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By D. Carlson

At the Freeport Indonesia Grasberg Mine in Irian Jaya, Indonesia, a system of underground drainholes and surface drain wells have been designed and are currently under construction. The underground drainholes are located at elevations of approximately 9,600 feet and the surface drainwells located at elevations ranging between 12,500 and 13,000 feet. Together they will be used to drain the ground water contained within relatively incompetent rock. This drain system will allow for the successful dry mining of the open pit, and provide slope stability of the pit wall. The surface drain well network, when completed will allow for the draining of ground water to the Amole Drift where the underground drainholes are constructed.

Jan 1, 1998

By P. Legast

Serpentinite minerals are available in large quantities from asbestos mining activity. The granular or fibrous serpentite, at temperatures greater than 700°C, will recrystalize into olivine, forsterite and enstatite. These minerals have been used and studied for decades and are environmentally safe. The thermal process changes the composition and properties of the original mineral. Therefore, the substitution of the original mineral cannot simply be made and the applications for these new synthetic minerals need to be redeveloped. The two original mineral forms allow a wide range of new synthetic raw materials which can be adjusted to specific applications or custom needs.

Jan 1, 1993

By H. Kempton

New methods for remediating metals-contaminated groundwater include in-situ emplacement of highly adsorptive substrates to permanently retard solutes. Substrates are introduced by sequential injection of soluble components that precipitate in the aquifer, forming a permanent high-retardation zone. This method overcomes the factors that limit pump-and-treat remediation; i.e, long-term source loading and slow desorption. Column tests demonstrated efficient substrate emplacement, increasing retardation coefficients of Cr(VI) by 20 and As(V) by 40. Similar effectiveness is expected for other heavy metals. Simulations using a coupled advective-geochemical model accurately matched substrate emplacement and arsenic attenuation, allowing extrapolation to other constituents and larger-scale applications.

Jan 1, 1999

By R. L. McNearny

A comparison study was conducted between an actual physical model and a numerical model based on the physical model of the block cave mining method. Results from the numerical analyses closely simulated the blocky behavior of the physical models, including bridging and interlocking of the simulated orebody during draw. The draw-down patterns and the rate of draw developed during numerical modeling also closely simulated the physical models. An unexpected result from the numerical modeling was the development of a zone of downward deflection which preceded the development of the zone of material movement.

