Search Documents

By B. C. Haimson

The Committee on Rapid Excavation of the National Research Council has recognized in its 1968 report the need for "improvement of rock-mechanics techniques for measuring subsurface stress field in deep boreholes and for determining stress distribution in walls of underground excavations". The technique recommended in this paper as being most suitable for both deep hole and tunnel wall stress determination is Hydraulic Fracturing. Using this method stresses are calculated directly from the fluid pressures necessary to initiate and extend a fracture away from a borehole. Stress determination by hydraulic fracturing is rather insensitive to inhomogeneity or anisotropy, is not limited in depth except by the length of the hole, requires simple equipment which is commercially available, and can be carried out by unskilled personnel. The method has been worked out theoretically and extensively tested and verified in the laboratory. A number of field tests in deep holes ranging from 300 to 6300 ft have yielded surprisingly good results. Preliminary underground tests have been very encouraging and most recent measurements in a tunnel complex at the Nevada Test Site yielded stresses that were both consistent and reasonable when compared with the expected directionsand magnitudes. It is recommended that hydraulic fracturing be considered as a method of in-situ stress measurement both in the pre-excavation stage of design and during tunneling.

Jan 1, 1974

By Jaril B. Lavrencic

The unique and irregulator distribution of working places in a mine always poses the two questions: - which and how much production equipment is to be used, - what production can be expected. Since the development of analytical methods would be impractical for such cases, a lot of computer programs has emerged in recent years trying to simulate the productiom process and thus find the best answer. The usege of a simulator has its dark side well felt by the author(s) of such a program: the credibility and the confidence of the customer. Using the simulator means to respect and to incorporate all the restrictions imposed by the narow underground space, methods of production, safety regulations etc., which can turn out to become a major programming effort. If the program is not properly structured, it will be used for a single special' case only, and never again. In this paper the structure and internal mechanism of the simulator is described for which the author believes that can easily be adapted to conditions of various underground and open pit mines. MINSIM tries to reach the following rather ambitious goals: 1) Estimation of the production before opening the mine, or a part of the mine. 2) Training the personnel to make decisions. 3) Making the daily time schedules for the entire fleet of the equipment units.

Jan 1, 1989

By James Sheridan

Risk can generally be defined as the possibility or chance of a loss corresponding to uncertainty. Analysis is the process for examining the components and relationships of a complex system in order to determine the impacts of its variables. Risk analysis is therefore a course of action taken to analyze multiple variables of a system that is subject to speculative outcome. When risk analysis is applied to mine development, it becomes the means for assessing and measuring those parameters that contribute to economic viability. Mining can be a risky business. It is composed of an assortment of factors that contribute to its financial outcome. Of these factors, the most consequential output is the net present value (NPV). Applying risk analysis in mine development can identify those factors having the most significant impacts and applying limits to those impacts. Mathematical computer modeling using Monte Carlo techniques is available and can be customized to suit specific mine development ventures. Essentially, those parameters that are not fixed values can have input variability. Rationally deduced engineering estimates should be the basis for determining the initial values applied as inputs in the models. Risk analysis therefore provides the user a means to identify, rationalize and assess the risks in mine development in an informed, calculated, and unbiased format for making economic decisions.

Jan 1, 2002

By J. Harrison Daniel

Increasing mechanization of underground mining operations throughout the years has reduced the dependency on large, concentrated working forces. Fewer workers in scattered locations, coupled with the versatility of diesel equipment to load and haul personnel, supplies, and mineral ore, has made diesel equipment attractive in mine feasibility and design studies. The use of the mobile equipment along with higher production or "bulk" mining methods provides for more efficient mineral extraction systems. These systems are expected to become more widespread until long-term research provides a further evolution to more complete automation of underground mining. The U.S. Department of the Interior, Bureau of Mines, has been conducting research to reduce the health and safety hazards posed by increasing use of diesel equipment and the higher power ratings being proposed. The goal is to provide for safe and efficient use of the equipment. The National Institute for Occupational Safety and Health has recommended that diesel exhaust be regarded as a potential occupational carcinogen adding importance to the Bureau's research program. The paper describes advances in engine design, the use of diesels in mining operations, and significant health and safety research accomplishments of the Bureau of Mines. These accomplishments will help assure that diesel equipment remains an option for determining the most efficient system to mine an ore body.

