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By K. V. K. Prasad

Solution of most engineering problems requires, in addition to vast numerical calculations, substantial use of practical judgement and expertise. With advances in applied mathematics and computer technology, the numerical aspects of problem solution have reached a considerable level of maturity. However, it is only recently that approaches like the expert systems methodology have been developed to incorporate the judgemental aspects as well. For rapid development and prototying of expert systems, expert system building tools or "shells" have become widely available. For the expert system developer, identification of the key characteristics of the problem domain and selection of the right expert system tool are of crucial importance. In this paper, the important attributes required in an expert system shell for use in the development of a mine ventilation planning expert system are discussed. These attributes are general in that most engineering problems in mining would have these requirements. Also, the results of an exercise undertaken to evaluate commercially available shells for application to mining engineering problems are presented.

Jan 1, 1989

By M. A. Giralico

Solvent Extraction (SX) technology has undergone significant refinements including outright process changes to achieve greater copper production rates with lower organic entrainment levels. LIGHTNIN has completed a detailed study aimed at improving on the conventional Holmes & Narver and Davy Power Gas type impeller designs1 by optimizing the mixing through the use of high efficiency pumper turbines instead of making system changes as others are doing. Since each individual installation requires a different design head and flow, LIGHTNIN has developed the R320 "family" of high efficiency, curved blade pumper turbines. These impellers are designed to maximize head and flow while reducing entrainment through lower power consumption, less shear generation and turbulence, elimination of air incorporation, production of the optimum droplet distribution, and lower tip speeds. These improvements also maintain the required mass transfer and copper recovery of the traditional impeller designs. The R320 impeller benefits have been quantified using Laser Doppler Velocimetry (LDV) and proven in multiple domestic and foreign installations at flow rates exceeding 15,000 GPM. Design comparisons of this improved impeller type versus traditional technology impellers in head, flow, power and entrainment are presented for review. In addition, the inherent benefits of axial flow, high efficiency impellers like the A3 1 0 and A6000 in auxiliary mix chambers will be discussed. The high flow, low shear characteristics of these patented impellers provide the necessary dispersion stability for mass transfer while speeding phase disengagement in the settlers due to low power and low shear input.

Jan 1, 1995

By G. Lodewijks

Today most belt conveyors used for the transportation of bulk solid materials are driven in a centralized way with all drives in one location. The dynamics of these systems has been studied since the early seventies of the previous century and are well understood. Compared to the more conventional belt conveyor system with a centralized drive station positioned at the head and/or tail of the system, a decentralized driven layout with drive stations distributed along the whole length of the belt offers a number of advantages. However, to make a decentralized driven configuration a good alternative to a centralized driven, the system designer will have to balance these benefits with the increased complexity. The full potential of a decentralized driven system can only be realized if the right balance is found between the locally applied drive force and the motion resistances occurring along the system. From previous research it was found that in a multiple driven belt conveyor system the most dominant belt behavior occurs in the belt section between the tensioning device and the first drive station. In this paper different possibilities are analyzed to improve this dominant belt response and optimize the starting behavior. This can be accomplished by changing the predescribed start up profile, starting the drive stations in sequence rather then all at the same time and altering the locations of the drive stations.

Jan 1, 2008

By S. K. Kawatra, K. J. Shoop

An analysis of an iron-ore processing plant showed that its performance was affected by seasonal temperature variations, resulting in reduced grinding efficiency during the winter months. Laboratory and pilot plant studies were conducted to determine the cause of the observed loss of efficiency at lower temperatures. Two types of experiments were performed: drop tests and wet grinding tests. Drop testing was performed to determine the effect of brittleness and frozen pore water on the breakage characteristics of the ore. The wet grinding tests were divided into laboratory tumble tests and pilot-plant tests. The combined results of drop testing and wet grinding were used to make predictions on the performance of plant-scale autogenous grinding. From the drop tests, it was determined that dry iron ore, basalt and sandstone did not change in brittleness over the temperature range studied (-25º to 25ºC). However, when the rocks were water-saturated, the highly porous sandstone became considerably more fracture-resistant upon freezing, due to "grouting" of the pores and preexisting cracks by ice. This effect was not seen for either the iron ore or the basalt, because they were considerably less porous than the sandstone. Tumble tests on both laboratory and pilot scales showed that both the addition of fines to the test charge and a reduction in temperature caused a decrease in the amount of new fines produced. This reduced fines production was the result of increased slurry viscosity when either the fines content increased or the temperature decreased.

