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By B. R. Waples

Sometimes a project is born easy, sometimes a project has a hard time being born. Probably every project can say we had tremendous problems to overcome and they would all be right. This project had all things happen to it. Born easy, a hard time after being born, there were tremendous problems to overcome but here it is, a major copper project, a major operation, and a new source of copper for Mexico and the world market. La caridad is an ore body located in the state of Sonora in northwestern Mexico. It is at an elevation of 1,200 meters above sea level and the nearest major city is Hermosillo, the capital city of Sonora. Hermosillo is located approximately 270 kms (about 168 miles) to the southwest of la caridad. North of la caridad, 130 kms (about 81 miles), is the U.S. border town of Douglas, Arizona, which has a sister city on the Mexican side of the border -Agua Prieta.

Jan 1, 1979

By Jianping Zuo, Chunlei Zhang, Yong Zhang, Shouyang Gao

To study the fracture evolution of overlying strata for ascending mining in a short-distance coal seam group, a two-dimensional physical simulation model was designed based on a specific geological condition. The fracture development zone was divided into the compaction zone and active zone by monitoring and analyzing the macro fracture evolution of the surrounding rock mass during the excavation of multiple coal seams. The secondary fracture development process of the overlying strata was demonstrated with a physical model. The quantity, length, and inclination of the fracture were calculated with MATLAB software, and the results were verified by geological radar. The total number of fractures between two coal seams increased with a “parabola” shape during the excavation of the lower coal seam, the crack angle was mainly vertical and horizontal, and the number of horizontal cracks first increased and subsequently decreased; the excavation of the upper coal seam caused the secondary fracture development process of the overlying strata, and the relief range and its extent increased. The mining-induced cracks from the lower and upper coal seams connected with each other, especially the permanent vertical fracture in the cutting room side and face side. Finally, the three-dimensional gas fissure was formed.

Nov 24, 2020

By David L. Martin

This paper discusses the development of a SLAM II* simulation model with imbedded optimization modules designed M evaluate mineral exploration and exploitation strategies. The model traces through a sequential exploration program, evaluating each deposit site based upon geologic information and potential profitability of the site. At a specified time during the simulation, a new production plan is developed for currently producing deposits which takes into account the planning horizon and deposits which are currently being explored. Potential uses of the model by geologists, engineers, and management decision makers include setting corporate objectives and policies on exploration and production. The model is also useful for testing past decisions to evaluate decision making criteria and evaluating mineral deposit profit potential.

Jan 1, 1983

By Saghar Farajzadeh, Fatemeh Kazemi, Ataallah Bahrami

Spirals, the most common equipment for the separation of heavy minerals such as chromite, are greatly affected by size distribution and the liberation degree (hence the specific gravity and size) of the feed particles. In this study, the efficiency of spirals in separation of low-grade chromite particles has been investigated by studying the distribution of grade, size distribution and liberation degree of feed, concentrate, and tailings of spiral. For this purpose, mass balance constraints were applied to the spiral-containing chromite processing circuit. Afterwards, the grade variations and size distributions have been investigated. According to the results, when the feed to the spiral has a larger size distribution, the enrichment ratio of the feed is 1.32 and, with the smaller feed size, this value has increased to 1.99. When the spiral feed has a larger size distribution and higher specific gravity, the recovery of chromite increases with increasing particle size up to 250 microns, and then with increasing particle size, recovery decreases with a relatively steep slope. Evaluation of spiral efficiency with respect to particle liberation degree has also shown that despite the high degree of liberation of spiral feed in size fractions smaller than 75 microns (88.9%), the liberation degree of spiral concentrate and tail in this faction is equal to and less than that of feed, which can indicate poor spiral performance in these size fractions.

