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By Peter J. Conroy

Introduction Most subsidence monitoring to date has been surface monitoring to develop empirical relationships of the magnitude and extent of subsidence effects. Federal regulations are forcing a better understanding of subsidence. Empirical methods of subsidence prediction may not be adequate, since the empirical relationships may not be valid between or even within coal fields. A better understanding of the mechanics of subsidence is required in order to develop and verify analytical models. This paper presents some of the results of surface and underground monitoring in longwall faces of a coal mine. The seam thickness in these mines ranges from 5 feet to 6 feet at depths of 600 to 1100 feet.

Jan 1, 1982

By G. T. Adel

During the past decade, researchers at Virginia Polytechnic Institute and State University have worked to develop a novel flotation process for treating very fine particles. This process, which is now commonly known as [microbubble column flotation] (MCF), has been shown to be very effective in a number of applications related to fine coal processing. These applications include the retrofit of existing preparation plant circuits and the recovery of additional coal fines from refuse streams. In addition, work conducted under the sponsorship of the United States Department of Energy indicates that the MCF process is capable of producing superclean and ultraclean coals from many eastern U.S. coals. This paper describes some of the basic problems associated with fine particle flotation and the design and operational features of the MCF process used to minimize these problems. Also presented are the results of ongoing pilot- and field-testing programs.

Jan 1, 1989

By Maurice Deul

Limestone can be used effectively in treating acid mine water. Aside from a lower cost than for other treatment agents, limestone has the advantages of easy storage and effectiveness even when impure and in slack sizes. Limestone incorporated into waste piles in layers or as riprap can inhibit acid formation; limestone rubble packed in a mine entry offers promise in formation of a low-cost autogenous resilient seal.

Jan 1, 1974

By Cherie M. Tilley

Dynatec Mining Contractors (Dynatec) entered into a contract with Barrick Goldstrike Mines (Barrick) to develop the deep gold ore reserves at the Meikle Mine north of Carlin, Nevada. The Ventilation and Production Shafts were started in early 1994 and were completed in December, 1995. The mine development and mine construction programs were completed in November, 1996. This paper describes the Meikle Mine development program.

Jan 1, 1997

By Fernando Concha, Arturo Barrientos, María Cristina Bustos

Manufacturers referred to high capacity thickening as a filtration operation rather than thickening in spite of the fact that it is performed in thickeners and that conventional thickeners can be operated as high capacity thickeners by changing the feeding level and operate it in a different manner. In this work we derive a phenomenological model for high capacity thickening based on mass and momentum balances. The difference with a conventional thickening is the presence of a surface source within the variable domain. The model can be used to design, simulate and to develop control strategies.

Jan 1, 1995

By Edward K. E. ] [Williams

Conditioning is any treatment of an ore with or without reagents which affect its floatability. While it can start in crushing or grinding circuits and continue into the flotation circuit, conditioning will refer here only to reagent treatment in an agitated tank designed for the purpose. Such treatment is often unnecessary with sulphide ores and collectors or with amines,* but it has long been recognized as essential with fatty acid collectors in the flotation of non-sulphide minerals, The requirements can be extremely variable, depending upon ore alteration, the presence or absence of slimes, and 1 the minerals to be separated. The study described here was concerned with the recovery of oxidized molybdenum minerals from an ore containing the element in both sulphide and oxidized form. Flotation of the iron minerals with which the oxidized molybdenum was associated was the basis for the process. Recovery and optimum concentrate grade without desliming depended upon a twenty to thirty minute conditioning of the pulp with flotation reagents at forty to fifty percent solids and at high turbulence. The objective in the study was the determination of design and operating criteria for conditioners in order to permit scaling-up of the results without repeating the entire study on a larger scale.

Jan 1, 1968

By Liu Hanzhao, Jin Yongduo

Many gold ores which are not only submicroscopic but also rich in arsenic and organic carbon, for example Dongbeizhai Mine, have been found in china. These ores belong to the most refractory ores The key to the recovery of gold from these ores is preoxidation. Dongbeizhai ores have been tested with biooxidation, chlorination, double oxidation, acidic and alkaline pressure oxidation, catalytic oxidation, NITROX and roasting. To date it appears that either roasting or pressure oxidation is optimal. It is suggested that the flotation-roasting (or pressure oxidation)-CIL process should be used to treat this type of ore.