Jan 1, 1998

By A. Davaliev, K. Hrkovic, V. Pavlovic

On the territory of Macedonia in South Yugoslavia primary and dory gold occurences were known since ancient times. Remnants of numerous goafs and remainders of washaries on river terraces and alluviums date right back to the times of Phillip II and his son Alexander of Macedonia and from Roman times, as well as from the Middle Ages witness exploitation of primary and secondary gold. More recent explorations on primary and secondary gold occurrences date from the period between two World Wars. Over that period a number of private companies, each on their own jointly, carried out gold exploration, particularly of alluvial occurrences on rivers emptying into River Vardar, starting from Skopje to the Greek frontier. The latest gold explorations carried out In the alluvium of River Konjska date back in 1976, and in 1978 old terraces of River Konjska were explored. The Visibility Study was prepared on possibilities of exploitation of gold from River Konjska alluvium. In the paper are collected the basic date an all known primary and secondary occurrences of gold, the results of the latest explorations, and the study itself. To-date geological explorations and analyses show very interesting potentionality of River Konjska and River Vardar alluvium, which proves continuing of he further explorations. For the moment, it is necessary to re-explore more complete view of the deposit. After that it will be possible to make complete techno-economical estimation of the auriferious alluviums and the conditions of the evaluations of the alluvial gold. 1. REVIEW OF PRIMARY AND SECONDARY GOLD DEPOSITS IN MAOEDONIA,YUGOSLAVIA 1.1. Primary deposits Scarse data are available for primary gold deposits in Macedonia` being unadequate for clear

Jan 1, 1988

By Erhard M. Winkler

The rapid decay and disfiguring of stone monuments in urban and desert rural areas has challenged conservators to protect stone surfaces from premature decay. They attempt to halt the natural process of stone decay and possibly to restore the original strength lost mostly by chemical weathering and the loss of binding cement. Ageneral solution is not possible because the physical and chemical characteristics must be considered for different stone types. The failures of stone preservation and restoration are greater in number than the cures. The need for repair of stone decay goes back to evidence of Roman replacement of decaying stone. The presence of excess water in buildings has long been recognized. Moisture tends to enter masonry from air in humid climates, a most important but often underrated factor (Fig. 1) suggesting that sealing should be the answer. Undesirable staining and efflorescence result in accelerated scaling. Today, the great variety of chemicals available to the modem conservator for sealing. consolidating, or hardening stone fall into two very different categories: surface sealers and penetrating stone consolidants, or a combination of both. SEALERS Sealers develop a tight, impervious skin which prevents access of moisture. Surface sealing has saved monuments from decay by eliminating the access of atmospheric humidity. Pressure tends to develop behind the stone surface by moisture escape. Efflorescence, crystal growth action, and freezing can cause considerable spalling (Anderegg, 1949). Flaking results when moisture is trapped behind the sealed surface. Yellowing and blotchiness are also frequently observed. The following sealants are in common use today: linseed oil, paraffin, silicone, urethane, acrylate, and animal blood on stone and adobe. Extensive cracking and yellowing has resulted soon after application. In the past many such treatments have created more problems than cures: 1. Linseed oil and paraffin have been in use for centuries. Embrittlement and yellowing occur rapidly because these are readily attacked by solar ultraviolet radiation. 2. Animal blood as paint has temporarily waterproofed adobe mud and stone masonry. The origin of blood paint has a religious background rooted in the Phoenician and Hebrew cultures. Instant water soluble dried blood can substitute for fresh blood. Winkler (1956) described the history and technique of the use of blood. 3. Silicones have proven very effective and are long lasting. In contrast, acrylates, urethane, and styrene are generally rapidly attacked by UV radiation (Clark et al., 1975). Sealing of Different Rock Types Granitic rocks have a natural porosity traced to 4.5% contraction of quartz, during cooling of the parent magma, compared with only 2% contraction of all other minerals; protection against the hygric forces may require waterproofing of granite in some in- stances. The Egyptian granite obelisk in London is an example. Soon after its relocation from Egypt to London, Cleopatra's Needle was treated, in 1879, with a mixture of Damar resin and wax dissolved in clear petroleum spirit; surface scaling became evident after half a year of exposure to the humid London atmosphere. The treatment of the ancient granite monument from Egypt has denied access of high relative humidity (RH) in London to the trapped salts inherited from the Egyptian desert and has protected the monument from decay (Burgess and Schaffer, 1952). The sister obelisk set up in Central Park, New York City, has fared less favorably because similar treatment was done too late, only after the salts hydrated and hundreds of kilograms of scalings disfigured the obelisk surface (Winkler, 1980). Surface coating of other common stones may be needed. Crystalline marble absorbs moisture from high RH atmospheres: dilation may ensue when curtain panels bow as the moisture starts to expand during daily heating-cooling cycles. A good sealer may prevent the moisture influx provided that no moisture can enter from the inside of the building. Limestones, dolomites and all carbonate rocks are subject to dissolution attack by rainwater, especially in areas where acid rain prevails (Fig. 2). The interaction of sulfates in the atmosphere with the stone can be halted by waterproofing to avoid the formation of soft and more soluble gypsum. The stone surface attack can be diminished if nearly insoluble Ca-sulfite crusts can form, instead of Ca-sulfate. Replacement of fluorite or barium compounds at the stone surface acts as a hardener, rather than a sealant. Sandstones have generally high porosity and rapid water travel can occur along unexpected routes and from any direction. Any surface sealing may do more damage by scaling and bursting than if the stone is left without treatment. Sealing of sandstones is therefore not advised at any time. Testing the efficiency of sealants: Several authors discuss waterproofing materials, silicones, urethanes, acrylates and stearates, as to their water absorption, spreading rates of water on the treated surface, water vapor transmission, resistance to efflorescence, and general appearance (Clark et al., 1975). De Castro (1983) measured the angle of contact of a microdrop (0.004 cm3) on a stone surface as characteristic of the wettability. Laboratory tests and limited field performance are described by Heiman (1981). The crest of a Gothic sandstone arch, which was sealed with silicone,

