Search Documents

By D. C. Wilder

Deformations during heating and cooling of three drifts in granitic rock were influenced by the presence of faults and shear zones. Thermal deformations were significantly larger in sheared and faulted zones than where the rock was jointed. but neither sheared nor faulted. Furthermore. thermal deformations in faulted or sheared rock were not significantly recovered during subsequent cooling thus a permament deformation remained. This inelastic response is in contrast with elastic behavior identified in unfaulted and unsheared rock segments. A companion paper (Butkovich and Patrick, 1986a) indicates that deformations in un- sheared or unfaulted rock were effectively modeled as an elastic response. We conclude that permanent deformations occurred in fractures with crushed minerals and fracture filling or gouge materials. Potential mechanisms for this permanent deformation are asperity re-adjustments during thermal deformations. micro-shearing, asperity crushing and crushing of the secondary fracture filling minerals. Additionally, modulus differences in sheared or faulted rock as compared to more intact rock would result in greater deformations in response to the same thermal loads.

Jan 1, 1986

By R. L. Grayson, S. Yuan

A stochastic model for evaluating the impact of the reliability and maintainability of shovels and trucks on the operational effectiveness of shovel-truck mining systems is presented. In the model, the Markov modeling technique is used to analyze the operating status of a shovel-truck mining system. Then, simulation is used to study the productivity of a shovel-truck system in a particular state. Finally, the relationship between the effectiveness of a shovel-truck system in terms of productivity and the reliability and maintainability of equipment is established. This relationship may be very useful to mine managers in making decisions in surface mining (e.g., regarding production process control, equipment replacement, and maintenance planning). A quantitative study is given to demonstrate how the reliability and maintainability of equipment affect the system effectiveness and how to pinpoint the parameter that has the most significant effect on the system effectiveness. The quantitative study indicated that in order to improve the system effectiveness significantly, the reliability and maintainability of the equipment need to be improved simultaneously.

Jan 1, 1995

By Howard M. Wells

The future is uncertain. In these circum- stances how can we rationally decide whether to commit funds to an investment that may or may not turn out to be successful? To date no certain answer to this problem has been found, nor is one likely to be found in the future. At best we can attempt to assess the possible outcome in terms of probability, taking into account all sources of information that may be available at the time the decision must be made. This subject is addressed with some trepidation and much humility. Any attempt to fore- tell the future is by its very nature controversial. The purpose of ' this .chapter is to present a proposed rationale for decision making under uncertainty which relates the probabilistic risk of the investment to the capacity of the firm to absorb possible unfavorable consequences if they should occur. It is not the intention to propose a cut-and-dried methodology but rather to examine the conceptual philosophy on which a methodology may be based.

Jan 1, 1979

By Ruoming Gong, Arindam Samanta, Ragula Bhaskar

Three studies conducted at the University of Utah relating to the effect of scrubbers on face airflow patterns, the resulting dust exposure of operators and the development of a throat scrubber for continuous miners are summarized in this paper. The first study involved full-scale laboratory tests to determine the potential dispersion patterns and transport of dust at a continuous miner face, using different ventilation configurations and a scrubber. Concentration maps were developed and potential exposures at operator positions were examined. The second study involved the development of a 3-D numerical model to predict airflow patterns generated by a scrubber at a continuous miner face. The model was designed to evaluate the role of various face parameters on airflow patterns at a miner face and to complement the full-scale testing. The third study involved the design and fabrication of a low profile hydraulically powered continuous miner throat scrubber. The scrubber uses three hydraulic motors and small diameter fans to draw about 3000 cfm (1.42 m3/s) of air and uses a flooded bed scrubber to filter dust particles.

