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By David A. Andrews

Coal occurs at many scattered localities in Arizona, California, Idaho, Nevada, and Oregon, but in most of the known occurrences thick coal beds are of small extent and the coal generally contains a high percentage of impurities. The coal beds occur at many different horizons in strata of Cretaceous and Tertiary age. Bituminous coal has been found in several areas, the most extensive of which is the Eden Ridge field of Oregon. Lignite also occurs in many places, but the only extensive deposit is in the Goose Creek field of Idaho, Nevada, and "Utah. The coal reserves of the region are largely of subbituminous rank; most of the subbituminous coal is in the Black Mesa field of northeastern Arizona and the Coos Bay field of Oregon. The Black Mesa field contains more than 80 percent of the coal reserves of all ranks but is remote from both transportation facilities and centers of consumption. Substantial reserves ill the Coos Bay field are favorably situated with respect to transportation and markets. ARIZONA Subbituminous coal occurs in the Black Mesa, Pinedale, and Gallup coal fields in Apache, Navajo, and Coconino Counties, Ariz. (fig. 1). Bituminous coal occurs in the Deer Creek field in Pinal and Graham Counties and in a small area in Apache County at the north-east corner of the State. All the coal beds are in strata of Cretaceous age. The coal in the Gallup field and at the northeast corner of the State lies in the Western edge of the San Juan structural basin. "Vest and south of this basin the coal-bearing strata have been removed by erosion except in high mesas.

Jan 1, 1947

By Ivan Jackson Madura

The new Paradisus Coco Beach Resort in Rio Grande (PR) is located on an old swamp area, which has been filled with relatively clean to silty sands. The swampy deposits consists of organic silts, peat and loose fine to medium sand and silty sand. The project requires the placement of 1.0 to 1.5 meters of additional fill together with the construction of light structures. The need for the fill will trigger the development of settlements in the underlaying weak and compressible stratum. Furthermore, the susceptibility of the loose sand to liquefaction during an earthquake was considered. This paper describes the soil improvement by means of vibro-replacement, the purpose of which was threefold: reduction in total and differential settlement, acceleration of settlements during the surcharge period and densification of the loose sand to reduce its liquefaction potential. The predesign is presented together with relevant construction details of the preliminary trial areas from which the final column diameter and grid spacing were derived. Instrumentation together with settlement observations during the surcharge period are presented as well and compared with the initial predictions.

Jan 1, 2002

By Göran Bäckblom

The Swedish mining companies LKAB and Boliden, the equipment supplier Atlas Copco, the general contractor NCC and the specialist company Reflex joined forces in 2005 to advance the field of rock technology for the purpose of mining and underground construction. The creation of the company Rock Tech Centre is part of the strategy developed by the Swedish mining industry to strengthen co-operation with industry, academia and society. This paper outlines the current R&D strategies developed for the industry in general, discusses what focus areas are selected and provides some details on the current RTC project portfolio, especially faster and better drifting.

May 1, 2006

The excavation of ramps and tunnels often requires high-speed development with (or without) the use of high-energy mining equipment such as loaders, dump trucks, TBMs and roadheaders. This high-speed development creates a challenge in terms of providing a safe and productive working environment. For example, heat from continuously exposed surrounding rock, heat from broken rock, heat generated by mining equipment, potential in flows of hot ground water, pollution from associated diesel equipment and the distance of the advancing face from fresh through-ventilation all have to be taken into account when designing ventilation systems for high-speed ramp and tunnel developments. This paper discusses methods of achieving acceptable environments at the face and along the length of the tunnel. The methodology has been successfully implemented in the development of long (up to 20 km) TBM drives in the Lesotho Highlands Project and in mining projects in hot rock using drill and blast methods as well as mechanized methods using continuous miners and roadheaders. The determination of heat loads includes calculation of the heat flow within the surrounding rock, evaluation of the operating cycle of the equipment and the contribution to the overall heat load of the broken rock as it travels out of the tunnel. The determination of heat loads from surrounding rock in new tunnels required a modification of the algorithms generally used for established excavations. The paper also examines the use of, for example, mobile duct and fan systems to ensure that fresh air is delivered to the specific areas where workers are located.