Jan 1, 1994

By S. Mathur

The southern Florida phosphate deposits that will be mined in the future contain significant amounts of dolomite. Because high MgO levels are undesirable in phosphoric acid production, several flotation schemes for the removal of the dolomite have been attempted. Alternatively, selective flocculation has been suggested as a potential process. A high MgO rock was simulated with a 30:10:60 mixture of apatite, dolomite and silica, respectively. Single mineral selectivity was observed in the apatite-silica and dolomite- silica systems using Polyacrylic acid (PAA) and Poly(ethylene oxide) (PEO) flocculants, respectively. However, no single mineral selectivity was observed in the apatite-dolomite system using PEO. Heteroflocculation, suspected to be the major reason for the loss of selectivity, was minimized by the addition of a site blocking agent (SBA), consisting of a lower- molecular-weight fraction of PEO. Process parameters such as size reduction schemes, flocculant/SBA dosage and pH were investigated to achieve the desired separation. The selectivity obtained in binary mixed-mineral tests was also achieved in the ternary mixed-mineral system, namely, the apatite-dolomite-silica system. In this report, surface chemical characterization of the samples and their flocculation behavior are discussed.

Jan 1, 1995

By F. M. Doyle, C. V. Diniz, A. H. Martins

A proposed process for the direct production of battery¬grade Mn02 leaches manganese ore with HCl to remove heavy metals selectively. The acidic manganese chloride solution produced is contaminated with Cu, Ni, Co, Pb and Fe at levels that preclude immediate utilization. This paper reports on screening tests to measure the uptake of Cu, Ni, Co, Pb, Fe and Mn from acidic chloride solutions onto different chelating ion exchange resins. Dow M-4195, which contains the bis-picolylamine,functional group, showed promise for detoxifying manganese chloride process solutions. Column ion-exchange tests demonstrated the ability of this resin to produce pure manganese chloride solution from an acidic manganese chloride leach solution contaminated by Cu, Ni, Co, Pb and Fe.

