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By R. O. Burt, D. J. Ottley

"SYNOPSISRecent developments in the use of the Bartles-Mozley table and the Bartles CTS screen are described for the gravity preconcentration of fine heavy mineral and metal particles present in low grade pulps. The B-M table is a relatively new device used for the recovery of particles of up to 100 micron size down to 5 microns or in the case of gold and platinum, down to 1 micron. The CTS screen is a wet screening device used for feed preparation ahead of the Bartles-Mozley table and will size effectively down to about 300 mesh. Results and operating data for a number of different materials are given including outline flowsheets; the effects of the major variables on the performance of the table are briefly discussed. The potential of the B-M table to treat a variety of different ores, coal, tailings, and waste products are considered. The utilization of the B-M table in association with other unit processes to improve overall results as well as to improve the economics of design and performance of plants are also mentioned.INTRODUCTIONA number of new gravity concentration devices have been developed in recent years for the recovery of fine heavy mineral and metal particles but for reasons which include low capacity, high capital or operating costs, competition from other and better processes, the absence of simplicity or reliability in operation etc., only a few which include the Bartles-Mozley table, have been proved to be of commercial application.The name of the machine is derived from the inventors name, Richard Mozley, who developed the B-M table at the University of Bristol in England. The table was subsequently taken up and patented, world-wide, by the National Research Development Corporation a British government agency. An exclusive license to manufacture the table was granted by NRDC to Bartles (Carn Brea) Ltd. in Cornwall, England."

Jan 1, 1973

The method of investigation was to study the distribution of ore in great detail, to make a thorough structural study of the lode and the mine area, and then to compare the results of the two studies. Such a comparison usually reveals a very close relationship between geological structure and ore distribution, and can often lead to important conclusions which would not be reached in the ordinary working of a mine.The Triton mine lies 30 miles E.N.E. of Cue, or 380 miles N.W. of Kalgoorlie, in typical pre-Cambrian rocks, consisting of gTeenstone lavas and tuft's, interbedded with slates and some sediments, and intruded by granite and porphyry. Fig. 1 (at end of paper) is a longitudinal section of the mine and shows that the workings consist of the main North Emu and the smaller South Emu, separated by a distance of about 1 of a mile. Both orebodies occur on the same lode, which strikes north and south and dips practically vertically. On the same line, and of 1/2 a mile and a mile respectively to the north of the North Emu, are the small Rand and North Rand workings, where a big width of lode material has proved to be very low grade. In the North Emu the lode width averages 12 to 15 feet; it is seldom less than 5 feet and in places reaches 30 feet. In the South Emu the lode is wide, but only portion of it is payable.The lode is a mineralised bed occurring between massive lava flows on the east and a mixed series of tuft's and thin lava flows on the west. The lode material is hard, fine grained, and dark coloured, and generally has a faint banding which is believed to indicate a tuft'aceous origin of the original lode rock. Microscopic examination shows that the original lode rock has undergone considerable albitisation;' there has also been considerable formation of biotite which gives the lode material a characteristic sheen. The mineralisation consists of abundant fine pyrite, which is auriferous, and a lesser development of pyrrhotite which is, however, barren of gold.THE OREBODIES AND THEIR CHARACTERISTICSThe distribution of ore is best studied from gold contours, as these reveal features that cannot be detected in an ordinary assay section. Gold contours (see Fig. 3) are developed' by plotting the width and grade of all development and stoping assays throughout the mine on a longitudinal projection, representing each sample by a coloured dot according to a suitably chosen range of assay values, and then outlining areas of similarly coloured dots (see H. J. C. Conolly, Econ. Geol., April, 1936). Both width and grade must be taken into account and the simplest method of gold contouring is to use dwt.lft. values, but difficulties arise here with big widths of low grade and small widths of high grade ore. To choose an extreme case, 30 ft. of 2 dwts. and 2 ft. of 30 dwts. both equal 60 dwts.lft., and would therefore be given the same value in dwt.lft. contouring...

