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By Jens Classen, Thomas Kurth, Karl G. Holter

High performance sprayed concrete equipment installed on two 9.4 m diameter hard rock TBMs enabled a continuous sprayed concrete lining for the entire contour in both tunnels to be performed concurrently with the advancing TBMs. Innovative layout of the sprayed concrete arrangements comprised ring beam constructions each with two independent spraying robots. Each of the spraying robots were independently connected to sprayed concrete pumps, as well as a high capacity concrete logistics system on the backup. The mix designs focused on long open-time, excellent pumpability and tough requirements on strength development. The achieved output capacities of the sprayed concrete amounts to an average of 15 m3 per hour. Peak capacities of 24 m3 per hour have been realized.

Jan 1, 2003

By Robert G. Benson, David M. Jones

The San Luis deposit of Costilla County, Colorado contains 11,021,000 tonnes (12,149,000 tons) of ore at 1.4 g/t (0.040 oz/st) gold in two mineable zones. Gold mineralization is associated with silicification and quartz-sericite-pyrite alteration localized in breccias along a low-angle "detachment" fault zone in Precambrian gneiss. Gangue minerals include chlorite, specularite, chalcopyrite, molybdenite, and fluorite. Mineralization is mid-Tertiary in age and may have an indirect genetic relation to the emplacement of felsic intrusions. Portions of the ore body are unconformably overlain by sedimentary rocks of the Tertiary Santa Fe Formation. The deposit formed during the early stages of extensional tectonism along the eastern edge of the present day Rio Grande rift.

Jan 1, 1990

By W. S. Versluis, G. W. R. Kuzyk

Atomic Energy of Canada, Ltd. (AECL) is constructing an Underground Research Laboratory (URL), a major component of-the Canadian Nuclear Fuel Waste Management Program. In July 1988. AECL and the US Department of Energy commenced a cooperative research program that included extending the URL shaft by 190 m (623 ft) to the 443-m (1,453 ft) depth. The shaft extension, 4.6-m- diam (15-ft-diam), was excavated by full-face blasting using a burn cut. A Galloway stage accommodated the research activities and the sinking contractor's requirements. Blast designs incorporated controlled blasting techniques to minimize blast-induced damage on the shaft walls. The full-face method has been very effective, with 3.5-m (11.5-ft) rounds being advanced.

Jan 1, 1990

By D. W. Park

Geologic condition is one of the most important factors for longwall mining operations, especially, the existence of faults limits the mineable area, or cause stress variations at the longwall face. Recently, a longwall panel passed through a fault at the Shoal Creek Mine of Drummond Company, Inc. The fault was situated diagonally along the longwall face and the coal seam was displaced up to 2.4 m (8.0 ft) in a mode of a normal fault. LoSCoMS (Longwall Strata Control and Maintenance System) was used for monitoring shield pressure every minute and interpreting data in terms of setting, developing and final pressures. The results of the analysis regarding the influence of the fault on the shield pressure are presented.

