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By F. J. Klingler, R. Hausmann, K. M. Swaffar, J. C. Neyer

This paper presents the results of a study of case histories of projects on which sinking caissons were used to construct shafts for tunnel construction and other underground works. Design methodologies are reviewed with respect to the impact of soil and groundwater conditions on the performance and constructability of sinking caissons. Factors which have led to success or failure are reviewed and evaluated, and recommendations for future investigation, design and construction activities are presented. Cost data for five recent projects are reviewed and compared to the cost of shaft installation by other means.

Jan 1, 1997

By D. D. Faulkner

Cable bolts anchored with traditional two component polyester resin cartridges have successfully supported difficult roof conditions in underground mines. Resin cartridges provide a cost-effective cable bolt anchoring system with consistent anchorage performance characteristics when properly installed. The most commonly used cable bolts in the U.S. mining industry are 270 ksi (1,862 MPa), 0.7 and 0.6 inch (18 and 15 mm), seven-strand smooth cable with resin mixing bulbs (also known as bird cages), and 40- and 30-ton nominal capacity, respectively. However, there are other types of cable bolt anchoring systems aside from bird cages. Recently, many questions have been raised regarding the anchorage characteristics of various types of cable bolts. Keystone Mining Services, LLC (KMS), the affiliated engineering company of Jennmar Corporation, conducted a variety of controlled tests developed to closely model actual underground installations. These tests compared the performance of three commonly used cable bolt varieties, including plain, bird caged and indented seven-strand cable. Details of the laboratory testing and comparative analysis of the results are provided.

Feb 23, 2014

By Brent K. Nelson, D. Lee Petersen, Charles R. Nelson

INTRODUCTION Tunnels are commonly constructed in the very weak St. Peter sandstone in the Twin Cities area of Minnesota. Historically, core recovery in this weak sandstone was very small in the critical weaker strata resulting in little preconstruction information on the ground conditions. Improved core recovery techniques have been utilized for recent projects, allowing rock quality rating methods to be developed for the recovered core. Down-the-hole tests, and the use of combination ratings between different types of core data provide for more detailed characterization of ground conditions. THE ST. PETER SANDSTONE The 45 m thick St. Peter is an unusually pure quartz sandstone. It underlies all the Twin Cities area, except where it has been eroded by the present day Mississippi River or by pre-glacial rivers. It forms conspicuous steep bluffs along the Mississippi River where the upper Platteville limestone formation protects it from erosion. Where the Platteville formation is missing, the sandstone slopes are often more gentle. Natural case hardening of the exposed sandstone bluffs often forms a resistant crust and reduces sloughing. This case-hardened surface is not representative of the sandstone back from the bluff.

Jan 1, 1987

There are presently in use many grinding mill control schemes and concepts. This paper presents one operating method of controlling the particle size of the cyclone overflows for proper metallurgical results and controlling the level of the cyclone feed sump and new feed rate to obtain lowest unit cost of finished (ground) material which is usually at the maximum grinding mill throughput. This system stresses simplicity of field instrumentation and control strategy. Both of these factors lead to better operator understanding and acceptance. The low capital investment of this system also makes it more attractive at the Buick Concentrator when compared to other more complicated systems utilizing mass flow measurement and a computer to calculate circulating load and infer particle size. Furthermore, it has the advantage of utilizing an actual measurement for control, rather than a difficult-to-maintain inferred value. There are several reasons for maximizing mill throughput at Buick. The milling rate before automatic control was too low when compared to mill throughput increases planned for the future. Through this new operating system, it appears Buick will not have to make major changes of mill motors and speeds to meet the increased? production rate. Also, since power costs continue to escalate, it is desirable to maximize the throughput to the grinding circuit and reduce overgrinding to achieve a reduction in power cost per ton of ore milled. Presently, 45% of the concentrators' total power is consumed in this grinding circuit.

