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By Y. J. Wang

The Hardy Cross iterative method is the most popular technique for solving a ventilation network problem with natural air splitting. This method tradition-ally solves each mesh equation by an approximation during each iteration. It is thus interesting from both theoretical and computational viewpoints to be able to solve for an exact solution to the mesh equation. Presented in this paper is an algorithm for computing the exact solution to the mesh equation with a variable fan pressure. The algorithm uses signum functions for air quantities to generate an alternative mesh equation in the form of a quadratic equation, which has two solutions defined by the well-known quadratic formula. The condition that the derivatives of the alternative and the original equations must be the same provides a basis for the correct choice between the two solutions.

Jan 1, 1997

By Ming-yi Zhang, Zhong-nian Yang, Xiao-ming Guan, Quan-wei Liu

"In slurry balanced shield tunneling, how to ensure the safety of construction and to reduce the influence on the environment has arisen wide attention of scholars both at home and abroad. But now it is still in the stage of experience as to the instability mechanism of the slurry shield tunneling excavation and its stability analysis. Based on the large-diameter model tests and FLAC 3D, the effect of the different waterhead (non-water, 0.9m and 1.1m) on stability of excavation face of slurry balanced shield is investigated, and the stability mechanics is proposed. The results show that: waterhead heights play an important role on excavation face instability features of slurry balanced shield in sandy stratum, Regarding the different waterhead heights, the development mode of the excavation face instability features can be divided into non-water mode, lower-waterhead mode and higher-waterhead mode; soil arching is existed in the process of excavation face instability, the settlement of ground lags behind excavation face failure, the soil arching will block or eliminate the effects of ground settlement; excess pore water pressure need to be considered besides earth pressure and hydrostatic pressure when the supporting force is calculated. INTRODUCTION With the development of the society, for the cities all over the world, the exploitation of underground space has become an important measure to solve the problems about population, resources and environment and an important way to heal the city syndrome and implement the sustainable development strategy of city. Constructing shield tunnel with large diameter is the major trend for development of tunnel construction (Yin, 1999). Instability of excavation face caused by relief of shield soil stress is still one problem that needs to be solved (Xiang, 2001). How to reduce the effects of construction on surrounding environment? How to accurately determine the instability of shield excavation face and to effectively and reasonably select the supporting force? These are the crucial problems which need to be solved during shield construction."

Jan 1, 2016

By O. J. R. Baena

Mining activity in the Segovia region in NE Colombia is the main source of employment in the local economy. This has created major problems of illegality and informality mining associated with a high social and environmental impact, as inefficient technologies are used and high consumption of toxic substances required in the process of gold recovery by amalgamation and cyanidation. In this work is presented mineralogical characterization of six local mills and studied beneficiation processes developed in them. With the results presented a proposed plant design that eliminates the use of mercury by replacing gravity concentration processes taking advantage of the characteristics of the treated material. Significant results were obtained regarding the recovery of precious metals and present a methodology that can be replicated in other mineral beneficiation plants that use gold amalgamation processes. This implies a significant reduction in mercury use and decreased risk of human contamination associated with this.

Feb 23, 2014

By C. L. Wilsey, K. M. Oakes, W. J. Reich, M. J. Protani

The time frame required to complete the National Environmental Policy Act (NEPA) process for a new mine or the expansion of an existing mine can range from nine to 24 months, or even longer. The time frame will vary depending on whether an environmental assessment (EA) or an environmental impact statement (EIS) will be completed Completing properly designed baseline studies to collect natural resource data to support the EA or EIS prior to the start of the NEPA process can shorten this time frame. In this paper, a two-year natural resource baseline study by Homestake Mining for the Ruby Hill Mine, Eureka County, NV, is used as a case study to describe how a properly designed and executed natural resource baseline study streamlined the NEPA process.