Jan 1, 2000

By A. Noble

The design of separation circuits can be a complex, labor-intensive and costly process. While the engineer?s experience along with extensive data sets and simulation are crucial tools for determining the final solution, a more fundamental approach is suitable to compare preliminary options and reduce the number of potential alternatives. In light of this need, the authors have developed the Circuit Analysis Reduction Tool (CART?). This software package relies on the fundamental principles of linear circuit analysis; however, the solution methodology has been streamlined to automatically incorporate stream splitting and unique separation performance for each unit. The resulting tool allows preliminary analysis of circuit designs without the need of detailed feed characterization. In addition to the basic analytical approach, this paper supports the veracity of the methodology with several simulated examples for various separation models.

Feb 27, 2013

By Dennis Ofiara

Several recent tunnel jobs have required special adaptations of hard rock TBMs. Some of the special job conditions are ?no blast? launch requirements, small shafts or launch pits, proximity to existing underground structures, and short tunnels where the TBM must be retrieved through the primary lining. This paper describes a few of these projects, and the machine adaptations that have made TBM excavation feasible.

Jan 1, 2008

By D. Randolph Berry

The United States Bureau of Mines (USBM) awarded a contract to Foster-Miller, Inc. to develop guidelines for the storage and use of Self-Contained Self-Rescuers (SCSRs) in underground non-coal mines. An SCSR is a device capable of supplying, in an emergency, one hour of self-contained oxygen (no breathing of mine air). The information and recommendations in this report were developed primarily from three sources: discussions with mine representatives (including management, labor, and government), site visits in underground mines I and a detailed analysis of every reported non-coal accident which produced d hazardous atmosphere during the 5-year period 1976-1980 -plus ten other major incidents from prior years. Volume IV has three major sections: Recommendations and Discussion (Section 2), Analysis of Mine Accidents (Appendix A), and a Summary of Discussions with Mine Representatives (Appendix B).

Jan 1, 1983

By Alan A. Campoli

The U.S. Bureau of Mines evaluated two different conventionallongwall gate entry systems in the Southern Appalachian Basin, where mining and geologic conditions are conducive for coal pillar bumps. These gate entry systems were in a coal mine located in the Pocahontas No.3 Coalbed under approximately 2,000 ft of overburden and a massive quartzite sandstone member, and both employed a center abutment pillar flanked by yield pillars. The 8O-ft-square tailgate abutment pillars within the first study area began bumping 500 ft in advance of mining. This was accompanied by face bumps on the tailgate corner of the longwall face. The 120-by 180-ft tailgate abutment pillars within the second study area did not begin to bump until mining was approximately 100 ft past. Coalbed stress change and abutment pillar dilation data demonstrated that a 15-ft-wide perimeter of yielded coal surrounded a highly stressed core in both sizes of abutment pillars. The 62 pet more core area per foot of gate entry in the larger abutment pillars prevented excessive load transfer to the corner of the tailgate panel and eliminated the face bumps experienced with the original gate entry design.

Jan 1, 1990

By K. E. Kolm, W. H. Langer

Developing natural aggregate resources (sand, gravel, and stone) creates environmental impacts. A systems analysis method has been designed to characterize the components of the environmental system, identify potential impacts to those systems, and evaluate the extent of those impacts. The step-wise method consists of problem definition, data collection, preliminary conceptualization and characterization, additional data collection, data analysis, and refinement. The method requires analyzes of various systems making up the environment, including land surface, geomorphic, subsurface, and groundwater systems. After system characterization is complete, the method focuses on identifying and evaluating potential environmental impacts to determine acceptable mining strategies.