Jan 1, 1977

By Snehamoy Chatterjee, Sanjay Kumar Palei, Smarak Das

Machine manufacturers’ recommendations on maintenance strategies of capital-intensive draglines are not always based on real data and therefore lead to losses from downtime. This paper proposes a preventive maintenance strategy for a dragline deployed in an opencast coal mine based on reliability-centered maintenance and failure-mode-effects analysis using real operational data. Reliability-centered maintenance replaced a cluster of critical failure components of the dragline while satisfying two specific conditions: (i) the components should be replaced at the earliest mean time to failure (MTTF) within the group and (ii) the time taken to replace all the parts should be equivalent to the maximum downtime within the group. Estimated threshold weightage factor identified twenty-six critical failure components for the preventive maintenance strategy, and clustering of components divided them into nine groups. In a group, the loss that is expected to occur by replacing some of the components before their failure, and the gain by reducing the overall maintenance downtime, has been explained through a cost-benefit analysis. The total net profit generated is calculated as US$200,178. This clustering activity also led to a reduction of annual downtime by 231 h, whose approximate market price as equivalent coal production costs $295,365.

May 28, 2020

By Wolfgang Pietsch

DR iron') is a generic term for metallized product that results from the direct or solid state reduction of iron ore. In direct reduction, iron oxides are reduced to metallic iron in the solid state without an intermediate melting step. MIDREX ® Iron is the DR iron material produced in the MIDREX ® Direct Reduction Process. Except for some thermal and mechanical degradation, the external physical form of as-reduced DR iron is the same as the feed material. Chemically, oxygen associated with iron is removed leaving a very porous structure. Figure 1 is the scanning electron micrograph (SEM) of the internal surface of a MIDREX Iron pellet obtained from a Swedish oxide pellet during reduction at 760 °C. Figure 2 is the SEM of a polished and etched cross-section through the same pellet showing the amount of intraparticle porosity. As a result of this high porosity, apparent density of DR iron is relatively low, typically a¬round 2 g/cm3, and specific surface is extremely high, typically around 1.0 m2/g or more. Both density and specific surface depend on the raw materi¬al and the operating conditions of the direct reduction plant. Normally, more than 97% of the available iron is reduced into metallic iron with the rest mainly in the form of wustite (FeO). During direct reduction, the gangue in the iron remains essentially unchanged. Removal of oxygen and the corre¬sponding reduction in weight result in a slightly higher percentage gangue in the product than in the raw material.

Jan 1, 1976

By G. Avolio, M. Gilbert

INTRODUCTION The city of Alexandria, Egypt is located on the Mediterranean Sea at the northwestern edge of the Nile River delta. The city is approximately 26 km long and 3 km wide bounded by the sea to the north and Lake Maryut to the south. The Alexandria Project is split into 2 phases: phase one included designs to update two existing primary wastewater treatment plants, five pump stations and over 75 km of sewer pipe, 18 km o f which is tunneled, (1500mm to 2750mm ID pipe). Currently the pipeline and pump stations are under construction. Phase two of the project includes expanding both the capacity of the treatment plants and the limits of the collection system. Included in this system expansion is the 3.5 km long, 2250mm ID Central Zone Conveyance, which is the subject of this paper. The project is under the direction of The Alexandria General Organization for Sanitary Drainage (AGOSD). It is an USAID funded joint venture of two American firms, CH2M - Hill and Metcalf & Eddy who share equally the major portion of the work and two Egyptian firms, Engineering Consultants Group (ECG) and Wairth Associates who are also partners. The venture, which is both design and construction management, worked under the name Wastewater Consultants Group, WWCG. Michael Gilbert was Chief o f the Geotechnical Department and Project Engineer for the Central Zone Conveyance. Gennaro Avolio was Geotechnical Exploration Manager for the Alexandria Wastewater Project.