Oct 27, 2020

A methodology has been developed and demonstrated to be effective in reclaiming surface-mined land for a forestry post-mining land use. The Forestry Reclamation Approach (FRA) has been applied, almost exclusively, to flat or gently rolling surfaces. One of the primary steps in the FRA is to loosely grade the top 1.22-m (4-ft) of soil or substitute root growth medium to avoid excessive compaction. Concern has been expressed by regulators and the public that loose grading on steep slopes could lead to slope failures, which is one of the issues that SMCRA sought to correct. A field investigation was conducted at a steep-slope contour operation in eastern Kentucky to test the applicability of FRA in this setting. Final grading was performed according to FRA standards. The surface consisted of two distinct substitute rooting media. One was unweathered gray sandstone and the other was a combination of gray sandstone, brown sandstone, and topsoil. A variety of native hardwoods was planted following the FRA guidelines. The slope was instrumented with 70 survey monuments to monitor for mass movement. The reclaimed spoil was also characterized using bulk density and penetrometer resistance methods. The characteristics of both spoils are similar to those observed on flat to rolling surfaces where the FRA has been used and, after one year, approximately 70% of the trees had survived. There has been no major mass movement of the slope and slope stability analyses indicate that the application of the FRA has little impact on the overall stability of the slope.

Jan 1, 2011

By A. Juganda, F. WILSON, G.E. BOGIN, H. PINHEIRO, N. SANDOVAL, J.F. BRUNE

To evaluate methane explosion hazards in underground longwall coal mines, researchers at the Colorado School of Mines developed a computational fluid dynamics (CFD) model along with a 1/40th-scale, optically accessible, physical model of a longwall mining section. In this project, CFD models assisted in the design of the physical model to ensure specifications were met to accurately represent the scaling physics as well as to assist in narrowing the experimental matrix and identifying key locations for sensor placement to measure velocity, pressure and gas concentrations. This research will help develop strategies for methane monitoring to prevent methane ignitions and explosions in longwall coal operations.

Dec 1, 2022

By Louis M. Schlesinger

KMG Minerals, Inc., a mica-feldspar-quartz producer in Kings Mountain, N.C., uses about 50% of its plant's -200 mesh slimes to manufacture brick. However, the company is unable to market the remaining 50% of this fine mineral mixture. The NCSU Minerals Research Laboratory operated a pilot plant to process these slimes to produce an additional product. The process, consisting of blunging and hydraulic sizing, was designed to separate a kaolin-enriched -270 mesh product from the bulk of the coarser +270 mesh "grit" minerals. Size analysis showed that this product was 80% finer than 20 microns and 50% finer than 6 microns (in equivalent spherical diameter). An evaluation indicated that it is a hydrous aluminum silicate that might be suitable in the filler and extender markets for traffic paint, some types of plastics, joint cements, and dusting compounds. Because of its high viscosity, it will be difficult to use more than a small percentage in cast ceramic bodies. However, it might be possible to use up to 10% in extruded ceramic bodies (i.e., electrical porcelain). The 15.2 cm (6 in,) diameter Linatex Hydrosizer was tested using a range of teeter water flowrates, so that the net rise velocity was varied from 0.10 cm/s to 0.40 cm/s. The solid feed rate to the sizer was maintained at approximately 1.1 t/hr/m2 (0.12 ton/hr/ft2). Tests were run using both "shallow" (i.e., 6 in.) and "deep" (i.e., 15 in. teetered beds. The best overall result was obtained when the sizer was operated with the "deep" teeter bed and a net rise velocity of 0.10 cm/s. About 97% of the +270 mesh material was rejected and approximately 79% of the -270 mesh material was recovered in a 14% solids slurry.

Jan 1, 1994

By Kanchan Mondal, Gopi Bylapudi, Anand Bhagwat, A. J. S. (Sam) Spearing

Corrosion of steel roof support systems can cause potential premature failure of the support, thus adversely affecting the excavation stability and rock-related safety. An in-house corrosion test system was designed and developed to test full-length roof bolts for material performance based on tensile load capacity and strength under different corrosive conditions found underground. Initially, ASTM A615 grade 60 steel roof bolts, which are the most commonly used bolt material in the United States, were tested with and without stresses in a simulated underground coal-mining environment for approximately six months. This paper mainly discusses the test system, protocol and system shortcomings, and makes recommendations based on the observations and results.