Jan 1, 1943

By Earl M. Woodward

INTRODUCTION Kerckhoff-2 is a 140 MW underground hydro-electric project designed and owned by Pacific Gas and Electric Company and constructed between May, 1980 and May, 1983 by Auburn Constructors. The project is located in the western foothills of the Central Sierra Nevada Mountains, about 30 miles northeast of Fresno, California, and develops the power potential of the lower San Joaquin River and its tributaries between the existing Kerckhoff and Millerton Lakes. The Kerckhoff-2 Project consists of project roads, adits, and access tunnels, service tunnels, power tunnels, powerhouse, tailrace tunnel surge shaft, buss shaft, intake structure, discharge structure, and switchyard. In the 1920s, the Kerckhoff 1 project, consisting of a dam, reservior, tunnel, and 34 MW powerhouse, was built in the same general area as Kerckhoff-2. The tunnel was constructed by conventional methods, and was left unlined. In time, other projects were built upstream, allowing the flow of the San Joaquin River to be regulated. The Kerckhoff 2 project is designed to harness that regulated flow, providing an additional 140,000 ON of power. Kerckhoff 2 will be the primary power plant; Kerckhoff I will produce power whenever the flow rate exceeds 4,800 cubic feet. The new power tunnel is built along the east side of the San Joaquin River between Kerckhoff and Millerton Lakes, parallel to the existing tunnel but extending approximately one mile further downstream.

Jan 1, 1983

By P. N. Anyalebechi

The effects of solidification rate (0.4-26.1 K/s) and alloying elements on the cast microstructures of aluminum alloy 5182 have been investigated with directionally cooled laboratory-size ingots. The alloying elements examined included Mg (3.6-4.7 wt.%), Mn (0.35-0.75 wt.%), Fe (0.11- 0.42 wt.%), Cu (0.03-0.25 wt.%), and Si (0.11-0.28 wt.%). These reflect the chemical compositions of AA 5182 end stocks with high recycled used beverage container (UBC) content. For a given chemical composition, the average dendrite cell and constituent phase particle size decreased with increase in average solidification rate. In general, within the level investigated, Mg did not have a significant effect on the types, volume fractions, and average sizes of the constituent phase particles. However, increase in Mn, Si, Fe, and Cu increased average sizes and volume fractions of the constituent phase particles.

Jan 1, 2010

This technical note describes a problem with WANG82, a ventilation network analysis programme. The problem was highlighted by Renison Ltd when using the programme on large, complex networks. Under certain circumstances the programme produced incorrect results or failed to converge to a solution.

Jan 1, 1986

By Harry Dobroski

Communications with moving tracked vehicles in a rail haulage mine pose a difficult problem. These communications take place from dispatcher to vehicles or from vehicle to vehicle via the trolley line, which is a very poor communications line. As a result, deadspots and high-signal areas can occur anywhere along the line, or signal can decrease simply as a function of distance. An analysis is made of the trolley line as a communications line, and methods of improving its characteristics are discussed. Data from inmine experiments are presented, showing actual improvements in communications. Recent Bureau developments in new hardware are also discussed. These include an adaptive speaker control for existing carrier phones and a new generation of improved carrier phones.

By Joe Roby

Rolling disc cutters are the business end of hard-rock and mixed-face tunnel boring machines (TBMs). Since their first successful employment on a TBM more than 50 years ago, disc cutter technology has constantly evolved, allowing modern TBMs to excavate very hard and abrasive rock efficiently. Disc cutters have also been employed successfully on earth pressure balance (EPB) and slurry machines, cutting rock under water and ground pressure. The range of materials excavated by machines today is broader, excavation rates are higher and cutter costs are lower than ever before, proving the value of investment in cutter development. Disc cutters are used on a range of tunneling equipment, from pipe jacked slurry micro-TBMs less than 1 m (3.3 ft) in diameter to 15 m (49 ft) in diameter, hard-rock boring TBMs. The geological conditions under which they are employed range from sands and gravels, with several bar of water pressure, to extremely hard, massive rock with UCS up to 420 MPa. Regardless of the type of machine or geology, one thing remains constant: changing worn out cutters is costly. When cutters must be changed in the middle of a tunnel, the contractor incurs the cost of downtime as well as the cost of refurbishing or replacing the cutters. In the case of catastrophic cutter failures, the project can be stopped completely for long periods, and the costs mount up rapidly while tunnel production is at a stand still. Catastrophic cutter failures include the occasion when hard-rock disc cutters are failed in groups (called a ?wipeout? phenomenon) and the operator fails to stop the machine, which results in severe damage to the cutterhead. The cause of this can be either an undetected failed cutter propagating damage to surrounding cutters or operator error in steering. Regardless of the cause, the resulting damage can take days or even weeks to repair. When cutters fail prematurely on EPB or slurry machines in certain geological conditions, it is impossible to evacuate the chamber and, therefore, impossible to get [ ] into the chamber to change the cutters. The solution is frequently an unplanned intervention shaft that must be sunk at great cost. The importance of being able to predict cutter life accurately, and in all geological conditions, cannot be overemphasized. For these reasons, cutters have been developed for specific machine types and sizes, as well as for specific geological operating conditions. Different size cutters are required for different size machines. For example, while 483- and 508-mm (19- and 20-in.) cutters are used on large diameter TBMs, it is impossible to employ cutters so large on a small micro-TBM. Also, the cutter must be designed for the specific geological conditions under which it will be operating. The disc cutter rings required to bore extremely hard rock are the most expensive of cutter rings. However, they provide little advantage in weaker rock formations where less expensive rings will do the job as well. It is important to choose the correct cutter for the machine and the geological conditions in order to get the best balance of cost and risk.

