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By W. M. Goodwin

The gold district of northwestern Quebec, though it has attracted such widespread attention during the past year, is still in the prospect stage throughout, and one must preface any remarks about it with the plain statement that its capacity to produce gold commercially is still subject to proof. However, this proof may be forthcoming any day, and from widely separated localities. Consequently it is of interest to note some of the features of the region and of the prospects now being developed. First I shall note the relation of this mining development to the province of Quebec and to the Dominion; then will follow a brief resume of the known geological facts; and finally I shall describe briefly some of the more advanced prospects developed during the past twelve-month. Those that have followed closely the fortunes of the new gold-field will find little that is new in what follows, but it may serve a useful purpose for others by bringing together scattered items of information and presenting them as a whole. GOLD MINING AND AGRICULTURE First let us consider the gold belt in its relation to the province of Quebec. Apart from the world-renowned asbestos camp south of the St. Lawrence, it is the only mineral development of major importance the province has experienced. It is the first important development in the province's vast area of Precambrian rocks, most of which remains as yet totally unexplored and unprospected. The relative importance of this first mining camp in northern Quebec cannot as yet be gauged, but it is bound to stimulate an active interest in the other mineral-bearing areas now known to exist, and in the vast unexplored spaces.

Jan 1, 1924

By Mark K. Larson

Researchers at the National Institute for Occupational Safety and Health?s (NIOSH) Spokane Research Laboratory are developing a borehole profilometer to dynamically measure the roughness pro-file of boreholes used to install roof bolts fully encapsulated with resin. Numerical measures of roughness were calculated from profiles of borehole surface roughness to determine potential roof bolt anchorage capacity. The concept of dynamically profiling was proven through the following series of laboratory tests: a sensitiv-ity test using various grits of sandpaper, a known-profile test along a section of a concrete hole, and a simulated borehole test in a pipe with machined grooves. Two profilometer prototypes were devel-oped that measure slight changes in the radius of a borehole using either strain-gauged, spring-steel arms or rigid, steel arms attached to a spring-loaded cone and a linear potentiometer. Both instruments performed reasonably well in the laboratory and were subsequently tested in boreholes drilled in two concrete blocks using different drilling techniques to obtain three different borehole surface roughnesses. A Z2 roughness parameter was calculated with data from the first profilometer, and an average radial increment was calculated from the test results of the second profilometer. Although both instruments were able to readily distinguish the difference between smooth and rough boreholes, the correlation coefficient (r2) for a linear relationship between Z2 and average radial increment was 0.577. Pull tests were conducted with resin bolts installed in the concrete blocks, but maximum pull-out strength could not be correlated to borehole roughness because in each of these tests, failure occurred at the resin-bolt interface. A more sophisticated prototype has been designed to measure surface roughness and also accurately determine the location and tilt of the instrument in the borehole. However, this instrument has not yet been fabricated or tested.

Jan 1, 2007

By Takuya Taguchi, Toshihiro Ogata, Atsuio Inoue, Shigeyuki Sasaki

Highly improved drilling machines and mucking machines have been used for the underground construction. To have rapid construction, the roles of blasting operation ha ve been growing more important. At the most tunneling of present, cartridged emulsion explosives have been used for a blasting in Japan. Under this circumstance, a blasting system of ANFO explosives using loading machine has been used recently for a tunnel blasting. However, ANFO has some problems, such as a useless explosives in wet boreholes, bad blasting fumes and the ammonia gas due to the decomposition of ammonium nitrate in contact with the sprayed concrete in tunnel.

Jan 1, 2005

By P. Bracher

Most efforts to mechanize low seam (narrow reef) mining of platinum ore are presently based on board-and-pillar methods with1.6?1.8 m in reef excavation. This paper attempts to substantiate the benefits of low profile mining: primarily improved head grade with resulting reduced tailings losses. Board-and-pillar equipment supplied by DBT, facilitating1.1?1.2m mining height has been in operation in an Anglo Platinum mine since September 2001. Major aspects of the equipment, battery scoops (LHDs) and rotary bolting rigs, are described and presently achieved results reported. The medium term industry goal is rock breaking without the use of explosives. An outline of present DBT developments is presented.

