Search Documents

By Clayton V. Deutsch

Indicator Kriging (IK) is being commonly applied to mineral resource assessment problems. More recently, indicator simulation has also been used for sensitivity analysis and difficult change of support problems. The essential theory underlying indicator geostatistics has not changed since its introduction 10 years ago; however, the last decade has produced many important developments in its implementation. The objective of this paper is to consider some of the more important implementation details. Examples from the Porgera gold deposit in Papua New Guinea are used to illustrate the steps in an indicator geostatistical study and the importance of various implementation decisions. Specifically, in many precious metals deposits the continuity of the grades is typically quite anisotropic. This anisotropy varies in both magnitude and direction throughout the deposit. Building a model of this anisotropy can considerably improve the local kriged or simulated points. One approach to build this model is presented. In addition, there is typically more than one mineralization style and geological rock type; the spatial character of the mineralization can be quite different within each geological rock type. The rational treatment of anisotropy and geological subdivisions is common to all mineral resource assessment procedures; the importance of this qualitative geological information is not diminished with more sophisticated techniques such as indicator kriging. This paper presents an overdue comprehensive look at the practical aspects of indicator methodology. Many of the techniques and procedures documented in this paper have been developed during the course of detailed mine feasibility studies.

Jan 1, 1992

By Robert A. Bauer, Paul B. DuMontelle

In 1985, participants of the multi-year Illinois Mine Subsidence Research Program conducted surveys of subsidence effects on crop production from current high-extraction mining methods, selected a site to characterize the profile, strain, fracture development in overburden materials and changes in aquifers produced by subsidence from high-extraction mining, characterized floor materia1 s in three mines, and established bibliographic reference and data base files. The Illinois State Geological Survey, University of Illinois at Urbana-Champaign, Southern Illinois University at Carbondale, Illinois Department of Mines and Minerals and Twin Cities Research Center of the U. S. Bureau of Mines are coordinating State and Federally funded research.

Jan 1, 1986

By R. J. Snoby, J. K. Alderman

Although once fairly common as a method of coal preparation in the United States, dry cleaning has virtually disappeared. Low-rank coals used for power generation in the western U.S. are suited for dry cleaning because water has limited availability in the American west. Surface moisture added through wet cleaning offsets energy improvement achieved from mineral matter reduction. Information will be presented on the commercial application of dry cleaning in North America, the historic development and current status of the technology, and the introduction of modern processing theory and control technology to the design of dry cleaning equipment and plants.

Jan 1, 2001

By S. C. Chelgani

The Thor lake deposit is a world class resource of rare earth (REE) metals and minerals in Canada. Development work to optimize a REE mineral recovery process flow sheet is underway, however, given the ore mineralogy; the developed reagent scheme is relatively complex. As part of a research project, micro flotation tests were conducted on a feed sample in order to examine factors affecting stream partitioning. SEM-EDX was performed to evaluate variability in grain composition between streams (concentrate and tails) and TOF-SIMS surface analysis was used to determine statistically significant differences in surface species particularly related to potential activation (or depression) of the examined mineral phases. SEM-EDX analysis reveal that the concentrate has a significantly higher proportion of REE bearing grains (carbonates and phosphates) relative to the tail (almost none were identified). Spectral fingerprinting by TOF-SIMS has allowed for the identification of all reagent species investigated. Reagent signal intensity discrimination on test stream mineral surfaces was observed by the TOF-SIMS analysis using reagents at plant concentration levels. TOF-SIMS analysis confirmed that REE bearing grains reporting to the concentrate are doing so in response to collector attachment whereas grains reporting to the tail are doing so in response to a lack of collector and/or in combination with the presence of the depressant. The surface analysis of gangue phases reveal a similar reagent discrimination; the signal intensity of collector species was significantly higher on the concentrate samples relative to the tails while depressant species were significantly enriched on the surface of the gangue phases in the tail samples. A detailed evaluation of the surface species representing the various reagents used in flotation scheme revealed a distinct competitive relationship between two of the reagents. The surface analysis identified that when used in concurrently, there appears to be a negative feedback resulting in a significant reduction in loading for several of the collectors on grains reporting to the concentrate. An evaluation of the effect of reagents on REE mineral in pilot plant is currently under way. Key words: Rare earth minerals, Flotation, Surface chemistry, TOF-SIMS, SEM-EDX