Jan 1, 1999

By G. Michael Lloyd

The term phosphate beneficiation often conjures up visions of processing technologies that physically separate the phosphate rock from some impurity and do not result in a change in the chemical nature of the phosphate rock. However, when we consider hydrometallurgical processing as a phos¬phate beneficiation technique we have to include all chemical treatments that convert phosphate rock into a more useful product. With most of the phosphate rock mined being used for fertilizer pro¬duction, the best known and most widely employed hydrometallurgical process is wet process phospho¬ric acid manufacture. In general, all phosphate rocks are so insoluble that there is no physical treat¬ment that will allow the phosphate content to be used by vegetation in a timely manner. However, after chemical treatment, 100% of the phosphate is readily available for vegetation nutrition. If there is a chemical beneficiation process that could be considered the standard method of treat¬ing phosphate rock it would have to be the wet pro¬cess for phosphoric acid production. In this process finely ground phosphate is reacted with sulfuric acid to give phosphoric acid and phosphogypsum. The phosphogypsum crystals are removed from the phosphoric acid solution and discarded; the phos¬phoric acid is further processed to give the finished fertilizer product. The primary reason that this pro¬cess was adopted so widely is because the phosphogypsum solid that is formed can be easily separated from the phosphoric acid, thereby removing the calcium portion of the phosphate rock and the sul¬fate portion of the sulfuric acid. Other acids have been used to treat phosphate rock but nitric acid is the only other acid used commercially. Nitric acid gives a mixture of phos¬phoric acid and nitrates that can be further pro¬cessed into N-P fertilizers, but the range of N/P grades that can be produced is limited. Hydrochlo¬ric acid has been used to react with phosphate rock, and it can be used to generate a pure phos¬phoric acid but only after solvent extraction to separate the calcium chloride from the phosphoric acid. And then there is the problem of what to do with the calcium chloride. The acid that has received the most attention as a substitute for sulfuric acid is phosphoric acid. In this process, the phosphoric acid reacts with the phosphate rock to give a mono-calcium phosphate solution. This process does not dissolve all the impurities in the phosphate rock, and these solids can be removed from the solution before sulfuric acid is added to convert the soluble calcium to insoluble phosphogypsum. Despite all the claimed advantages, this process has not found favor. A suc¬cessful application of this process to treat some of the lower grade phosphate rocks being used today would seem to have some distinct advantages. Other beneficiation schemes have been pro¬posed or practiced on specific phosphate rocks on a limited scale. These include calcination followed by water leaching to remove lime, weak acid

Jan 1, 1999

By G. Schriever, H. Thiel, E. J. Foell

A long-term, large-scale, disturbance-recolonization experiment with relevance to the environmental effects of deep seabed mining is described. The study is funded by the German government and was launched in the abyssal eastern tropical South Pacific Ocean in February-March, 1989. After obtaining pre-impact baseline environmental data, a 10.8 km2 (4.2 sq miles) circular area of seafloor was disturbed using a specially designed "plow-harrow" device. An initial post-impact sampling series was carried out immediately after disturbance followed by a second post-impact sampling series six months after the disturbance. Plans call for repeated visits to the site at two year intervals to monitor the anticipated slow recolonization process until the area is inhabited by a new, stabilized community.

Jan 1, 1993

By M. A. Mahtab, N. M. Cruickshank, M. T. Wane

Gas outbursts occur as sudden eruptions of gas and minerals from the face of a mine heading as the heading approaches potentially burst prone (or anomalous) zones of rock. Such outbursts have resulted in considerable damage to equipment, and in some cases lives have been lost. Characterizing these anomalous zones and detecting their presence is therefore vital to safe mining. Certain significant characteristics associated with the outburst-prone zones are: (1) the presence of fluid inclusions, (2) unstable stress conditions, (3) characteristic geologic structures, (4) certain physical properties of the rock, and (5) microseismic activity. Geophysical and engineering methods for detecting these characteristics are discussed and are considered with respect to their past success and future potential for predicting gas outbursts.

Jan 1, 1987

By G. D. Criswell, F. Palkovits, J. M. Johnson

A paste technology investigation was completed for non-pozzolanic fly ash from Units 3 & 4 of PPL Montana’s Colstrip Steam Electric Station. The purpose was to assess the feasibility of converting from dilute slurry deposition of ash products to a system using thickened or paste ash to reduce excess water storage in the impoundment, reduce seepage losses, and increase storage efficiency. The investigation included laboratory and field testing to characterize the rheological, geotechnical and dewatering properties of the ash products, an assessment of potential seepage reductions and an evaluation of potential for increased ash storage capacity by modifying impoundment operating procedures. The studies concluded that the conversion project was feasible, cost effective, and permittable. Critical facilities for the conversion project are currently under construction.

Jan 1, 2004

By J. Kemeny, B. Norton, T. W. BoBo

Digital image analysis systems to quantify particle size of crushed materials have successfully been applied in large-scale mining operations throughout the world. Particle size measurement at various crushing and sieving stages, especially in aggregate production, will facilitate the industry’s desire and need to achieve higher levels of process control and automation. This paper will 1) summarize applications of digital image analysis in the industrial minerals industries and introduce the Split-Online technology; 2) detail an actual recent test application of digital image analysis that ultimately lead to the installation of an automatic, non-invasive particle size distribution monitoring system; 3) document how this information is being applied: and 4) summarize the new Split-Online Aggregates Module now available.

