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By F. A. Molloy

As a result of feasibility studies made in 1975 a 3-0 seismic reflection survey was shot over part of the Veendam salt pillow during 1978-1979. The Zechstein salt pillow, located in the northeast of the Netherlands near the town of veendam, occurs at a depth of 1400 m and contains three carnallite rich horizons over an interval of 300 m below top salt. MgCl2 brines are produced from these layers as feedstock for a magnesia plant, which starts up in 1981. Prior to the acquisition of the seismic data four wells had been drilled. The thickness of the carnallitite layers encountered in these wells varied between 50 and 125 meters. In view of these variations it was necessary to obtain a reliable isopach of the different layers. The 3-0 seismic survey covered an area of ± 4x4 km with a sampling interval of 20 m in all directions. The data was recorded it an area array using a 120 channel instrument. Final presentation of the data was in the form of 3-0 migrated acoustic impedance cross sections. The quality and resolution of the seismic data allowed reliable structural and isopach mans to be made. It was shown that the carnallitite layers are continuous over the area surveyed, whilst local thickening is "fault" related. Having this information brine production locations could be choosen in the thicker parts, allowing maximisation of production potential whilst avoiding faults and fulfilling mining regulations. A subsequent benefit of this approach is the possibility of using the seismic data to predict ore grade. Using the available wells as calibration points the acoustic impedance response of the seismic at the well was matched to the ore grade found. From these points a synthetic section was made with varying ore grades. Pre¬liminary results are encouraging and the liability of this predictive tool will be evaluated in the light of future drilling.

Jan 1, 1981

A significant technological development is discussed for the processing of certain problem power plant flyashes which contain a high water soluble mineral content and which are known to yield inferior flyash based brick. This development is based on the addition of hydrochloric acid to the flyash-bottom ash-sodium silicate blends used for the production of flyash based structures. Favorable changes are evident in (1) sodium silicate consumption, where often approximately one-half of the amount used for making brick from normal flyash is required; (2) processing costs; and (3) strength and appearance of the resulting freshly formed green and fired structural products. In some high cost instances-(above the cost of 30 dollars or less per thousand brick estimated for normal flyashes) hydrochloric acid additions can replace or reduce other costly additives required with problem flyashes to result in a savings of as much as nine dollars per thousand brick. These developments offer promising possibilities for utilizing problem flyashes as well as flyashes which may come into contact with water soluble, sulfur as a result of the eventual application of certain experimental air pollution control processes.

Jan 1, 1968

By Edwarde R. May

The Flambeau volcanogenic massive sulfide deposit located in northwestern Wisconsin occurs within the southern lobe of the Canadian Precambrian Shield. The steeply dipping tabular body occurs in a complex pile of cyclic schistose intermediate to felsic fragmental volcanics. No chloritic alteration pipe is recognized but adjacent rocks have undergone magnesia metasomatism and subsequently were metamorphosed to the upper greenschist and lower amphibolite facies. Although modest in size the deposit is of special interest in that it has an extensive and well preserved supergene enrichment blanket. Economic minerals found within a pyritized quartz-sericite schist are chalcocite and bornite overlying primary chalcopyrite.

Jan 1, 1976

By E. R. Palowitch

On February 5, 1973, Eastern Associated Coal Corp began shortwall mining in their Federal No. 1 Mine, thus marking the first attempt in the United States at modern shortwall mining, i.e., using a continuous miner to extract coal open-ended from pillars 100 to 200 feet wide, under the protection of a self¬-advancing roof support system (1)1/. Since then, four additional shortwall faces have been operated. While the number of face-years of shortwall experience in the United States is limited, this experience has been anything but uniform. Differences in operator motivation, coalbed parameters, geologic conditions, panel dimensions, and face equipment all have contributed to a wealth of knowledge which can provide guidance for the design of future shortwalls. The purpose of this paper is to review the history of shortwall mining in the United States and to assess its value to the U.S. coal industry in terms of the health and safety of the miner, the percentage of coal recovered, coal production, worker productivity, and relative cost performance.

Jan 1, 1976

By J. L. Parks

Designs, installation procedures, and performance characteristics of martensitic cast steel concaves are reviewed. Longer wear life, fewer pieces to install, and eliminating the need to scarf joints are the principal benefits of using martensitic steel to replace austenitic 12% Mn (Hadfield's) steel, the traditional concave material for large gyratory crushers. Installation procedures that reduce the risk of breakage are described. Operating practices that affect concave performance are also discussed.

Jan 1, 1992

By M. J. Friedel

The U.S. Bureau of Mines (USBM) investigated the use of seismic refraction tomography (SRT) for identifying changes in pillar loading at the Foidel Creek coal mine near Steamboat Springs, CO. The inherent three-dimensional problem of directly imaging coal pillar conditions is reduced to a single plane by considering only the load transmitted from the pillar to the adjacent floor rock. Floor strata velocity tomograms (at two pillar locations) illustrate that loading conditions are non-uniform and non-unique. Also, time sequence monitoring, as the longwall face advanced, demonstrated that SRT can be used to image spatial changes in loading conditions. SRT offers the mining engineer a simple and flexible technique for evaluating pillar conditions, and thus, both present and alternative mine designs.

