Search Documents

By Robert F. Randolph, Arnold C. Love

This study describes the positioning strategies used by operators of radio controlled underground mining machines. The observations have implications for task design to insure adequate visibility and task performance. Radio controlled continuous coal mining machines have allowed many mines to increase safety and production by placing human operators away from the hazards of an unsupported mine roof. The operator is no longer confined to an operators component and visibility can be enhanced with proper positioning. Also, the operator is no longer subjected to the shocks and vibrations of the mining machine. The operator's ability to move freely about the worksite requires a careful analysis of several competing safety and production considerations. Thirty-five operators of remotely controlled continuous mining machines were observed using work sampling followed by interviews to determine where the operator was positioned and what he or she was watching. These observations were separated according to the task being performed by the continuous mining machine and summarized as position density plots. The specific task of tramming in reverse through a crosscut is analyzed along with more general summaries of the time miners spend outside of the policy-defined operating positions while performing other production tasks. The operators were: observed to frequently vary from company standard operating procedures (SOP). Many of the variations from company SOPS were based on task demands. Interview responses indicated that portions of the mining task place visibility demands on the operators that are difficult to accommodate within existing procedures. An improved task design process would include these visibility requirements. Also, the operator's vision can be augmented thorough video cameras in future teleoperated mining systems, and the operator can be increasingly isolated from environmental hazards.

Jan 1, 1992

By F. F. Peng, S. S. Peng, V. Z. Sun

A detailed study of ponding phenomenon relative to surface subsidence due to longwall mining was conducted for various surface stream conditions. Based on field monitoring, the stream-ponding process and three forms of stream water are described. Also discussed are the criteria of stream ponding and the influences on the ponding process by two key factors: the angle of stream flow and the change in the stream-bed gradient. A numerical (mathematical) model, which combines trend surface technique that describe the topographical features in the vicinity of a stream and the modified influence function, which represents the profile of the surface subsidence trough (or basin), is constructed to predict the formation characteristics of stream ponding in terms of location, boundary and accumulated water volume of migratory and stationary ponds produced by the stream-ponding process. Three cases are analyzed using the model to predict the interaction of the underground operations and the environmental impact due to stream ponding. The feasibility of various mitigative measures are assessed.

Jan 1, 1997

By D. M. Bodily, M. D. Deo, E. M. Whitney

Field data from coalbed methane wells indicate a significant variation in composition as a function of flow rate and time. In particular, San Juan Basin wells have displayed an increase in C02 concentration over time. Prediction of gas quality is critical to the economic evaluation of any coalbed project. Previous models have forecast only pressure and production profiles, ignoring compositional variations. In this study a multicomponent model that incorporates binary isotherms for methane and carbon dioxide has been developed. An extended Langmuir isotherm is used for the adsorption representation and a constant separation factor (similar to relative volatilities in distillation) describes the phase distribution of the species. This separation factor depends both on the surface characteristics of the coal and on the adsorbing species. The chromatographic separation equations have been superimposed on Darcy's law flow. The formulation allows decoupling of the pressure and compositional partial differential equations. The equations have been cast in dimensionless form and solved for pressures and compositions. It is observed that the composition of the preferentially adsorbed C02 increases at the wellbore as a function of dimensionless time. The dimensionless time is directly proportional to the real time and coalbed permeability and is inversely proportional to the gas viscosity, coal porosity and the square of the length of the reservoir. As the separation factor increases, the compositional variation increases. This variation in produced C02 concentration is also greater when the initial C02 concentration in the reservoir is higher. A sensitivity study has been performed to identify the effects of important parameters such as isotherm variables and reservoir characteristics on pressure and composition profiles.