Jan 1, 2003

By Christian F. Baiz

A new agenda has risen. Born out of governments' policies and world economies, the years ahead will carry with them reduced growth. For inflation dependent and capital intensive industries, such as metals and mining, as well as most other natural resource industries, a period of long-term contraction in outmoded and costly capacity will evolve. This will be supplanted by new, lower cost capacity in some cases, but only if the total cost of production, including cash operating and debt service costs comes in at or below current market conditions. The industrial outlook can be characterized as bearish. As one major U.S. bank economist put it, mining companies planning their five-year forecast from 1984 out, should take the current market conditions and straight-line them to the end of the decade. With low growth and low inflation, the real price of metals will remain flat or slightly declining. As a result, capital funding will be problematic. The low cost producer, that is one with low cash costs and low principal and interest costs per unit of production, will succeed.

Jan 1, 1984

By Wayne C. Smith

Both water pollution and proposed solid waste disposal regulations have a definite effect on the copper leaching industry and some of the major factors affecting the industry are discussed in this paper. New developments of the NDPS are discussed with emphasis on the "toxic" or priority pollutants and EPA's philosophy on the control of these pollutants, The protection of groundwater is the prime aim of RCRA through solid/hazardous waste management. Some of the major elements of the RCA regulations that will affect the copper leaching industry are discussed.

Jan 1, 1980

By W. G. Pariseau

"BACKGROUND The Crandall Canyon Mine (CCM) is located in the Wasatch coal field in central Utah. Extensive longwall mining at CCM preceded a decision to recover coal left in barrier pillars on each side of a set of main entries extending far into the mine. During mining in March, 2007, a major bump occurred that led to cessation of mining in the barrier pillar on the north side of the mains and to begin mining in the south barrier pillar. Subsequent loss of ground control in August, 2007, through coal pillar bursts had tragic consequences with loss of six miners and shortly afterwards three rescue team members. An MSHA report describes the events in detail (MSHA, 2008). An important lesson to be learned from CCM is the need to select a computer program suitable for pillar design. Computer programs are engineering tools; selecting the right tool for the job is essential. In this regard, a minimum program requirement is capability for computing stress distribution within a pillar and adjacent roof and floor strata. The reason is simple: strength of rock is stress dependent; both vary from point to point in pillars and adjacent strata. Preferably, one should follow the evolution of stress as the mining plan is executed from start to finish to assure safety or to warn of a potentially hazardous situation developing as mining progresses. The approach to the problem posed by barrier pillar mining at CCM is conventional in the sense of applying well known finite element modeling techniques to analysis of a proposed mining plan. The engineering purpose is to evaluate the mining plan with respect to ground control questions including roof, floor and pillar safety. Results of previous two dimensional finite element analysis indicated pillar safety was by no means assured (1, 2, 3). Geometry of barrier pillar mining is limited in two-dimensions, for example, crosscuts are not seen in vertical cross sections. While three dimensional analyses are preferred, even moderately sized regions often lead to very large problem sizes that exceed computer capabilities. However, a recent development in finite element modeling of tabular deposits allows for whole mine analysis in three-dimensions. This technique involves a dual node – dual mesh concept. Both have been used separately in much earlier work, but are only now are used in combination. Estimation of subsidence at a kilometer scale and details of stress, strain and displacement about barrier pillars, main entries and pillars, and so on at a meter scale are possible (4). No compromise involving empirical formulas or similar guess work is required. Indeed, all calculations are based on first principles: physical laws, kinematics, and material laws. Effects of joints and in situ variability or uncertainty in strata properties, elastic moduli and strengths, may be included for greater realism. An important objective of the present study is to assess the role of three-dimensional pillar geometry in arriving at conclusions regarding barrier pillar mining versus two-dimensional results."

Jan 1, 2015

By Mark C. Williams, Thomas P. Meloy

Particle shape characterization is a complex task made more difficult because of the human eye's sophisticated recognition of shapes, giving rise to the assumption that shape analysis is considered a simple problem. Further exacerbating the problem is the question of whether particles have a general shape. Old and new shape measuring techniques are discussed, particularly the new image analysis methods techniques such as Fourier, Haar, Walsh and Delta. Problems with the current image analysis equipment and future research equipment needs are presented.