Jan 1, 1989

By Kenneth L. Rubow, Virgil A. Marple, Ye Tao

Techniques are being developed for measuring the mass concentration of respirable diesel exhaust particles found in underground coal mines. Studies have been conducted over the past five years to investigate size selective sampling techniques to measure the respirable mass concentrations of diesel exhaust and mine dust aerosol particles in underground coal mines. Results from these studies have been used to develop design and performance criteria for a personal diesel exhaust aerosol sampler. Three personal diesel exhaust aerosol samplers have subsequently been designed and evaluated in both laboratory and field settings. These samplers use size selective classifiers for the determination of the respirable mass concentrations of mineral dust and diesel exhaust particles. Their designs are based on the premise that diesel exhaust particles are predominantly less than 0.8µm while mineral dust is greater than 0.8 µm. One design, selected for field evaluation, consists of a 10 mm nylon respirable dust cyclone followed by a 0.8 µm cutpoint impactor and afterfilter. The cyclone removes the large nonrespirable particles while the inertial impactor stage, collects the mineral dust on an impaction plate and allows the diesel particles to penetrate to an afterfilter. The two sample fractions of the respirable particles (<0.8 µm and >0.8 µm) are gravimetrically analyzed to determine the concentrations of the diesel and mineral dust portions in the respirable coal mine aerosol.

Jan 1, 1991

By Karel SPIRKO

The one-dimensional mathematical model of unsteady-state heat conduct ion through multilayer (wall and floor of airway consist of several layers of material and rock) and two-surface (dry and wet surfaces) airway wall and airway floor with convective heat and moisture transfer between their surfaces and mine air with time dependent changes of temperature and humidity has been developed on the basis of introduction of acceptable simplifications of description of heat and moisture transfer between rock mass and mine air. The analytical solutions for calculation of the surface temperature of any type of surface of airway wall/floor and for calculation of water vapour pressure near the wet surfaces at given time are obtained by means of the model presented. These solutions are illustrated for the case of general harmonic course of air temperature and humidity. Balance of heat and moisture transfer between surfaces of airway wall and floor and mine air is solved by an iterative method in the partial sections of airway. The temperature and the humidity of mine air on the outlet of each partial section of airway at given time are its resolutions and they are the input data for following partial section. By this way it is possible to solve complicated dynamic changes of mine air temperature and humidity in an air way system by relatively simple mathematical apparat.

Jan 1, 1991

By David A. Gulley

One of the advantages of the market¬place, economists believe, is that it automatically generates information which would otherwise be hard to come by. For example, supply and demand signals imply something about private and social sacrifices and benefits. This information is seldom perfect, and can neglect some costs and benefits, but it nevertheless is crucial data. Moreover, marketplaces can also eliminate the need for some information. For example; since market participants are voluntary actors, only those transactions are culminated in which a mutual gain occurs. This eliminates the need for some cost-benefit calculations. A corollary to this standard economic doctrine is that whenever a government or other party supplants a marketplace, it must generate some of the information either lost or newly-needed. (Schultze, 1977) In 1981, following a ten-year moratorium the United States government resumed leasing of publicly-owned coal. When the government designed this program, the goal was to guide the marketplace, rather than merely to respond, as a landlord, to the market&apos;s wishes. This goal has been modified somewhat, due both to the changing political climate and to the practical difficulties of implementing so ambitious an undertaking. Nevertheless, during this period of program design and implementation, part of the challenge of creating and using the necessary information fell to the professional modelling fraternity.