Jan 1, 1994

By R. Bhaskar

An airborne dust cloud is an ensemble of particles of varied size, density, shape and states of aggregation. An understanding and quantifying of the dispersion and deposition of the dust generated in mines is essential to the development of measures for reducing worker exposure to dust. In coal mining, the major portion of the dust is generated during the cutting of coal using either a shearer or a continuous miner. The major phenomenon affecting ambient concentration is the deposition of dust. Particle deposition may take place due to the effect of gravitational, inertial, electrostatic, and thermal forces, and mechanisms such as Brownian and eddy diffusion, and inertial impaction. The three major mechanisms of deposition in turbulent flow in mines are diffusion (Brownian and eddy), sedimentation and inertial impaction. The mechanisms determining particle deposition are size dependent.

Jan 1, 1990

By M. S. Enders

The McDonald deposit is a volcanic-hosted epithermal gold resource that is estimated to contain 251,000 kg of gold in 375 Mt of ore at an average grade of 0.7 g/t gold. Phelps Dodge exploration geologists, working for the Seven-Up Pete Joint Venture, discovered the deposit in 1989. By the end of 1992, 494 drill holes for over 113,000 m of drilling, bulk sampling, soil geochemistry, geophysics, metallurgical testing, engineering, and environmental studies had been completed to support feasibility studies. The discovery of McDonald required vision, persistence, and commitment of everyone from the geologist on the drill rig to the senior management of the company.

Jan 1, 1995

By F. Calizaya

This study summarizes the ventilation requirements for a highly mechanized P.T.Freeport Indonesia's underground mine operation in Irian Jaya, Indonesia. The Deep Ore Zone (DOZ) is a copper-gold deposit being developed underneath the current Intermediate Ore Zone (IOZ) mine. One of company's current plans is to prepare this mine for a steady oreflow of 25,000 tpd by year 2003. This study includes the estimation of airflow requirements for various mining activities, the design of major intakes and returns, the determination of airway resistances and specifications of fan duties. It also includes the results of air pressure/quantity measurements in existing airways and the standards stated by the current Indonesian mining law.

Jan 1, 1998

By T. Eggenberg

Mechanization and automation of logistic equipment has become one of the main key factors in raising productivity and competitiveness especially for complex and larger mining or tunneling projects. The Lake Mead Intake Tunnel #3 shaft mucking installation is a good example to demonstrate the potential that is found in an overall optimized logistic. It starts with the planning and results in using customized installations which fulfill the specifically defined requirements for the project. Rowa developed a solution and supplied a shaft mucking system using a discontinuous double drum hoisting concept with shaft buckets, loading, and unloading devices. With this fully automated system a continuous muck flow of 437t/h can be achieved.

Jan 1, 2010

By G. Plenge, M. Diaz

Silver-bearing, bulk sulfide concentrates from several Peruvian mines were autoclaved in a l9-L (5gal) laboratory autoclave in Lima, Peru. Cyanidation of autoclaved concentrates, following a hot lime jarosite destruction step, extracted more than 98% of the silver and more than 95% of the gold. Autoclave operating parameters, such as time, temperature, pulp density and autoclaved solids recycle, were investigated and reaction rates determined. The problems of excessive heat generation, silver solubility during autoclaving and formation of pellets containing unreacted sulfides were addressed. The data presented will be used to design a continuous autoclave pilot plant to provide reliable scale-up data for a 50 to 100 t/d (55 to 110 stpd) facility.

Jan 1, 1994

By Stephen J. Brower

Located in Central Nevada, The Round Mountain Gold deposit has been continuously mined since 1977. Present proven and probable reserves are 226 Mt (250 million short tons) at 1.1 g/t (.032 oz per short ton). The current open pit mining rate of 118 Kt (130,000 short tons) per day is producing 41 Kt (45,000 short tons) per day of ore to be processed by heap leach methods. At this rate, the current reserves provide a 16 year mine life. The high mining rate and strict ore delivery requirements mandate comprehensive and realistic mine planning. The mine planning process is described in three general steps: Deposit Modeling; Mine Design; and, Production Coordination and Support.

Jan 1, 1989

By Rex C. Bryan

An application of geostatistics to financial decision analysis is the linking of reserve parameters estimation precisions to a mine economics computer program calculating profitability. The estimates of economic reserve parameters are obtained by the kriging method, while precision are calculated by a technique more akin to the polygon method. To indicate the effect of the variables probability distribution on a distribution of profitability, their values are sampled by a Monte Carlo technique and entered into a mine economics modelling program developed by T. R. Ellis. The distribution of profitability calculations are in essence, a superior method of sensitivity analysis. The method is applied to a roll-front uranium deposit in the Powder River Basin, Wyoming.