Jan 1, 1993

By A. B. Mayer

A generic task summary for design and implementation of hydrogeology programs at open-pit mine operations is presented as a guideline for management. Rigorous assessment of the local and regional hydrogeologic system is necessary to plan dewatering activities and to address environmental concerns. Dewatering activities include calculation of dewatering requirements, design of dewatering systems and evaluation of dewatering-water disposal areas. Environmental concerns include calculation of dewatering and water-disposal impacts, mitigation of soil and ground-water contamination and acquisition of water rights. Three-dimensional numerical models are commonly used to support these analyses. A thoroughly developed hydrogeology program provides an interactive basis for dewatering feasibility decisions and for support of environmental permits and regulatory compliance.

Jan 1, 1993

By Boris M. Vorobjev

The paper in question discusses a wide range of topics on the coal mining environment in general and on computerized coal mine environment systems in particular. The emphasis is being made on methodological aspects of coal mine environment with reference to computerized monitoring systems Classification of computerized coal mine environment monitoring system is suggested by the author with specific reference to coal mining operations. Coal quality control system at all levels (coal face to regional levels) is also discussed briefly hereunder, since coal quality is one of the major factor for environmental management. An integrated coal mining economic and environmental management super-system is presented in this paper Review Of the UN/DTCD, UNDP European Regional project "Computerized Coal Mining Systems" is presented here. Conceptualization of a new European Regional project on Coal Mining Environment and Economic Management is also a topic discussed in the paper.

Jan 1, 1992

High pressure grinding rolls have found widespread acceptance for cement processing, and are now making their debut in the metalliferous minerals industry. Significant energy and wear material savings appear achievable in many applications. This paper re- views the technical literature on this important, emerging technology.

Jan 1, 1997

By Alfredo Dammert

The paper presents the results of a model built at the World Bank in order to analyze the aluminum industry. Bauxite demand for the year 2000 is estimated as a function of alumina refineries' requirements and of non-metal uses for bauxite. Bauxite supply by countries or regions depends on economic factors such as investment costs, operating and transportation costs, as well as on tariffs and levies. Various scenarios are considered as a result of varying the assumptions of the model.

Jan 1, 1984

By J. R. Palmes

Flocculation of coal fines with varying degrees of wettability was studied under well defined hydrodynamic conditions. In this study, three coal samples were tested with three different flocculant types. The results revealed that flocculation depends strongly on both the coal surface properties and the type of flocculant used. A hydrophobic flocculant was found to be effective for hydrophobic and slightly oxidized coal, a semihydrophobic flocculant was found to flocculate, to different extents, all of the samples except the oxidized cool, and polyacrylimide flocculated all of the coals, which is a clear indication of its insensitivity towards coal wettability.

Jan 1, 1994

By O. J. R. Baena, I. C. Sánchez, J. L. G. Guzmán

Frontino, a municipality in western Antioquia, Colombia, has more than 200 years of mining tradition. Currently, mining activities are carried out for lode gold using subway tunnels, where the grinding of the material is done in "cocos", whose energy depends on internal combustion engines and ACPM, environmentally polluting and inefficient methods. In accordance with the Sustainable Development Goals as an initiative developed by the UN, different mining methodologies that are aligned with these are constantly being analyzed. This study proposes to eliminate the use of hydrocarbons in artisanal mining, mainly promoting Sustainable Development Goals 7, 9, 11, 12, and 13. This will be achieved through an energy transition to renewable energy sources that take advantage of the topography and water resources of the area, providing advantages to the communities that live there, such as lighting, electricity for cooking, ventilation for mines, etc

Mar 2, 2022

By Tony Dunn

FMC Corp. achieved a significant cost reduction at its Green River, WY soda ash operations using a new proprietary solution-mining and processing technology. In phase one of the program, trona ore is dissolved, recovered and processed with the new technology. It is then fed into an existing refining plant, replacing dry mined and calcined trona ore. Phase two produces a final high-purity product. It also increases capacity by 635 kt/a (700,000 stpy). Both phases were completed under budget and ahead of schedule. This $120-million expansion project uses a new process and a new team to derive soda ash in a more cost-effective and environmentally friendly manner. The team successfully introduced solution-mining technology - with a liquid solution injected into previously mined sections of the mine. This shift in techniques signified a new era for soda ash production. The project is an example of teamwork at its best. For it to be successful, FMC had to work within several different areas inside and outside of the company. Engineers, contractors, mechanical operators and technical people were needed who could blend in with FMC's existing in-house team.