Jan 1, 1987

By José Maria Silva, Eugênio Oliveira, Ruberlan Silva, Thiago Souza, Lucas Reis, Lorena Guimarães, Matheus Bianchetti

Copper mine operations consistently generate a large quantity of tailings after their concentration processing. These tailings are either piled up or stored in a dam, where both alternatives of disposal lead to environmental impacts. The dam copper tailings have a huge potential for by-product production thus improving sustainability and profitability in industrial operations. This paper describes a study aiming at producing a magnetite pellet feed as a by-product from a dam chalcopyrite flotation tailings and generating free magnetite non-magnetic rougher tailings. The chemical assay and mineralogy analysis of dam copper flotation tailings indicate low Fe grade (6.34 wt%), high SiO2 grade (63.14 wt%), low magnetite (3.6 wt%), and high iron silicates content (22.72 wt%). The complex mineralogy of these tailings leads to the need of grinding the rougher magnetite pellet feed as fine as 80% of particles smaller than 20 μm ( P80) aiming at improving magnetite liberation. The proposed process route comprises a scalping screen, low field rougher, and cleaner magnetic separations using a drum magnetic separator (80 kA/m or 1000 Gauss), followed by silicates reverse cationic flotation as a recleaner step. With this process route, it was possible to produce a high-quality magnetite pellet feed reaching 68.00 wt% of Fe, 2.13 wt% of SiO2, 0.51 wt% of Al2O3, and 95.1 wt% of magnetite. The Blaine specific surface area was 2300 cm2/ g, being in the range recommended for pelletizing (1900 up to 3000 cm2/ g). The total mass, Fe, SiO2, Al2O3, and magnetite recoveries were 2.77%, 29.71%, 0.09%, 0.12%, and 73.17%, respectively. Most of the magnetite losses, around 20% of total magnetite fed, occurred in the oversize of the scalping screen. Additionally, it generated non-magnetic rougher tailings with less than 1.0 wt% of magnetite that could be used as by-products and reduced the amount of tailings disposal in a dam. This study contributes toward the sustainability of operation, minimizing tailings disposal.

Sep 28, 2022

By Muhammad Zia-ur Rehman, Sajjad Ahmad Baig, Gao Lei Fu, Muhammad Mohsin, Sobia Naseem

The environmental sustainability is linked back to human sustainability; the sustainability development comprises the environment, society, and economics. This study mainly focused on mining sustainability and its impact on the environment of Pakistan. For measuring the level and environmental mining sustainability nature to Environmental Impact Assessment (EIA) of the world’s second largest salt mine “Khewra,” Folchi and Phillips environmental sustainability mathematics (PESM) models are applied. The results indicated that Khewra was deemed to be potentially sustainable for the environment and quality of salt. The results suggest the delicate balance of maintaining sustainability successfully, regarding the mining process in Pakistan which has been affecting the local environment and community so badly. The paper lays emphasis on the potential significance of the model’s application for the attainment of sustainable mining goal. This study is essential for researchers,

May 11, 2020

By K. Kim, H. Gao

A site-characterization strategy formulated for the probabilistic assessment of rock mass properties is presented. The strategy, which takes into account the variability of rock properties and the stochastic nature of the rock-failure process, entails determining probability distributions of rock properties by utilizing extreme value statistics and Monte Carlo simulation. Laboratory and, field test data are analyzed and presented to illustrate the methodology. The results indicate that the distributive characteristics of rock mass can be estimated by using this proposed method. The results of the analysis can be incorporated into the design of underground structures. Then, the relative uncertainties of the failure probability of the structures can be assessed.

Jan 1, 1997

By H. Hamza

Oil sand tailings are disposed of in large ponds in which MFT (Mature Fine Tailings, a stable suspension of fine particles in water) forms after many years of settling. Long-term storage of large volumes of MFT is costly to maintain and also poses an environmental liability. The Advanced Separation Technologies laboratory at CANMET Western Research Centre has worked closely with oil sand companies to eliminate MFT generation by applying paste technology to oil sand tailings. In this process the fine tailings are flocculated to produce a thickened material that has the potential to consolidate to a dry landscape, while warm water is recovered and recycled for reuse in the extraction process. This paper presents some results of an extensive technical program involving bench-scale tests for flocculant selection and continuous thickener pilot tests.

