Search Documents

By S. M. Moore

Each year more than 400 coal miners are injured (fatal and non-fatal) by rock falling from between or around roof supports. Many of these injuries could be prevented by the installation of roof screen (wire mesh). However, many coal mines may be reluctant to use roof screen because of the added cost. The goal of this study was to determine the potential saving in workers? compensation (WC) premiums that could be achieved due to a reduction in rock fall injuries after roof screening. The WC rate-setting methods utilized by IL and KY were investigated in this study. Using actual data obtained from MSHA, national and state WC bodies and individual insurance companies (e.g. average cost per injury, loss cost rate, number of injuries per year, number of injuries preventable each year with roof screening), hypothetical mines (representing two mine sizes: 67 and 150 employees) were constructed with realistic ranges for estimates of injuries and WC premium costs. Using each state?s actual WC rate-setting formulas, total savings in WC costs after a three-year period were determined. Across both states, savings in WC premiums ranged from 1.8% to 14.6% when injuries were reduced by 10% to 20%. Additionally, an economic analysis was performed for an existing mine consisting of 67 employees. For this mine, the annual cost of a roof screening program was estimated at $240,000. If the screening prevented 13 ?struck by? WC claims over a 3-year period at this mine, the reduction in WC premiums alone could pay for the entire screening program.

Jan 1, 2010

By S. Cotten

The regulations for current coal mine refuge alternative (RAs) require that there be sufficient life support to sustain survival of the maximum number of RA occupants for a minimum of 96 hours. This minimum duration assumes that rescuers can access the RA through the mine within four (4) days of the onset of the mine emergency. But what if mine rescue teams cannot reach the miners within the RA before the RA air supply is severely limited or exhausted? What could be done to extend the duration of the RA life support capability into the 97th hour and beyond? In addition, what might be done to enable more rapid rescue of the miners if they could not be reached through the mine in a timely manner? This paper describes a systems approach to address the potential need to extend the duration of RA life support beyond current design limits. New capabilities that need to be developed in advance of such a dire need include more reliable emergency communications, highly mobile and efficient drilling rigs, enhanced directional drilling techniques, and a standardized RA external life support interface along with RA internal design modifications to accommodate use of an external supply. The following sections describe the need, intent, and technology gaps associated with each of these capabilities. Government agencies and the mining industry should consider initiation of a program to investigate, design, and develop effective means of extending the current 96-hour time restriction on coal mine refuge alternative life support. The development process should begin with a focused study to refine the overall operational concept, investigate the current state-of-the art of critical technologies, identify specific technology development priorities, and make recommendations for a development program to provide in an organized, efficient, and timely manner a solution for extended refuge alternative life support and occupant rescue.

Jan 1, 2011

By Ergin Arioglu, Werner Burger

"SUMMARY The Istanbul Strait Road Crossing Project includes a 3.34 kilometer subsea tunnel excavated by TBM with an excavation diameter of 13.71 m. The tunnel will incorporate two road decks, each employing two traffic lines and shoulder with the daily capacity of 100,000 light vehicles. The tunnel alignment crosses full face rock sections with heavily fractured zones due to tectonic events as well as a long central stretch of difficult mixed face and very variable soft ground conditions. The demanding ground conditions and the large diameter in combination with realized face pressures well above 10 bar required a highly specialized and well adapted TBM. The paper describes the project challenges and the related technical solutions incorporated within the TBM design as well as the real site experience. INTRODUCTION In 2013, a 13.71 m diameter Mixshield was manufactured in Germany for the Istanbul Strait Road Crossing Project. The delivery of the TBM in late 2013 was a major milestone for the Istanbul Strait Road Crossing Project, also known as the Eurasia Tunnel Project. The Eurasia Project (www.avrasyatuneli.com.tr/en) consists of a 14.6 km route including a 5.4 km tunnel segment in its central part crossing the Bosphorus. The 3.34 km subsea section of the tunnel was excavated in closed mode using a Mixshield TBM. The remaining tunnel length is constructed by sprayed concrete lining (SCL) method followed by a cast in place (CIP) lining or by cut and cover (CC) structures for the TBM transition boxes (Figure 1, right). Other project sections on the European and Asian side consist of upgrading and widening surface access roads towards the tunnel. Conceptual ideas of connecting Asia with Europe via a tunnel crossing the Bosphorus have been around for an extended time and only became realistic towards the end of the 20th century based on significant technical developments in mechanized tunneling. Feasibility studies for a new Bosphorus crossing in 2003 and 2005 confirmed and suggested a road tunnel in its present alignment as the preferred solution. Following an international tender process the Ministry of Transport, Maritime Affairs and Communications of Turkey assigned ATAS, a special purpose company formed by Yapi Merkezi (Turkey) and SK E&C (South Korea), to design, build and operate the Eurasia Tunnel Project. The Implementation Contract was signed in February 2011. In 2012, Herrenknecht AG was selected as the supplier for the 13.71 m Mixshield TBM."