By David G. Van Hersett

The single most unique design feature of the Centralia Coal Mine is the public information program. Just what the heck does public information have to do with the development of a coal mine? The utilities of today have had to build larger and larger plants to keep down the costs of power to the consumer. The large plants require huge amounts of capital, take up large areas of real estate, consume unprecedented amounts of coal, and generate large quantities of waste products which have to be reckoned with. Coal mines supplying these plants have also increased in size and production to meet the power plants' unending appetite for coal. This means the disturbance of great areas of land and significant alterations to the landscape. Today's public is greatly concerned about the environment in which he is living. The great size of a power plant with its large stacks, coal piles, and the coal mine with its large earth movers, disturbed acreages and the resulting waste products of both operations appears to present a threat to his environment. Because of this,' many power plants and coal mines are having public acceptance problems. This has resulted in the passage of stringent legislation and in some cases brought upon construction delays for major power plants.

Jan 1, 1970

By J. G. Smith

Of the variables affecting the electrical properties of coal measure rocks, water content is by far the most important, This paper describes specially developed apparatus and methods of measuring electrical conductivity and permittivity at constant humidity conditions. Electrical properties variations were measured for Applachian and Illinois, U.S.A. coal 2 basin samples in the frequency range 2 X 10 to 2 X 10 Hz. Coal measure rock electrical behavior, when correlated with mechanical behavior, is potentially useful in a number of mining applications.

Jan 1, 1985

By M. Kaya

This paper presents an experimental method to determine the degree of gangue entrainment in mechanical flotation cells and proposes new and inexpensive methods to lessen it. The applicability of froth washing and vibration was studied in laboratory, pilot plant, and plant scales. The effect of wash water on metallurgical performance was tested with various streams from the Falconbridge Strathcona mill at laboratory, pilot, and plant scales, with the 2nd cleaner at the Eastmaque Kirkland Lake mill, and with the 2nd and 3rd zinc and 3rd and 4th copper cleaners at Les Mines Selbaie mill. It was found that gangue recovery was closely related to water recovery in all systems. Wash water at an optimum superficial rate from 0.03 to 0.07 cm/s reduced entrainment by anywhere from 30X to 70X. Wash water can be further assisted by mechanical and ultrasonic vibration of the froth. A further rejection of 10 to 20X becomes possible. As a result of this work, a number of plants in Canada and in the United States have evaluated and/or are now using froth washing.

Jan 1, 1990

By R. R. Klimpel

The use of chemical reagents in flotation has been studied in great detail, e.g. (1, 2, 3, 4). Important progress has been made on the understanding of surface chemistry concepts involved in flotation. However, such scientific studies are often very complex even for rather simple idealized systems. Therefore, the deve- lopment of predictive or quantitative tools for plant engineering evaluation is still in the evolutionary stages. Until further progress in fundamental work is achieved, the operating engineer is faced with semi-empirical physical testing of reagent changes on several sizes of the actual equipment under study to be confident of the economic viability of any change.

Jan 1, 1980

By Gilbert A. Bonforte, Hugh P. Caspe, Tracy K. Lundin

The Narragansett Bay Commission (NBC) Combined Sewer Overflow Abatement Program is a major effort to address and mitigate discharges from combined sewer overflows in the Providence, Rhode Island area. The proposed system consists of three deep rock tunnel segments totaling 17.8 km (11.1 miles) in length that will provide 860,000 cu m (227 million gal) of storage at depths up to 99m (325 ft). This paper discusses 13.5 km (8.4 miles) of 6.64m (21.8 ft) finished diameter tunnel, four construction shafts, 19 dropshafts and one large diameter pump station shaft tapered from 1 5.2m (50 ft) at the surface to 27.4m (90 ft) at depth. All facilities are in preliminary design.