Jan 1, 2003

Traditional vat leaching has been done on a batch basis, which involves loading the vats, leaching, drainage, washing, draining again, and unloading. As a result of these many steps and the attendent cost of labor, vat leaching is generally not an economic proposition. Also, like heap leaching, there is a tendency for channeling to occur within the bed, whether the leach solution flow is by percolation upwards or downwards. No doubt experimenters over the decades have been enticed by the idea of fluidization induced by upward flow through the ore bed. If the bed could be fluidized, then a continuous flow of material could be set up, dispensing with the high cost of loading and unloading the vat. A quick calculation of solution flow requirements, however, soon reveals that the volume of constant liquid movement necessary to sustain fluidization is prohibitive from a power and cost standpoint. The premise of the Mackie Vat Leaching Jig (MVLT) concept was that the large volume of liquid flow required for fluidization could be achieved instantaneously, and that during this small element of time, the solids would flow under the influence of the hydraulic gradient in the vat. If this procedure could be repeated in a cyclic manner, then a steady-state condition could be set up. Experiments in the laboratory demonstrated that solids flow could be achieved in this manner.

Jan 1, 1991

By Jay L. Hodkinson

Replacement of an aging twin span river crossing in Vermont required a temporary bridge to accommodate traffic during construction. Soils beneath the temporary approach embankment consisted of very soft organic clayey silt underlain by interbedded, loose alluvial fine sand and silt/clayey silt. Reinforcement was required for the southern temporary approach embankment to limit settlement and to increase global stability factors of safety. A ground improvement design was developed using Rammed Aggregate Pier® reinforcement and was included in the contract documents as an FHWA Category II Experimental Feature. Instrumentation intended to document the performance of the supported embankment was installed. Piers were then constructed and monitoring commenced as embankment and bridge construction occurred. Weekly instrumentation data reports indicated continuing excess pore water pressure, settlement, and lateral deformation of the subgrade soils as the embankment and temporary bridge abutment was constructed. In response to the unanticipated monitoring results, further investigation indicated that significant deviations from the conditions and basis upon which the ground support design was developed were made during construction. This paper discusses these deviations and their specific impacts to embankment support performance, how these deviations occurred, the role that the ground support system played in maintaining global stability, measures taken to limit further detrimental impacts to the embankment, and provides recommendations for contract document preparation and construction oversight to prevent similar situations from occurring on future projects.

Jan 1, 2011

By Y. Nien Wang

The Devil?s Slide portion of Highway 1 between Pacifica and Montara is often closed due to the instability of the adjacent slopes. Following many years of public input and careful evaluation of alternatives, Devil?s Slide will be by-passed via two inland tunnels, providing a safe, dependable highway between Pacifica and Montara. For the twin tunnels, each 9m diameter tube will accommodate only one traffic lane. Each tunnel tube will accommodate a 3.6 meter roadway, 0.6 meter and 2.4 meter inside and outside shoulders respectively, and 1.2 meter walkways on each side. Cross passages will connect the bores at about 120 meter intervals and jet fans will provide tunnel ventilation. The twin tunnels are approximately 1,250 meter long and 9 meter wide. Excavation will progress from south to north using tunneling techniques that rely on inherent rock strength for support known as the New Austrian Tunneling Method (NATM). Both tunnels will be excavated at the same time, one tunnel face approximately 40 meters ahead of the other. Staggering the tunnels reduces the likelihood of damage from blasting in alternate tunnels. The work schedule is 24 hours a day, 7 days a week resulting in a 24-month timetable to break through to the north portal.

