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By E. Farrokh

CSM and NTNU models are among the most commonly used models in TBM performance evaluation. Due to increasing application of TBM in different tunneling conditions, modification became necessary for these models. Sensitivity analyses on these two models indicate that both models are very sensitive to machine characteristics. Analyses performed on CSM database for cutter load and penetration rate prediction indicate while the r-square of the CSM model is reasonably high for the predicted cutterload, the r-square value for the penetration is low. In order to increase prediction capability of CSM model for penetration rate the model was reevaluated using non-dimensional analysis and the original database of Colorado school of mines. NTNU model is evaluated using Monte Carlo simulation and regression analysis. The results of analyses indicate that the majority of the variation of the penetration in NTNU model can be explained by only three parameters. This might indicate that the effects of other factors are overshadowed and it is worthy to reevaluate NTNU model using original database and more updated statistical methods to avoid overlapping of different parameters correlations.

Feb 23, 2014

By E. A. Rychkun

Mining and environmental objectives have traditionally been in conflict. This conflict reflects a delicate balance between the need to spend money to protect the environment, and the need to save money by extracting minerals efficiently. In an increasing number of cases, profit margins diminish rapidly with new environmental regulations and reactionary measures. Forced cleanups and increasing restrictions are unwelcome expensive processes. A practical solution lies in planning rather than reacting. This requires the ability to precisely quantify and qualify environmentally sensitive problems by providing effective engineering tools to model, visualize and analyze subsurface conditions. Prevention of environmental conflicts, and effective cost control are both rooted in the mining company's ability to construct accurate models, monitor changes, assess contamination risks and to design effective remediation plan. This paper presents a case study where these issues are addresses through the application of a new and innovative technology.

Jan 1, 1993

By John William Carlson

The Y2K or "Millenium" bug is a tiny critter, comprising no more than two digits in a date field. This bug, like its' more lethal cousins of biological and computer virus fame, has the potential to derail the economy of the U.S. and the rest of world. Whatever the reader's perception, rest assured that you will be affected by Y2K along with every person in the civilized world. How did we get to this position? It is really quite simple. The Y2K problem is a creation of computer programmers who, in an effort to conserve valuable memory in the early days of computer development, used two digits as shorthand- to define the year in date sensitive applications. Instead of typing in "1982," our experts employed "82." They believed-correctly­that the problem of limited memory would be solved by technology and assumed (nasty word) that software would be modified to take care of any problems associated with a date rollover in the year 2000. Their assumption resulted in the problem facing us today.

Jan 1, 1999

By Walter J. Pachucki

Mining equipment maintenance costs account for a major portion of a mine’s total operating expense. A reduction of maintenance costs while providing required equipment availability translates directly into increased profit for a mine. Therefore, having in place a successful maintenance program can be management’s most direct route to increased profits. One key element of a successful maintenance program is a practical and effective recordkeeping and information system. In recent years, many mining operations have invested in the development or purchase of computerized maintenance information systems. Computerized maintenance information systems can serve as a valuable tool in managing mining-equipment maintenance. They can also be a costly, frustrating waste of time. Why are some systems successful at one operation but a failure at others? Should all mines use computerized maintenance information systems? How does management decide what maintenance software is best for their operation? In an effort to to answer these questions and to better understand what is required to make a mining maintenance information system successful, a study was recently conducted on maintenance information systems used in the mining industry.

Jan 1, 1991

By André Vervoort, Jef Caers

Compound lognormal distributions serve as new generalized distribution laws for analyzing and estimating ore value distributions or related properties such as the average ore grade. These models are an alternative to the well known lognormal distribution. They are the translation of general geological constraints on the genesis of the deposit cumulated in suitable statistical properties. In this paper a maximum likelihood framework is established for estimating the parameters of such laws or parameter functions thereof. It is shown that under certain conditions maximum likelihood estimation is accurate and efficient in estimating the mean value even when relatively few samples are available. The method is based on a numerical maximization of the likelihood function of these models given the data. Confidence limits on these estimates are set up using resampling techniques such as the bootstrap. By this a complete methodology is presented for inference on ore grade distributions such as is shown in an example of gold data from the Merriespruit mine (South Africa) and the diamond size distribution of the Bougban deposit (Guinea).