Jan 1, 2009

Study on the Effects and Mechanics of Na2SO3 to Chalcopyrite and Galena

Sep 13, 2010

By P. Ulrich, V. Svalbonas

The early to mid 1980s was a period of mining consolidation, and many senior design engineers retired from the mill industry. Similar conditions have existed in the last few years. This creates a loss of a tremendous amount of experience. This paper is a look back by two senior mill designers who survived the dips in both time periods. From a continuous design practice of over 25 years, mill designs and fabrication practices are surveyed with a view of identifying what works, and is necessary, and what doesn’t, or is not necessary, in the creation of a safe, economic, long-lived grinding mill.

Jan 1, 2001

By Massimilinao Svetina

In 2010 Danieli & C. S.p.A. put into operation a new Pickling Tandem Mill in Cremona (Italy) at Acciaieria Arvedi, the last Pickling line coupled Tandem Cold Mill (PLTCM) in Europe. The plant was tailor-made to suit the specific requirements of this customer; a very broad range of sizes and grades (IF to AHSS as well as DP and TRIP1000) including ultra-thin hot band can be processed, achieving a total capacity of 1.6 Mt/y. The Danieli & C. S.p.A. Turboflo® process was selected because of its proven efficiency and ability to handle ultra-thin gauges at speeds exceeding 400 mpm in the pickling tanks. All the equipment, i.e. pickling section and rolling mills was provided with the last generation of Danieli market-oriented technologies. Danieli & C. S.p.A. - with the support of Arvedi and feedback from the field - is continuously improving its technical design solutions and optimizing plant operations.

Aug 16, 2017

By Manqiu Xu, Pete Winn, Steve Wilson

"In the flotation of ultramafic ores at Thompson mill, Inco Limited, CMC is used as both a floatable rock depressant and electrostatic serpentine slime dispersant. CMC, being a high molecular weight polymer, creates a serious handling problem in its introduction into the flotation processes. Typically, it is added as a 1-3% solution. This requires an enormous handling facility and makes its metallurgical gains uneconomical.Laboratory studies have shown that dry CMC addition as opposed to wet addition is feasible, as long as sufficient conditioning time is provided. Dry CMC addition into the grinding mill is also possible but its effectiveness is slightly reduced as compared to dry addition after grinding mills. Dry CMC addition using a vibratory feeder into the mill discharge is successfully applied in the treatment of ultramafic ores at Thompson mill.INTRODUCTIONManitoba Division MineralogyAt Inco’s Manitoba Division, two distinctly different sulphide ores are processed at the Thompson mill - primarily by froth flotation. The Thompson and Birchtree mines are both located within the Thompson Nickel belt. Sulphide mineralogy is relatively simple and includes both hexagonal and monoclinic pyrrhotite, pentlandite and minor chalcopyrite hosted in metasedimentary and metavolcanic rocks. The significant difference between the two mines is the amount of ultramafic rock associations in the host material. Increasingly, more of the ultramafic associated ores from the Birchtree mine are being processed through the mill with a characteristic poor metallurgy."

Jan 1, 2000

By C. Ringas

Pipelines are used extensively in industry to convey various products. Internal corrosion of pipelines can lead to perforation and leakage of the product. A growing problem, not often accurately recognized, is internal corrosion of pipelines caused by bacteria. Microbiologically-induced corrosion (MIC) refers to corrosion caused by a variety of micro-organisms. This form of corrosion is not widely recognized in many industries, although it is widespread and causes many corrosion problems in pipelines, both internal and external. Sulphate-reducing bacteria (SRB) are responsible for the bulk of the corrosion problems caused by MIC. Corrosion caused by SRB is found extensively in water pipelines conveying raw, potable and waste water, as well as in pipelines conveying slurries. This problem also occurs in pipelines conveying crude oil. This paper describes internal corrosion problems of slurry pipelines caused by bacteria and outlines mitigation methods to improve slurry pipeline integrity, thereby extending the life of such pipeline

