Section Spud shaft showed a nonlinear elastic relationship between applied load and induced deformation. This nonlinear behaviour does not appear to be dependent on borehole orientation but in the case of the Amandelbult and Union sites appears to have been influenced by the stress condition of the rock mass at the time of drilling. Cores drilled at these two sites under destressed conditions, such as over a stope, showed a linear elastic response to the applied load whereas most of the cores drilled under relatively high radial stresses were nonlinear. The Impala 10 shaft tests, however, all showed strong nonlinear behaviour irrespective of the stress condition of the rock mass at the time of drilling, although high stress conditions may have influenced the severity of the nonlinearity. A comparison between underground stress change measurements and an elastic model indicated that the rock mass became nonlinear when the virgin stress condition was relaxed to about 10 MPa. The cores for laboratory testing were retrieved from vertical boreholes drilled up from the centre of a stope and from horizontal boreholes drilled over pillars and stopes at about 600 m, 1 100 m and 1 400 m below surface for the three sites respectively. The k-ratios under virgin conditions were estimated from sockets, modelling and stress measurements to be 1.0, 1.3, and 0.5 for the Amandelbult, Impala and Union sites respectively. Of the three sites, therefore, Impala 10 shaft appears to have had the highest virgin stress state. Tests performed on similar rocks from shallower depths at Impala Platinum essentially showed a linear relationship between stress and strain. From the small Impala Platinum rock test database available to the project, it appears that the nonlinear elastic behaviour initiates at this mine from about 1 000 m below surface and seems to become progressively more nonlinear below this depth. In addition, the nonlinear elastic rocks are weaker, have a lower Young?s modulus and a higher Poisson?s ratio than their linear elastic equivalents. Interestingly the tangential Poisson?s ratios of the nonlinear elastic materials are often greater than 0.5 at 50% of the failure stress, suggesting an early failure initiation. The paper describes the microscope and modelling work done to determine the causes of the nonlinear behaviour and discusses some implications of the behaviour for deep-level mining.

Jan 1, 2009

By Kenric C. Owen

INTRODUCTION Situated 23 miles east of Pretoria the Premier Mine started diamond production in 1903. Two years later it produced the largest diamond yet discovered, the 3 106 carat Cullinan stone. For the period to 1932 when the mine was closed down due to economic circumstances, open cast mining was practised using inclined rope haulage traction and by this time had produced 48.5 million carats of predominantly industrial quality diamonds from 148 million tons of ore. In 1945 it was decided to re-open the mine using underground mining methods. A system using long hole benching was devised (Hodgson and Sewel 1960). This system was later modified but still forms the basis for approximately fifty percent of production. Following the successful introduction of block caving on associated diamond mines in the Kimberley area (Gallagher and Loftus 1960) this mining method was introduced to the Premier Mine in the late 60's and now accounts for nearly 50% of production. This paper will discuss block caving at Premier Mine in the light of our experience and discussion will be directed to the main geological and structural features of the orebody and host rocks and the related constraints imposed on the mining methods. Reference is made to the long hole benching mining method for comparative purposes. GENERAL DESCRIPTION OF OPERATIONS The ore from the block caving and bench mining areas gravitates via ore passes to a twin haulage, 500m below surface. Electric 13 tonne locomotives, each hauling a train of 10 Granby type cars, deliver the ore to two 42" x 48" (1.06m x 1.22m) jaw crushers. The ore is reduced in size to minus 0.15m before being hoisted to the treatment plant on surface. Hoisting is done with 12.5 tonne bottom discharge skips in a five compartment rectangular shaft using two 3 240 H.P. semi automatic Ward Leonard winders. A small single drum service winder operates in the other compartment. Men and materials travel in a separate shaft in a 5,4m x 2,8m cage operated by a Koepi winder. These two shafts are also the main intake airways to the mine. The two main extraction fans capable of 250 m3/s at 3,2 kPa are situated on surface and are connected to the underground workings by an incline and a network of air passes and return airways. GEOLOGY Although there are numerous occurrences of kimberlite bodies in the district, the Premier Mine kimberlite pipe is the only economic orebody. It is roughly oval in shape with surface dimensions of 900m on the long axis and 450monthe short axis. The surface area is 320 000 m2. The kimberlite has intruded a massive body of felsite and norite which is intersected by a number of faults. The contact between the kimberlite and host rock is clear cut and dips inward at an average angle of 80°. Cutting across the pipe and the country rock is a 75 metre thick gabbro sill, the top of which intersects the pipe below the 347m level and dips at 15' to the north west. The kimberlite has been metamorphosed a distance of some 20m both above and below the sill contacts. Age measurements on biotite from the gabbro date the sill as 1 115 million years, thereby providing a minimum age of the pipe. (Pre Cambrian). All other pipes in South Africa are of Cretaceous age (60 million years). A simplified geological plan and section of the Premier Mine orebody is shown in Figure 1. It is thought that the kimberlite intruded in at least three distinct phases. The kimberlites of these different phases can be distinguished most easily by their characteristic colour. BROWN KIMBERLITE. This is the oldest kimberlite and forms a crescent shape in plan on the south eastern side of the pipe. In depth it increases in relative area. Although the brown kimberlite carries the highest diamond grade in terms of carats per ton all the various kimberlites in the Premier pipe are economic to mine.