Jan 1, 2001

By V. Pawlowsky-Glahn, E. Pardo-Igúzquiza, J. J. Egozcue, R. A. Olea

Compositional data constitutes a special class of quantitative measurements involving parts of a whole. The sample space has an algebraic-geometric structure different from that of real-valued data. A subcomposition is a subset of all possible parts. When compositional data values include geographical locations, they are also regionalized variables. In the Earth sciences, geochemical analyses are a common form of regionalized compositional data. Ordinarily, there are measurements only at data locations. Geostatistics has proven to be the standard for spatial estimation of regionalized variables but, in general, the compositional character of the geochemical data has been ignored. This paper presents in detail an application of cokriging for the modelling of compositional data using a method that is consistent with the compositional character of the data. The uncertainty is evaluated by a Monte Carlo procedure. The method is illustrated for the contents of arsenic and iron in groundwaters in Bangladesh, which have the peculiarity of being measured in milligrams per litre, units for which the sum of all parts does not add to a constant. Practical results include maps of estimates of the geochemical elements in the original concentration units, as well as measures of uncertainty, such as the probability that the concentration may exceed a given threshold. Results indicate that probabilities of exceedance in previous studies of the same data are too low.

Jan 1, 2015

By João Carlos Jânio Gigolotti

O avanço tecnológico tem gerado demanda crescente por materiais que possam ser utilizados em alta temperatura e ambientes oxidantes, o que inclui ligas intermetálicas MR–Si–B (MR = metal refratário) com estruturas multifásicas. Assim, este trabalho teve por objetivo estudar a microdureza de ligas do sistema Hf–Si–B na seção isotérmica a 1600ºC, na região rica em Hf. Ligas Hf–Si–B foram fundidas com lâminas de Hf (min. 99,8%), Si (min. 99,998%) e B (min. 99,5%), em forno a arco e tratadas termicamente a 1600 ºC em atmosfera de argônio. As relações de fases nessas ligas foram identificadas por difração de raios-X e por contraste, em imagens obtidas via microscopia eletrônica de varredura no modo elétrons retroespalhados. As ligas tiveram sua dureza medida pelo método Vickers (microdureza) com cargas de 0,05 kgf e 0,2 kgf e tempo de aplicação de 20 s. Os resultados, obtidos da média aritmética das medições realizadas nas regiões heterogêneas de cada liga, mostraram uma dureza média de 11,08 GPa, com pequeno coeficiente de variação de 3,8%. Os boretos HfB2 (19,34 GPa) e HfB (11,76 GPa) apresentaram dureza mais elevada que os silicetos Hf2Si (8,57 GPa), Hf5Si3 (9,63 GPa), Hf3Si2 (11,66 GPa), Hf5Si4 (10,00 GPa), HfSi (10,02 GPa) e HfSi2 (8,61 GPa).

Aug 17, 2017

By J. N. Van der Merwe

The results of over 900 coal strength tests done during the period 1993?1994 for the SIMRAC project COL021A were re-analysed with a view to find a method to delineate areas or seams that can be grouped together for analyses of coal strength and strength decay characteristics. It was confirmed that the strength of a coal specimen increases linearly with increasing diameter-to-length ratio and decreases exponentially with increasing size of specimen. However, by extrapolation of the data, it was shown that beyond a diameter of approximately 2 m, the size effect is insignificant. For larger specimens, the diameter-to-length ratio (referred to as the width-to-height ratio for full scale mine pillars) alone continues to influence the strength. The slope of the linear strength vs. diameter-to-length ratio relationship is independent of the size of the specimen and is not unique for coals from different mines. However, the intercept of that relationship is unique and is a function of specimen size. This offers a previously unknown method to distinguish between the coals from different mining areas and coal seams. Ranked from weakest to strongest, the samples tested from the different mines are in the order shown below, which roughly corresponds to the judgement of practising rock engineers in the field: ?Sigma ?ZAC ?Goedehoop ?Kriel ?Bank ?Blinkpan ?Secunda ?Greenside Arnot ?Khutala ?Delmas