Jan 1, 2002

By W. R. Reed, J. P. Rider

"The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) recently developed a series of models using computational fluid dynamics (CFD) to study airflows and respirable dust distribution associated with a mediumsized surface blasthole drill shroud with a dry dust collector system. Previously run experiments conducted in NIOSH’s full-scale drill shroud laboratory were used to validate the models. The setup values in the CFD models were calculated from experimental data obtained from the drill shroud laboratory and measurements of test material particle size. Subsequent simulation results were compared with the experimental data for several test scenarios, including 0.14 m3/s (300 cfm) and 0.24 m3/s (500 cfm) bailing airflow with 2:1, 3:1 and 4:1 dust collector-tobailing airflow ratios. For the 2:1 and 3:1 ratios, the calculated dust concentrations from the CFD models were within the 95 percent confidence intervals of the experimental data. This paper describes the methodology used to develop the CFD models, to calculate the model input and to validate the models based on the experimental data. Problem regions were identified and revealed by the study. The simulation results could be used for future development of dust control methods for a surface mine blasthole drill shroud. IntroductionIn surface mines, production drilling is an essential process in blasting to fracture the hard rock overburden for removal. During the process, considerable amounts of respirable dust are produced. Past sampling at the shroud area of blasthole drills had documented time-weighted-average respirable dust concentrations ranging from 8.68 to 95.15 mg/m3 (Organiscak and Page, 1995) and 1.04 to 52.30 mg/m3 (Listak and Reed, 2007). These high dust concentrations, which may contain silica, can lead to respirable dust overexposures for the miners working nearby. These overexposures can lead to silicosis, an occupational lung disease that has no cure and is ultimately fatal.Two basic methods are used to control drilling dust: a wet suppression system or a dry collection system (Cecala et al., 2012). Dry drilling techniques using a dust collection system are preferred in rural mining locations where a constant water supply is not available, and in the case of rotary drilling where water is associated with accelerated bit wear due to bearing degradation and hydrogen embrittlement. In addition, dry drilling eliminates freezing-related issues with water in colder climates. Dry dust collectors are highly effective at removing dust, especially the finer material, as long as they are properly operated and maintained (Listak and Reed, 2007; Organiscak and Page, 2005)."

Nov 1, 2016

By Staff

In 2012, the estimated value of mineral production increased in the United States for the third consecutive year. Production and prices increased for most industrial mineral commodities mined in the United States. While production for most metals remained relatively unchanged, with the notable exception of gold, the prices for most metals declined. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Minerals? contribution to the GDP increased for the second consecutive year. Trends in other sectors of the domestic economy were similar to those in mineral production and consumption rates (Table 1). After continued decline following the 2008-2009 recession, the construction industry began to show signs of improvement late in 2011 and throughout 2012, with increased production and consumption of cement, construction sand and gravel, crushed stone and gypsum, mineral commodities that are used almost exclusively in construction.