Jan 1, 1995

By Boris M. Vorobjev

The paper in question discusses a wide range of topics related to computerized coal mine monitoring systems starting with the history of development and application of computerized monitoring coal mine systems and finishing with modern trends in the design and updating of such systems. The paper focuses exclusively on methodological and technical aspects of computer-based coal mine monitoring systems and their applicability in both surface and underground coal mining operations.

Jan 1, 1989

By W. G. Courtney

The prevention of frictional ignition with a ripper-type continuous mining machine using conical bits was investigated in the laboratory using cutter-drum-mounted water sprays. Results indicated that frictional ignition during dry cutting of sandstone with conical bits was readily obtained even at low drum rpm, while wet cutting with a carefully-designed water spray nozzle located behind the bit substantially reduced the likelihood of frictional ignition. However, the orientation and operation of the spray nozzle is critical and involves almost no margin for error. A Lee-Norse 265 ripper drum has been modified to include durable water seals and is presently being field tested underground.

Jan 1, 1987

By Robert J. Guardia, James Rustvold, Robert A. Robinson, Christopher A. Robertson

In 1999, the Bonneville Power Administration (BPA) replaced approximately 730 m(2,400 ft) of damaged 42- and 36-inch concrete pipe by microtunneling Permalock pipe through sand and partly below groundwater. Microtunneling saved $3.5 to $5 million from the estimated cost of a shored excavation and avoided a railroad and contaminated valley fill. A slurry microtunnel boring machine (MTBM) was used for two segments where groundwater was present and a wheel excavator MTBM was used for one segment where groundwater was not present. This paper describes design and construction of this project that was completed within 2% of the bid and engineer’s estimate.

Jan 1, 2001

By M. M. Hajdasinski

In his recent paper, Torries (1998a) came to the defense of the much-criticized internal rate of return (IRR) as a project evaluation and ranking criterion. Torries also offered his own approach to the IRR-based project ranking, which he believes to be a more practical alternative to the conventional incremental-ranking approach, which Torries considers to be misleading. In an earlier paper (Hajdasinski, 2000), the author demonstrated that Torries' arguments vindicating the IRR concept are invalid. This paper provides logical and numerical evidence that the same is also true with regard to Torries' IRR based project-ranking approach.

Jan 1, 2000

By James A. Brierley, Rong Yu Wan

Bacterial pretreatment was evaluated as a process for enhancing gold recovery from a refractory ore from Newmont Cold's Cold Quarry deposit. This ore is refractory due to sulfide locking of the gold and preg-robbing carbon. The microbe Thiobacillus ferrooxidans effectively oxidized the sulfide component of the ore, but the preg-robbing carbon continued to be active. Thiourea was examined as an alternative to cyanide for extraction of the gold from the biooxidized ore. The thiourea, coupled with CIL, was effective for gold extraction resulting in up to 89% gold recovery for the sulfidic-carbonaceous refractory ore. The thiourea gold complex appears not to be bound by the preg- robbing carbon of the ore when in the presence of recovery carbon (CIL)

Jan 1, 1990

By Lee W. Abramson, Glenn M. Boyce

A dowel testing program was conducted as part of the Interstate Route H-3 Trans-Koolau exploratory tunnel project on the island of Oahu, Hawaii. The testing evaluated the performance of dowels to be used as initial ground support for two 12- by 15-meter (40- by 50-foot) tunnels within weathered basalt. The program tested four dowel types of three different lengths. Both grouted and friction dowels were tested. The program determined which dowels were more effective in carrying load and noted any special procedures that would be required during construction. This paper presents the test results and discusses how these results were used in the design.

Jan 1, 1991

By A. J. Monhemius, R. G. Reddy, G. W. Warren, E. Peters

Thermodynamic solubility of chromium in pickling solutions (i.e., HF- HN03-H2O solutions) was determined as a function of HF and HNO3 acid concentrations at 298K. Pure Cr, AISI type 316 and 416 stainless steel were used in this study. The results showed that the solubility of Cr increased with increase in the concentrations of HF and HNO3 acids in solutions. The solubility of Cr increased in the order of pure Cr > 416 SS > 316 SS. The theoretically calculated Cr solubility data were in reasonable agreement with the experimental data.