Jan 1, 2003

By Kenneth M. Maas

The Bureau of Mines inventoried all lands in Alaska to determine the availability of land for oil, gas, and coal leasing. Acreage for onshore oil, gas, and coal basins was digitized as was land ownership data. Regulatory policy concerning oil, gas, and coal leasing for various government agencies and private concerns was determined. Oil and gas basins underlie 79.4 million acres of Alaska's 378 million acre landbase. Federal agencies manage 44 million of these acres. The Bureau of Land Management is the lead agency for most oil and gas leasing on Federal lands. Lands have to be specifically opened for oil and gas leasing to be available. The state of Alaska manages 21.1 million acres underlain by these basins. More than 80 percent of this acreage is available for resource development. Native corporations manage the remaining 14.3 million acres of favorable oil and gas land. Coal basins underlie nearly 51 million acres of Alaska. Of this land, 26.4 million acres are under Federal jurisdiction. The state manages 17.3 million acres of land underlain by coal basins. Nearly 7.3 million acres of favorable coal lands are managed by Native corporations.

Jan 1, 1991

By Russell Barr

Strategic alignment throughout a mining organization is critical to effective strategic execution and good business performance. The alignment of strategic goals and objectives in the different operations and functions in a large global operation is a challenge facing executive management in light of legacy organizational structure and processes. An additional confounding factor in strategic alignment of acquisition and new project expansion is that mining projects and operations are frequently multi-cultural in terms of country origin as well as organizational culture. This brings together many cultures to accomplish the project or complete an acquisition (Financial Times, 2006). The mining industry presents numerous challenges to executives and mine management by the nature of the operation and organizational processes used in running it. For example, there seems to be an inherent conflict between the individual goals of the components that constitute a mineral processing operation (the mine, the mill, the smelter and the refinery), and lowest cost production of the final product. Managers of these component operations have specific objectives passed down from the corporate executives. Those site managers tend to be compensated based on throughput and perform to this main metric. This tendency to maximize throughput for an individual operation can contradict the general process flow of a best-fit solution to producing the final product at the lowest cost. In an effort to become more aligned, firms are increasingly using balanced scorecard derivatives at great cost and effort (whether internally or externally sourced) in an attempt to help with strategic alignment. Balanced score-cards have been effective in providing a good strategic scorecard to companies with some measure of strategic alignment. Many firms make this effort of using balanced scorecards. However, most firms are not strategically aligned or, at best, are sub-optimized, in terms of strategic alignment (Kaplan and Norton, 2006). The tendency in mining operations is to focus on operating individual components as optimally as possible and stretching existing assets to the best possible production rates. ?Making tons? is the common operational focus. Numerous factors underpin this focus and can affect the ability of the operation?s ability to align properly with the corporate strategy and strategic goals. Critical factors are legacy organizational structure, culture, processes and performance measurement systems. Changing anyone of these factors to affect better strategic alignment requires significant attention to managing change.

Jan 1, 2008

This chapter summarizes data on crude mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are tables that show the principal mineral commodities exported from and imported into the United States, and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of volume I and in the State chapters of volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at 'any of several stages of extraction and processing, the stage of measurement used In this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the product of auxiliary processing at or near the mines.

Jan 1, 1977

By Robert McClure, Carlton Lehman

Rendering safe explosives in an urban environment presents a unique challenge due to the safety concerns and disruption to the general public. Potential damage to the surrounding homes, businesses, utilities and transportation infrastructure are some of the major concerns when planning the render-safe operation. Engineering controls to mitigate blast effects, such as damaging air over pressure levels, material ejection and ground borne vibration, need to be implemented as part of the operation. Monitoring of seismic and air overpressure during these operations are needed to protect against potential claims when controlled or unplanned detonations occur.