Jan 1, 1995

By Leonard Harris

Since the end of the cold war following the collapse of communism, enormous amount of funds are pouring into the developing countries including investments by mining companies for the development of gold and silver mines. A great deal of these funds are destined for expenditure in areas riddled with bandits, terrorists and active and latent criminals bent on stealing the mine operators hard earned production on its way from the mines to markets. Brambles Security Services employs experts in the field of safely transporting gold and silver products under various alternatives and aimed at relieving the mine owners of this responsibility. This paper examines the various service options available.

Jan 1, 1997

By Steven A. Elmquist

INTRODUCTION R&D activities are needed, at a minimum, for a company's competitive survival followed in importance by the growth and diversification of the company. For most industrial companies, however, R&D is the business area that has been the most difficult relative to confident long-range financial commitments and effective control and relative to its value as a long-term investment. Investors look not only at the current profitability of the company but increasingly at the plans, actions, and quality of the personnel in position to improve the market position and profitability of an organization. "The strongest predictor of investment value is the degree of innovation of the 'company.' I believe this is true of both strategic planning and R&D activities." R&D is the lifeblood of a company's future. If this basic premise-R&D for survival and growth-is believed to be true, why is it necessary to "Sell R&D in your organization? My personal experience, in a number of organizations, is that R&D budget is perceived as a business element area that could be delayed or reduced to improve the bottom line during difficult business conditions. I believe the following quote speaks volumes about this subject-"There is only one thing I know for certain about research, and that is it costs money-lots of it." -Unnamed, Hard- headed Financial Executive. A business must make money and be profitable in order to maintain and create jobs, pay taxes, cover working capital and costs of goods sold, and most importantly, create value for its shareholders. The foremost element of selling R&D, therefore, is to consistently demonstrate the R&D group's contribution to the bottom line.

Jan 1, 2004

By W. G. Pariseau

Conventional barrier pillars in underground coal mines are intended to protect mains and sub-main entries for relatively long periods of time. Inter-panel barrier pillars that may be used in especially deep coal mines, say, below 800 m (2,400 ft), are intended to protect longwall panel faces and adjacent panel entries for the life of nearby panels. Barrier pillar failures have serious consequences, especially when failure is sudden and catastrophic. Design of barrier pillars is thus of considerable importance to safety and efficiency of operations. Locally, failure occurs at the limit to elasticity when stress tends to exceed strength. Strength of rock is stress dependent, so an analysis of stress is central to rational design of barrier pillars. There are several approaches to stress analysis for coal mine pillar design that range from the simplified but popular tributary area method including variations that use empirical definitions of the tributary area (volume) to more sophisticated numerical methods such as the boundary element method and the finite element method. Despite ease of use, empirical methods are limited and always suspect when applied to conditions beyond their scope of definition, while boundary element methods do not generally include pillars in the solution domain. The finite element method is not so restricted and thus is a natural choice for conventional and inter-panel barrier pillar safety analyses. Caving of roof strata certainly affects the distribution of stress about longwall faces and nearby barrier pillars. Conventional wisdom that considers roof strata to respond as cantilever beams indicates the longer the span the greater are loads on longwall faces and face supports. Failure of roof beams, caving, shortens spans and relieves face and support loads. The same view is applicable to barrier pillars in that long roof spans outside of barrier pillars leads to higher pillar loads than short spans. Hence, caving should be beneficial to barrier pillar safety. However, the benefit may be small depending on the extent of caving and only in the form of a slight reduction in overburden weight transmitted to the barrier pillar, especially in case of inter-panel barrier pillars. FINITE ELEMENT MODEL Finite element models for stress analysis in rock mechanics are formulated in consideration of physical laws, kinematics, and material laws. These models meet the essential requirements for equilibrium of stress, satisfy strain displacements relations, and in a general sense, relate stress to strain through material laws, often referred to as constitutive relations. The last may be complex and replete with nonlinearities. A de facto engineering material law is the elastic model in the form of Hooke?s law for linear, homogeneous materials that may be anisotropic. A limit to elasticity is imposed by strength in the form of a failure criterion or yield function that accommodates triaxial stress states. Examples used in rock mechanics are the well-known Mohr-Coulomb (MC)criterion, the popular Hoek-Brown (HB) criterion, and the Drucker-Prager (DP) criterion. The first is linear in stress, while the second is nonlinear. Both do not include any effect of the intermediate principal stress. The last is also linear in stress but includes the intermediate principal stress. All show an increase in the major principal stress at failure with confining pressure. In the UT2/3 finite element programs, the failure criterion Y is a nonlinear, anisotropic form and is also the plastic potential [1]: [YJI=+ 11NYJI=+- (1) ] where N is an exponent, usually 2, and J2 and I1 are nonlinear anisotropic forms of the second invariant of deviatoric stress and the first invariant of principal stress. The form (1) reduces to DP when N=1and isotropy prevails. When Y = 1, the limit to elasticity is reached and plastic deformation is possible. The material constants that enter (1) are all computed from unconfined compressive, tensile, and, in case of anisotropy, shear strengths. These latter strengths may be estimated from conventional laboratory test data. Of course, joints in field-scale rock masses induce different values. How different is often a matter of conjecture. For comparative studies, laboratory rock properties seem adequate. Inelastic, that is, plastic behavior occurs with strain beyond the elastic limit. Strain hardening, ideal plasticity, and strain softening are possibilities. Ideally brittle behavior with complete loss of strength is an extreme form of strain softening [2]. Caving may also be considered as strain softening with a less drastic reduction of material properties. As intact roof strata fail, fall, and form a rubble pile below, a new material is formed with greatly reduced elastic moduli and strengths, say, 1/100th of the original intact moduli and strengths. From another viewpoint, caving is simply a natural cut and fill process. Input for stress analysis by the finite element method includes: 1. Preexcavation stress state 2. Geology (stratigraphic column) 3. Structure (major faults, joint sets) 4. Elastic moduli 5. Strengths, and specific gravities of each rock type 6. Excavation sequence Output from an analysis includes distributions of: 1. Stress 2. Strain 3. Displacement 4. Local factor of safety (element fs) The last is defined as the ratio of strength to stress and in view of the failure criterion (1), is the ratio [fsJstrengthJstress=] where the numerator is the maximum possible value and the denominator is the actual value of the square root of the second invariant of deviatoric stress. This invariant is a measure of shear stress intensity but also reduces to uniaxial tensile and compressive strengths as the case may be. An fs greater than 1 indicates an elastic state of element stress; a value of 1 indicates the limit to