May 1, 2013

By E. Piesch, M. Urban, G. M. Hassib

INTRODUCTION In radon dosimetry diffusion chambers with passive [a]-detectors are now in current use to investigate the long-term accumulated indoor exposure of radon and daughters. For the diffusion chamber developed at Karlsruhe the electrochemical etching technique (ECE) was applied to reveal [a]-particles in polycarbonate plastic detectors. Compared to conventional etching, the main advantages of the ECE are the large track diameter, simple track counting in a single field of about 1 cm2, stability of the latent tracks to humidity and temperature and ability for a long-term accumulation up to 1 year. The electrochemical etching system was designed to etch in one run about 101 foils by using a 200 W high voltage generator. The commercial available radon dosimeter system is applied for a country wide program of measuring radon in dwellings. Because of an increasing interest of radon monitoring in mines, environmental monitoring and personnel dosimetry the properties of several track etch detectors have been studied. In the comparative study, Makrofol E, LR 115 and CR 39 were used in the diffusion chamber to investigate the etching techniques, the relative efficiency, the measurable [a]-energy range, and the counting statistic for the measurement of radon concentration. THE KARLSRUHE DIFFUSION CHAMBER The design of the Karlsruhe diffusion chamber is presented in Fig. 1. The upper part of the chamber is closed by a fibreglass filter to separate radon from aerosols, heavy dust particles and radon decay products. Inside the diffusion chamber [a]-particles from radon and daughters are detected by two passive radon detectors, one on the bottom of the chamber and the other in front of the filter. With the fibreglass filter applied the diffusion time is about 1 minute for radon. Therefore, also short-term variations in the radon concentration are recorded by the track detector. Mainly because of the short halflife of thoron (56 s) only about 7 % of the thoron concentration is expected in the diffusion chamber. Radon monitoring provides the estimation of the long-term accumulated mean value of the radon concentration with a lowest detectable concentration of 0.1 pCi/1 after 3 months accumulation by using polycarbonate track etch detectors, an electrochemical etching technique and track counting in a single field of 1 cm2. The diffusion chamber was optimized for the polycarbonate track detector with respect to chamber geometry and detector position [1]. Table 1 presents data for 3 different diffusion chamber designs. The radon sensitivity of the diffusion chamber depends on the [a]-energy discrimination and the angular response of the [a]-track detector. The difference between foil No 2 and foil No 1 can be explained by an additional plate-out effect of radon daughters on foil No 3. The high sensitivity of foil No 3 compared to that of foil No 2 is caused by an increase of the effective volume and the effective area for [a]-particle from radon and from plated-out decay products, respectively. Additional experiments have been performed in order to investigate the electrostatic properties of the plastic material and the properties of the diffusion filter [1]. The properties of bare a-detectors were compared with those inside the diffusion chamber. In contrast to laboratory results, dust particles deposited on the detector surface or in the environment of the detector obviously affect the reproducibility of the bare detector significantly. After 4 months exposure in dwellings the scatter of 10 dosimeters exposed in the same room exceeds a factor of 3 compared to 15 % for the diffusion chamber. COMPARATIVE STUDY OF TRACK ETCH DETECTORS Detector types and evaluation technique In the comparative study the properties of the following plastic track etch detectors have been applied: - LR 115 from Kodak Pathé, France, is a red dyed cellulose nitrate layer of 13 µm thickness on a 100 µm thick polyester support. The holes appears as bright spots in a dark red background. In an optical microscope counting of through etched [a]-tracks which must penetrate the detector layer - CR 39 from Pershore, England, is an ally1 diglycol carbonate plastic of about 300 m thickness. The normal etched [a]-tracks are counted by an optical microscope and the ECE [a]-tracks by a microfiche reader.

Jan 1, 1981

By B. Oraee

Tunnels as any other structures are affected by different loads and stresses. Generally, the loads on tunnels consist of both static and dynamic loads. These loads must both be considered in the tunnel design process. In this paper, the stability state of Jiroft water-transform tunnel is evaluated. Firstly, the in-situ stresses and then using Kirsch?s equations the induced stresses due to static loads in walls and crown of tunnel are calculated. Consequently, the strain caused by probable earthquake without considering the interaction between the concrete lining of tunnel and rock mass using seismic analysis is calculated based on free-field deformation. When the strain is determined, the simplified method of closed-form solution, Wang?s equations and Penzien?s equations are used to estimate the applied forces on the tunnel due to earthquake such as axial force and bending moment on a tunnel section taking into account the interaction of the tunnel concrete lining and rock mass. Results of this study show that the loads applied to the tunnel as a result of earthquake waves can be affect the stability of underground structures, especially long structures such as tunnels.

Jan 1, 2011

By J. W. Keck

Pilot plant grinding and concentration test results indicate that conglomerate native copper ore can be ground and concentrated using conventional techniques. Single stage autogenous grinding and rod mill-ball mill grinding required the same amount of energy far the required comminution. Metallurgical results were comparable for both types of grinding investigated.

Jan 1, 1973

By I. A. Tinto

Labrador City is located in the southwestern portion of Newfoundland-Labrador, approximately 965 kilometers north-east of Montreal. The mine and beneficiation complex of the Iron Ore Company of Canada, known as the Carol Project, is situated 535 metres above sea level in a climatic region characterized by cold winters and short, cool summers. History The iron Ore Company of Canada commenced work in the area in 1949, however, it was not until 1958 that the decision was made to proceed with mining operations. The ore body consists of Specular Hematite (Fe203) and Magnetite (Fe304) with small quantities of Limonite and Geothite. The average grade of the ore bodies is 39% iron.