Jan 1, 1982

Some basic terms used in cost management and accounting include: - Cost. A sacrifice made to acquire goods or services, measured by the price paid. Technically, the sacrifice is called a cost until the benefits from the goods or services have expired, at which time the sacrifice is called an expense. In this text, the terms "cost" and "expense" are used interchangeably. - Revenue. An increase in the value of the firm resulting from the sales of goods and services. - Income. The excess of revenues over costs for a specified period. The term is often used with modifiers to indicate specific quantities on an income statement (e.g., pretax income; net income). - Activity. A measure of production work. Traditionally, physical production volume (tons of ore or units of product) has been used as the measure of activity. Other measures include direct labor hours, equipment operating hours, and quantity of materials or supplies consumed. - Responsibility center. A segment of an organization that is responsible for a specified set of activities. In mining, individual operating divisions can be treated as responsibility centers, known as profit or cost centers. Departments within a division are generally treated as cost centers. - Cost center. A portion of an organization having responsibility for achieving specified levels of cost. - Profit center. A portion of an organization having responsibility for achieving specified levels of profit (revenues and costs).

Jan 1, 1999

By Harold A. Taylor

The first use of graphite is lost in the mists of time. It was used by primitive man to make drawings on the walls of caves and by the Egyptians to decorate pottery. As early as 1400 AD graphite crucibles were being made in the Haffnerzell District of Bavaria. Through the Middle Ages graphite was confused with other minerals, especially galena and molybdenite. Two common names that are still being used for the mineral are plumbago, meaning lead-silver, and black lead. The latter name implied that graphite is either composed of lead or at least contains a large percentage of it. Gessner is credited with having recognized it as a separate mineral in 1565, but its composition was not determined until 1779, when Scheele demonstrated that graphite oxidized to carbon dioxide, thus proving its carbon constitution. In 1789, Werner named it graphite from the Greek word graphein, meaning to write. The United States has long relied on foreign countries for its graphite supplies. This reliance has been due more to the lack of suitable domestic graphites than to any particular preference for buying minerals overseas. Sri Lankan graphites were imported as early as 1820, and Madagascar graphites have been imported since the properties on that island were opened up about a hundred years later. Mexico has long supplied the United States with most of its requirements for amorphous graphite.

Jan 1, 1994

By S. E. Phillipson

Underground mine mapping is a critical component of understanding the controls on ground instability. Many relatively localized examples of ground failure are associated with geologic features, such as faults, joints, compaction zones, or sedimentological transition zones. In contrast, long-running, directional roof falls are associated with regionally directed horizontal stress fields, which are induced by tectonic plate interactions in the earth?s crust. When stress-related features are distinguished from geological features, underground mapping can be an effective method for inferring the direction of horizontal stress at individual mines. Comparisons with data compiled in the World Stress Map confirm that underground mapping can be a valid method for determining the orientation of maximum principal horizontal stress at a variety of scales, ranging from individual mines to an entire mining district or coal basin. Comparisons are presented between the maximum horizontal stress directions inferred by MSHA?s Roof Control Division through underground mapping and the azimuths of maximum horizontal stress in the World Stress Map database for North America?s Pennsylvanian-aged Appalachian, Illinois, Black Warrior, and Arkoma Basin coal fields. The comparison indicates that azimuths are similar for both data sets, even where variations in the direction of horizontal stress are present. It is interpreted that inconsistencies in direction are attributable to near-surface affects such as deeply incised stream valleys, or to fault zones that represent heterogeneities in the crust.