Feb 1, 2020

By N. Ragoonanthun

Paper written on project work carried out in partial fulfilment of B.Sc. (Mining Engineering) degree This report investigates the optimization of a raiseline in order to open up the ore reserve quicker. The project was carried out at Mponeng Mine (an Anglogold shaft formerly known as Western Deep Levels 1 Shaft and South Mine, in Carletonville). The project was divided into two focus areas namely: ?To design an optimum layout of a raiseline, which includes the scheduling of all activities for the establishment of the infrastructure. Consideration was given to the blasting practice, mining cycle, orepass placement and slusher positioning. Two designs were carried out on the above basis. ?The design of a ledging operation/practice to match the optimized layout of the raiseline. The ledging cycle design involved a thorough investigation into the possible use of drill rigs, Electronic Delay Detonators (EDD) blasting technology, longer drilled holes, Threshold Blasting (THROB),and water jet cleaning.

Jan 1, 2003

On the 26th of June 2000 a hydraulic fill retaining barricade failed at the Bronzewing mine in Western Australia. The barricade failure resulted in the release of 19,000 m3 of saturated hydraulic fill into the mine and caused the deaths of three miners. Following this tragic accident, the practices and procedures of mines using hydraulic fills came under intense scrutiny by regulatory bodies and mining companies. At this time, the use of hydraulic fill at Normandy?s zinc/copper Scuddles mine was suspended and waste rock became the sole backfill material in use underground. By 2003, development of the adjacent Gossan Hill mine had progressed to a point where a self supporting fill material was required to enable full recovery of high grade ore. Cemented hydraulic fill (CHF) was identified as the optimal fill type and work began on designing appropriate management procedures and controls to ensure the safe implementation. This work included definition of the fill properties, plant design and construction, reticulation system design, design of stope barricades and drainage systems and fill placement control and monitoring practices. CHF placement began on 16th July 2004 and has continued to date. Significant operational experience has since been gained in areas including plant performance, fill product quality assurance, barricade construction, stope drainage and in-situ performance.

May 1, 2007

By Pedro Condori

Usualmente, la minera Atacocha está expuesta a grandes precipitaciones pluviales durante una larga temporada húmeda. Por lo que es necesario eliminar gran parte del agua colectada por las lluvias a través de las plantas de tratamiento de aguas de exceso que garanticen los contenidos metálicos por debajo de los limites máximos permisibles. En ese sentido, el presente texto describe la aplicación de un modelo matemático para comprender, manejar y optimizar las diferentes variables que afectan al proceso del tratamiento. El modelo está basado en los fenómenos de transporte de solución a través de la pila y la cinética de cianuración de los metales contenidos en el mineral, el cual permitirá simular los cambios en los parámetros operacionales y metalúrgicos como diferentes tipos de mineral, flujos entre plantas Merrill Crowe y CIC, un mejor tratamiento de excesos de agua para minimizar su efecto en la producción de oro y el manejo óptimo de soluciones y predicciones a futuro de producción de oro.

Sep 9, 2007

By Shahram Tafazoli

This article presents a novel technology for sensing the size of rocks after blasting in hard rock mines. Blast engineers require rock size statistics to carefully adjust the blasting parameters. The rock fragmentation requirements vary depending on the ore type and crusher specifications. The most popular statistical parameters in the industry are the so-called P numbers (e.g., P80 and P100). A machine vision based system is introduced here for automatic image collection and fragmentation analysis of the material right inside the bucket or dipper of mining shovels. A heavy-duty camera provides the required imaging data to an embedded computer mounted inside the cab. A custom machine vision software continuously analyzes the captured bucket images and stores the suitable ones in local storage which are then fed to a Desktop software for automatic fragmentation analysis. This technology has been developed by Motion Metrics International and is commercially available as FragMetrics?.

May 1, 2009