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By Clifford McCartney

The PropsetterTM System has been designed and developed to cost effectively solve problems experienced with conventional underground supports used in tailgates, headgates, bleeder entries and as supplemental supports. The PropsetterTM System utilizes the strength and orthotropic properties of timber to achieve initial stiffness and controlled yield as the roof and floor converge. Utilizing a prestressing system developed in South Africa by our parent company, the PropsetterTM prestresses/preloads the roof and floor on installation. The PropsetterTM System consists of five integrated elements which are easily assembled to achieve the objectives of ? Improved support. ? Improved safety, ? Reduced cost, ? Reduced material handling, ? Improved installation productivity, and ? Improved ventilation.

Jan 1, 1995

By S. Shankar

Available literature on the effect of re-entrainment on overall airborne dust concentration in mine airways or the fundamental mechanisms of coal dust re-entrainment in mine atmosphere is scant. Therefore, as part of the Respirable Dust Center's ongoing research, a three part study was envisaged: study of the re-entrainment phenomena of anthracite and bituminous coal dust particles in a wind tunnel under the influence of varying air velocities; study of the same in the Lake Lynn Laboratory Mine of the USBM with both airflow and walking by personnel causing re-entrainment; and mathematical modeling and computer simulation of the re-entrainment phenomenon. In this paper, results from the re-entrainment studies in the wind tunnel and the Lake Lynn Laboratory Mine are presented. Further, the results from the wind tunnel studies are compared with the results from in-mine studies conducted at the Lake Lynn Laboratory Mine of the USBM. Comparing the results from the two studies it was observed that increasing air velocity increased the rate of re-entrainment, but increased time of exposure decreased the airborne dust concentration. Compared to same size particles, a mixture of sizes created more airborne dust concentration when re-entrained. It was also observed that contribution of airborne dust concentration due to airflow was negligible compared to the contribution due to walking.

Jan 1, 1995

By Howard Brown

High purity, high brightness limestone deposits in the San Bernardino Mountains and Mojave Desert region occur in upper Paleozoic carbonate rocks which are part of an upper Precambrian and Paleozoic sequence that unconformably overlies crystalline basement. The Paleozoic strata are divided into formations and members, and correlated with strata of the inner Cordilleran miogeocline. The region has been affected by multiple Mesozoic intrusive, contact, and regional metamorphic events. Structure is complex, and includes polyphase Mesozoic folding and thrusting, and complex Cenozoic structures. The area continues to be seismically active. High brightness (white), high purity crystalline limestone deposits are uncommon because their formation is dependent on several geologic processes which include; 1) depositional environment, 2) contact and or regional metamorphism, 3) folding and faulting, 4) uplift and erosion, and 5) preservation through geologic time. The complex geologic history of the San Bernardino Mountains and Mojave Desert region has allowed the formation of several large high brightness, high purity limestone deposits which are currently being mined or will be mined in the future. Specialty Minerals, Inc. (formerly Ptizer), Pluess-Staufer (California), Inc. and Partins Limestone, Inc. produce high brightness, high purity limestone from several quarries in the San Bernardino Mountains. These active mines combined with undeveloped deposits controlled by Pluess-Staufer in the San Bernardino Mountains, New York Mountains, and Bristol Mountains in the Mojave area, contain proven and or indicated reserves sufficient to sustain production through the 21st century Detailed geologic mapping, intimate knowledge of stratigraphy, recognition of complex structures, sampling, drilling and assay data, are proven tools in the discovery and delineation of high brightness, high purity limestone deposits in the San Bernardino Mountains and Mojave Desert region of southern California.

Jan 1, 1995

By A. J. Jager, J. A. Ryder, M. U. Ozbay

This paper deals with procedures used for designing pillar systems in hard-rock tabular mines operating at shallow depths, typically less than 1000 m. A comprehensive review if current practice identifies four types if pillars, namely non-yield, yield, crush and barrier pillars, and the main principles for designing these pillars are outlined. It is shown that the current design methods for pillar systems in South Africa are mainly empirical, each mine developing its pillar-design methods based largely on practical experience. This results in varying pillar layouts, even between neighbouring mines, despite similarities in geology, and depth if mining. It is suggested that some current layouts may fall short if being the best as regards safety, the maximum safe extraction percentages, or flexibility in accommodating future mining scenarios in deeper or otherwise different geological conditions.