Jan 1, 1981

The Molycorp operation at Mountain Pass, California, is unique in that it is the only place in the world where bastnasite is mined. The orebody is a metamorphic carbonatite; the mineral of importance is bastnasite, a fluocarbonate containing principally cerium, lanthanum, neodymium, and praseodymium, with small amounts of samarium, gadolinium, and europium. In addition, appreciable quantities of barite, calcite, and strontianite are present. Molycorp had mined and processed the bastnasite ore since the early 1950s at a rate of about 100 tpd by a unique hot flotation process in a plant originally used for cyanidation of gold ore. The concentrate was primarily used in high quality glass polishing, lighter flints, ceramics, and in specialty steel making. Then in the early 1960s, Molycorp and the Colorado School of Mines Research Foundation developed a solvent extraction process to recover europium from the bulk rare earth concentrates. In 1965 a new SX plant was constructed to produce this material for use as a red phosphor in color television tubes. Because of the demand for this material, a new 500 tpd concentrator was designed and constructed in 9 ½ months. Then, because of a sharply increased demand for europium, the plant was expanded to 1200 tpd only four months after completion of the original construction. The crushing section of the new plant was designed similarly to those portable units used in road construction and arrived on the site in ten major pieces. Foundations were concrete piers; and after their completion, the entire crushing plant composed of primary and secondary crushers, conveyors, and a screen was erected in fourteen days by a crew of ten men assisted by a mobile crane. Pit-run ore is loaded into 35-ton trucks by a 7 yd (5.4 cu m) loader, trans- ported to .the crushing plant, and dumped into the 65 -ton concrete pocket. A 42 in. by 20 ft (1.07 m by 6. 1 m) apron feeder feeds ore to the 30 in. by 42 in. (760 rnrn by 1070 mm) single toggle jaw crusher. Crushed ore is trans- ferred by a scissors conveyor to a 5 ft by 14 ft (1.52 m by 4. 27 m) double- deck screen which produces a final ¾ in. (19 rnrn) product with the oversize being treated in a 4 ¼ ft (1. 3 m) standard cone crusher. Cone crusher product is returned to the first scissors conveyor to join the primary crusher product. Dust collection is by a wet scrubber, and an operator's control room is located to overlook the primary. The entire crushing is in the open, and a 30-ton mobile crane is used for maintenance. Molycorp’s two-stage crushing plant is an excellent example of functional design for a small mining and milling operation.

Jan 1, 1978

By P. L. Crouse, S. J. Lubbe, M. J. Kabangu

A selective extraction and separation of zirconium by solvent extraction with 1-octanol is proposed. The process is based on the dissolution of the metal basic carbonates in hydrochloric acid in the presence of potassium fluoride, using 1-octanol as extractant. The effect of several process parameters, including hydrochloric acid and potassium fluoride concentrations, reaction time, and phase ratio between the aqueous and the organic phase was investigated. Zirconium is enriched in the organic phase. The best extraction and separation results were obtained with the basic carbonate dissolved in 10% hydrochloric acid and 1.5 M potassium fluoride. The optimum reaction time was 15 min with an organic to aqueous phase ratio of 2:1. Based on the selectivity of zirconium over hafnium in the organic phase, a McCabe-Thiele diagram was constructed. A near complete stripping of zirconium from the organic phase was achieved using a 3 M sulphuric acid solution. Additional studies are required in order to determine the reaction mechanism and the chemical speciation of the current investigation.