Jan 1, 1999

By Barry J. Hansen, Ruston A. Ford

Production of mine backfill from the tailings produced in a proposed Crandon concentrator is described. A process has been developed capable of producing suitable fill for the mining method selected for the Crandon orebody. It maximizes the placement of pyrite underground as fill and segregates tailings into pyrite and nonsulfide fractions. To determine the suitability and engineering characteristics of the backfill product for use underground, laboratory and physical stope simulation model testing was conducted. The results of the testing and the application of those results to the design of the backfill system ultimately affecting mine geometry and subsequent mine production will be presented.

Jan 1, 1981

By Sean Peterfreund, Grant Finn, Ty Jahn

For urban underground development involving tieback anchors for excavation support, authorities having jurisdiction typically require tiebacks to be de-tensioned before project completion. This paper updates “A Proactive Approach to Tieback Anchor De-tensioning” (by Peterfreund and Finn, published in the 2017 RETC Proceedings), which discussed a new method employed in a cut-and-cover transit station project. Since publication of that paper, 237 tiebacks were successfully and rapidly detensioned from using a small-diameter drill to cut strands from the surface. To the authors’ knowledge, this was the first intentional large-scale use of a drilling method for this purpose.

Jun 13, 2023

By Q. X. Yun, S. H. Liu

This paper provides a new approach to determine the opening layout in underground mining methods by means of genetic programming. Based on a set of random combination of openings, the layout of openings will gradually improve with the help of genetic operations, including reproduction, crossover, mutation and fitness calculation. The optimal solution will finally emerge according to Darwinian principle: "the survival of the fittest ".

Jan 1, 2002

By D. M. Anderson

The current mine closure process is faced? with the formidable challenge of controlling environmental and legal liabilities that are associated with mine closure. The current level of environmental statutes and regulations, and the legal/liability considerations, has evolved through regulatory enactment of mine reclamation laws and other existing environmental laws, such as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Management tools and techniques to limit risk exposure and financial losses should be employed as an active measure throughout the mine life, including closure and post-closure.

Jan 1, 1995

By M. Sengupta, N. I. Johansen, A. K. Sinha

In Arctic surface mines, frozen ground adds to the complexity of slope stability analysis. The seasonal temperature change may thaw permafrost, and this thawed ground is often unstable. A computer program, GEODYNE, was used to simulate the movement of the thaw front in bare and insulated permafrost slopes. The simulation shows that the insulation can be used on mine slopes to prevent thawing.

Jan 1, 1990

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 Eric K. Albert

Computer oriented simulation techniques can be effective in the design and analysis of complex mining systems. In fact, a number of computer software products are available for mine systems simulation. However, previous models have tended toward being either data-intensive and deterministic, or data-limited and highly stochastic. The need for a fully integrated package with a simplified user interface has never been more apparent. In this paper, the design of a surface mining simulation model documented in Albert (1986) is described. The basic features of the surface mining system and their counterparts in the simulation model are discussed. The methods and algorithms used to implement these subsystems are presented. Considerations of information management and software design are illustrated, especially as they apply to the application of the package by a mining engineer. An example is provided to demonstrate the concepts embodied in the model and to show how a surface mine is simulated from mine parameters.

Jan 1, 1989

By W. G. Pariseau, S. C. Schmelter

The destabilizing effect of water pressure on rock-mass stability is examined quantitatively by the finite element method. A coupled code that accounts for the simultaneous effects of rock-mass deformation and transient fluid flow is used for this purpose. The traditional soil-mechanics assumption of an incompressible fluid is shown to be untenable for the analysis of porous, fractured rock slopes. A Mandel-Cryer effect, whish is a transitory but elevated and potentially destabilizing water pressure following a cut, was not observed.