Jan 1, 2009

Careful financial analysis of capital investments has always been a vital task in mining which is one of the most capital intensive sectors of the economy. Furthermore, mining costs have leapt ahead at an astonishing rate in recent years not just due to accelerated inflation, which affects everyone, but also due to the imposition of enormous costs of enviromental regulation and the continuing decline in ore tenor. Not only have unit costs risen, but the amount of effort expended to recover a pound of metal has increased due to the inexorable decrease in ore grades. New low-margin, high-volume mining investments place increasing importance on sound financial planning. Owing to the enormous investments involved, a greater share of individual corporate resources is committed to these projects than is normally the case in other industries. Thus, the consequences of failure are extremely grave, and a close examination of all inputs to the evaluation equation is clearly indicated.

Jan 1, 1979

By V. Svalbonas

When the Trelleborg Divisions of Boliden Allis and Mineral Processing Systems (MPSI) merged, a unique opportunity occurred for two independent mill fabricators to compare design pro¬cedures and the research upon which they were based. Several semiautogenuous (SAG) mill analyses are compared using Boliden Allis and MPSI methods. The differences and similarities are then used in a correlation of critical stress definitions and the acceptable design and inspection criteria. Given the opportunity to compare the total philosophies and methods of several companies involved in the design and fabrication of grinding mills, it was important to first develop the comparison method and ground rules. One option was to compare analytical methods by details such as numerical techniques and accuracies. However, this option was discarded in favor of a more general approach. The question that was finally posed was in two parts. Given an identical mill requirement: • What would be the difference in the analytical design result, and to what aspect of the analytical process could this difference be attributed? • What would be the difference in approaches to obtaining the final hardware in subcontracting, both in specifying and Quality Assurance surveillance? By using this comparative approach, questions of relative conservativeness and reliability would automatically be answered.