Jan 1, 1989

By H. E. M. N. Moursy, Hassan El-Shall, M. N. Ahmad, Ponisseril Somasundaran, C. R. Holland, D. Chandler, G. Walker, Regis Stana, Patrick Zhang

The reaction kinetics of the acidulation of Moroccan phosphate rock (32% P?05) using 45% nitric acid were investigated using the Shrinking Core Model (SCM) , a newly developed Diffusion Model (DM) and a newly developed Combined Reaction and Diffusion Model (CRDM). This was achieved buy conducting a number of experiments in a controlled batch reactor system at different temperatures. The conversion and the reaction rate were calculated at different time intervals. The SCM based on reaction time and the CRDM characterize the acidulation process of phosphate rock. Diffusion of nitric acid and the products of acidulation at the early stages of reaction through the phosphate rock were found to be the rate-controlling step, resulting in a dif- fusion coefficient, which controls the mass transfer process. The reaction kinetics were found to fit first-order kinetics especially during early stages of reaction time. The deviation of the kinetics from first-order at later stages was due to the fact that the overall reaction was mass transfer controlled with respect to nitric acid and products diffusion.

Jan 1, 2002

"Replacing the century old rail tunnels that run beneath the Hudson River and carry about 200,000 passengers per day between New York to New Jersey has been a high priority for many years. But after Superstorm Sandy hit the east coast of the United States in 2012, the urgency to replace the tunnels increased dramatically. The Hudson Tunnels project is one of nine projects that make up the larger $30 billion Gateway Project. The Gateway Project has been called the most urgent infrastructure program in the country and the Hudson Tunnels is the most critical part of the project, as it will build a new rail tunnel under the Hudson River and rebuild the existing and deteriorating North River Tunnel that connects New York and New Jersey.“Superstorm Sandy proved the level of resiliency of the tunnels, which was not very good,” Amtrak deputy chief engineer structures James Richter told attendees of the George A. Fox Conference in New York City on Jan. 23. Age and corrosive salts deposited by flood waters from the storm in 2012 have affected interior concrete and copper wiring in the tunnels. “Since then, things have been deteriorating and getting less reliable.”Richter, along with Mohammed Nasim, senior director engineering design, both with Amtrak, spoke at the 2018 George A. Fox Conference where more than 350 tunneling and underground construction professionals attended the conference at the Graduate Center of the City University if New York to share insights about the complexities many of them face on daily basis.Under the theme of “Managing construction of complex underground projects: Strategies for tunneling in populated areas,” the one-day conference featured presentations from some of the top minds in the tunneling and underground construction industry. The presentations touched on everything from the highly technical challenges of constructing tunnels through changing geology while working beneath cities and rivers, to navigating the complex financial issues and contracts that come with the projects that have many stakeholders.All of those challenges, and more are part of the Hudson Tunnels project. It is one of the best examples of the full complexities of a complex tunnel project, with the added pressure of securing funding from state and federal government entities under an increasingly tight deadline."

Jan 3, 2018

By L. B. Phelps

Current mining regulations require revegetation in reclaiming surface nines. Excessive soil compaction can be an impediment to successful revegetation in poor soil conditions common to Eastern coal nine sites. A field study was performed to determine the bulk densities of soils that had been spread by either bulldozers or scrapers at a strip nine site. Moisture-density relationships for the soils were determined from the field samples. These were compared with stockpile samples compacted by the Standard Proctor compaction test. The results of the study indicate that the degree of compaction could be lessened through proper soil handling procedures.

Jan 1, 1986

By Hillary W. St. Clair

In a previous report 1/the author showed that the essential information from particle size analyses of grinding mill products can be represented by three or four parameters derived from the first four moments of the particle size data. These parameters may be used in gamma or beta distribution functions to estimate the weight fraction in any given size range. Moment analysis was used to study the progressive changes that take place in particle size distribution when a homogeneous isotropic mineral such as quartz is reduced in size by impact crushing. 2/ This report briefly reviews the essential features of moment analysis and describes extension of this method to size reduction by ball mill grinding.