Feb 27, 2013

By D. Z. Mraz, R. S. Jones

Unlike in coal mines where caving methods are used, the subsidence over potash mines in Saskatchewan, Canada, is a function of gradual mining convergence. Because of the presence of high pressure water aquifers over the evaporite salt formations, the mines have to be designed as regionally stable and no caving is allowed. The extracted area converges gradually and the convergence is mainly a function of the extraction and the mining method employed. Consequently, the subsidence rate is very slow and the bridging of the over-lying strata is a considerably more important phenomenon than elsewhere. The paper evaluates a case history of convergence and subsidence in a deep potash mine in Saskatchewan.

Jan 1, 1986

By J. Evans

Including: Tailings thickeners, CCD?s, paste thickeners, HI-rate thickeners, lamella thickeners, high compression thickeners, clarifiers etc. Flocculant dosing control for mining thickeners and clarifiers is influenced by a number of process factors. 1. Flow rate into the thickener or clarifier a) As the flow rate increases into the thickener or clarifier ?retention time? decreases which causes a greater affect hydraulically on the settling solids. So as the flow rate increases it will generally mean an increase in flocculant dosing rate. b) As the flow rate decreases into the thickener or clarifier the retention time increases which reduces the hydraulic affect on settling, improving settling rates. This will generally mean that as the flow rate decreases, we will decrease the flocculant dose rate.

Jan 1, 2011

By Steven Norris, William Moler, Michael Cole, Patrick Doig, Debi Lewis, Craig Pyle, Matthew Crow

The recently completed Lower Northwest Interceptor Program (LNWI) in Sacramento, California comprises, ten pairs of micro tunnels totaling 4,369 m (14,417 ft),three horizontal directionally drilled bores totaling 956 m (3,154 ft), and two large diameter tunnels under the Sacramento River totaling 1,198 m (3,953 ft). This paper briefly summarizes surface and subsurface conditions, and planning and design considerations. It then goes on to describe problems encounterd with each trenchless crossing, as well as lessons learned with respect to shaft construction, ground control at shafts during tunnel break-in and break-out, frac-out and heave, settlement, obstructions, coordination with permitting agencies, and application of geotechnical baseline reports.

Jan 1, 2007

By Clement K. Chase

Since the dawn of cyanidation leaching techniques for precious metals, certain manganese-bearing silver ores have been a problem due to low silver extraction. Since simultaneous occurrence of silver and manganese is common in nature, this situation has made many otherwise attractive silver deposits uneconomic in the past. Several older techniques have been useful but at $1.29 per ounce of silver, the economics were unfavorable. With the new look in silver prices and some improvements in processing technology, neglected silver districts offer new promise.

Jan 1, 1981

By M. K. Larson

Proper employment of numerical stress analysis design tools is based on the demonstrated ability of a model to capture key elements of the geologic site model and accurately simulate how these elements interact with a mine design. While these tools have progressed markedly, they are, at heart, a gross simplification of the abundant complexity of a natural setting and its response to mining. A generic deep longwall site model was developed that includes aspects of the geology of deep coal mines in the Wasatch Plateau and Book Cliffs coal fields of Utah. The site model contains a set of common features and observations of how these features typically respond to mining. This site model was the basis for evaluating use of empirical, boundary element and volume element stress analysis tools to analyze the distribution of stress around a deep longwall panel. More specifically, this evaluation examined shifting of stress to panel abutments and gob, distribution of stress in the abutment, and deformation and failure of bridging strata. Measurements of abutment stress changes at two sites in the Wasatch Plateau region were used to illustrate model calibration. Overall, these comparisons highlight the considerable differences between methods. Volume element tools can incorporate considerable detail and have fewer underlying assumptions, but this detail carries a considerable computational cost. Boundary element tools are much more efficient. But this efficiency also comes at a cost of added assumptions. These assumptions were challenged by the presence of a strong sandstone unit in the overburden, leading to boundary element results that depart significantly from volume element results. Empirical rules are the simplest, but are even more burdened by assumptions, many of which are implicit in underlying cases. Insight into the nature and impacts of underlying assumptions in each method is essential to proper use of results in mine design. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health