Jan 1, 2004

By J. R. Batista, J. C. Young

Leachates from gold heap-leaching mines may contain selenium concentrations as high as 2 mg/L. Previous studies report satisfactory selenium adsorption by activated alumina from relatively "clean" drinking waters. However, the findings of these studies cannot be directly applied to the treatment of mine leachate where other ions compete for the alumina adsorption sites. This study evaluated the adsorption of selenium from a mine leachate to develop design parameters for a full-scale activated alumina process. The study revealed that 68% of the selenium in the leachate could be removed by alumina at pH levels greater than 5.0. At pH levels less than 4, silica was poorly adsorbed by alumina, and selenium adsorption was improved. Silica adversely affected the selenium adsorption capacity.

Jan 1, 1998

By Cheryl M. McInnes, Graham J. Sparrow, James T. Woodcock

Three composites, assaying about 3 g/t Au and 0.75% Cu, were investigated. Each contained oxide copper minerals, iron oxides, and silicates. One composite also contained copper and iron sulphides. Maximum gold extractions by thiourea leaching were obtained after copper removal by acid pre¬leaching at pH 1.5 and redox potentials of 400 mV (Pt versus SCE). Best thiourea leaching conditions were pH 1.5, redox potentials over 200 mV, and 0.4% thiourea. This gave 90% gold extraction in 2 h with thiourea consumptions of 25 kg/t. Lower potentials gave poorer extractions. Ferrous iron additions before leaching halved thiourea consumptions. Longer leach times and the presence of sulphide minerals sometimes resulted in reprecipitation of gold.

Jan 1, 1989

By H. Para, A. Aguirre, G. Artadi

Mining is a very important economical activity in Peru which has been recently developed without considering environmental aspects. Here, we show an experience at the Milpo mine, situated 4,200 meters above sea level; a mining company that has the value of being one of few from the last decade that is engaged in consolidating a model of environmental protection. The model includes aspects of contamination prevention and control, with bioindicators such as pasture cultivation, vegetables, forests, and hydrobiological species breeding. Socially, through means of development programs in natural areas, forestation and support to rural agriculture, together with environmental education, it is being demonstrated that it is possible to ensure tangible results in environmental conservation and the well-being of the populations around the mine.

Jan 1, 1998

By B. E. Dindsale, P. B. Altringer, R. H. Lien

The Bureau cf Mines, U.S. Department of the Intericr, is investigating biolcgical and chemical deccntaminaticn of cyanide- containing leachates and residues. Biolcgical cyanide cxidaticn, using bacteria isolated from a precious metals tailings pond, destroyed >85 pct of the cyanide in several prccessing solutions containing up tc 280 ppm CN. Reaction time varied from about 4.5 hr in a trickling reactor using quartz as a bacterial substrate to 2 mo in unagitated, covered flasks. Chemical techniques were used to destroy the remaining complexed cyanide down to 1 ppm. Exploratory tests were also conducted using spent ore from heap leach operations as the bacterial substrate to determine if biological cyanide oxidation could be used to destroy the residual cyanide in spent heaps.

Jan 1, 1991

The Bureau of Mines, U.S. Department of Interior, is currently investigating strata interactions associated with the mining of multiple coalbeds. Strata interactions due to subsidence are a result of undermining. This study involves underground investigations at a mine where room and pillar panels are actively being developed through an area of the Sewickley Coalbed which was subsided by undermining of the Pittsburgh Coalbed. Research to date indicates that undermining had little effect on upper mine pillar stability, but had a more severe effect on the development and maintenance of entries. Roof-to-floor measurements recorded over four times more convergence in entries developed over gob as compared with entries developed over support pillars in the lower mine. Consequently, this has led to major roof falls in the active panels, resulting in considerable production delays and supplemental roof support costs.