Jan 1, 2016

By Andrea Koschinsky, Akira Usui, Michael Bau, Katja Schmidt, James Hein, Thomas Kuhn

Marine ferro-manganese (Fe-Mn) crusts and nodules are metal-rich chemical sediments that are archives of paleoceanographic proxies and potential metal resources and targets of deep-sea mining. Traditionally, crusts and nodules are subdivided into hydrogenetic, diagenetic, and hydrothermal types. While hydrogenetic Fe-Mn crusts are a potential resource for Co, Te, Pt, and REY, nodules are enriched in Cu, Ni, Mo, and Li, and hydrothermal deposits may be enriched in individual metals such as Mo, Ba, and Li, depending on the temperature and composition of the hydrothermal fluid. The different types of marine oxidic Fe-Mn precipitates, therefore, have different economic potential. Hence, a robust classification is not only helpful in the general geochemical characterization of such precipitates (and as such is a useful teaching tool, for example), but may also simplify the evaluation of their importance as a potential metal resource, which helps to prioritize exploration targets for deep-sea mining.

Sep 1, 2014

By George R. Stephans

The Climax Mine is a panel caving mine which has had a long history of incidents of severe ground control problems. The nature of the ore deposit, which lends itself to the caving meth- of of production, a1 so makes the mine susceptible to large scale stress concentrations which are referred to as ?weight? problems. These problems have increased with increased production and also with expansion to deeper mine levels. During the past twenty years the mine has had to learn to cope with these problems in order to remain in operation. A number of practical guidelines and useful techniques have emerged from these efforts. The purpose of this paper is to share a few of these ideas. The Mine is located near Leadville, Colorado on the continental divide at an elevation of 3450 meters. The ore body is a large low grade deposit of disseminated molybdenum sulfide. It measures about 1200 to 1600 meters in diameter and it had an original depth of about 660 mters. The Mine has been in operation since 1918 and the massive nature of the ore body together with its blocky, highly fractured condition made it natural for the caving system to have been adopted for production at an early date. Open pit mining was started in 1973. The total plant has a capacity of more than 50 thousand tons per day, and more than 400 million tons of reserves at an average grade of 0.310 percent molybdenum disulfide remain to be produced.