Jan 1, 2000

By A. G. Naguib

In essence, any magnetic separator operates on the basis of imparting a preferential magnetic force on particles of higher magnetic susceptibility which are to be separated from particles of lower magnetic susceptibility. A certain amount of directional deviation to the particles takes place thus allowing for collecting each category of particles separately. The forces in action on particles in a wet magnetic separator of the established designs can be analyzed in a simple manner as shown in Figure 1.

Jan 1, 1972

By Erich U. Petersen, Robert B. Coleman, William J. Tafuri, Donald M. Hausen, P. R. Taylor, Douglas N. Halbe, D. W. Rodolff

The definition of refractory gold ores and concentrates, including mineralogical characteristics, is reviewed. The chemistry of roasting and process conditions such as feed size, temperature, and time are discussed. A typical metallurgical program for developing a roasting process scheme is presented. The application of various types of furnaces for roasting is described. Requirements for scrubbing off-gases to meet environmental air emission regulations, and general information regarding engineering design parameters for roasting are presented. Roasting is sound technology for processing refractory ores and concentrates, but it is essential that the metallurgy of each ore or concentrate is well defined before commercialization. A fluid-bed roaster is the preferred type of furnace for roasting. Environmental regulations for air emissions must be carefully addressed.

Jan 1, 1990

By Omar A. Muhtadi, R. Bruce Thorndycraft, David A. Milligan

9.1 INTRODUCTION Precious metals in a leach solution are extracted, concentrated, and purified to complete the process begun in the heap and to produce an end product which will provide an economic payback to the mine developer/operator. Several different processes are required to convert the dissolved precious metals into pure metal bars. This chapter discusses the actual production of metal once it has been recovered from the pregnant leach solutions by the zinc cementation (Merrill -Crowe) or carbon adsorption processes. Metal production is generally taken to mean the production of a fairly pure "dore" bar. This chapter also reiterates some information from Chapter 8 in a slightly different context, since the focus of Chapter 8 was a fairly detailed description of the two actual recovery processes, whereas the focus of this chapter is metal production. The sale of an intermediate precious metal product is possible (as opposed to the production of dore bars at the mine site); however, the value of the precious metals is reduced by the various charges and risks associated with precious metal processing. For this reason, most operators choose to produce the most refined metal possible in order to maximize project economics. Precious metals may be extracted from the leach solution by both conventional and unconventional processes. The conventional processes are activated carbon/electrowinning (ACE) and zinc precipitation (ZIP). The unconventional processes are resin ion exchange, solvent extraction, and direct electrowinning. A typical ACE process has two circulating loops. The first loop adsorbs the cyanide-metal complexes from the dilute leach solution onto the activated carbon. A second, separate solution loop removes the cyanide-metal complexes from the activated carbon into a strong solution, the electrowinning electrolyte. Activated carbon is transferred from one fluid loop to the other. The operating cost of the ACE process is directly proportional to the quantity of carbon stripped and thus to the quantity of precious metal produced. A typical ZIP process contains a single circulating loop. The solution is filtered, deaerated, contacted with zinc, and filtered again. The barren leach solution is then returned to the heap. The zinc sludge recovered in the