Jan 1, 1982

By Prisbrey K., N. Choi, A. Burbank

Large tonnages of low grade refractory gold ores are not presently being treated because they resist direct cyanide heap leaching and because they are too low in grade for more expensive oxidizing pre-treatments. If they could be oxidized while remaining in heaps, they could be economically leached with cyanide. The solution is to use bacteria to partially oxidize the encapsulating pyrite mineral which allows cyanide dissolution of the gold in a separate treatment. A variety of refractory ores from different locations was crushed to minus three quarters inch, loaded into columns, and inoculated with T. ferrooxidans. The bacteria attacked the pyrite causing biooxidation, and gold recovery increased 30 to 120 percent after three months curing.

Jan 1, 1990

By John Reynolds, Robert Sloan

The Escondida copper mine is located in the northern Atacama Desert of Chile at an elevation of 3,050 m. approximately 160 km southeast of the port of Antofagasta. The mine is a joint venture between BHP-Billiton, Rio Tinto, a Japanese consortium and the International Finance Corporation. The most recent expansion, Laguna Seca, has increased the total capacity to the level of 220,000t/d ore throughput. The ore body, a typical porphyry deposit, is situated on the major Chilean west fissure fault system and contains primary sulphide ore grades between 0.6% and 2.0% copper. Primary sulphide mineralization consists of chalcocite pyrite, chalocopyrite, bornite and covellite. Significant copper oxides overly the sulphides in many areas.

Jan 1, 2005

By J. P. Sieverson

The Comprehensive Environmental Response, compensation, and Liability Act (CERCLA -commonly referred to as Superfund) was passed into law in December 1980 in the wake of such incidents as Love Canal and the Valley of the Drums. Superfund was originally perceived as a way of cleaning up spills of hazardous substances and/or cleaning up abandoned hazardous waste dumpsites. In February 1981, Michael Cook, EPA deputy assistant administrator for hazardous emergency response, called Superfund "a tremendously powerful law. It could revolutionize the way the environment is protected, but we certainly don't intend to realize the full potential of the law for some time." These words have proven prophetic for Asarco's East Helena Smelter.

Jan 1, 1988

By P. Gelfi, G. Hill, A. Showell, V. Martins, R. Dunne, R. Jenkins

Carbon attrition losses are not usually a prime consideration for CIP equipment selection and CIP plant design. However, the costs as a result of carbon attrition and associated gold lost with carbon can be high. Recorded carbon losses for Newcrest operating gold plants were shown to vary widely from plant to plant. The Tuckabiana plant recorded an overall loss of only 0.3g carbon /t ore which is very low by industry standards. A comparative carbon management study was undertaken by Newcrest to highlight the reasons for the excellent record of Tuckabiana operation compared to other Newcrest plants. This paper discusses the results of the comparative study and high­lights areas of concern with respect to carbon attrition.

Jan 1, 1995

By Gabriel E. Zárate, Juan C. Guzmán

In Chile there are significant amounts of gold in flotation tailings that could be recovered, being heap leaching the most promising alternative. In order to determine the feasibility of treating these tailings by this method, a detailed study is carried out using 4 representative samples. After defining the best conditions an economic evaluation is done for a plant treating 200 tpd, sensibilizing with respect to parameters such us gold price, tailing grade and capital costs. The results show that it is technically feasible treat these gold tailings by heap leaching with gold extractions over 70 %. It is also economically feasible for gold grades higher than 0.5 g/t and gold prices over 350 US/oz.

Jan 1, 1987

By I. K. Gilmore

Texasgulf Inc. currently operates an open pit phosphate mine in the central coastal plain of North Carolina. The area of phosphate deposition lies within the Aurora Phosphate district which consists of an embayment which is in the center of the Neogene phosphate deposition. A variety of solid and liquid fertilizer products are produced at the Texasgulf complex. One of these products is known as North Carolina Natural Phosphate (NCNP). New potential for use of unacidulated natural phosphate, now exists in regions with acid soils due to the discovery of the findings from recent research, cost advantages, and moves to reduce chemical inputs.

Jan 1, 1995

By Peter Zhang, Daniel Su, Mark Van Dyke, Heather Dougherty

The integrity of shale gas wells in longwall chain pillars under the influence of longwall mining is a safety concern for both coal and gas operators. Previous modeling studies of gas wells in longwall pillars have shown that a FLAC3D model can predict longwall-induced stresses and deformations in gas well casings with reasonable accuracy. The predicted casing deformations can be verified by multi-finger caliper survey. This study concerns the influence of longwall mining on eight shale gas wells in a shale gas well pad located in the chain pillars between two adjacent longwall panels under 1,030 feet of cover. FLAC3D modeling was performed to predict longwall-induced deformations in gas well casings based on site-specific mining and geological conditions. Small deformations less than 0.5 in were predicted in the intermediate casing above 600 ft depth, and very small casing deformations less than 0.15 in were predicted below 600 ft due to high abutment pressure and high frictional resistance along the weak bedding interfaces. After the first panel was mined, a 56-arm caliper survey was performed on one of the wells to measure the longwall-induced casing deformations in the intermediate casing. The predicted casing deformations were then compared with the measured deformations, which indicated that the prediction was generally in good agreement with the measurement in terms of deformation locations and magnitudes. Findings from this study provide valuable information not only for stability assessment of shale gas wells in longwall chain pillars but also for developing engineering guidelines to preserve casing integrity through adequate pillar and casing design.