Jan 1, 1993

By Satya Harpalani, Xue Zhao

This paper discusses the results of an experimental investigation to study the release of methane in coalbeds. Absolute porosity of coal samples was first determined experimentally. Following the porosity measurement, adsorption/ desorption tests were carried out to determine the gas content of coal and the rate at which it is released. Finally, micrographs were obtained using electron microscopy and the use of a physical model, developed to explain the gas flow behavior of coal, was justified. The results of this study indicated that the measured absolute porosity of the coal sample was between 5 an 6%. This was significantly lower than the porosity estimated by comparing the micrograph area occupied by the pores and the area of observation for several micrographs, suggesting that coal has a large number of pores with a very small volume. The micrographs also clearly indicated that coal has a large interconnected network of cleats and microfractures. The adsorption/desorption experiments showed a hysteresis between the adsorption and desorption isotherms. Also, the rate of desorption was found to be strongly dependent on the particle size of the specimen.

Jan 1, 1989

By E. Kokinou

The main scope of the present study is to investigate the suitability and sensitivity of the magnetic susceptibility as a pollution monitoring tool in urban areas. For this purpose, a municipal park located in the centre of Chania city, which may be affected by traffic and domestic heating pollution, was selected as the study area. In the context of the present work, magnetic susceptibility measurements were conducted in two phases. Surface soil samples were collected in 2006 from the area under investigation and they were analyzed in order to estimate the spatial distribution of the magnetic susceptibility. One year later, mapping of the magnetic susceptibility has been contacted in situ using Bartington MS2D and MS2F sensors. Additionally, soil samples were collected from selected positions in order to compare the values of the magnetic susceptibility with that estimated in 2006 research. Both investigations indicate high values of the magnetic susceptibility around the park near the roads and in a small area inside the park where a café is located.

Jan 1, 2008

By Donald E. Ranta

Many portions of the mining industry are under intense pressure to reduce costs while commodity prices languish. In response, global Internet-based marketplaces to deliver business-to-business (B2B) e-commerce solutions are being established to reduce costs and improve efficiencies across the mining industry supply chain as well as with customers. Over time these marketplaces will likely evolve to create an integrated supply chain solution, layer in value-added services, and develop mining community portals with industry content. Significant opportunities to help reduce costs and create value are available in mining e-procurement as well as in on-line product sales. The supply chain for the industry is highly fragmented and many mining companies have numerous inefficiencies in procurement. An e-procurement marketplace (or "exchange") can immediately address these inefficiencies and offer numerous benefits to buyers and suppliers. These benefits include improved sourcing options, inventory cost reduction, transaction cost reduction, access to value-added services, lower customer and supplier acquisition costs, improved reach, and improved information flows.

Jan 1, 2001

By A. Platts, K. Leung, P. Rohner, P. Munro, B. Coulter

The Hilton Concentrator treats a laminated stratiform silver- lead-zinc ore to produce separate lead, zinc and bulk concentrates. Commissioning commenced in December 1989. Grinding circuit performance is above design with a mean flotation feed sizing of 80% passing 65 microns at 800 000 tonnes / year throughput. Grinding is done in two stages with an open circuit low diameter : length ratio SAG mill followed by a closed circuit ball mill. SAG mill control philosophy is to maintain a fixed feedrate for stability of flotation and to control mill charge weight to a setpoint with feed water. It is planned to increase throughput to 1 million tones / year in the second half of 1991. Proposed milling circuit modifications include close circuiting the SAG mill by recycling a portion of the ball mill cyclone underflow, increasing the SAG mill speed from 73% to 79% of critical and offloading of lower than feed grade -20mm /+7mm SAG mill ore scats. This paper will describe current mill operating practice with operating data and key mill developments since the beginning of operations.