Jan 1, 1996

By C. Yao, T. M. Yegulalp

The scale effect on rock properties has been discussed and studied since the introduction of the weakest-link idea by Weibull (1939). In this study, the capabilities of a dynamic lattice network model to simulate failure of rock under uniaxial tension is utilized. A number of randomly distributed microcracks that contribute to the development of uneven stressfields are introduced. In addition, each unit element in the model is assigned a random value representing its strength properties. Each application creates a randomly created specimen that is subjected to uniaxial tension. The specimens are grouped into three sets according to their size. The results of the study show that the scale effect is present in a statistical sense, i.e., the observed statistical distributions of strength for each specimen group is distinctly separate, and they follow the expected inverse relationship between strength and size. The observed probability distribution for each group of specimens give rise to the estimation of a different set of parameters. In this paper, the potential relationships among these parameters as a function of specimen size is investigated.

Jan 1, 1999

By Bernard A. Kilgore

Kaolin is a hydrated aluminum silicate mined primarily in middle Georgia along the "fall line", the location of the coast line in prehistoric times. It is used extensively as a filler for paper, insecticides, tires, plastics, a pigment for paints, as a coating for fine gloss paper, and for high grade ceramic products, such as catalytic converters. During its journey from the open pit mine to its final use, kaolin takes many forms, and must be handled in many different ways. The purpose of this presentation is to follow kaolin through its process and briefly describe some of the methods Georgia Kaolin Company, one of the world's largest kaolin producers, uses to handle and convey its product and some of the peculiarities involved.

Jan 1, 1983

By N. W. Johnson

The behavior of non-sulphide gangue in chaloopyrite flotation circuits has been investigated. Plant and laboratory tests were carried out on five different ores, and linear relationships were found to exist between the rates of recovery of water and free nonsulphide gangue in the concentrates although there was evidence from pilot plant tests that these were linear approximations to parabolic curves over the limited regions which were observed. There was evidence that the free non-sulphide gangue enters the concentrate by hydraulic classification and a classification function has been proposed to define this behavior. This function is suitable for inclusion in a mathematical model of the process.

Jan 1, 1972

By Brij M. Moudgil

Separation of oil shale from waste material or into high grade and low grade fractions can have a major influence on the economics of the surface (ex-situ) retorting process. Different components of shale rock vary significantly in physical and surface chemical properties such as specific gravity, color, water wettability etc. Various techniques which utilize the difference in one or more of the above propartis have been proposed to preconcentrate the oil shale before retorting. A discussion of the techniques proposed such as gravity separation, sorting and froth flotation is presented.

Jan 1, 1982

By Thad J. Bydlon

Uncertainty of future energy supplies has forced industrial nations to diversify both their energy mix and their energy sources of supply. As a result, U.S. coal exports have grown substantially during the past several years. Projected long-term worldwide economic growth suggests that a well-established trend has been set for increased foreign demand for U.S. coal. As export volumes increase the need for careful planning to prevent bottlenecks and to provide for the uninterrupted flow of coal increases. It also will place increased emphasis on identifying the most economic transportation alternatives. These planning and evaluation functions are greatly facilitated if a systematic method is available for modeling the complex interactions of a coal export system. One such model, developed by the Anaconda Minerals Company, is the Coal Export model.