Jan 1, 1982

Remote methane detection State and federal regulations require frequent measurements to verify that safe methane levels are maintained in underground coal mines. Ventilation control is the primary means of maintaining safe methane levels. In the immediate face area, where the highest methane levels occur, methane measurements are required every 20 minutes during active mining. To perform these measurements, temporary roof supports must be erected. This allows a miner to reach the face. There a hand-held methanometer is used to make the measurements. This procedure is time consuming and potentially hazardous. To facilitate the measuring process and reduce the miner's exposure to roof falls, the US Bureau of Mines has developed a prototype optical device. It can measure methane remotely from distances up to 12 m (40 ft). The device uses two infrared signals, reflected from the coal face, rib, or roof. One signal is absorbed by the methane, the other is not. The ratio of the two signals determines the average methane concentration in the face area. The prototype detector has also been successfully tested at the Lake Lynn, PA Laboratory. Instantaneous responses were obtained for methane in the ventilation airflow and for methane layered near the roof. Conventional methanometers required from five to 25 seconds to respond to the methane in the ventilation airflow. They did not respond to methane in the roof layer. For more information about the Bureau of Mines' remote detection research, contact Richard W. Watson, US Bureau of Mines, Pittsburgh Research Center, Box 18070, Cochrans Mill Road, Pittsburgh, PA 15236 or call (412) 892-6630. Ignition suppression system The incidence has increased of fractional spark ignition at the mine face. One reason is the advent of mechanical mining. Another is the more difficult ventilation conditions associated with deeper and more extensive underground workings. To cope with the problem of frictional ignition, the Bureau of Mines initiated research to develop a system that would provide rapid detection of incipient methane-air ignition. Then, rapid dispersion of a quenching agent would ensure that the methane flame was extinguished while it was still relatively small. This concept was successfully demonstrated by suppressing explosions in the Bureau's Bruceton, PA experimental mine. But the bulkiness of the early storage-dispersal system proved impractical to retrofit onto face equipment. In a cooperative effort by the Bureau and the Mine Safety and Health Administration, a more compact system has been developed and is being tested. A continuous mining machine has been equipped with four 1.8-m-long (6-ft-long) and two

Jan 9, 1987

By Erik Klohn

The El Soldado copper deposit occurs in volcanic rocks of alkaline affinity of Lower Cretaceous age. The orebodies are discordant and show strong structural and lithological control. The mineralizing event was accompanied by hydro- thermal alteration expressed as carbonatization, silicification, and chloritization. Individual orebodies contain bornite-chalcopyrite cores which are surrounded by haloes dominated by chalcopyrite and pyrite respectively. The sulfur isotope composition of copper sulfides strongly suggests the sulfur is of magmatic origin. Fluid inclusion studies show the mineralizing fluid to be a highly saline NaC1-CaC12, brine. No evidence of boiling was found. The deposit is most likely of epigenetic origin. Hydrothermal fluids were produced during crystallization of a sodium rich trachytic magma during the waning stages of an episode of alkaline magmatic activity. Similar copper deposits along the Chilean Coastal Range may also be associated with alkaline host rocks.

Jan 1, 1986

By Cary Hirner, David Stacey, William A. Rochford

Design considerations and construction techniques were implemented to address groundwater infiltration from a confined aquifer during the excavation and lining of the Cady Marsh Flood Relief Tunnel. This 3-m finished diameter, 2-km long tunnel was successfully completed cost-effectively in an urban setting near East Chicago, Indiana. The soft ground was mined using a conventional tunnel boring machine with hydraulically actuated flood doors and supported with steel ribs and timber lagging. The tunnel was lined with cast-in-place concrete. Dewatering was implemented in settlement prone, boulder-laden ground in residential neighborhoods during construction to depressurize and partially dewater the aquifer at the tunnel horizon. This paper describes the design decisions and construction methods utilized to mitigate and limit infiltration into the tunnel during construction and operation, as well as manage ground settlement.

Jan 1, 2007

By Jan K. Wolski

Detection of the air recirculation branches within a large ventilation network may be difficult, therefore a PC computer routine has been developed to perform this task in an efficient and reliable manner. This paper describes the method illustrated using a network with complex multi-recirculation circuits. The fact that only the air flow directions and not the flow rates are used in calculations is of some interest. The air recirculation during a real mine fire is demonstrated using the PCVENT program, whose version 4.0 includes current information about any recirculation branches during network calculations or during a fire simulation. This paper also discusses some transient problems related to air recirculation, and gives examples.

Jan 1, 1993

By W. L. Jacobsen, T. L. Dyer

Cortez Gold Mines is completing a Feasibility Study for a new open pit gold mine in north central NV. The production schedule calls for a peak in material movement. This schedule is based on current operational efficiencies and equipment parameters observed at the company’s existing open pit operation. To mitigate risks of over/under predicting production, simulation modeling was used to validate the loading and haulage requirements during the peak production period. The advantage of simulation is the ability to provide a realistic model of a mining operation based on scheduled, and unscheduled random events during the period under analysis.