Jan 1, 1992

By Greg Barfoot, Kurt Keskimaki

The Henderson Mine is located approximately 50 miles west of Denver, Colorado. A project is underway to replace the existing rail system which transports molybdenum ore 15 miles from the mine to the mill using three flight conveyor system. The first conveyor is a 1 mile, high lift conveyor which transports the ore from an underground crushing station to the end of the existing rail tunnel. The second conveyor is 10 miles in length and utilizes the existing rail tunnel to transport the ore from the mine, which is on the east side of the Continental Divide, to the mill located on the west side. The third conveyor takes ore from the tunnel portal to the mill through a series of 7 horizontal curves and inclines up to 15 degrees. The project applies advanced conveyor design to tackle the installation of the system in an operating mine and achieve the highest possible level of reliability. This paper outlines the design process for this system, discusses the options which were evaluated and how the current design evolved.

Jan 1, 1998

By P. E. Richardson, N. P. Finkelstein, Z. Chen

The large band gap and insulating properties of sphalerite have limited the application of standard electrochemical techniques for studying its reactions with flotation reagents. This problem has been overcome by developing electrodes that rely on the surface conductance produced when sphalerite is activated with copper or other heavy metals. A brief exposure of the mineral in copper sulfate solutions results in electrodes that exhibit significant electrochemical activity characteristic of copper sulfides. Voltammetry studies conducted on sphalerite activated in 10-4 M CuS04, solutions at pH 4.6 provide information on both the amount and the nature of the activation product(s). It is shown that copper activation is strongly dependent on the electrochemical potential applied during activation. Activation at potentials increasingly negative of the rest potential causes a progressive increase in the amount of copper on the surface; activation at potentials positive of the rest potential decreases the amount of copper on the surface. The results indicate that both the kinetics of copper uptake and, possibly, the chemical composition (stoichiometry) of the activation product are controlled by the electrochemical potential.

Jan 1, 1995

By B. K. Baird, P. C. Satchwell

The application of cutoffs during and after pit optimization is examined for a lower-grade multimetallic copper deposit. Pit optimization requires calculation of the net revenue associated with each mining block. The calculation incorporates parameters such as metal prices, grades and expected recoveries, mining and processing costs, smelting and refining charges, and penalty element and royalty charges. Sensitivity analysis during pit optimization reveals which parameters have significant effects on the total contained resource tonnage and total contained nondiscounted revenue in the optimized pit. The cumulative effects of changing several of the more-significant parameters are investigated The application of a copper cutoff grade to a block inside the optimized pit could result in the less-than-optimal extraction of the resource. A block with a copper grade below the applied cutoff could be economic due to the presence of other metals. Conversely, a higher-copper-grade block may be subeconomic. Also discussed are the merits of applying a copper-grade cutoff, an "equivalent-grade" cutoff and a dollar-per-ton cutoff to blocks inside the optimum nit.

Jan 1, 2002

By J. A. Chermak, D. D. Runnells

Sulfide-bearing waste rock, ore and tailings have the potential for generating acid rock drainage (ARD) when exposed to an oxidizing environment. The possibility exists of utilizing the acid produced to react with lime and/or limestone to form a self-sealing cap on the reactive waste rock and tailings. Laboratory column experiments were conducted using acid-generating waste rock with a surface amendment of limestone and/or lime. Artificial rainwater was introduced and allowed to drain through the columns. Results demonstrated that the limestone and lime reacted with the acidic rock, resulting in the precipitation of a hardpan layer of gypsum and amorphous iron oxyhydroxide at the surface. The hardpan layer significantly reduced the effective permeability of the column. Based on the results of this study, it should be possible to create hardpan layers as chemical caps to significantly reduce the infiltration of rainwater and snowmelt into acidic waste rock or tailings material in the field. Unlike traditional capping methods, e.g., clay and high-density polyethylene (HDPE) covers, chemical caps should be self-healing.