Jan 1, 2009

By R. Karl Zipf

Highwall mining is an important surface coal mining method, and it may account for approximately 4% of total U.S. coal production. Highwall stability is the major ground control related safety concern. Ground control plans for highwall mining should specify hole width, web pillar width, barrier pillar width and number of holes between barriers. This paper offers simple design charts for these parameters aimed at providing “ball park” checks. Web pillars containing pre-existing auger holes are analyzed and a design chart for estimating their minimum width is also presented. Finally, close proximity multiple seam highwall mining, which may have caused several serious highwall failures, is analyzed. Web and barrier pillar recommendations for this special situation are presented.

Jan 1, 2005

By J. P. Ducarme

Numerous fatal/nonfatal accidents involving underground workers struck by powered machinery occur yearly, with continuous miners and roof bolters involved in the majority of these accidents. In an attempt to reduce these accidents, researchers at the the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Research Laboratory conducted studies of operator interactions with the motions of continuous mining machines and roof bolter boom arms. These operators generally perform their tasks in close proximity to the equipment in confined workspaces, often employing awkward postures. Since experiments with human subjects using the actual equipment were not feasible due to safety concerns, researchers opted to conduct controlled experiments in laboratory settings. Utilizing motion capture technologies and computer simulations, the studies collected data on equipment and operator movement in a range of seam heights and working postures. This article details the results of these studies to examine operating speeds based on usage and seam height.

Jan 3, 2010

By B. K. Blashich

In responding to mine fires and explosions, accurate and timely analysis of the mine atmosphere is critical in making decisions regarding firefighting, mine rescue and mine recovery operations. For many years instantaneous analyses were available to rescue workers using handheld or portable gas detection equipment, including infrared, electrochemical, or catalytic measuring devices for a limited number of specific gases such as oxygen, methane, carbon monoxide and carbon dioxide. Instantaneous sensing technology is not available for all gases, such as nitrogen and hydrocarbons, found in a mine fire atmosphere and cross-sensitivity can be a problem with this technology. For these reasons, air samples are collected for injection into a gas chromatograph for a complete and accurate analysis for all gases including oxygen, nitrogen, methane, carbon monoxide and carbon dioxide, as well as ?fire gases? such as hydrogen, ethylene, ethane, and acetylene. This method requires additional time for transporting the samples to the laboratory near the mine, as well as an instrument operator to inject the samples for analysis. The use of a portable micro gas chromatograph with a continuous and automatic injection system has been implemented by the Mine Safety and Health Administration (MSHA) during mine recovery operations. The device directly samples the mine atmosphere from an underground location every twelve minutes and automatically analyzes the samples for all of the mine fire gases. The portable unit utilizes micro technology and the operating software has been modified to perform the calculation of sample results in and Excel® spreadsheet without user interaction. This paper describes the micro gas chromatograph system and its use at a recent mine recovery operation. The automated remote operation of the micro gas chromatograph has been shown to be a good alternative to infrared and electrochemical sensors used for mine atmosphere analysis.

Jan 1, 2009

By M. Z. A. Bakar

A series of full scale laboratory linear rock cutting tests was carried out with a long bladed single disc cutter (292 mm diameter, 11mm wide constant cross-section blade) on dry and water saturated sandstone blocks using a linear rock cutting machine (LRCM). The muck collected from the cutting tests has been analyzed to establish a link with the specific energy (SE) of the operation. Coarseness index (CI), a non dimensional parameter, has been found to be a useful indicator of the relative efficiency of the cutting operation. An inverse relationship of the form SE = k CI-n is observed between SE and CI with very high CI usually corresponding with the lowest values of SE. The power n of the relationship for both dry and saturated rock tests is much less than the values found in the previous studies using constant cross section disc cutters and is believed to be dependent on the strength of the rock and the cutter type used. Although the average CI is found to be lower for saturated rock than for dry rock, at the same time saturated rock cutting is found to be less energy intensive (in terms of SE) than dry rock cutting. Moderate correlation exists between the production rate or yield and the SE of the cutting operation for both dry and saturated rock, which can provide some useful information about the field production rate discounting the effect of discontinuities in the rock mass.