Jan 1, 1982

By Roy Moreby

Dartbrook Coal is currently developing a modern, high production (3.5 Mtpy) single longwall retreat coal mine in the Upper Hunter Valley of NSW, Australia. The location is a green field site, with no surface or underground mining operations ever having taken place in the initial target seams. The coal seams of the working section, floor and immediate roof average a total 20 m in thickness and contain a mixed carbon dioxide 1 methane seam gas ranging from 6.5 to 11.0 m3/t. The target seams have undergone detailed characterisation to assess hazards and quantify the controls required to minimise associated risks during mining. Risks identified during initial phases of exploration and 14 months of development include: • High gas emission during development. • Probable high longwall gas emission rate. • Medium to high propensity to spontaneous combustion • Possible carbon dioxide outbursts on geological structures • The main controls currently in place include, • Mine geometry and ventilation circuits • Exploratory drilling ahead of development • Intensive in seam pre drainage • Goaf drainage plants • Comprehensive monitoring systems • Underground environmental management plan. • Pre mining predictions of gas emission provided an indication of gas emission rates which have proven to be an under estimate. Current mine issues are; • Both surface fans are at full capacity (250 m3/s 1.4 kPa) • Both gas drainage pumps are at full capacity (2.3 m3/s) • Alternatives to extensive in seam pre drainage being investigated (surface to in seam hydro fracture) Review of mine design underway This paper describes the seam characterisation, assessment of mining hazards and summary of the management plan developed to address the risks identified. A review of current mine underground environmental performance is also provided

Jan 1, 1997

By R. J. Sandberg

The Copper Creek area, part of the Bunker Hill District, Pinal County, Arizona, lies within the southwest porphyry copper province of North America at the intersection of a northwest trend and an east-northeast trend of Laramide porphyry copper deposits. The Copper Creek area has been mined and explored for copper and molybdenum since the early 1900?s. The majority of this work focused on the more than 400 surface exposed breccia bodies. In the 1960 to 1970?s deeper drilling discovered a deep porphyry copper-like setting. Redhawk Copper currently has NI 43-101 compliant resources of about 0.652 billion pounds of measured and indicated and 2.745 billion pounds of inferred copper equivalent in breccia hosted and porphyry style deposits. See Figure 1.

Jan 1, 2010

By I. WILKOMIRSKY, J. BECKER, F. Parada

Purification of molybdenite concentrate from copper concentrates was performed by sulfation. The sulfation of molybdenite concentrates was carried out with pure sulfuric acid (> 96%) at 160–190 °C to study the influence of the reaction temperature and reaction time on the residual copper in the molybdenite concentrates. A purified concentrate with less than 0.1 wt% copper and low levels of other metals were obtained. For up to 7.1 wt% copper, the conditions required are a temperature of 190 °C, a reaction time of 14 h, and a moly/acid weight ratio of 1/1. Furthermore, several designs of sulfation reactors were evaluated in order to obtain the desired level of copper in the product and to analyze the influence of the operational and design parameters on the reactor dispersion number (Le). The basic design for an 80-t/day plant fed with 4 wt% copper molybdenite concentrate requires five backmixed reactors in series, each measuring 8 m3, operating at 190 °C and with a reaction time of 10 h. The reactor must be protected against severe corrosion by the hot sulfuric acid with either Teflon, glass or ceramic.

Jun 14, 2022

Asgco’s design of the Arrowhead Ceramic Lagging provides solutions to problems experienced with conveyor belt slippage around the drive pulley and severe wear problems on snub and bend pulleys. Asgco has developed a range of pulley lagging from ceramic, drive rubber and non-drive rubber lagging that is available in abrasion-resistant SBR and MSHA grade rubber for conveyor pulleys from slow belts all the way through to high-speed, high load belts. There is a growing need for a maintenance-free and reliable pulley lagging to ensure conveyor belts run to their highest efficiency.