Jan 1, 1997

By Harold B. Goldman

On the basis of tonnage, the sand and gravel industry is the second largest nonfuel mineral industry in the United States. In 1990, the production of sand and gravel was 927 Mt valued at $3.4 billion. California, which leads the nation with more than 126 Mt, together with Texas, Washington, Michigan, and Ohio, account for 36% of the total production in the nation (Table 1). In commercial usage, sand applies to rock or mineral fragments ranging in size from particles retained on a No. 200 Sieve (0.074 mm openings) to those passing a No. 4 Sieve (4.76 mm openings). Gravel consists of rock or mineral fragments larger than 4.76 mm, ranging up to 88.9 mm maximum size. The construction industry consumes 97% of the sand and gravel produced; the remainder is sand used for specialized products such as glass (see chapter on Industrial Sand and Sandstone and Glass Raw Materials). Utilization The building industry uses sand and gravel chiefly as aggregate in portland cement concrete, mortar, and plaster; the paving industry uses sand and gravel in both asphaltic mixtures and portland cement concrete. Aggregate is commonly designated as the inert fragmental material that is bound into a conglomerate mass by a cementing material such as portland cement, asphalt, or gypsum plaster. Sand and gravel is also used as construction fill, road base and subbase, and decorative material. Portland Cement Concrete Aggregates: Portland cement concrete consists of sand and gravel surrounded and held together by hardened portland cement paste. Concrete mixes commonly contain 15 to 20% water, 7 to 14% cement, and66 to 78% aggregate. Sand and gravel used as concrete aggregate have to meet many requirements (Goldman and Reining, 1983). Premature deterioration of concrete has been traced in many instances to the use of unsuitable aggregates. Asphaltic Aggregate: Asphaltic mixtures used predominantly for paving consist of combinations of sand, gravel, and mineral filler (material finer than 0.076 mm), uniformly coated and mixed with asphalt produced in the refining of petroleum. Sand and gravel used as asphaltic aggregate must meet the same general physical requirements as materials used for portland cement aggregate. GEOLOGY General Requirements of Aggregates Construction aggregate has many requirements that are difficult to meet if only unprocessed material from natural deposits is used. Suitable material is composed of clean, uncoated, properly shaped particles that are sound and durable. Soundness and durability are terms used to denote the ability of aggregates to retain a uniform physical and chemical state over a long period of time so as not to disintegrate when exposed to weathering and other destructive processes. Individual particles must be tough and firm, possessing the strength to resist physical stresses and chemical and physical changes, that may cause swelling, cracking, softening, and leaching. The aggregate should not be contaminated by excessive clayey material, silt, mica, organic matter, chemical salts, and surface coatings. Physical Properties: The quality of aggregate depends upon its physical and chemical properties. These, in turn, may be inherent mineralogical and textural features of the rock or may be the effects of later changes such as tectonics, mechanical or chemical weathering, or incrustations. The physical properties most significant for concrete use are: 1) abundance and nature of fractures and pores, 2) particle shape and surface texture, and 3) volume changes which may occur because of freezing and thawing or wetting and drying. An aggregate is considered to be physically sound if it is adequately strong and capable of resisting the agencies of weathering without disruption or decomposition. Minerals or rock particles that are physically weak, extremely water absorptive, and easily cleavable are susceptible to breakdown. The use of such materials in concrete reduces strength or leads to early deterioration by promoting weak bond between cement and aggregate, or by inducing cracking, spalling, or popouts. Severely weathered, soft, micaceous, or porous materials may cause localized stresses to develop in concrete by swelling and shrinking during wetting and drying or freezing and thawing cycles. Physical Suitability of the Various Rock Types. Sedimentary rocks have a wide range in physical and chemical qualities. Sand- stones and limestones, if hard and dense, are ordinarily satisfactory, but many sandstones are friable and excessively porous and commonly are clay-bearing. Shales generally make poor aggregate material, being soft, weak, and absorptive. Most igneous rocks are satisfactory, being normally hard, tough, and dense. Tuffs and certain flow rocks may be extremely porous and have high water absorption and low strength. Metamorphic rocks differ in character. Most quartzites are massive, tough, and dense. Fine-grained marbles are usually durable, but coarse-grained marbles have low abrasion resistance. Gneisses are ordinarily very tough and durable. Some schists contain micaceous minerals that are undesirable because they are soft, laminated, and absorptive. Micaceous minerals are susceptible to splitting along cleavage planes and thereby impair particle strength and durability. Some schists and slates in particular are thinly laminated and tend to assume flat slabby shapes that lack strength-and do not pack well. Any or all of these rock types may be rendered undesirable because of harmful exterior coatings. Weathering processes, particularly the action of ground waters, deposit these coatings. The most common coatings are calcium carbonate, clay, silt, opal, chalcedony, iron oxide, manganese oxide, and gypsum. Particles with these coatings are undesirable as aggregates because the bond between particle and coating may be weak, and decreasing the strength of the aggregate-cement bond.

Jan 1, 1994

By J. G. Groppo

A beneficiation process has been developed to provide selective separation of unburned carbon from high LOI fly ash. Previous reports of utilizing froth flotation to achieve selective separations required long residence times and high reagent costs. A proprietary reagent system has been developed to address both of these limitations. Based on the results obtained from laboratory and pilot-scale investigations, a flowsheet design has been developed to produce two distinct usable products from class F fly ash; low LOI ash and a high carbon product suitable for reburning or further upgrading. A process flowsheet and description are presented.