Jan 1, 1972

By D. G. Chedgy

Environmental improvement efforts are focusing with increasing intensity on pollutants resulting from combustion. The high cost of removing these pollutants at the power station is well documented. Physical coal cleaning has always been and should remain the most economic method of reducing sulfur oxide emission from coal combustion. It is critical in the selection of preparation plant circuitry to consider capital and operating costs, as well as the level of sulfur reduction. This paper describes the technical criteria which must be used for efficient process selection and summarizes the cleaning systems available or in development.

Jan 1, 1990

By K Louie

When BHP Copper's Lower Kalamazoo Project commenced production in January 1997, two of the four original hoists had been converted to hoist ore from the Lower K level. Conversions on these hoists not only allowed hoisting from a much deeper level, but also created a higher hoisting efficiency and higher capacity as well. Conversions included new drums, new cables, SCR drives and other solid state control technologies not available when the original hoists were installed. Two of the original hoists were installed in the 1950's and the other two were installed in the 1970's.

Jan 1, 1998

By E. Lee

The behavior of As bioleaching using Acidithiobacillus thiooxidans (A. thiooxidans) in mine tailings containing highly concentrated As contents (i.e., As=33877 mg/kg) was systematically evaluated according to the changes in temperature (25?40°C, pulp density=0.5%, pH=1.8), pulp density (0.5?4%, temp=30°C, pH=1.8), and initial pH(1.8?2.2, temp=30°C, pulp density=0.5%). The changes in temperature and pulp density affected the As leaching behavior more than the change in initial pH did. Based on the pH and oxidation-reduction potential (ORP) results, the As leaching was attributed to solution acidification. In particular, As leaching was accelerated with increasing sulfate production in the reacting solution. After bioleaching, surface of tailings examined that many pores which dissolved As were formed by a chemical reaction due to bacteria. The As bioleaching efficiency by A. thiooxidans was enhanced by the oxidation of both the added elemental sulfur and the sulfur compounds in the mine tailings. The As bioleaching efficiency was maximized at 50.5% under conditions of an initial pH of 2.2, reaction temperature of 30°C, and pulp density of 0.5%.

Feb 23, 2014

By Robert M. Dreyer

Thirty years ago it was possible to locate a quarry site for crushed rock for concrete aggregate by finding the nearest solid rock bluff accessible by road, But times have changed and the location of a quarry site to furnish crushed rock for concrete aggregate now has become rather complicated, Although both sand and gravel can be used for aggregate, this discussion will be confined to crushed rock in the regions around a metropolitan area. Let us assume that a consultant has been retained to advise on the desirability, and the possibility, of opening a new quarry within a given area. The problems are geological and ecological. Since the geological problems are simpler, they will be discussed first. Generally, the first step is to make a market study of competitive aggregate sources within the projected area. Assuming that the quality of aggregate to be sold by competitors as well as their mining costs will, within narrow limits, be the same, the problem becomes essentially a study of haulage costs from established quarries into the projected new area. Since haulage cannot be effected along straight lines and since each quarry operator may have different unit haulage costs, a map showing lines of increasing cost intersecting points on roads available for truck haulage radiating from competitive quarries can be rather complicated. Such a map, more-over, changes each time a new haulage contract is negotiated by a