Jan 1, 1998

By B. Moudgil, Hassen El-Shall

Particle shape and size distributions are among the most important parameters that affect the filtration efficiency of phosphogypsum in wet- process phosphoric acid production. Cost-effective enhancement in filtration rate is desired by phosphoric acid producers for higher plant capacity and lower operating costs. In this regard, numerous research efforts have been carried out in different laboratories as well as in pilot and plant testing. Nevertheless, changes in phosphogypsum crystal shape and size distribution deserve special attention. In this study, the results obtained in the presence of Crysmod and Hiflo-S5 surfactants are discussed. The influence of such additives on crystal morphology and size distribution are studied under different sulfate contents (supersaturation). The obtained data are correlated with process efficiency parameters such as filtration rate, digestion of rock, and recovery of phosphate values. Up to 60% increase in filtration rate is obtained. In addition, an increase in digestion efficiency and P205 recovery is achieved due to addition of surface active agents. The observed beneficial effects are explained in the light of the changes induced in crystal habit, size, and size distribution.

Jan 1, 1999

By E. Topuz, M. J. McPherson, I. M. Konduri

The research is carried out to investigate the flow mechanics and effectiveness of face ventilation using induction fans, as an effort to provide a more efficient alternative to conventional auxiliary duct or brattice ventilation systems. The induction effects and plume longevity of fluid jets are being studied with the help of a plexi-glass model, using water as the fluid medium and creating a system that is dynamically similar to the flow in mine headings. This scaled model represents a typical 1.5m x 6m x 25m heading connecting to a crosscut. Reynolds Number criteria are used to obtain dynamic similarity of the flow in the designed model to simulate real mining conditions. The role of various parameters such as nozzle position in three dimensions, airway roughness, nozzle geometry, and flow rate in the jet are studied. During the laboratory tests, flow visualization techniques, coupled with still and video photography, were employed to identify the flow patterns. The results indicate that in typical coal mine headings, jet fans can produce effective face ventilation for distance up to 30 meters.

Jan 1, 1995

By J. A. McKeown, B. M. Sanders, A. Dadgar, R. H. Sergent

This paper describes the leaching of gold with Geobrom® 3400 from a very rich (6.2 kg/tonne) black sand concentrate and its subsequent recovery by ion exchange resins and solvent extraction. The dissolution of gold from black sand ranged from 94 to 96%. Gold loadings and recoveries of nearly 100% were achieved by both ion exchange and solvent extraction methods. The kinetics and equilibrium of loading gold onto ion exchange resins and its elution from the resin were studied. The commercial ion exchange resins PAZ®- 4, DOVEX®- 21K, and Amberlite® XAD- 7, and Great Lakes Chemical experimental GLR-30 were evaluated in this work. Diethylene glycol dibutyl ether was used in all the solvent extraction work for gold recovery from Geobrom leach solution. The consumption of Geobrom was about 130 kg per tonne of the concentrate processed. Therefore, the cost of lixiviant to extract 3.11 x l0-2 kg of gold from the black sand was only about $1.00. Based on the electrochemical regeneration of bromine, the economics of bromine process vs. cyanidation were investigated.

Jan 1, 1990

By Mark A. Alspaugh, E. A. “Bud” Viren

The driving force behind most advances in technology is need. In the early 1980s, underground coal miners in the USA wanted to build longer conveyors to handle larger capacities but continue to use fabric reinforced belting with mechanical fasteners. Conveyors with intermediate drives were certainly the answer but achieving reliable designs required a significant learning curve. Basic design methodologies had to evolve including advanced simulation of starting and stopping along with complex control techniques and logic. Some components also evolved as specific performance requirements changed Today, in addition to underground mining, the technology has been used extensively in the tunneling industry where the need is for control of belt tensions to negotiate tight horizontal curves. Even though intermediate drives are not used extensively on the surface yet, the lessons learned will find their way to long overland surface conveyance where smaller components are more available and reliable, and often with less capital cost. This paper will document the evolution of intermediate drive technology over the last 30 years and will show examples of its current use.