Jan 1, 1996

By Dirk van Zyl

It can systematically assess if the control and management systems designed for protection of sensitive ecosystems are adequate. The results of the assessment can help to identify key elements in the project that pose higher risks due to uncertainties in design. These assessments can then be used to make recommendations to further manage and reduce risks as the project is developed. QUALITATIVE RISK ASSESSMENT The general principles of a risk assessment are well summarized by Kaplan and Garrick (1981): "In analyzing risk we are attempting to envision how the future will turn out if we undertake a certain course of action (or inaction)." Fundamentally, therefore a risk analysis consists of an answer to the following three questions: What can happen? (i.e. what can go wrong?) How likely is it that that will happen? If it does happen what are the consequences?" Risk assessments can be performed using various levels of sophistication depending on the amount and accuracy of data available. A qualitative risk assessment uses descriptors throughout to express the level of risk. The definitions of the descriptors are presented in terms of the magnitude or concentration of contaminants. The results of a qualitative risk assessment can be used to: a)Document the evaluation and decisionmaking process. Although differences of opinion may exist about the definitions of the descriptors, the process is well-documented; b)Express the relative risk associated with specific activities or design elements; and, c)Select those failure modes or release mechanisms that may result in significant risks. These mechanisms can then be further developed in quantitative risk assessments. A qualitative risk assessment can be performed in a systematic approach using four steps (Van Zyl, 1987): A qualitative environmental risk assessment can be used to describe the risks associated with the development of a new mine and to make an evaluation of the adequacy of its design for environmental protection. The relative magnitude of risk associated with selected failure modes and exposure/consequence scenario assessments is the final result of a qualitative risk assessment. These failure modes are based on site specific areas and components, and mining and construction phases. The four steps of a risk assessment (hazard assessment, exposure assessment, consequence assessment, and risk characterization) are used in the development of a qualitative risk assessment. Relative magnitudes (using a five point scale of negligible to high) for each step, can be quantified in a qualitative risk assessment. Development of the descriptors for the relative magnitudes in each step is a very important part of a qualitative risk assessment. The success of a qualitative risk assessment depends on the adequacy of the information base and the subjective judgements made in each step. The quality of the risk assessment is, therefore, dependent on the experience of the assessors. A mining project in a sensitive coastal environment is presented as an example to demonstrate the application of a qualitative risk assessment. INTRODUCTION Environmental impacts from mining operations have been a significant factor in the last century. This was especially the case prior to the development of a better understanding of environmental processes and the potential impacts of acid rock drainage (ARD), and associated heavy metals, or the uncontrolled disposal of tailings and waste rock (Smith, 1987). Much care has been exercised over the last two decades in designing and operating mines to limit the environmental impacts as far as possible. All new mines are specifically designed with mitigative methods to manage such potential environmental impacts. Attention is directed to ARD impacts, safe disposal of mine waste rock and tailings, transportation and storage of chemicals and fuels, and final reclamation. A qualitative risk assessment can be used to address all project systems and activities that may potentially pose a risk to the environment.

Jan 1, 1992

By J. Paraszczak

Water-powered jackleg rock drills, introduced recently in South African mines, are reported to be more efficient, faster and more comfortable to operate than conventional pneumatic drills. Comparative testing of these drill types was performed in Quebec. Based on the test results and on time studies performed in the mines, water-powered drilling was reviewed. The review considered the drilling rates achieved, the infrastructure needed, side effects and health and safety considerations. This study shows that the application of water-powered drills may, under specific conditions, help increase the footage drilled and may improve the working environment. Examples of such applications are presented in the conclusions.

Jan 1, 1997

In this study, numerical simulations of yield pillars employing the finite element method with time-dependent Drucker-Prager material model are conducted. The stress control mechanism of yield pillars on weak floor strata is studied. The development of pillar yield zone, the distribution of pillar stress and the development of failure zone in the weak floor strata are investigated. The study indicates that a properly selected yield pillar size may significantly reduce the peak stress induced in the weak floor strata and effectively control the development of failure zone in the floor.

Jan 1, 1999

By Tim Wolf, Barry Fink

Mine site managers reported occurrences of locking assembly bolt failures on the Enlow Fork Coal Mine's slope belt conveyor. The observations were made after a number of years of operation and raised questions as to the status of the assemblies in operation. These questions prompted a detailed review of the situation by independent consultants. Using operational history of the conveyor and confirmation of belt loads by static and dynamic methods, a locking assembly fatigue curve was created to suggest expected service life. From this work, suggestions were made to modify the pulley assemblies for extended service life.