Jan 1, 2008

By Abbott T. M

Alcoa of Australia operates three Alumina refineries in the South West of Western Australia at Kwinana adjacent to the South suburbs of Perth and at Pinjarra and Wagerup in rural settings 100 and 150 kilometres south of Perth respectively (see Figure 1). Alcoa's total alumina production is currently around five million tonnes per annum and this will increase to 5.5 million tonnes by early 1990. Further expansion of production is likely if current world aluminium demand trends continue. Alcoa's refineries utilise bauxite mined in the nearby Darling Range which is low grade by world standards having around 32 % by weight extractable alumina (by comparison Weipa bauxite yields around 55% alumina). This means that for every tonne of alumina produced two tonnes of solid wastes remain and therefore while we in Western Australia can boast of hosting the largest alumina industry in the world with around 18% of total world production we suffer from having the lion's share or 40% of the world's bauxite residues to dispose of. In its Western Australian setting the management of these residues in a manner which is acceptable to the community creates many challenges. These are primarily due to the mass and volume of waste produced, its chemical and physical characteristics and the environmental features of the local area including close proximity of neighbours, competing land uses and the presence of natural resources such as surface water and groundwater. In addition the trend towards more stringent statutory environmental controls and greater political and community awareness of environmental issues means that we must be able to demonstrate improvements that will reduce the considerable adverse impacts of past practices. Of course we must also try to keep the overall cost of residue disposal as low as possible to maintain our competitiveness with refineries which may have much smaller volumes of waste to dispose of and less environmental constraints.

Jan 1, 1989

By Orville R. Lyons

THE removal of moisture from coal has been a coal-preparation problem ever since the first wet-washing preparation plant was placed in operation. Today, when most of the coal produced in the United States is wetted at the working face when mined, or is cleaned by wet methods, the removal of moisture is a necessity for any one or a combination of the following reasons; (1) to avoid freezing difficulties during shipment, (2) to increase the B.t.u. content, (3) to effect savings in freight costs, and (4) to so improve the coal that it may be used for specific purposes-for instance, in the production of briquettes or the production of metallurgical coke-or so that it can be treated by dry cleaning methods. In general, the amount of water retained by coal particles varies with the size-consist of the coal. Fine coal has a larger surface area per unit weight than does coarse coal, so its capacity for retaining moisture is proportionately greater. The removal of moisture from coarse coal is relatively easy, while the removal of water from minus 10-mesh coal or finer is a major problem, usually requiring an individual solution at each preparation plant. As a result, a multitude of methods and a variety of equipment have been designed to solve both general and specific moisture-removal problems. Definitions In order that misunderstanding may be eliminated insofar as possible, it is necessary to define the terms to be used. The moisture content of any given increment of wet, washed coal is made up of two parts, inherent and surface moisture. Inherent moisture has been defined in various ways and as yet no standard definition has been agreed upon. However, in general, it is considered as the moisture that is present in the coal in the bed. The important point to remember is that coal with any amount of inherent moisture, whether 2 or 20 per cent, will appear dry if there is no surface moisture. Also important is the fact that inherent moisture can be removed, in part, by air drying at atmospheric temperatures. Surface moisture is that attached to the surface of the coal particles or that retained in cracks and fissures other than capillary openings in the coal substance. Essentially, insofar as the bituminous coal and anthracite indus-

Jan 1, 1950

By Richard H. Sprute, Dennis J. Kelsh

Slow-settling, fine-grained suspensions can often be dewatered and densified by applying direct current between buried electrodes. Although water removal rates and power expenditures depend on physical and chemical properties of the treated slurries, metal mine tailings from Idaho, Colorado, and Mexico have responded well in laboratory testing, as have 29 samples of ultrafine coal waste from mines in nine states. This Bureau of Mines report reviews field tests at two Idaho metal mines and describes the recent installation at the Henderson molybdenum mine near Empire, Colorado, and the treatment of coal sludge at a Clinchfield Coal Co. preparation plant near Dante, Virginia.

Jan 1, 1980

By Paul C. Schmall, Thomas Tuozzolo, Arthur B. Corwin

The Lenox Avenue Reconstruction Project involved the excavation and replacement of 750 m (2,500 ft) of deteriorated subway invert concrete, 5 to 7 m (15 to20 ft) below water table in very permeable ground. The Replacement work was done over an 8 month period, while maintaining track service through this subway section. The project was dewatered with a single 125 l/s (2,000 gpm) wellpoint system,750 m (2,500 ft) in length, which was installed from inside the active tunnel structure and configured to coexist in the subway tunnel with operating trains as well as the construction activities. A thin diaphragm jet grout wall was utilized on one end of the site to cut off the flow of water across a difficult geological interface that was situated immediately below the tunnel invert. The thin diaphragm jet grout wall permitted the large 116th Street Station area to be dewatered completely with well points from outside of the excavation.