Jan 1, 2012

By Dermot Winters

The Surface Mining Control and Reclamation Act (SMCRA, or the Act) was enacted on August 3, 1977. The Act was written, in part, to put an end to uneven environmental standards and to establish minimum national standards. Certainly, one of the motivating factors for passage of the Act was the success of the Federal Coal Mining Health and Safety Act of 1969 in reducing deaths and injuries in the coal industry nationwide. Section 516 (b) (1) of the Act requires *that subsidence be prevented from causing material damage to the extent technologically and economically feasible except in those instances where the mining technology requires planned subsidence in a predictable and controlled manner. Section 516 (c) of the Act authorizes the regulatory authority to suspend underground mining if there is imminent danger to inhabitants of urbanized areas, cities, towns, and communities. On December 13, 1977, the interim program, which applies a portion of the performance standards of the Act, was promulgated. Then on September 18, 1978, the proposed permanent program was published for public comment. Finally, on March 13, 1979, the final permanent program was promulgated and the States were given a period of time to submit their programs for approval.

Jan 1, 1986

By N. I. Aziz, I. Tague, P. Mackenzie-Wood

The recent mine disasters in Australian coal mines have initiated an introduction of Self-Contained Self-Rescuer (SCSR) as component in the development of new escape strategies for miners. These self-contained self-rescuers are closed circuit, demand sensitive breathing apparatus that make oxygen available to the wearer for a nominal period of time. Their operation is completely independent of the surrounding atmosphere. Once properly donned, the SCSR can assist a miner to escape from an area containing smoke, toxic gases or an oxygen deficient atmosphere. The duration of a typical SCSR is usually taken at the point of complete collapse of the breathing bag which is accompanied by an increase in breathing resistance and inhaled levels of carbon dioxide. Because the oxygen consumption (V02) and the heart rate are correlated, a prediction of V02 and consequently the duration of an SCSR can be made by monitoring the heart rate. Thirty-seven volunteers participated in field simulated escape trials at four underground coal mines. The results from the field trials suggested that oxygen consumption depends on the heart rate, the body weight and exercise rating of the miner. All the volunteers were asked to fill out the questionnaires to evaluate the performance of the units. The miners indicated that they could tolerate the inhaled temperature without any difficulty to breathing resistance. A complete statistical analysis of the field results is also presented.

Feb 24, 1997

By S. J. Schatzel

Coal mine longwall face ventilation is an important component of the overall mine ventilation system. Increases in the production rate due to higher capacity mining equipment tend to increase methane emission rates from the coal face, which must be diluted by the face ventilation with a minimal opportunity for assistance from additional control equipment (i.e., surface boreholes). Increases in panel length, in some mines approaching 6,100 m (20,000 ft), and panel width provide additional challenges to face ventilation designs. Face ventilation can also be affected by communication with the methane-laden gob gas reservoir. Except in a two-entry system, belt air cannot be used to ventilate the face in the US, except in limited cases. This relatively recent requirement has further challenged the mining industry in maintaining adequate longwall face ventilation. To assess the effectiveness of current face ventilation practices, a face monitoring study was combined with a tracer gas test on a longwall face. The study was conducted at a US mine operating in a thick, bituminous coal seam with some self-heating tendencies. Multiple gob gas ventholes were located near the face and produced a small portion of ventilation air in their production flow. Initial results show that emission rates on the longwall face showed a very limited increase in methane concentrations from headgate to tailgate despite the occurrence of methane delays during monitoring. Increases in methane concentrations in the tailgate entry in the vicinity of the longwall face T-junction appeared to be produced primarily by gas flow from the gob, not from increased emissions from the face. Barometric pressure variations were substantial over the course of the study and varied on a diurnal basis, as is typical of many mining operations. Suggestions are forwarded for reducing longwall face methane concentrations.