Jan 1, 1999

By T. B. Jarboe, H. Wen

Introduction The 150 MW circulating fluidized bed (CFB) power plant described in this article is the product of recent Bechtel experience in the industrial power and steam market, where the economic feasibility of fluidized bed projects has been proven. The ability of CFB boilers to burn low grade fuels makes it possible to burn low ranking coals or coal wastes. These include anthracite culm, coal mine rejects, and coal wash-plant-waste slurries. This article also addresses the impact of fuel characteristics on plant design. This includes solids handling, steam generation, sulfur capture, and auxiliary load requirements. The uncertain economic environment in which utilities must now operate has shifted the industry's interest away from large, base-loaded generating units to small, more versatile installations. Utilities now consider purchasing new generating capacity in smaller increments and staging its deployment to correspond with demand increases. In this way, they lower their risk in the increasingly hazardous art of long-range load forecasting. This strategy has many advantages. Multiple, smaller units have inherently greater turndown capability and better availability than a single larger unit of the same size. In addition, the smaller units will each have better cycling capability. And, with CFB combustion, the smaller units will have greater fuel flexibility. General plant description The 150 MW powerplant described here is a grassroots CFB unit. Fluidized bed technology differs from conventional combustion techniques. With CFB, solid fuel, together with inert material such as sand, gypsum, limestone, or ash from the fuel, is kept suspended in the combustion chamber. This is done by using the action of the fluidizing air distributed below the bed. Fluidization promotes the turbulent mixing conditions required for good combustion. The turbulence causes the entire mass of solids to behave like a liquid. The result is improved mixing. This allows heat to be generated at a lower and more uniformly distributed temperature that is below the ash fusion temperature of most coals. The fluidizing mechanism offers several other advantages over conventional combustion. There is less volatilization of alkali compounds, which cause deposits on boiler tube surfaces. And there is less sensitivity to the quantity and nature of the ash in the fuel. The low combustion temperatures prevent vitrification of the ash particles and minimize problems associated with furnace slagging. The ability to select from many fuels is one of the major advantages of CFB combustor technology. Fuels that can be burned in CFB plants to produce steam and electricity include: low grade coals with high ash or sulfur, lignite, peat, wood and pulp products, biomass, refuse, anthracite culm, petroleum coke, and oil shales. The plant's turbine cycle uses superheated steam at 12.4 MPa (1800 psi) and 538°C (1000°F), with single reheat to 538°C (1000°F). Two high pressure and three low pressure, closed, feedwater heaters are furnished. So is a deaerator, which is an open, direct-contact heater. The CFB plant exceeds EPA's New Source Performance Standards (NSPS) for air emissions. The design limits sulfur dioxide (SO,) emissions to 0.25 kg/GJ (0.6 lb per million Btu). SO2 reduction occurs in the combustor by reac-

Jan 11, 1988

By K. P. Unrug, E. Thompson, S. Nandy

The method of coal pillar design involves primarily two aspects: the geometry of the pillar and the strength of the coal. However, the strength of the coal has to be emphasized with respect to the entire pillar dimension rather than isolated strength values of coal samples taken and measured from different locations. As of now, the presently applied pillar design systems do not specify clearly what the coal sample strength really represents. The intention of this paper is to introduce the concept of seam strength as opposed to the current practice of using coal strength as a prime design criteria in the formulation of pillar calculations. Seams are most often composed of multiple layers of coal, partings, and bone in various configurations, changing within the vertical section of the seam even in relatively close locations. The difference in strength between the weakest and strongest component of the coal seam could be as much as five times or more. An experimental approach based on multiple uniaxial compressive strength tests performed on coal samples from the Coalburg and Warfield seams from eastern Kentucky was undertaken. Analysis of the results led to the conclusion that for pillar dimension calculations, both the weighted mean of the seam strength and the strength of the weakest stratum should be considered, rather than the relatively vague aspect of coal strength. The design of pillar dimensions based on the aforemen¬tioned criteria should assure a more realistic design performance.

Jan 1, 1987