Jan 1, 2001

According to the Darcy?s law, filtration rate should increase with increasing pressure drop (?P) across a filter cake. In centrifugal filtration, ?P is created by the free water present on the surface of a filter cake. Thus, ?P can become negative when the free water disappears from the cake surface, which makes it difficult to achieve low cake moistures. In the present work, we have developed methods of overcoming this problem by either increasing the air pressure inside or applying vacuum outside a centrifuge. Laboratory dewatering tests conducted using these provisions showed that the moistures of various minerals and coal fines can be reduced to the level that can obviate the need for thermal drying. The new concept has been successfully tested both at pilot- and full-scale, which lead to commercial deployment through Decanter Machine, Inc., under the trade name Centribaric® centrifuge. Keywords: dewatering, hyperbaric centrifuge, pressure drop, Darcy?s law, Centribaric® centrifuge

Sep 1, 2012

By OÆBrien D. R

Up until June 1988, Mount Thorley Coal Handling and Preparation Plant disposed of tailings by two methods. Approximately half of the plant tailings was mechanically dewatered by solid bowl centrifuges mixed with plant reject and was subsequently disposed in mine overburden spoils; the remainder was pumped to tailings ponds. Both future mine planning and environmental constraints could not allow for the long term construction of more tailings ponds so, following evaluation of available dewatering technology, belt press filters were selected for the treatment of tailings in excess of the capacity of the existing solid bowl centrifuges. Commission of the four 2.5 metre wide belt press filters soon showed that marked differences in performance were experienced when treating different coal seams. Further analysis showed that the coal tailings from different seams were quite different in terms of clay mineralogy, and these differences could be correlated with varying degrees of filter performance. Poor filter performance was experienced with coal tailings rich in sodium montmorillinite clays. A number of variables were investigated including in-line mechanical mixing of flocculant and feed slurry, cation exchange reagents such as gypsum, and upstream addition of cationic flocculant. In order to achieve satisfactory performance on the worst tailings, a combination of all of the above was required. In this paper, the reasons for selection of belt press filters and the program of investigations and testwork required to arrive at satisfactory belt press filter performance for the treatment of troublesome bentonitic rich tailings are discussed.

Jan 1, 1989

By F. Peer

In most coal preparation processes, water is a necessary medium, but the presence of water in coal after it has been cleaned has a negative impact on transportation costs, handling and specific energy values. The utilization of super absorbent polymers (SAP) in the nappy application is well known. The concept of utilizing these polymers was investigated for the purposes of dewatering coal and other fines, generated by preparation processes such as flotation. SAPs are granular highly cross-linked synthetic copolymers with excellent water-absorbing properties. The dewatering process is characterized by three main stages: (a) contact of super absorbent polymer with high-moisture fine coal; (b) separation of dewatered fine coal from super absorbent polymer; and (c) regeneration of used super absorbent polymer, by exploiting its response to changes in conditions such as pH or temperature. Preliminary tests showed the separation step to be very difficult. The novel idea of encasing a given amount of polymer in a water permeable cloth solved this problem (of separating the swollen polymer from the dewatered coal). Preliminary tests investigating the effectiveness of the sachets of polymer showed a drastic decrease in the moisture contents of slurries. Furthermore, it was shown that it was possible to regenerate the polymer (still within the sachets) through thermal drying. A full-scale experimental programme was then followed to accurately determine the feasibility of using sachets of SAP. The experimental variables were initial slurry moisture content and polymer dosage. It was observed that the sachets seemed to work fastest and most effectively at high moistures and also at higher dosages of SAP. Regeneration of the polymer was also investigated, using two methods: thermal regeneration and pH-induced regeneration. The experimental variables, for investigating the regeneration process, were method of regeneration and grade of water used. Thermal regeneration at 70°C seemed to work successfully. Although the cost of using thermal energy is still a problem, the safety aspect (fire hazards) has been addressed since the polymer does not ignite when heated, unlike fine coal particles that may do so. The alternative method of regeneration, which exploits the pH-sensitivity of the polymer, was less successful, and further work needs to be conducted.