Jan 1, 2002

By J. P. Savely

This paper describes the development of a trim blast design to improve the stability of a final pit wall. Description is given of the effects of rock characteristics, rock type, and pit plans on the blast design. Currently, six benches have been mined with trim blasting. A more stable final wall has resulted and the successful program has reduced mining costs over an extended time period. Low-cost blast monitoring and field observation were used to determine peak particle velocity and blast damage. Using criteria developed from this relationship, trim blasts were designed and evaluated.

Jan 1, 1987

By James P. Cooney

The global mining industry is in the process of redefining its activity and purpose in terms of sustainable development. This process is impelling a growing number of companies to engage their stakeholders on environmental and social issues. Nongovernmental organizations (NGOs) have customarily acted as critics of the mining industry's performance. A new relationship between mining companies and NGOs is emerging in the context of sustainable development, ranging from dialogue to joint action. If positive interaction among mining companies and NGOs is to succeed, clear terms of engagement must be articulated, and measurable progress toward achieving both corporate and NW objectives must be demonstrated. The experience of Placer Dome is illustrative of the rewards and challenges of engaging with NGOs.

Jan 1, 2001

By K. S. E. Forssberg, K. Hanumantha Roa

Batch flotation tests are carried out with phosphatic material from LKAB, Sweden containing carbonatic and siliceous gangue while using sodium oleate as collector and sodium silicate as modifier. The pulp liquid is analysed for oleate, silicate, carbon dioxide, calcium, magnesium and phosphorous after each flotation test under different reagent conditions and flotation pH. Theoretical calculations of thermodynamic chemical equilibria in apatite-calcite-sodium oleate-sodium silicate system have been carried out with the help of SOLGASWATER computer program. During the calculations, the chemical variables are maintained similar to the operating chemical variables in flotation. A comparision between the experimental and theoretical chemical equilibria has been made and the flotation behaviour of apatite is discussed with reference to the theoretically calculated pulp model.

Jan 1, 1993

By C. Milne, T. M. Dyhr, T. E. Wilson

As time progresses, new concerns regarding long-term post-mining effects are identified, increasing mine closure costs. Regulators responding to public interest must take a “worst case” view and require post-closure monitoring or remediation processes. Although closure costs depend on the size and type of operation, general cost categories are defined, and median values (per acre, or per unit of production) are identified. Closure cost categories, as well as amounts, have increased with time. Except for increased efficiency in earth-moving and water management (surface or subsurface), there are no apparent offsets to a steady rise in closure costs. When the historical trend of closure costs is considered, it is probable that additional cost categories will come into being. For mine operators, the challenge will be to anticipate them and devise cost-effective remedies.

Jan 1, 2003

By John R. Marks

The recent trend in the ventilation of deep under- ground metal mines in the United States is to rely more and more on refrigeration for air cooling. This paper describes the layout and the economics of the refrigeration method used by Hecla Mining Company at the Star Mine. An economic analysis must compare the benefits of an engineering system against the costs. The benefits of refrigeration, for example, are increased production rates, a better safety record, improved employee moral, and generally lower airflow requirements. Air-conditioning costs include capital expenditures for equipment, labor and supply costs for maintenance, and power costs for machine operation. A study of whether or not to install refrigeration becomes academic when a mine reaches the critical ventilation depth1 (the depth at which adiabatic compression alone produces station temperatures equal to the desired stope temperatures). Ventilation planning alternatives for such mines, including the Star Mine, are limited to the different methods of refrigeration usage. In this case study of the Star Mine, the refrigeration layout is described in detail. After the system performance is discussed, air-conditioning costs are calculated. The paper then concludes with a cost- benefit analysis of the Star Mine refrigeration system.