Jan 1, 1985

By Richard E. Barrett

The relationship between coal characteristics and power plant performance has become a matter of increasing interest to utilities. This relationship can affect the value of coals, decisions as to coal washing, setting penalties for delivery of coal that fails to meet specifications, and justifying buying better coals (at higher costs) before public utility commissions. The study described in this paper was directed to identifying how coal characteristics impact on boilers and related coal and gas handling systems. TVA data for the period 1962-1980 was the basis for the study. Models were developed for boiler efficiency, boiler availability, and maintenance costs as a function of such coal characteristics as ash, sulfur, and moisture content and boiler age. Boiler load and maintenance efforts were considered as variables in some of the models, but were found not to be statistically significant. Although the results of this study are strictly applicable to only the TVA system, they can serve as guides or first approximations for other utilities.

Jan 1, 1983

By Molood Saeedi, Nima Sadeghi, Eskandar Keshavarz Alamdari

This study showed the kinetics of gold chlorination leaching from an anode slime complex containing copper, silver, barium, selenium, and tellurium. AgCl and BaSO4 control the rate of gold leaching, and the interface transfer and diffusion across the product was selected as the desirable kinetic model. The concentration of hydrochloric acid, chlorine gas flow rate, pulp density, and temperature have been precisely studied. The results showed that temperature and hydrochloric acid have a favorable influence on the leaching rate. However, the chlorine gas flow rate is inactive in the reaction rate. Furthermore, the leaching rate decreased with an increasing pulp density. The leaching process was controlled by the interface transfer and diffusion across the product, and the activation energy was determined to be 13.66 kJ mol–1.

Oct 19, 2021

By K. V. Raj

"Air inversion is a meteorological phenomenon generally occurs during winter times. Release of pollutants below the inversion height in an open-pit mine during periods of weak winds and consequently weak vertical mixing may result in very high concentrations of primary and secondary pollutants, causing serious consequences for health and safety of miners. Mine operations cease if the concentration of NOx or CO exceeds the threshold limit value (TLV) of the pollutants. Artificial ventilation is required to dilute the pollutants to an extent that mine workers can safely resume work. Studies of the turbulence parameters suggest that effective ventilation of the pit and removal of pollutants can be accomplished if a large enough mixing length in the open pit can be created. Turbulent mixing by eddies of different length scales under an inversion layer is product of wind shear, thermal gradient and buoyancy. The main result of turbulence is mixing of the atmospheric profile and transport of momentum. Computational fluid dynamics (CFD) Simulation results of a novel mitigation approach using cloud cover will be presented in this paper. INTRODUCTION In extreme climatic conditions, deep open-pit mines tend to trap pollutants at the pit bottom due to air inversions. Keeping open pits adequately ventilated is a considerable challenge for the mining community. Mine operators in cold regions are very familiar with this problem, the severity of which can be judged from Figures 1 and 2. The top portion of the figures show clear sky and snow covered benches. The brown haze, containing various contaminants accumulated over time in the pit under the air inversion, can be seen in the bottom portion of the figures. Several Arctic or subarctic mines have reported air inversions. Even Rio Tinto’s Bingham Canyon pit in Utah has reported local air inversions from time to time [1].Mitigation of pollutants in deep open-pit mines in the Arctic is a challenging task. Release of pollutants below the inversion height in an open-pit mine during periods of weak winds and consequently weak vertical mixing may result in very high concentrations of primary and secondary pollutants, causing serious consequences for human health. Mine operations cease if the concentration of any one of the pollutants (NOx or CO) exceeds the TLV. Sustained cessation of a mine operation has serious economic consequences. For continued mining operation, the levels of pollutants must be below the TLVs. If no significant synoptic meteorological situation changes during an inversion, a warm air mass sits over the cold air mass within the open pit. Artificial ventilation is required to dilute the pollutants to an extent that mine workers can safely resume work. Some of the early approaches in artificially ventilating open pits were attempted in the USSR. Most of the studies by Soviet researchers suggested the use of turbojets and turbo-propeller engines, airscrews, axial pit fans, and meteotrons [2, 3]. However, the majority of these studies were only theoretical in nature, with no evidence of an approach that really worked in practice."

Jan 1, 2017