Jan 1, 2009

By Leonard G. Austin

INTRODUCTION Run-of-mine (ROM) coal generally falls into two major groups: that from underground mining (continuous mining machines) and that from strip mining. Continuous miners produce a finer product and strip mining a coarser product that is crushed to produce the desired size. Further size reduction depends on the proposed use or uses for the coal. For example, for pulverized coal power plants as a rough general rule, the coal is ground or pulverized to 80% less than 200 mesh (0.075 mm) before it is blown into the boiler furnace as a coal-air suspension. For solvent-refined coal processes, the desired size is about <30 mesh (< 0.60 mm); in fluidized bed uses, the coal is typically < 8, in. (< 1.6 mm); for Lurgi pressure gasifiers, the desired size is 1 to 2% in. (25 to 63 mm). Coal preparation plants typically work with a coarse size fraction of 6X 1/14 in. (150X32 mm). The past decades has shown a steady increase in the tonnage of coal cleaned, 1 but it seems probable that the next decades will produce much wider applica- tion of deep coal cleaning before use and that the stages of crushing and pulverization from ROM coal to end use will be integrated with coal cleaning processes. Since different cleaning processes work better with different ranges of coal size and the degree of cleaning possible is intimately connected with the size of coal, a systems design engineer will need as much information as possible concerning the size distributions produced by different types of machines and how these can be modified by different ways of operating the machines. In general, the following questions will be of concern: 1.What type of crusher or grinder is best, or most satisfactory, for reducing a given feed size and type of coal to a desired product size? Frequently, the desired product is smaller than some nominal size, but with as few fines as possible, or the fraction in some size range has to be as high as possible. 2. How big does the machine have to be for a given throughput rate? 3. How much electrical energy (or its equivalent) is required per ton of product? 4. How does the size distribution vary with change in throughput rate, and is a control scheme necessary or desirable? 5. Can the size distribution be readily varied if desired? 6. What is the optimum way to operate a machine in a given system? This section will emphasize certain general principles which guide us in answering these questions. PARTICLE SIZING Since particle size and size distribution are the raw information with which we work, it is worthwhile to review the terminology used. In this regard, see

Jan 1, 1991

By L. Berwick, A. Karunanayake, D. Skutt, H. Heath, J. Wang

Thallium (Tl) is a highly toxic heavy metal, soluble over a wide pH range. Tl levels may exceed discharge limits in mining-influenced water associated with processing gold, lead, cadmium, zinc, and copper ores. In this work, the effect of sodium permanganate (CARUSOL® C liquid permanganate) on Tl removal from mining wastewater was studied. Factors influencing Tl removal, namely permanganate dosage/demand, coagulant and flocculant use, order of chemical addition, and co-existing metal ions were examined. The results show that permanganate addition is very effective at removing Tl to below target limits and can provide a unique solution for improving wastewater quality and optimizing overall treatment costs. In addition, several on-line monitoring techniques were evaluated for process optimization. The Hach DPD Free Chlorine method was optimal, allowing plant operators to rapidly and easily spot check effluent samples for excess permanganate dose.

Mar 2, 2022

By Glenn A. Hazen

Longwall mining is the preferred method for removing underground coal since a larger amount of coal can be removed faster and with less waste when compared to the room-and pillar type mining. Thus, the coal tonnage removed each year by longwall mining methods has increased dramatically. However, a high extraction rate results in surface subsidence which has adverse effects on the environment and on surface structures. Predictions of structural damage are dependent on the magnitude of the expected horizontal strains. Three methods for predicting subsidence characteristics are considered in this paper: the graphical method, the profile method, and the finite element method. All three methods can be used to predict ground movements and horizontal strains. However, the finite element method, which takes into account the structural properties of the stratigraphy and equilibrium of the overburden, is theoretically the more logical choice for use in subsidence prediction.