Jan 1, 2006

By V. Gangrade, J. Addis, S. Vanderslice

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are conducting research to improve the ventilation of large-opening underground stone mines. The mine ventilation in these mines are characterized by: (1) challenges related to keeping airflow velocities high enough to effectively remove or dilute airborne contaminants, (2) low pressure losses needed to move large air volumes of air, and (3) costly stoppings needed to direct ventilation airflows. Each of two field studies was dedicated to specific focus areas. The first focus area was the characterization of underground mine ventilation airflow. The primary means of airflow control in stone mines is through the use of freestanding booster fans. The primary goal of this study was to identify the effectiveness of various fan types and optimize their placement. Both traverse and grid-based airflow readings were taken at various distances from the fans, ranging from 70 ft to 425 ft away from the fan. The air readings were taken using a vane-anemometer and a handheld hotwire anemometer. The data was used to develop precise computational fluid dynamics models. The second focus area was to determine diesel particulate matter (DPM) concentrations in the mine. For large-opening underground stone mines, controlling DPM exposures dictates the design of the ventilation system. Therefore, researchers carried out the DPM sampling campaign to identify potential areas of concern within the mine. The samples collected during the campaign were analyzed using NIOSH Method 5040. The sampling was done using the Mine Safety and Health Administration’s (MSHA) compliance sampling methodology.

Feb 1, 2023

By P. J. Ryan

Phelps Dodge’s Candelaria copper-gold mine is located 20 km (12miles) south of Copiapó in northern Chile’s Atacama province (Region III) (Fig. 1). The Candelaria Mine is about 800 km (500miles) north of Santiago and 75 km (47 miles) east of the Pacific Ocean. Its elevation is 600 m (1,970 ft) above sea level. The Copiapó River Valley is 6 km (4 miles) northeast of the mine site. It is the only major source of water in this arid region. The average rainfall is 14mm/a (0.5 in./year). During 1995, the mine produced 521.4 kt (574,800 st) of copper concentrate containing 150 kt (165,000 st) of salable copper and 3 t (98,800 oz) of gold. The 1995 unit cash cost was less than 50 cents/lb of copper. This makes Candelaria one the world’s lowest cost copper producers.

Jan 1, 1996

By Dipl. -Ing. H. -J. Sager

The ‘Westerschelde Tunnel’ underpasses the estuary of the Schelde in the Netherlands. The tunnel will consist of two tubes which are driven by two hydroshields (slurry shields). The tunnels will each have a length of approx. 6.6km and a bore-diameter of 11.33 m. Demanding ground conditions had to be considered during the design of the shield machines. Loose sands, extensive clay formations and high ground water pressures of up to 6.5 bar will be encountered during the tunnel drive. The tunnelling activities will start in the middle of 1999 and are scheduled to end by the end of 2001.

Jan 1, 1999

By Y. Akin

The floatability of a typical boron mineral, colemanite (Ca2B6O11.5H2O), is shown to be hindered by the presence of montmorillonite type clay minerals. The clay is found to act in the form of slime coating. The mechanism of slime coating is investigated using pure colemanite and clay and their mixtures with an anionic reagent in a microflotation cell. Adsorption, flotation, solubility, zeta potential and scanning electron microscope studies reveal that slime coating occurs through electrostatic attraction. It is possible to minimize the effect of slime coating either at high surfactant concentration or at high pH values.

Jan 1, 1997

By M. L. Free

Several studies of the fluorite/oleate flotation system have shown that under certain conditions calcium dioleate is formed at or transported to the fluorite surface. Adsorption of significant amounts of calcium dioleate is generally observed above oleate concentrations of -6 -5 between 4 x 10 and 4 x 10 M, yet little explanation of the onset of calcium dioleate adsorption is provided. In this study in-situ and ex-situ FTIR/IRS experiments have been performed in connection with thermodynamic solution phase analysis to better understand oleate adsorption as well as the onset of calcium dioleate formation. Results from this study are analyzed and compared to industrial practice.

Jan 1, 1995

By A. E. Isaacson

Researchers at the Bureau of Mines, U.S. Department of the Interior, developed and tested equipment to measure corrosion rates on a commercial-scale mill. Bench-scale experiments were also designed for duplicating ore grinding conditions closely enough that realistic rate determinations can be made in laboratory tests. Rates measured in a laboratory system compared favorably with those measured in the field. Cast steel was found to have corrosion rates in a copper mill and laboratory test cell of 22 and 21 mpy, respectively. Corrosion was found to account for less than 5 pct of the total grinding media wear in the operations studied.

Jan 1, 1989