Jan 1, 1980

By L. M. Petrie, D. C. Marozas, S. E. Paulson

The US Bureau of Mines (Bureau) is conducting research to evaluate the potential for developing an in situ leach mining process that will selectively extract manganese from oxide ores, leaving gangue relatively undisturbed. To accomplish this, a geochemical approach based on deposit-specific information, such as mineralogy and geology, is used to constrain the operating parameters of the system. Among the studies being conducted are: • leaching experiments to define reaction mechanisms and kinetics, • detailed petrologic characterization at the microscopic scale to assess manganese distribution and leaching efficiencies, • deposit characterization and evaluation, and • development of potential manganese recovery schemes. Data from these studies are being used to develop engineering design information for an in situ mining process. Specific details of the Bureau's research project are discussed, including results obtained to date.

Jan 1, 1993

By Keith A. Heasley

The objective of this paper is to back-analyze the August 6th ,2007 collapse at the Crandall Canyon Mine in order to better understand the geometric and geo- mechanical factors which contributed to that collapse. In this work, the LaModel boundary-element program along with the best available information is used for the back- analysis. To initiate the analysis, a six step base model of the mining in he Main West area was developed. This base model included a step for each of the critical stages in the mining of this area. Next, calibrated values for the critical input parameters: rock mass stiffness, gob stiffness and coal strength, were developed and optimized based on the best available information. Finally, the model was used to simulate the final mining scenario. As a result of this back analysis , a number of conclusions can be made concerning the mine design and the August 6th collapse: 1) Overall, the area was primed for a massive pillar collapse because of the large area of equal size pillars, 2) The abutment stress from the active retreat sections and the adjacent longwall panels were significant contributors to the collapse, 3) From the modeling alone, it is not clear exactly what triggered the August collapse, although the active mining is a reasonable assumption.

Jan 1, 2012

By J. Mark Richardson

Steady-state flowsheet simulators for mineral processing plants have evolved to a current high level of utility and accuracy. Reliable, general-purpose, semi-empirical models now exist in nearly all unit operations categories particularly in the areas of comminution and classification. .These models, installed as user-selectable functions within the integrated frame- work of flowsheet balance-solver software systems, can be strung together to represent any plant configuration. In addition, CAD-like graphics, data reconciliation and model parameterization functions have become standard features of the current generation of integrated plant simulators. These advances have given engineers the capability to investigate many different plant scenarios while requiring a minimum of actual plant testwork. This paper describes a methodology and an integrated software package which are being successfully applied in a number of operating plants worldwide to predict plant performance under changing conditions. Those conditions which can be changed include effect-of ore type, feed size, water addition rates, equipment geometries and flowsheet modifications. By using data from actual plant optimization exercises in real mills, the paper illustrates and out- lines a technique which includes plant data collection, ore breakage testing, flowsheet simulation, model-fitting (parameterization), data adjustment and model experimentation. Brief descriptions of some unit operations models, such as autogenous mills and cyclones, are provided as examples of the current state of such models. Ore breakage testing and its relation to certain models is also discussed. Computer- generated size-distribution graphs, along with tabular data generated by the simulator, round out the presentation and serve to demonstrate the real- ism and accuracy of the models. The paper concludes with a partial list of cases where this technology has been successfully applied.

Jan 1, 1992

By Roman Pyrih, Jim V. Rouse

Because cyanide is a naturally-occurring chemical, geochemical and biogeochemical mechanisms exist to retard or attenuate the movement of cyanide and its compounds in the subsurface and to degrade such compounds into low-hazard reaction products. The attenuation capacity of subsurface earth materials can be measured, predicted, and enhanced by simple and inexpensive procedures. The paper describes methods of testing the geochemical and biogeochemical attenuation capacity of the subsurface and offers general suggestions for methods of enhancing such capacity. It also presents examples of data which documents such attenuation.

Jan 1, 1991

By K. R. Wood, P. M. Blythe, J. A. Finch, M. L. Lavallee

A new analytical approach for characterizing and improving the performance of ball milling is presented. Individual ball mill circuit design and operating variables can be related to overall circuit performance through two distinct parameters for classification and breakage. The ball mill circuit functional performance equation is presented. Applications in the industrial plant and in the research field are discussed.

Jan 1, 1991