Jan 1, 2006

A parametric study was conducted to establish the optimum operating conditions for the column flotation of fine coal. The parameters examined in this investigation included collector and frother dosages, feed solids content, and the volumetric flow rates of feed slurry, air and wash water. Despite the wide range of conditions studied the experimental data were found to fall along single grade-recovery curves, just below the maximum separation predicted by the release analysis technique. The deviation of the parametric test data from the release curve was attributed to the nonselective entrainment of mineral matter associated with poor froth washing. The operating point on the characteristic recovery-grade curve was found to be primarily determined by feed rate and aeration rate.

Jan 1, 1992

By S. G. Malghan

Flotation is the primary method for copper minerals separation from porphyry ores. The need to process difficult-to-float porphyry copper ores presents challenges to engineers and scientists in several areas. This paper is concerned with summarizing generalized problems faced in the processing of porphyry ores and treatment methods to overcome the specific problems. Though some of the problems are interrelated the problems have been classified into three broad catagories. The case studies of some of the successful applications of innovative methods to solve problems related to ore mineralogy, metallurgical aspects of ore treatment and process variables show that quite often the problems are solvable by a judicious choice of flotation variables.

Jan 1, 1984

By Mirjana Boskovic

LKAB’s Kiirunavaara Mine is a sublevel caving iron-ore mine located above the polar circle in northern Sweden. The mine has been proclaimed seismically active since 2008 after a magnitude 3 seismic event, according to Swedish National Seismic Network (SNSN). At that time the Kiruna Mine did not have mine-wide seismic system. Since then, the Kiruna Mine experienced several damaging seismic events of which the largest one on the May 18, 2020. The magnitude, based on the moment tensor inversion results on data from the SNSN as well as seismic stations in Finland and Norway, is estimated to 4.2 ± 0.2 moment magnitude. The seismic event on the May 18, 2020 was located in the middle of the one of the productions areas and caused the major damage in the mine, damaging several kilometres of drifts on six mining levels, some of them beyond the practical repair. These damages affected four of ten production areas on several levels, some more some less. Luckily, no person got injured from the seismic event and the very long aftershock series. An important part in the whole process after the seismic event was information flow and decision-making process. It was very important to keep workers and community informed as that contributed transparency of decision-making and decreased the speculations. Resuming the production in the damaged areas in the safe manner, very soon become main focus for the mine management. It was obvious that not only rehabilitation of the areas is needed to resume the production. It was A MUST to understand the factors behind the seismic event and its mechanism to be able to avoid same situation and prevent seismic event of similar size. Mine engineers had to think outside the box to find the solutions to ‘rescue’ every drift that they could to be able to make good enough base for continued mining of the area. The paper describes actions taken in a very complex process of recovering the area that we from the beginning thought need to be abandon. Seismological analyses of the event on May 18, 2020 and past activity in the area, damage mapping, detailed studies of structures and geology, numerical modelling as well as engineering judgement were used as base for all our decisions how to proceed in attempt to restore mining of the area heavily damaged by 4.2 moment magnitude seismic event, in a safe way.

Apr 26, 2022

By Stacey Leichliter

The Cripple Creek and Victor (CC&V) Gold Mine (Cresson Project) (Fig. 1) is undergoing an expansion to extend production to the year 2025. This expansion involves building a high-grade ore mill, another valley leach facility (VLF) for heap leach operations and expanding the overburden storage areas. The current operating pits are progressing downward from the oxide ore into a more sulfide and telluride-rich orebody. There is still oxide ore present in the current pits and planned pits not yet mined. There is an increased need for two recovery processes for these two different types of ore. The key component to this expansion is the high-grade ore mill, which has gravity, flotation and carbon-in-pulp (CIP) circuits. The mill will be the main recovery process for the higher grade, more sulfide/telluride-rich ore. This ore type does not recover well on the heap leach pad due to its refractory nature. Geometallurgy is vital for ore characterization for the two recovery methods. Geometallurgy helps develop indices that are used to predict parameters that influence overall recovery and production, such as hardness, crushability, grindability, pH fluctuations, gravity (coarse) gold, flotability and cyanidability. Using geology and mineralogy along with other analytical data, geometallurgical models are constructed and applied to the resource block model for proper planning and extraction of the gold. Geometallurgy aims to analyze the variability in the different responses to the parameters to help reduce risk (costs) and optimize recovery (profit).