Jan 1, 1992

By Steven Schurman

Acid Rock Drainage (ARD) is one of the most serious and persistent pollution problems facing today's mining industry. ARD is formed when pyrite (FeS) is exposed to natural weathering conditions. Pyrite weathering, formally the oxidation and hydrolysis of pyrite, leads to the generation of soluble, hydrous iron sulfa-salts and the production of acid in the form of H+. The resulting effluent is water that is characterized by high levels of iron (and any other metal contained in the rock undergoing weathering) as well as high concentrations of sulfate and a low pH (acid). Rocky Mountain Remediation Services, L.L.C., has developed a patents pending Envirobond'™ product, Envirobond™ ARD, to treat acid rock drainage. Treating pyrite with Envirobond™ ARD inhibits the oxidation and hydrolysis of pyrite thus curtailing the pyrite oxidation cycle.

Jan 1, 1999

By John W. Carson, David S. Dick

The last few years have produced new methods of characterizing flow properties of bulk solids. Abrasive wear and particle attrition can now be accurately measured in a laboratory and scaled up to field condi¬tions. In addition, the effect of large par¬ticles on a material's flow properties (cohe¬sive strength, bulk density, wall friction) can be determined as well as the effects of var¬ious additives such as freeze conditioning agents. New developments have occurred with devices to improve the reliability of solids flow. Much attention has been paid to find¬ing ways, by using inserts, to provide a mass flow pattern with relatively shallow hopper walls. Such devices can also provide reli¬able in-bin gravity blending of bulk solids or completely nonsegregated discharge. Other developments have occurred in the area of belt-to-belt transfer chutes and sealing screws. The technology and hardware for running bench scale flow tests on bulk solids samples and transforming the results into reliable designs has been in existence for nearly 30 years (Jenike, 1964; Marinelli and Carson, 1986). It has been shown repeatedly that reliable materials handling systems can be designed to avoid the problems of no-flow due to arching or rat-holing, erratic flow, segregation, loss of capacity, or spontaneous combustion. Running flow properties tests and carefully designing a bulk handling system are not expensive, particularly when compared to downtime costs and continual flow problems. New developments in characterizing flow properties of bulk solids include: • a shear tester for measuring the properties of run-of-mine ores containing large par¬ticles; • attrition testers to simulate a wide range of flow conditions; • a tester to measure the wear rate of liners in bins, feeder parts, etc.; • a dustiness tester to measure the potential for dust and the effect of dust control meas¬ures; and • techniques for measuring the strength of frozen ores and the effect of freeze condi¬tioning agents. In the area of improving the flow of bulk solids, there are new techniques for ensuring reliable flow without using up excessive headroom. These include: • belt-to-belt transfer chutes to handle po¬tentially sticky, abrasive, and dusty ores; • designs for the interface between a bin/ hopper and apron or belt feeders to avoid hangups and minimize feeder loads; methods to feed solids reliably into a pres¬surized process; and designs for handling systems that will mini¬ mize attrition, avoid segregation, or auto¬matically blend materials together. Characterizing flow properties Large shear cell It has long been known that the cohesive strength of a bulk solid is due mainly to its fine fraction. However, the effect of the larger particles (that were assumed to re¬duce the strength) could not be measured. The development of larger scale (205 mm¬diam and 0.6 x 0.9 m or 8 in.-diam and 2 x 3 ft) shear testers has made it possible to measure the properties of a wider range of materials. Now cohesive strength measurements can be made with up to 100 mm (4 in.) particles. The results obtained from the large shear testers, together with the results of the nor¬mal shear tests on the fine fraction, are used in the design of reliable stockpile reclaim systems and crusher feed systems. A high percentage of large particles can reduce the measured shear strength of a bulk solid. However, segregation may alter the size distribution and should therefore be considered (Carson, Royal, and Goodwill, 1986). In addition, larger particles will

Jan 1, 1989