Jan 1, 1971

By Lawson. Heather

"The purpose of this study is to explore how the geochemical and petrographic components of coal may impact its physical properties, as well as how these components correlate with a history of reportable dynamic failure in coal mines. Dynamic failure events, also termed bumps, bounces, or bursts, are the explosive failures of rock in a mining environment. These events occur suddenly and often with no warning, resulting in worker injury up to and including fatality in greater than 60% of MSHA reportable cases. A database of variables was compiled using publicly available datasets, which included compositional geographic, strength, and Hardgrove Grindability Index (HGI) data (ACARP, 1998). Results indicate that bumping coals are less mature, lower in carbon, higher in oxygen, softer, and less well cleated than coals that do not bump. High liptinite content was found to correlate with higher average UCS values. However, no clear, direct correlation between UCS and dynamic failure status was observed. The findings of this study establish that differences exist between coals that have experienced reportable dynamic failure accidents versus those that have not. These differences are inherent to the coal itself, independent of mining-induced risk factors. Results further illuminate how compositional attributes of coal influence physical properties and begin to clarify potential links between geochemistry and dynamic failure status. Only through the better understanding of risk can more effective mitigating strategies be enacted.INTRODUCTIONDynamic failure events, also termed bumps, bounces, or bursts, are the sudden failures of rock in a mining or quarrying environment. Failure occurs when the rock’s critical bearing capacity has been exceeded and the rock fails energetically through the outward expulsion of rubblized material (Peng, 2008). These events occur suddenly and often with no warning, resulting in worker injury up to and including fatality in greater than 60% of reported cases through the Mine Safety and Health Administration (MSHA). Much research has been devoted to the prevention of these events. The effects of overburden depth and stiffness, mine design, mining practices, and in situ stresses are well documented (Agapito and Goodrich, 2000; Brauner, 1994; Campoli and Kertis, 1987; Holland and Thomas, 1954; Iannacchione and Zelanko, 1995; Lawson et al., 2016b; Mark, 2016; Newman, 2002; Peng, 2008; Whyatt, 2008). Despite these significant advancements in coal mine ground control, however, events continue to occur. Proactive risk mitigation remains an important research area. This is particularly true in underground coal settings, where the rockmass is layered, lithologically diverse, and does not exhibit consistent material properties across deposits.Many conditions have been associated with the occurrence of dynamic failure phenomena, including:"

Jan 1, 2019

By J. C. Purcupile

In this time of increased coal demand, a faster and safer method for roof support is needed. This report outlines the preparation and testing of a machine which we feel will help answer this need. The results of the tests are encouraging, and indicate that further exploration of the method should be continued.

Jan 1, 1975

By Seppo] [Kreula

Outokumpu Oy has acquired considerable experience with on-stream X-ray fluorescence analyzers and with computer control of flotation processes over several years. It became evident at the outset of this work that a reliable and accurate on-stream analyzer was more than a collection of different pieces of hardware linked together. Extensive work was done to develop an integral analyzer system, beginning with process samples through the spectrometer to report typewriters, recorders and the control computer. To date, over ten Courier-300 analyzer systems based on this development have been installed world-wide, several of which provide the key information for successful computer control systems. Computer control of flotation processes has been under development at the Pyhäsalmi concentrator since 1968. Two different control strategies have been implemented. The copper flotation is controlled by means of a mathematical model and economic criteria, whereas the "evolutionary operation principle" is applied to the zinc flotation. The computer control system installed at' the Vuonos-mine has been developed according to the same guidelines. In order to consolidate this wide experience, a flotation computer control system, Proscon-100, was developed by Outokumpu Oy, and the first system was installed at Kotalahti in 1972. In addition to the technological experience, enough information has also been gathered to illustrate the economical, benefits accruing through the use of these advanced tools of automation.

Jan 1, 1973

By A. R. Laplante

A test to determine the amount of gravity recoverable gold (GRG) in an ore is described. Typical GRG results are given; an error analysis is detailed; possible uses are discussed. Of the 38 samples tested, the lowest GRG content was found to be 25% (most below 25 11m, or 600 mesh), and the highest 94% (most above 300 11m, or 50 mesh). The average GRG content was 63%, with a standard deviation of 19%. Error analysis shows the test to be reproducible within 5 to 10%, depending on the size distribution and grade of GRG, and the sample extraction protocol. When using the same primary sample, reproducibility improves, 2 to 5%, depending on the amount of gold coarser than 850 11m (20 mesh) and sample weight. The test has been applied to greenfield project and retrofit applications, to determine the suitability of gravity recovery. For existing circuits, it has been coupled with a model of gravity recovery for optimization studies.

Jan 1, 1996