Jan 1, 2007

By G. Bellefleur, K. Stevens, E. Adam, D. Synder, G. Perron, C. Müller

The Downhole Seismic Imaging consortium was initiated by the Geological Survey of Canada and three Canadian mining companies to assess the usefulness of borehole seismic techniques for the exploration of massive sulphide deposits within areas of steeply dipping stratigraphy. Field tests were conducted over two sub-economic massive sulphide deposits located in Norman West, Ontario, and Halfmile Lake, New Brunswick, using various shot configurations and a three-component borehole receiver array. The Norman West deposit, or structures associated with the deposit, produce detectable seismic reflections as far away as 1500 m. However, these reflections are difficult to distinguish from fault reflections and lithological contacts near the base of the Sudbury Igneous Complex. At Halfmile Lake, the rock properties are favourable for direct orebody detection. The Halfmile Lake deposit has a clear but relatively complex seismic signature on the downhole data, showing not only P-wave reflections, but also strong reflected S-waves and modeconverted waves. Such prominent S-waves and converted waves have not been recognized previously in borehole or surface seismic data acquired over massive sulphide deposits. These waves add complexity to the interpretation but provide additional imaging capabilities. Reflected S-waves and converted waves should be considered when designing seismic surveys for mineral exploration.

Jan 1, 2004

THE science of topography deals with the various natural and physical features of the earth's surface. These features are determined by the manifold constructive and destructive processes of nature, and their many diverse forms and characteristicsare dependent primarily upon geologic structure. Thus it is that a close relationship exists between the rocks of a region and the topographic features of the lJountry wherein they occur. Again, the existence of all sorts of mineral wealth is dependentupon the nature of the rocks, and their extension is directly connected with the topographic features represented upon the enclosing land-area.In studying any district with a view to deciphering its geological structure, to locating any mineral deposits it may contain, and to ascertaining, so far as a surface-examination may show, their probable and economic possibilities, it is therefore ofprimary importance to have at hand a correct topographical map of the area under investigation.GENERAL REMARKSThe actual amount of topographic detail shown will depend upon the money and time available for topographic surveying and upon the scale upon which the final map is to be produced...

Jan 1, 1912

This paper summarizes the progress of geological exploration at North Broken Hill Ltd.The North Mine orebodies occur in knots of minor folds on a simple limb structure which is itself highly folded, giving rise to two distinct orebodies pitching N. at av. 42° down to 2,920-ft. level, where the pitch steepens to near vertical as a result of complementary shear movement on the Globe-Vauxhall Crush Zone.The lack of adequate marker beds and top and bottom relations makes the resolving of the complex structural environment of the orebodies most difficult.To test the deeper ground of each side of the De Bavay Fault on the 2,600-ft. level the footwall drive was extended 3,556 feet and over 20,000 ft. of drilling completed from three transverse fans, only one of which intersected the orebodies due to steepening of pitch.The problem of locating the North Mine orebodies N. of the DeBavay Fault remains speculative because the exact position of them S. of the fault is still unknown. Exploration beyond the fault in the search for ore had two lines of mineralization to consider, an eastern one through Cosgroves-Round Hill, long regarded as the continuation of the main lode, and a western one passing through Silver Hill Silver Peak.From surface 45,000 ft. of drilling was completed in five sections, establishing that the structure was dominantly synclinal with a flatdipping E. limb, the W. limb and adjoining structures being involved in the Globe-Vauxhall Crush Zone. Mineralization, though weak, was remarkably persistent but the economic mineralization exposed at surface has not persisted with any continuity.Deep exploratory drilling below the bottom level (3,370 ft.) has established high-grade ore to a depth of 4,095 ft. and also has proved its existence within the Globe-Vauxhall Crush Zone.INTRODUCTIONThis paper summarizes the progress of geological exploration at North Broken Hill Limited from the inception of the Geological Department in 1941 until the end of 1955. The writer has drawn freely on departmental records for the period prior to 1947.

Jan 1, 1956

By W. Petruk

Imaging is a fundamental requirement when characterizing minerals, ores and related products. Images are used for presentation, texture analysis, characterization, image analysis, identification, etc. The image mode that is utilized is dependent upon the application, mineral properties and available instruments. Different instruments produce images that display different features; in order of increasing complexity they are: hand specimens, a non-polarizing microscope, polarizing optical microscope, scanning electron microscope (SEM), low vacuum SEM, microprobe, secondary ion mass spectrometer, staining, cathodoluminescence, tomography and others. Image analysis uses images produced with either an optical microscope or a SEM, but the SEM images are superior in this application.