Jan 1, 1995

By P. J. Suardini, S. K. Kawatra

A number of on-stream coal slurry analyzers are presently being developed and commercialized for measuring ash and solids in coal process streams, particularly around flotation circuits. The eventual goal of these efforts is to develop on-line quality control systems for flotation circuits and other fine-coal cleaning operations. As part of this on-line monitoring and control effort, it is important to gain a better understanding of the response of industrial flotation circuits to changing operating conditions. This paper summarizes the results from a detailed sampling program performed at an industrial coal flotation circuit in western Pennsylvania. The testing focused on evaluating the response of the circuit to changes in reagent dosages, operating conditions and feed compositions. The testing indicated that it is desirable to maintain high collector-to-frother ratios to enhance coarse particle flotation. The recovery of fine impurity particles was also proportional to water recovery, due to hydraulic entrainment. Key words: Industrial, Coal, Flotation, Circuit, Reagent, Response.

Jan 1, 1995

By Sen A. K

The Chiria Iron Ore deposit falls within the well-known Horse-shoe-shaped Singhbhum-Bonai-Keonjhar belt in India, where most of the deposits supplying ore to various steel works of Steel Authority of India Limited (SAIL) and Tata Iron and Steel Company (TISCO) are located. With an estimated reserve of about 2000 million tonnes of ore (at 55 per cent Fe cut-off) spread over four contiguous blocks, it is the largest iron ore deposit in India and one of the largest in world. The present study is confined to only one of the four blocks of Chiria viz North Block, comprising an area of 2.11 km2. `Corporate Plan 2005' of SAIL envisages development of a large open cast mine at Chiria to meet its enhanced requirement of iron ore by 2001-02 AD.

Jan 1, 1995

By Ho D, Yang J

The ready availability of powerful desktop workstations, which combine 3D real-time graphics and processing speed better than that of supercomputers of a few years ago, now allows the cost-effective solution of real world geomechanics and underground mining strength simulations. The inclusion of geotechnical factors such as rock joints and porous flow on strength and stability are discussed together with the range of available deformation and failure models for soil, rock and concrete. This paper describes the capabilities provided by finite element graphics and analysis software for modelling and sequential investigation of both excavation and lining, or rock bolting, construction sequences. Examples of the use of finite element models in mining are also included in the paper, together with a discussion of the required people, software and computer hardware resources required to achieve timely and productive results.

Jan 1, 1995

By D. B. Sikka, R. B. Bhappu

Porphyry-type copper-molybdenum (Cu-Mo) deposits typically occur in the Phanerozoic rocks and have been well-documented. During the past two decades, a number of porphyry-type Cu-Mo deposits that range in age from 1055 Ma to 2970 Ma have been identified in the Precambrian rocks of Australia, Canada, China, Finland, India. Namibia and Zambia. The Malanjkhand porphyry copper deposit M.P., India is estimated to contain 789 Mt (870 million st) averaging 0.83% copper (mill headgrade); 0.004% molybdenum; 0.2 g/t (0.006 oz/st) gold; 6 g/t (0.175 oz/st) silver and a cap of 7.5 Mt (8.2 million st) of oxide ore averaging 0.8% copper. The economic potential of the expanded copper mining milling, smelting and refining complex is expected to yield cathode copper 118.6 kt (130,700 st); molybdic oxide 830 t (914 st); gold 1.9 t (61,732 oz); silver 46.6 t (1.5 million oz); sulfuric acid 240 kt (264,500 st), copper from leach dumps 11.5 kt (12,600 st); nickel 24 t (26,400 st); cobalt 84 t (92,600 st); bismuth 16 t (17.6 st); selenium 48 t (53 st), tellurium 4.8 t (5.3 st).

Jan 1, 1995

By Theophili CN, Kapenis AP

Seismic tomographic imaging has been applied to determine the blast induced damage zones in bauxite pillars in underground mining. At the retreating stage, when pillar dimensions are reduced from 8 x 8 m to approximately 5 x 5 m, the' seismic tomographies reveal, through measurements of the P-wave velocities which is a measure of the degree of fracturation of the pillar rock mass, the presence of three zones within each pillar. In the external zone, where velocities recorded are below 750 m/s. extensive pillar damage occurs which is attributed to both the growth and coalescence of pre-existing cracks and even the creation of new cracks in the rock mass. This effect is in agreement with literature, when considering the peak particle velocity as a criterion for rock failure in tunnels. In the intermediate zone, where velocities range between 7S0-1000 m/s, damage to a much lesser extent occurs which is due mostly to growth of pre-existing cracks and widening of their apertures. The inner zone, where velocities exceed 1000 m/s, is considered to be unaffected by blasting. Simple remedial measures of low cost, which are based on blasting mechanics are proposed to minimise the blast induced damage zone and consequently the transition zone.