Jan 1, 1988

By Rudolf Kvapil

INTRODUCTION Sublevel mining is a mass mining method based upon the utilization of gravity flow of the blasted ore and the caved overlying waste rock mass. As with any other mining method, sublevel caving has advantages and dis¬advantages which must be carefully considered and evaluated. The major advantages of sublevel caving are dis¬cussed as follows: Because all of the mining activities are executed in or from relatively small openings, sublevel caving is one of the safest mining methods. Drifts, which are the pri¬mary working places, are distributed in a uniform pat¬tern on all levels. Normally the maximum dimensions of the sublevel drifts are about 5 m wide and 3.7 m high. The transportation drifts can have the same section, or the height may be increased to about 4.5 m when trucks are loaded in the transport drifts. The stability and safety of such drifts in competent rock can be easily controlled by smooth blasting or by a combination of smooth blasting with shotcreting. In less competent rock masses, stability can be achieved by combined reinforc¬ing, for example, by a combination of smooth blasting, shotcreting, and rockbolting. The major mining activities can be broken down into three groups: drifting and reinforcing; ore fragmenta¬tion, i.e., production drilling and blasting; and ore draw¬ing, loading, and transportation, and all are relatively simple. Because of the repetitive nature of the mining system, one can standardize almost completely all min¬ing activities. This means that a high degree of work efficiency can be achieved. Because the components of mining production in sublevel caving can be standardized, a high degree of mechanization is possible. In modern sublevel caving the sections of drifts and tunnels are sufficiently large to allow the introduction of large trackless mining equip¬ment. The advantages of a trackless system can be then broadly utilized not only for direct mining but also for all services, including the transportation of mining per¬sonnel to the working place. The flexibility of mining is very good. Standardiza¬tion and specialization of mining activities and equip¬ment on separate levels (lower level or levels in de¬velopment, upper level or levels in production mining) together with the trackless system yield a high degree of flexibility. This allows a rapid start-up of mining and good flexibility in making production rate changes. The method lends itself to good work concentration, organization, and working conditions. Normally, on the lower levels, various phases of development are under¬way. Upper levels are in various stages of extraction. Therefore the work can be easily organized into a sys¬tem which excludes interference between mining activi¬ties. Safety of mining (in small dimension openings), good work organization, high mechanization using large modern mining equipment, etc., comprise very good working conditions. Naturally such a system enables a high work concentration and rationalization of separate specialized mining activities and therefore mining by sublevel caving can be effective and relatively in¬expensive. The major disadvantages of sublevel caving, on the other hand, are: There is a relatively high dilution of the ore by caved waste. Various types of ore loss can occur. When the ex¬traction limit (that point yielding the maximum accept¬able amount of dilution) is reached, the remaining highly diluted ore represents an ore loss. Some ore is lost in passive zones located on the level of extraction between the active zones of the gravity flow. Part of the ore from these passive zones can be recovered together with ore extraction on the lower sublevel, but some un¬diluted and often not fragmented ore located in passive zones above the plane of the footwall is lost. In gen¬eral, these losses are larger as the inclination of the ore body and the footwall is reduced. A relatively large amount of development is re¬quired. This includes transport drifts, usually located in the footwall waste rock on each sublevel, and sub¬level drifts, which connect the active mining areas to the transport drifts and as a result are partially in ore and partially in the waste rock of the footwall. The waste rock length increases as the inclination of the ore body and footwall decreases. It also includes orepasses, used for transport of the ore or waste from the separate sublevels downward to the main haulage level, and normally driven in waste; and inclined drifts or tunnels, which provide a connection for the trackless equipment between the main haulage level and the separate sublevels and are driven in waste. Finally there is the de¬struction of the surface through subsidence. To maximize the ore recovery, minimize the dilu¬tion, and achieve a high efficiency of mining by sub¬level caving, good data regarding the gravity flow pa¬rameters for the blasted ore and the caved waste are of utmost importance. The exact type and amount of data required depend upon the purpose and needs of the study. For the first feasibility study, it may be sufficient to utilize the data from other sublevel caving operations with similar conditions and circumstances. For any higher level of mine planning it is clear that more exact data, including analytical and experimental analyses up to full-scale in-situ testing, are necessary. Basic gravity flow principles and design guidelines for the application of the sublevel caving mining method are presented in the following sections. Although some¬what simplified, they should provide a basis for mine planning and operation. The gravity flow principles described can be effectively applied to other mining situations, with some modification. Also, steep dipping coal seams can be effectively mined by modified sub¬level caving.

Jan 1, 1982

By E. Woodburn, R. P. King, R. Putman

Flotation plant simulation, a relatively recent methodology in mineral processing, is defined and corresponding uses are discussed. Typical simulation structures are compared. Current problem areas exist although these are not insurmountable. Following a brief state of the art discussion, the N. I. M. simulation program is reviewed. In general, digital plant simulation is expected to be of substantial benefit in the near future.

Jan 1, 1976

By R. Buchan

A number of mineral processing techniques have been adopted for the separation of the plastics making up a typical beverage bottle, and a complete flowsheet developed. Thus, size reduction, heavy media separation and flotation were used to separate PE, PVC and PET from their mixtures with cellulose fibers and aluminum, which makes up the cap of such bottles. It is shown that while heavy media separation allows the separation of a PVC/PET mixture from the solid waste, froth flotation can be readily used to separate PVC and PET from a mixture of the two. For this purpose, the differential action of an alkaline aqueous solution (PH=II) which contains methanol and MIBC as surface tension control agents has been found to be a suitable flotation medium. This paper reports some aspects of the flotation flowsheet developed for the separation of plastics from municipal solid waste mixtures and PVC from PET.