Jan 1, 1987

By R. E. Utting

INTRODUCTION Until recently, gamma doses had been largely ignored in Ontario uranium mines. This has been due to the assumption that these doses are small and have been more or less unchanged with time and hence their effects have been included automatically in the epidemiological studies that led to the establishment of radon daughter exposure limits. This assumption had to be challenged for two basic reasons. The first was that radon daughter exposures to miners have been progressively reduced over the years due to improved ventilation and ever more stringent regulations, while gamma exposures have presumably remained relatively unchanged. Therefore it must be assumed that the ratio of gamma to radon daughter exposure has gone up. The second reason is more philosophical. It is clearly inappropriate to make judgements on the significance of a potential industrial hazard when the magnitude of that hazard has not been fully assessed. Having decided that some sort of assessment of gamma exposures to uranium miners must be made, it was than necessary to determine how this should be done. Several options were available, for instance: (i) Wholesale personal gamma dosimetry for all mine and mill workers, (ii) Personal gamma dosimetry only for those workers suspected of receiving the higher doses, coupled with area monitoring to estimate the exposures of other workers, (iii) Area monitoring coupled with dose rate times time calculations for all. This would correspond to the generally prevalent method of assessing radon daughter exposures. It was argued that since radon daughter exposures are the major radiological hazard in uranium mines, to invest resources for assessing a lesser hazard to a greater degree of precision was not cost effective. (iv) Since gamma dose rate is related to ore grade, individual doses could be assigned from knowledge of work location and ore grade. Before deciding which of these options would be most appropriate, it was necessary to have some idea of the magnitude of the problem. Very few data were available in the literature and with the exception of a few spot dose rate measurements, and the results of a few gamma dosimeters issued to selected individuals by some of the mining companies, nothing was available. A rule of thumb of obscure origin is often quoted within the industry indicating that gamma dose rates underground will be about 0.25 mR/h per lb/ton or 5 mR/h per % U. This had been used by some to justify neglecting gamma radiation at least for ore grades of the order of 0.1% or 2 lb/ton, on the grounds that gamma dose rates would be of the order of 0.5 mR/h and therefore give rise to annual doses of only about 10 mSv (lrem). That is, it was assumed that gamma radiation was of limited concern compared to the hazard associated with the inhalation of radon daughters. We were thus faced with the situation of just assuming that no regulatory limits were being breached. This situation could not be allowed to continue. A program was initiated to investigate the gamma doses absorbed by uranium miners in three mines in Ontario, and extensive gamma surveys were conducted in the Quirke 2 mine of Rio Algom Ltd, Elliot Lake; Denison Mine, Elliot Lake; and Agnew Lake Mine, Espanola. Negative reaction was received from several mine company officials to the possibility of all miners being required to wear personal gamma dosimeters due to the logistical difficulties involved, and therefore part of the project was aimed at determining if a reliable correlation between gamma dose rate and ore grade in the work location could be deduced, in order that dose rate times time calculations might be used for gamma dose assessments. The results of these programs provided evidence that the gamma dose for some employees in the three mines investigated may be a significant fraction of the current maximum permissible annual dose of 50mSv (5 rem). When combined with radon daughter exposures in the manner recommended by the ICRP at their 1980 Brighton meeting (ICRP 80) the results indicated that some individuals will come close to the resulting limit and may even exceed it. The results also indicate that is probably not feasible to develop a reliable formula for

Jan 1, 1981

By Y. C. Kim

For the past quarter of century, much more effort and research have been expended in developing the "optimum" ultimate pit limit design algorithms and much less to solving the "optimum" open pit production sequencing. However, the potential economic benefit to an operating mine is far greater for the latter than the former. Unfortunately, the problem of "optimum" open-pit production sequencing has not been fully solved to date. This paper first reviews the past and currently used methodologies for developing this sequence. The staggered pit phase geometry problem of advanced stripping and operational constraints such as ore and waste tonnage requirements by period and necessary contiguity of mining faces are the main reasons why the "optimum" production sequencing problem has not been solved as yet. This paper also explains why any method which attempts to simplify the problem using ultimate pit limit design algorithm will fail to reach an "optimum" solution.