Jan 1, 2001

By Nick Salisbury, Alan Howard, Scott Tunison

INTRODUCTION Geotechnical investigations for tunneling projects typically use vertical test borings and, to a lesser extent, angled borings. Horizontal drilling applications were often limited to specialty testing programs and to perform probe drilling from a tunnel boring machine (TBM) as part of production tunneling. The former often involved cumbersome setups with skid rigs and cribbing in a pilot tunnel or shaft. The latter usually was limited to generic probing for rock quality and ground water conditions with no sampling. Neither yielded continuous core at production rates suitable for design and construction planning. Conventional vertical investigations still make sense in many instances, particularly for tunnels planned beneath urban settings where truck access is convenient and where the tunnel horizon is not readily accessible via a portal or shaft. However, equipment is presently available to conduct horizontal geotechnicall investigations at reasonable production rates and cost. Advantages include continuously sampling the tunneling horizon and minimizing “access drilling” to get the zone of interest at the underground construction horizon. Horizontal boring lengths of up to approximately 800 m are considered feasible and those in the range of 150 to300 m are now routine. These capabilities make horizontal borings an attractive option to consider when looking at deep tunnels beneath ridges, especially where access is limited. Fewer drilling staging sites can also mean reduced environmental impacts when investigating tunnels proposed beneath sensitive lands such as public wilderness areas. Investment in early construction packages to develop portals for investigation access and, possibly in excavating test shafts for the same purpose should even be considered. Potential benefits in the form of achieving improved overall project costs using horizontal borings exist because of the significant additional data collected in the tunnel horizon. For this reason they should be considered during the routine cost-benefit analyses generally conducted for planning geotechnical investigations for tunneling. The authors also believe that collection of such data will reduce Geotechnical Baseline Report (GBR) conservatism and lead to lower potential for

Jan 1, 2005

By John R. Zelonka

Models made by encasing strain-gage networks in epoxy are described and evaluated. With this technique relatively complex models can be constructed in which any number of gages can be located and alined precisely. Although the gages are an integral part of the model matrix, they create no important mechanical or thermal stresses. Model construction techniques and experimental data proved reproducible and reliable. In addition, the sGlution obtained with these models to the problem of the state of stress around a circular hole in a plate subject to a plane stress condition was in agreement with theoretical, photoelastic, and finite-element solutions.

Jan 1, 1970

By S. Ngidi

Palabora Mining Company operates a low grade underground copper mine situated in the Limpopo Province, South Africa. Full production was first reached in May 2005 after a successful transition from an open pit operation to an underground block cave operation. The operation faces a number of technical and operational challenges, not the least being fragmentation of a competent rock mass and external dilution. The cave is subdivided into three main sectors being the east, the west and the central sectors. Caving was initiated from the weaker central sector, which has the majority of its drawpoints located directly under the open pit bottom currently filled with about 130 million tons of waste material from the pit wall failure incurred in 2004. About 48% of the ore reserve has to be extracted from the western sector, which has a much courser fragmentation compared to the other two sectors and only 25% from the central sector with the finest fragmentation. The main constraint during the ramp-up stage has been secondary breaking of drawpoint blockages. Ground-breaking secondary breaking and cave management initiatives and practices have made it possible for Palabora to realize and sustain high production rates.

Jan 1, 2007

By Jamal Rostami, Ebrahim Farrokh

Selection of tunneling method, specially the use of shielded machines for application in deep rock tunnels can be heavily impacted by presence of ground convergence and squeezing conditions. Tunnel convergence is a function of ground conditions (i.e., rock mass behavior, groundwater, in-situ stresses), size of the opening, and TBM operational parameters. The case study of Ghomroud water conveyance tunnel project in Central Iran, which is under construction using a double shield TBM, is used to examine the effect of rock parameters on tunnel convergence and hence on the need for over excavation and shield lubrication to avoid problems with the shield getting stuck. Although it is impractical to perform a continuous assessment of rock mass conditions within the shield or in the lined tunnel, results of field observations and subsequent studies show that the amount of the tunnel convergence has direct correlation with the percentage of fines and large rock fragments in the muck and TBM thrust/torque/ROP. These relationships have been examined and will be presented in this paper.

Jan 1, 2007