Jan 1, 1995

By M. M. Champion

INTRODUCTION Since the first introduction of explosives into mining operations, safety considerations have prohibited the use of machinery in association with the explosives. Only within the last 25 years has this situation changed appre¬ciably; the closest thing to "machinery" used by a powderman in the "old days" was his wooden tamping stick. With the blackpowder and dynamite used during the first 150 or so years of mining blasts, substituting a drill steel or a metal "spoon" invited serious disaster. With the advent of ammonium nitrate-fuel oil (ANFO) explosives (1950s) and water-gel explosives (1970s) for underground blasting, machinery started to play a large part in blasting procedures. The lower sensitivity of ANFO and water gels allows these prod¬ucts to be loaded in a variety of safe ways. Not only has this meant cost savings in labor and blasting materials, but it has also resulted in whole new mining concepts where the limitations of dynamite previously made those concepts uneconomical, impossible, or excessively risky. Increasingly (totally for some mines), the traditional tamping stick has given way to a variety of pneumatic machines for loading explosives and blasting agents. The resulting blasting operations have become safer, more efficient, less uncomfortable for personnel, and a major step forward in mining technology. ANFO LOADING EQUIPMENT Three basic types of loaders are used for ANFO explosives, these being the pressure-vessel loaders, Venturi loaders, and combination loaders. Pressure-Vessel ANFO Loaders ANFO consists of prilled ammonium nitrate (porous pellets I to 2 mm in diam) and fuel oil in the appro¬priate 94 to 6% blend. The material is fairly dry, pourable, and easily conveyed by an air stream. One device or system for handling (hole loading) ANFO is the pressure-vessel loader. ANFO is dumped into the vessel or "pot," and the vessel then is pres¬surized. The ANFO is conveyed out of the bottom of the vessel into a semiconductive hose that has been inserted into the blasthole. Fig. 1 illustrates a typical pressure-vessel loader in use. Applications: The use of pressure-vessel loaders is widespread in room-and-pillar mines, including salt, potash, trona, lead, and other rubber-tired mines where the heavy pressure vessels can be mounted on a vehicle for transport from face to face. The vessel often is large enough to hold eight or more 23-kg (50-1b) bags of ANFO, so several faces can be loaded before refilling. Pressure-vessel loaders also are suitable for effec¬tively loading long holes such as those that are 6 m (20

Jan 1, 1982

By Robert M. Stevens, Arnoldo Acuña

INTRODUCTION In the early 1950s, underground miners and tunnel¬ing contractors were experimenting with ways to supple¬ment or eliminate track-bound loading and hauling equipment. Diesel-powered crawler and rubber-tire mounted front-end loaders and trucks designed for use on the surface were being modified and tried with limited but encouraging success. Miners began working with interested manufacturers to explore the develop¬ment of vehicles specifically designed to meet the de¬mands and constraints of underground material han¬dling. By the mid 1960s, load-haul-dump (LHD) vehicles were firmly established as a fundamental part of what has become known as the "trackless" mining concept, used in many mines and many countries around the world. The flexibility, mobility, and versatility of these units have given the industry a useful tool and have added new dimensions to mine development and produc¬tion. Many old mines have been redesigned to accom¬modate these trackless vehicles, and few new mining plans have failed to find some use for the concept during some phase of development and production. By 1977, several manufacturers in several different countries were producing a variety of LHD vehicles to meet the growing worldwide demand. GENERAL DESCRIPTION LHD vehicles combine certain characteristics of conventional front-end loaders and dump trucks, spe¬cifically designed for materials handling in underground mining and tunneling. The design intent is to provide one vehicle with one man, with the vehicle loading itself, hauling the load over level or inclined haulageways, and dumping the load. A typical production cycle of the most popular units has the operator driving the vehicle forward, forcing the bucket into the muck at or near floor level, and using the tractive effort of the vehicle and the prying action of the bucket to roll out and tilt back the load as shown in Fig. 1. With the bucket rolled back into the carrying position on the boom and the boom resting on the main frame of the vehicle, the load is hauled (trammed) to the dump point as shown in Fig. 2. At the dump point, the boom is raised, the bucket is rolled forward, and the load slides out as shown in Fig. 3. After dumping, the bucket is rolled back to the carrying position, the boom is returned to rest on the main frame, and the unit is driven back to the loading point for another load. There are two other types of LHD units that are slightly different in the cycles that they perform. One uses a hopper arrangement carried on the front of the machine, with a small bucket mounted ahead of the hopper. Several passes with the small bucket load the hopper, which is dumped by opening its floor. Al¬though this concept is several years old, it has gained less than 0.5% of the total market. The most recent LHD concept differs in that it has one bucket nesting inside another. The smaller inner bucket is loaded first, and it is then tilted back and above the larger bucket. When the larger bucket has been loaded, it is rolled back, and the total load is trammed to the dumping point. The dumping operation tilts the buckets in the reverse order from that of the loading operation. The impact of this new concept on the mining industry has not been measured yet. This chapter concentrates on the LHD vehicles employing the cycle described by Figs. 1 through 3, since these LHD units constitute an estimated 99% of the units in current use. MAIN VEHICLE FEATURES In general, the LHD vehicles available from most manufacturers share the same basic features.