Jan 1, 2004

By Noris Del Be1 Belluz

Drilling underground in the Grasberg dewatering drifts has routinely hit water aquifers with high flow rates and pressures. Two types of holes are used. Pilot holes probe ahead of the tunnel development to intersect aquifers ahead of the face. And dewatering holes dewater rock formations that will drain water from the Grasberg pit and allow tunnel development to proceed safely. Recently, static pressures of >8.3 MPa (> 1,200 psi) have been recorded with flows from a 100 mm (4 in.) HQ core hole measured at 5,700 L/min (1,500 gpm). The waterflows can be slightly acidic, necessitating the use of stainless-steel collar gear to resist corrosion. These rates were anticipated and contingencies were planned early on to deal with these conditions. PT Freeport Indonesia (PTFI) established procedures to maintain the safety of the drill crews, to enable coring of the rock, and to maintain the safety of the miners driving the drifts. The collar gear controls the waterflows because these drill holes are a vital source of water for the concentrator.

Jan 1, 1998

By Arafat Ghosheh, Yousuf Abu-Rish, Darwish Amara, Mohammed Baderkhan

The Jordan Phosphate Mines Company is one of the world's major phosphate rock and phosphatic fertilizers producers (the second largest phosphate rock exporter), with ore reserves exceeding 2 billion tonnes, mainly located in the Eshidiya area. The Eshidiya phosphate deposits, 120 km north-east of Aqaba, are of sedimentary origin (as are all phosphate ore in Jordan). Three exploitable beds (Al, A2, and A3) with variable content of P205, CaO, SiO2, etc., are processed in order to produce 68-70,73-75, and 75-77% TCP grades. The A3 bed, which is characterized as the most siliceous containing 40-48% TCP, requires physical beneficiation using wet scrubbing, screening, and desliming by hydrocylone, followed by anionic conventional flotation to achieve 75- 77% TCP grade. For the last 15 years extensive laboratory and pilot tests (including physical, chemical, and mineralogical studies) were carried out. After operating the industrial plant, certain modifications were deemed necessary to adjust the operational parameters and the final flowsheet, which was followed to obtain the targeted quantity and quality of concentrate.

Jan 1, 1999

By T. R. Ellis

The author attempted to concurrently apply the US Uniform Standards of Professional Appraisal Practice (USPAP) and the Australian VALMIN Code to a complex mineral property appraisal assignment and previously to some modest assignments. This led the author into many severe difficulties. These difficulties included the high standards needed in the work of others and information and statements required from the client under the VALMIN Code. The exercises highlighted many positive features of both sets of standards. However, the author concluded that, without modification, VALMIN is incompatible with USPAP and the US regulatory environ¬ment. The author found that VALMIN violates US legal decisions regarding real property appraisal due to its requirement to include many items of business value. The US Securities and Exchange Commission's prohibition on reporting quantitative resource estimates proved to be a severe problem under VALMIN. Some VALMIN requirements could not be met due to the extent and quality of documents specified. Implications and thoughts regarding the development of a set of US minerals appraisal standards are discussed. Management considerations for complex mineral-property appraisal assignments are also presented.

Jan 1, 2000

By R. J. Sweigard, R. V. Ramani

The effects of postmining land use planning are addressed in this paper. These effects may include savings in reclamation costs and increased value of reclaimed land. However, this may result in greater planning costs and possible delays in production. Therefore, an economic analysis was undertaken in an effort to determine the importance of each potential result and to quantify the overall economic impact of postmining land use planning. A discounted cash flow analysis was performed using a surface mine cost model to analyze the sensitivity of selling price to changes in various postmining land use planning parameters. As a result of this analysis, it was determined that the profitability of a project is most sensitive to delays in production, particularly if the delay occurs after major investments have been made. Many methods have been proposed for evaluating postmining land use alternatives (Sweigard and Ramani, 1981). Both quantitative methods, such as benefit-cost analysis (Brock and Brooks, 1968), and nonquantitative methods have been proposed. The application of one specific analytical method is pursued in this paper.

Jan 1, 1988