Jan 1, 1993

By Betty L. Gibbs

Using a PC can help an operator analyze data more effectively and respond quickly to changing conditions. The cost of microcomputers is low, and fit into the budget of even small mines. Many software packages are also low cost and general software such as spreadsheet, word processing, and data base management programs can help the small miner organize and evaluate information very quickly. A basic hardware configuration is proposed, including hardware upgrades and general and technical mining software packages. The hardware and software suggested can be used by very small as well as larger operations. PC's can be incorporated into all phases of a mining operation at a minimal cost and capabilities can be expanded as the operation grows.

Jan 1, 1987

By Y. M. Jiang

Longwall faces can move at high advancing rates, but many geological variations can cause unexpected instabilities and production losses. The rapid movement makes it necessary to evaluate different geologic conditions in the rock mass as fast as possible to assess their effects on the longwall face and shields. It is believed that prompt awareness of geologic conditions is the key to preventing instability at a longwall face. This paper introduces the application of fuzzy set theory for characterizing and evaluating roof conditions. Real-time monitored data coupled with fuzzy set analysis provides valuable information, such as shield leg pressure, developing load on shields, intervals of periodic weighting and the ratio of developing loads during periodic to normal times.

Jan 1, 1997

By M. J. Scoble

There is no straightforward and systematic method for adequately measuring blast damage in on-going mining operations. This paper considers various techniques available for the measurement of blast damage, making particular reference to recent underground hardrock mine studies. This paper concludes by indicating the importance of understanding and accounting for geology and emphasizes the need for a robust damage-audit procedure.

Jan 1, 1997

By Staff

GENERAL DESCRIPTION The Lucky Friday mine is located in Mullan, Sho-¬shone County, Idaho. The mining method is horizontal slice cut-and-fill (with timbering for support or un¬timbered) using hydraulic sand. Cemented sand fill at a 1:17 ratio is used in sill pours and at a 1:7 ratio for the final 152 mm (6 in.) capping in successive stope floor pours. Annual production with 100% cut-and-fill mining is 167 829 t (185,000 st). The average depth of mining is 1296 m (4250 ft) and the average travel time to the stope is 45 min. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size The ore body is 396 to 488 m (1300 to 1600 ft) long on strike, 1421 m (4660 ft) on dip, with an average width of 2.3 m (7.5 ft). Dip varies from vertical to1.2 rad (70°) Ground Conditions, Ore Value, and Production Requirements The ore body contains quite strong argentiferous galena and quartz. The hanging wall and footwall are strongly sheared and fractured. Ore value is $211/t ($192/st).

Jan 1, 1982

By R. A. Lohnes, S. M. Levorson

As part of research to develop a coal handleability index that predicts the ease with which coal will flow through a handling system, comparative tests were conducted with a Johanson Indicizer and a low-stress triaxial apparatus on 12 coals at a variety of gradations and moisture contents. The lndicizer test provides a rapid method for generating data associated with coal handling characteristics. The arching index measured with the Indicizer is a function of the geometry of the apparatus as well as the properties of the coal. The handleability index determined from triaxial data is a more direct measure of coal characteristics. The handleability index shows a wider range of values than the arching index and, therefore, appears to be more sensitive to coal variations. Neither the arching index nor the ratholing index, as measured with the Indicizer, agreed well with the handleability index. This is attributed to differences in sample preparation as well as to the tests themselves.

Jan 1, 1993

By Wayne R. Charley

High operating costs and environmental restrictions have combined to increase smelting costs for precious metals to a level where many mining companies cannot afford to operate. The need for a hydro-metallurgical process to produce bullion with an efficient, economical and environmentally safe method is well recognized by the industry. This paper describes the research and development program conducted by Behrent Engineering Company in its investigation of the use of an acidic solution of thiourea for the extraction of precious metals from concentrates and high-grade ores. The areas discussed are: process design parameters, health and environmental aspects and economics of the process. The scope of this paper includes the leaching process, the recovery of precious metals from pregnant solutions and the production of dore'. Thiourea leaching offers a complete alternative to smelting and cyanidization for those concentrates and ores amenable to this process.

Jan 1, 1984