Jan 1, 1982

By T. Negeri, Y. Breau, M. Plante, A. Orumwense

As part of a joint project on fine particle processing, sponsored by the Consortium de Recherche Minérale (COREM), Natural Resources Canada (NRCan) and Hydro-Quebec, two flotation plant circuits were sampled to identify and quantify the causes of mineral losses within several particle size ranges. Size distributions, size-by-size assays and global chemical assays (Cu, Zn, Fe, S) were determined for the major streams. Size distributions were measured in 13 classes by sieving, cyclo sizing (-45 µm), and laser beam diffraction analysis. BILMAT, a material balance computation software package, was used to optimise the sampling, to estimate the unmeasured variables, and to assess and improve the quality of the information generated. The methodology has been extended to correct cyclo sizer data and reduce discontinuities of up to 20% at the transition from sieves to cyclo sizer. The paper describes the methodology and the main conclusions emerging from material inventory of the flow sheets.

Jan 1, 2003

The Longwall Strata Control and Maintenance System (LoSCoMS) is designed to monitor shield pressures in real-time from longwall faces and to provide on-line information related to underground strata behavior and longwall mining operation. The information includes shield pressure data with statistical analysis of setting, developing and final pressures, prediction of shield pressures for the following shift or day, etc. and maintenance data on the shields. The LoSCoMS has been installed and tested at Shoal Creek Mine operated by Drummond Company, Inc. The system is providing valuable information to mine operators for better understanding of underground behaviors. As a result, it has become an effective tool for minimizing ground control hazards and reducing out of seam material.

Jan 1, 1997

By Nolan B. Aughenbaugh

Zoning and environmental restrictions on land usage now make open- pit quarrying more and more difficult, especially near urban areas. One option for quarry operators is to go underground for mineral production. While underground-mining costs are higher than those for open-cut work, there are several compensating advantages. In many cases it is possible to produce the same material underground without affecting land values, and the surface is preserved for industrial, residential, or agricultural purposes. Proper planning can yield underground sites which have great potential value for industrial plants, warehouses, or other business uses. It is essential to plan underground mineral extraction using a three-dimensional modular-room architectural concept to fully exploit secondary space utilization. Prior to the start of underground mining an operator must make a careful geological engineering study to deter- mine the suitability of the deposit and must prepare a plan for safe and economical mining for the purpose of converting to secondary usage.

Jan 1, 1974

By J. D. Miller

On the basis of nonequilibrium zeta potential measurements by laser-Doppler electrophoresis, the sign of the surface charge of alkali halides in their saturated brines has been established. The results are generally as expected from simplified lattice ion hydration theory. This recent electrokinetic information coupled with the stability and prevalence of collector colloids in such soluble-salt flotation systems suggests that the selective flotation of alkali halides is due to the adsorption of oppositely charged collector colloids by heterocoagulation. Experimental flotation results confirm this surface-charge/collector-colloid adsorption model and are presented herein.

Jan 1, 1992