Jan 1, 1995

By Michael G. King

The primary non-ferrous metals industry is the principal supplier of the minor metals selenium, tellurium and bismuth. It is also a major supplier of antimony. These minor elements are recovered from by-products of base metals production. To ensure that these elements remain available, the cost of production must be compatible with four other factors - method of production, available supply, technological niches, and product stewardship. This paper first describes the relationship between the copper industry and the production of tellurium and selenium. The more complex relationship between the lead industry and bismuth production is then discussed, followed by comments on antimony availability. Product stewardship programs are essential to the growth or certain specialized markets for these metals. Smelters and refineries of non- ferrous metals will play a major role in the recycling of scraps and wastes from these markets. Examples on how such materials can be recycled are given in the paper.

Jan 1, 1995

The geologic settings, geochemistry of host rocks, mineralogy and metal values in modern back-arc volcanic-hosted massive sulphide (VHMS) mineralisation are very similar to those in many ancient polymetallic VHMS deposits. The geology, distribution and styles of seafloor mineralisation in modem back-arc basins, especially the eastern Manus and Lau Basins, southwest Pacific, are compared to VHMS deposits in the Mount Read and Mount Windsor districts of Australia . Based on exploration and research in modem back-arc settings, geologists are now observing the direct analogues of the polymetallic VHMS deposits currently being exploited in ancient back-arc volcanic belts throughout Australia and the world.

Jan 1, 1995

By Corby G. Anderson

For over a century, the Sunshine Mine in Idaho has been a major producer of silver. An estimated 335,000,000 troy ounces of silver has been mined. This has established the Sunshine Mine as the largest single source of silver in the world. Because the dominant silver containing mineral is tetrahedrite, a copper and antimony sulfide, normal metallurgical treatments to recover the precious metal are not practical. Thus, over the course of the company's history, novel, hydrometallurgical technologies have been developed on-site to handle complex, precious metal containing materials. Recently, the use of Sunshine technology has been extended to the recycle of secondary materials. As well, the use of Sunshine technology by other organizations for treatment of both primary and secondary feedstocks containing precious and base metals is an area of growing interest. This paper will provide an overview of Sunshine hydrometallurgical technologies including the applicability of Sunshine technology to the recycling of precious and base metals.

Jan 1, 1995

In order to satisfy environmental and mine operational requirements it is becoming increasingly important to minimise ground blast vibrations at certain locations. These locations are often in soil or on large resonant structures such as grain silos, highway bridges or even the walls of an open pit. A soil monitoring exercise was carried out to evaluate the common practice of coupling vibration detectors to the ground using spikes. At a series of locations in an operating quarry the spiked array response to single blastholes was compared with that of an accelerometer array attached to a calibrated embedded mount. The results clearly showed that the spiked arrays over-estimated the true ground vibration by 46.5 per cent on average, with a maximum observed error of 99.2 per cent. These errors are considered too large for compliance monitoring where accurate vibration levels are required for comparison with prescribed limits. Although spike coupling is convenient, its use for compliance monitoring should be viewed with caution. Unfortunately, however, many manufacturers supply their detectors as spiked arrays. A structural monitoring exercise was also carried out to evaluate the vibration response of a grain silo, highway bridge and a pit wall to the initiation of single blastholes. In this case accelerometers and standard geophones were firmly attached to the bridge which resonated at low frequencies. The results clearly show that, due to their limited low-frequency response, the geophones typically measured only half the true vibration level as measured by the accelerometers.

Jan 1, 1995

By J. Gathje

Normal process development for pressure-preoxidation treatment of refractory gold ores starts with laboratory batch autoclave tests. That is followed by continuous autoclave pilot-plant testing to confirm the process options. This scheme will generally provide good information showing the effects of grind size, time and temperature. And it will indicate whether autoclave preoxidation will produce solids that are amenable to cyanidation for gold recovery. However, several test programs have shown that the cyanide-leaching responses of treated solids from the batch tests can differ considerably from those achieved by the continuous pilot-plant autoclave. It has become apparent that laboratory investigations should extended to include the use of a semicontinuous autoclave test procedure. Santa Fe Pacific Gold conducted several months of metallurgical investigations for a major refractory sulfide gold deposit. The project started with batch tests to investigate and optimize the primary variables, such as grind size, retention time and temperature. These tests were conducted using a representative whole ore composite.