Jan 1, 2012

By Congling Shi, Marek Borowski, Yue Wang, Jianwei Cheng, Xixi Zhang, Xuan Xu

As the first barrier to prevent accidents caused by explosions in underground coal mines, the integrity and stability of mine seals have great effects on mine workers’ lives and underground production safety. In this paper, the mechanical responding performance of typical mine seals under the impact load are studied by using numerical simulation method. By such simulation studies, the safety of different seals subjected to the explosion load is evaluated. Seals’stability are also investigated under effects caused by various influence factors including thickness of mine seal, cutting depth into surrounding rocks, rock type, and the roof-tofloor convergence under given the explosion load. The research results can provide theoretical basis and reasonable improvements for mine seal’s construction practices for improving its anti-explosion performance.

By Congling Shi, Marek Borowski, Yue Wang, Jianwei Cheng, Xixi Zhang, Xuan Xu

As the first barrier to prevent accidents caused by explosions in underground coal mines, the integrity and stability of mine seals have great effects on mine workers’ lives and underground production safety. In this paper, the mechanical responding performance of typical mine seals under the impact load are studied by using numerical simulation method. By such simulation studies, the safety of different seals subjected to the explosion load is evaluated. Seals’stability are also investigated under effects caused by various influence factors including thickness of mine seal, cutting depth into surrounding rocks, rock type, and the roof-tofloor convergence under given the explosion load. The research results can provide theoretical basis and reasonable improvements for mine seal’s construction practices for improving its anti-explosion performance.

By Robert A. Jankowski, J. Harrison Daniel, Fred N. Kissell

Introduction Longwall coal mining in the US has steadily increased since its introduction in 1960. There are now 108 systems operating. (Sprouls, 1986). Advantages of longwall mining include higher productivity, improved safety, and greater coal recovery. Respirable dust, however, is one of the more serious obstacles to realizing the full potential of longwall mining. Early in 1980, the US Bureau of Mines (USBM) initiated extensive in-house and contract research to identify and evaluate effective methods of controlling respirable dust exposure of longwall face personnel (Niewiadomski, Jankowski, and Kissell, 1981). It was found that several control procedures must be combined to assure compliance, using control techniques appropriate to the dust source. These techniques can typically be grouped into the following categories: reduction of dust generation; dilution of dust; capture or knockdown of dust; and dust avoidance. Control techniques can be divided into basic and effective dust control techniques; additional necessary controls; and optional supplementary controls. This information should allow longwall mine operators to select control methods applicable to their particular operations and to develop a dust control plan that meets Federal dust standards. Basic and effective dust control techniques There are three basic dust control techniques (Taylor and Jankowski, 1982) that should be implemented on all longwall mining operations. • A passive barrier or external water spray system design that confines shearer generated dust near the face and away from the operators. • Large quantities of water through the sprays, particularly the drum sprays, to aid in dust knockdown and prevent dust becoming airborne. • A cutting sequence that allows the shearer operators to work primarily on the intake-air side of the lead cutting drum. Shearer clearer There are some poorly designed shearer-mounted spray systems with nozzles directed upwind at the cutting and loading zone of the intake-side drum. These actually carry dust away from the face and upstream of the drum. Where, it mixes with the clean intake air (Fig. la,) and is carried out into the walkway over the shearer operators. The Bureau developed a novel shearer spray system, called the shearer clearer. It takes advantage of the air-moving capabili-

Jan 10, 1986

By O. A. Bascur

The lack of integration of mining and metallurgical information with sufficient detail for analysis causes inefficient operation and hence sub-optimal energy and water use. It is difficult to analyze the performance of mining and metallurgical processes without an integrated view of mine transactions, stockpile inventories, process flows and assays. To take action requires real time information from manufacturing assets, corrected for gross errors from trucks, shovels, conveyors, faulty sensors, bad instrument calibration. This paper presents an infrastructure with advanced tools that sift through available data, identify and eliminate gross errors, and transform the data into business information for continuous improvement and optimization. Collaboration is a key component of improving efficiency of energy and water use, and the evolution of Web technology enables collaboration and troubleshooting of plant information to more quickly act on issues to reduce wasteful operation. Keywords: Mine Concentrator Optimization, Real Time Performance Management, Data Unification, Integration of Operational and Business systems, Mass and Energy Balances, Real Time Web Services, Equipment Availability, Efficiency.

Jan 1, 2009