Jan 1, 1994

By A. Pincomb

After determining minable acreage, tons are calculated by multiplying minable acreage by average thickness and by a volume-tonnage conversion factor. Converting from tons in the ground to tons sold across the scale takes fines and internally used and wasted stone into consideration, resulting in minimum losses of about 10% for limestone and 15% for sand and gravel. A high degree of certainty about thickness, lateral continuity and geologic character defines proven reserves. Assuming continuity of these characteristics defines probable reserves. By using tpa estimations and annual tonnage requirements, the life of a deposit can be quantified. The decision can then be made regarding the necessity of securing more acreage. Some landowners choose to multiply aggregate price, operating income, or a royalty rate by tons to arrive at a value for their reserves. In doing so they probably overstate the value of their land.

Jan 1, 2003

By Robert C. White, Kurt W. Keskimaki

The Henderson Mine is a large underground panel cave molybdenum mine located near Empire, Colorado. Diesel equipment is employed for all development work, as well as production ore handling. Due to fluctuating demand for molybdenum, production rates have varied from 16,000 to 32,000 metric tons per day (18,000 to 36,000 short tons per day) over the last four years. In order to obtain the maximum air flow for minimum power cost the Henderson mine has completed the following modifications to the ventilation system: removal of large intake fans, elimination of underground booster fans, shutdown of tunnel exhaust fans, completion of the number 5 exhaust ventilation shaft, and use of partially debladed main exhaust fans. These changes have reduced the annual cost of mine ventilation at the Henderson Mine by over 80 per cent, a very critical cost savings in today&apos;s competitive molybdenum marketplace.

Jan 1, 1989

By E. Valdiviezo, J. F. Oliveira

Adsorption of residual flotation reagents onto equilibrium fluid cracking catalysts is a promising method of purification of flotation process water. In the present paper, adsorption of sodium dodecyl sulphate (SDS), dodecyl ammonium chloride (DAC) and sodium oleate onto a spent catalyst from petroleum industry was studied by analysing the residual concentration of the surfactant after contact with the zeolite catalyst. The adsorption of the DAC was rather low but SDS and sodium oleate presented a high affinity for the catalyst surface. The loading capacity was 4.2 kg/ton for SDS and 5.5 kg/ton for oleic acid. After the treatment of the loaded catalyst with a HCI 1 N solution these surfactants are desorbed and the catalyst may thus be regenerated. This would be an additional advantage to its low cost, not to mention its condition as a discarded product and its availability in large tonnages.

Jan 1, 1995

By Mario E. Rossi

The concept of entropy is classical in thermodynamics and information theory. Its potential use as a measure of the ordering of a spatial system is discussed. Although entropy has been discussed previously in the framework of spatial statistics and for univariate distributions, a bivariate data-based estimator has not until now been defined. Different statistical distributions maximize entropy, depending on the univariate, bivariate, or n-variate constraints applied. For bivariate distributions, with a known mean and known covariance, it can be shown that the distribution that maximizes the entropy of the system is the bivariate gaussian. A nonparametric bivariate entropy estimator is introduced, derived directly from the experimental cumulative frequency distribution. Assuming that this experimental bivariate distribution is representative of the population distribution, then a measure of departure from gaussianity can be introduced as a relative entropy estimator. Practical applications for the entropy estimator are discussed, and an example developed.

Jan 1, 1992

By George L. Baloo, Dave Kwiatkowski, Jose G. Cañlzales

Capital project funding for a medium to large materials handling project often includes a budget for procurement of supplier-recommended spare parts, and it is the Project Team&apos;s responsibility to select these parts. With today&apos;s economic climate, limited budget, and other factors, the spare parts selection process is a difficult and arduous effort. This decision carries with it a risk to plant operations and in some cases the commodities producers. Too often the decision-making process is not documented, and the reasons for eliminating and reducing quantities are based on "best guess " Recently on the Solids Handling Phase 2 Project in Jose, Venezuela, the Project Team took a unique approach to this problem. This paper discusses the analytical approach taken by the Project Team, the database system that was developed to manage this problem, lessons learned, and their applicability to pre- project planning and preliminary design.

Jan 1, 2004