Jan 1, 1995

By L. F. Zeiler

In the past, health concerns in coal mines have primarily centered on those elements which have been essentially inherent to the mining environment. These would include respirable coal mine dust, respirable crystalline silica, excessive noise levels, and diesel exhaust particulates. Commercially-available chemical products are prevalent on mine property. These potentially toxic materials are chemical formulations that can degrease, clean, and lubricate metal parts, separate coal from rock in float/sink operations, and aid in roof consolidation, among other uses. As the general public has become more aware of the hazards of chemical exposures, miners have likewise become more concerned about working with an ever-expanding variety of chemical products on the job. Often, product or chemical specific hazard communication training is inadequate or ineffective, and miners do not know exactly what the ingredients are in the products they handle, or the health hazards involved with their use or misuse. Currently, the Mine Safety and Health Administration (MSHA), by law, enforces 1972 Threshold Limit Values (TLV). MSHA is making preparations to adopt new personal exposure limits for enforcement. The values given throughout the article are 1994 TLV's and are not enforcement standards, but are used for discussion purposes. They reflect the current scientific thinking regarding personal exposure to these chemical agents. An overview of these products is presented, and the potential health hazards associated with their use are discussed. Controls needed to prevent overexposures, such as proper handling procedures and personal protective equipment, are covered. Methods used to collect and identify contaminants are presented.

Jan 1, 1995

By Martin L. Smith

Mine waste characterization and risk assessment currently focesses on water quality and largely ignores boththe charteristics of the wastes themselves and how wastes interact with the environment. Characterization of the parameters that control contamination of pore waters and their migration can quantitatively assess risk and remediation strategies in terms of cost effectiveness and risk reduction. Since mine waste characteristics are spatial, geostatistical methods should be used for characterization and assessment. A number of geostatistical methods are reviewed in terms of their application to mine waste sampling, modeling and risk assessment and management.

Jan 1, 1995

By Terry Mudder

Long-term anaerobic biochemical treatment for draindown of residual solutions is a cost-effective way to close a heap-leach pad. This article presents a laboratory evaluation of anaerobic biochemical treatment of cyanide heap-leach pad solutions. The traditional approach to heap-leach pad closure is to rinse the pads with multiple pore volumes of fresh or recycled treated water. The effluent from an initial rinse is often treated and recirculated until the solutions passed through the heap meet the appropriate numeric and narrative water quality standards. Column rinsing tests are completed during project planning to determine the number of pore volumes of fresh or recycled treated water required to rinse the pad to meet long-term closure requirements. A traditional closure plan generally includes provisions to sample the rinse effluent and rinsed solids (the Meteoric Water Mobility, Procedure or USEPA 1312) to verify that chemical requirements are being met.

Jan 1, 1995

By KNona C. Liddell

The time and spatial dependence of component and species concentrations during in situ uraninite leaching have been modeled using a reactive transport model based on partial equilibrium between reactive minerals and the solution. The flow field is represented by mixing cells in series. The effects of the H2O2, (NH4)2CO3, and NH4HCO3 component concentrations have been simulated, and results are presented for a one-dimensional flow field.

Jan 1, 1995

By Quast K. B

Samples of limestone and micaceous hematite have been ground in a laboratory batch mill using equal weights of either rods or balls. Values of the Schuhmann distribution modulus, a, have been shown to depend on grind time and do not remain constant as often reported. The linear reduction in a with grind time was attributed to a change in grinding mechanisms with time. The product sizing from ball milling limestone showed a bimodal distribution, but rod milling produced a unimodal size distribution. The product sizing from milling micaceous hematite was difficult to interpret due to the major influence of the shape factor on the transition from screen sizing to cyclosizing.

Jan 1, 1995

By John F. Papp

Based on a review of historical domestic and international chromium metal production capacity, production, consumption, trade, and trade literature, world annual chromium metal production capacity in 1995 was estimated to have been 38,300 metric tons, a drop from 43,500 tons in 1994. World chromium metal production and consumption were estimated, on average from 1984 through 1992, to have been 21,000 tons per year. U.S. consumption was estimated, on average over the same time period, to have been 6,200 tons per year. The major world chromium metal producers between 1984 and 1995 were China, France, Germany, Japan, Russia, United Kingdom, and United States. From 1984 through 1992, world trade averaged 8,400 tons per year. Germany and the United States accounted for over 75 percent of imports on average during the same time period. U.S. chromium metal import value rose from under $1 per kg before 1964 to over $6 per kg in 1993. Over the same time period, prices rose from about $4 per kg to about $10 per kg. Chemical specifications have become more stringent. Detailed chromium metal trade, prices, value, chromium metal chemical specification, and production capacity by country are reported. A shift in trade patterns was anticipated as Japan exits production and displaces Germany as the second largest importer and as Russia increases its role in world trade.

Jan 1, 1995