Jan 1, 2003

The moisture content of clean coal contributes significantly to the product's transportation costs, handleability characteristics and/or energy value. A major contributor to the total moisture is the ever increasing proportion of fine coal in

Jan 1, 1994

By A. H. Shapiro, W. –F. Leung

A decanter centrifuge of novel design was developed for the dewatering of fine-solids slurries having micrometer-range particles that form pastelike, flowable, hard-to-dewater cakes. The design combines a compound beach with a cake flow control structure that allows expressed liquid, from the cake in the dry beach region to be returned to the liquid pool while maintaining a high-solids throughput. To provide optimal performance with various operating parameters (i.e., feed rate, centrifugal gravity, pool, differential speed, concentration of feed solids and slurry type), the cake flow control is adjustable. The second part of the beach is preferably at a zero angle. Tests showed that the new design allows increases in solids dryness and solids throughput. Key words: Dewatering, Centrifuge, Slurry, Fine particles, Beach decanter, Cake-flow control

Jan 1, 2003

By A. H. Shapiro

A decanter centrifuge of novel design was developed for the dewatering of fine-solids slurries having micron-range particles that form paste-like, flowable, hard-to-dewater cakes. The design combines a compound beach with a cake-flow control structure that allows expressed liquid from the cake in the dry beach region to be returned back to the liquid pool while maintaining high solids throughput. In order to provide optimal performance with various operating parameters (feed rate, centrifugal gravity, pool, differential speed, concentration of feed solids, and different slurry types), the cake-flow control is adjustable. The second part of the beach is preferably at zero angle. Tests showed that the new design allows increases in both solids dryness and solids throughput.

Jan 1, 2001

By S. C. Langvik

The presentation named 'Dewatering of fines by Rotary Vacuum Disc Filters' has an opening why the filtration process is important to the Iron Ore Industry. It goes on to describe the various types of dewatering machines which have been used in this industry in the last 30-40 years, and where the vacuum disc filters now dominates. It presents also the most important design changes which have been made during this period to enhance performance. Further are discussed the principles of filtration and the factors and parameters which influence performance and operating costs. As a closing is presented today's ideas and thoughts about what can be foreseen of design modifications and improvements in disc filter design in the coming ten years.

Jan 1, 2001

By Gökhan Çevikbilen, Ümit Karadoğan, Sevde Korkut, Berrak Teymur

This study proposes a methodology for dewatering of mine waste using a multistage process, combining geotextile tubes and anionic polyacrylamide (PAM), which accelerates the recycling process of water for aggregate mine waste facilities. For this purpose, waste from a rock quarry located in Istanbul was investigated. Flocculation tests revealed that the use of anionic PAM at an optimum dosage reduced sedimentation time and decreased turbidity. The compatibility of geotextiles and mine waste conditioned with different dosages of the effective PAM was evaluated by rapid dewatering tests, considering the water content of the filter cake, amount of infiltrated solid content, and rate of filtration. Geotextile dewatering tests were also performed on PAM-free and conditioned suspensions. The dewatering process was optimized by the use of a geotextile tube in two stages: (i) on the unconditioned suspension and (ii) on recovered PAM-conditioned leachate. Directing PAM-free non-hazardous soil-based material obtained in stage i to alternative beneficial uses is suggested, to minimize the volume of waste. Furthermore, recycling of the effluent obtained at the second stage of the proposed method will ensure more efficient water reuse

Sep 29, 2022

By Ralph M. Foecking

The disposal of the phosphate slimes produced by Florida beneficiation operations is perhaps the biggest single problem of the phosphate mining industry. This is an old problem which has not been solved and which is becoming increasingly severe. In a typical phosphate mining operation, the phosphate rock mined is initmately mixed with sand and clay, constituting what is known as matrix. During the beneficiation, the clay and other fine materials are separated usually at -150 mesh, and washed from the phosphate rock in a form of diluted slurry known as phosphate slimes. The quantity of slimes solids and their composition vary considerably with the location but usually represent from 25 to 35% of the ore mined. Because of the affinity that clays have for water, large volumes of water are required to separate the granular material in the matrix forming a dilute slime suspension (1.5 to 3% solids) of colloidal material, which settles very slowly, and thus requires immense impounding areas, which never becomes totally usable land. These ponds also contain about 25 to 35% of the total P205 values mined. The magnitude of the problem represented by the slimes can be appreciated better if we realize that there are around

Jan 1, 1971