Jan 1, 1985

By Charles N. Alpers, Jane M. Hammarstrom, Robert R. II Seal, Nora K. Foley

Geoenvironmental models are compilations of geologic, geochemical, and hydrologic information that describe both the pre- and post-mining environmental signatures of mineral deposits. The environmental behavior of seafloor massive sulfide deposits varies according to deposit type. This study has divided massive sulfide deposits into six categories: (1) Noranda-type, (2) Kuroko-type, (3) Cyprus- type, (4) Bathurst-type, (5) Besshi-type, and (6) sedimentary-exhalative deposits. In addition to Fe and Al, the heavy metals most commonly associated with drainage from these deposits are Cu, Zn, Cd, Pb, and As. Metal ratios of mine drainage and natural background waters tend to reflect the primary character of the ores. Variations in pyrite and pyrrhotite contents are reflected in lower pH values associated with pyrite-rich deposit types.

Jan 1, 2000

By G. G. O. O. Uwadiale, M. A. Kollere, M. A. U. Nwoke

Birnin Gwari and Alawa graphite deposits were upgraded by flotation. Using 0.5 kg/t kerosene and 0.25 kg/t sodium silicate, flotation concentrates grading 90.7% and 88% Cg with recoveries of 86.2% and 84% were produced from Birnin Gwari and Alawa graphite samples, respectively. The combination of 0.5 kg/t kerosene, 0.2 kg/t pine oil and 0.25 kg/t sodium silicate yielded high-grade graphite (92.3% Cg) with a recovery of 83.9%. Flotation with refined rubber nut oil and kerosene, at a 1:1 ratio, produced a concentrate grade of 86.3% Cg with a recovery of 90.4%. With acid leaching of the flotation concentrate, a high-grade graphite concentrate containing 98% Cg was produced.

Jan 1, 1998

By Richard L. Ranich, Frank F. Aplan, J. B. Hiskey, Robert S. Thompson, B. J. Scheiner

Acidic waters typified by acid mine drainage, copper dump leach solutions and steel pickle liquors will typically contain SO4-2 and cations such as Fe+3, AI+3 and for the pickle liquors, sometimes Cr+3. These acidic waters will often react with limestone, present naturally or introduced for purposes of solution neutralization, to form reaction - inhibiting coatings of gypsum and gelatinous, metal hydroxide precipi¬tates. The coating thickness, as a function of pH, was quantified for both reactive (calcite, limestone) and non-reactive (quartz, barite, fluorite) minerals, and the data were related to the hydroxy species diagrams and to solution turbidity measurements. Coatings were found on the reactive minerals at a lower bulk solution pH than on the non-reactive minerals.

Jan 1, 1993

By V. Perdikatsis

The aim of this paper is the study of the pollution of soils in greenhouses because of the use of pesticides. The degree of pollution was studied in relation with the mineralogical and pedologic properties of the soil. The study was con-ducted in the region of Kountoura, Palaiochora, situated in the south of the prefecture of Hania/Greece. Several samples of soil, originated from 4 greenhouses were analyzed. 5 pesticides with organic drastic compounds were chosen for analytical determination using GC-MS from 18 which were applied in total during the period of sampling. It was concluded that the adsorption of pesticides in the soil of greenhouses is connected with the percentage of the clay fraction and the content of organic carbon.

Jan 1, 2006

By John W. Conn, Harry C. Verakis

An explosion in an underground coal mine can have a devastating effect on the main fans used to provide mechanical ventilation. The Code of Federal Regulations, Title 30, Part 75.310 (CFR, 1992), specifies that each main mine fan shall be offset by at least 15 feet (4.6 m) from the nearest side of the mine opening unless an alternative method of protecting the fan is approved in the ventilation plan. Also, each main mine fan shall be protected by one or more weak walls or explosion doors. This paper presents venting and fan configuration designs which provide a comparable degree of safety for explosion protection. Design flexibility is enhanced and a means for consistency in safety judgements is afforded.

Jan 1, 1993

By S. P. Brown, J. E. Worthington

Increasingly, exploration geology seems to be growing into a practice overly separated from production geology, yet the eventual purpose of exploration is a producing mine. To help in the search for new deposits, exploration "lessons" will be drawn from the papers given at the Fall AIME Applied Geology Symposium. In addition, examples will be re-emphasized to show how early observation of matters now routine to mine work (for example, hydrology, rock mechanics, oxidation state) can help increase the effectiveness of exploration.

Jan 1, 1992