Jan 1, 2013

By Colin Lawrence, Michael S. Schultz

Due to the planned deepening of the NY Harbor, NYCEDC/NYCDEP is planning to replace two existing water lines between Brooklyn and Staten Island with one deeper water pipe. The crossing, just north of the Verrazanno Bridge is 1.75 miles long. The new pipeline will be tunneled using gasketed concreted segmented liners. Apressurized face machine will be used through the soft ground. This will be the first subaqueous application using this technology in New York City. This paper discusses the planning, design and risk issues associated with the crossing and the challenging soil conditions that resulted in the decision to use a pressurized face machine.

Jan 1, 2007

By Marina Carreiro-Silva, Cátia Cardoso, Bruce Shillito, Lisa Mevenkamp, Alastair Brown, Maria J. Bebianno, Juliette Ravaux, Inês Martins, Nélia C. Mestre, S. Sousa Vânia

Mineral extraction activities in the deep sea will expose the local fauna to potentially toxic compounds. However, very few data are currently available on the complex ecotoxicological risks to deep-sea fauna from the potential release of heavy metals, trace metals and Rare Earth Elements (REEs). Nonetheless, this is key information essential to support the regulation of industrial activities in the deep sea. One of the fundamental issues that the MIDAS project will address consists in exploring the concept of whether the existing toxicity test protocols and limits established in shallow-water species are applicable to deep-sea mining. We will detail the specific challenges to recommending exposure limits within the deep sea and show preliminary results of comparative toxicity tests in the shallow-water and in the deep-sea environment.

Sep 1, 2014

By K. Lapakko

Several static tests estimate the capacity of mine waste to produce and neutralize acid and are used as tools for predicting metal-mine waste drainage quality. Various methods and their accuracies are addressed. More accurate quantification of these capacities, as well as their availability and reactivity, may be necessary to predict drainage quality from some mine wastes. Chemical analyses, x-ray diffraction, optical microscopy, scanning electron microscopy, and electron beam analyses are among the techniques commercially available to more accurately quantify these capacities and provide insight into their availability and reactivity.

Jan 1, 2003

By M. Hepokoski, M. Klein

"Mine refuge shelters are designed to protect mine workers from hazardous environmental conditions after a mine disaster, but high temperature and humidity levels inside these shelters may pose a significant safety risk. Due to the safety risks associated with human testing, detailed thermal models of shelters and human occupants have been developed using TAITherm simulation software. These models are used to predict the temperature and humidity within the shelter resulting from metabolic heating, evaporation due to sweat and respiration, moisture and heat from the shelter’s carbon dioxide scrubbing system, and heat transfer within the shelter. A detailed human thermoregulation model simulates the sensible and latent heat generated by the shelter occupants, and predicts the occupant’s body core temperature and moisture lost due to sweating and respiration. This information is used to assess the safety of the shelter. This paper presents the technical details of the human thermal model, validation comparing the human model to human subject test data, and results of a mine shelter analysis. IntroductionPortable mine refuge chambers are used in U.S. coal mines to provide protection to mine workers from hazardous conditions following a traumatic event. Although these shelters are designed to supply clean air and sustenance for up to 96 hours, prolonged exposure to the mine shelter environment itself can pose a substantial risk to human safety. Heat generated by the shelter occupants combined with heat from the carbon dioxide (CO2) scrubbing system can raise the shelter interior temperatures and relative humidity to dangerous levels that can lead to heat stress in humans. Unfortunately, the thermal burden associated with mine shelter exposure is not well characterized due to potential hazards associated with underground human subject testing. In order to assess the thermal burden on people within a mine shelter environment, a detailed thermal model was created to accurately predict the temperatures and humidity levels within the shelter, and the impact of these environmental conditions on human occupants. The model consists of a mobile inflatable tent-type mine shelter with 23 humans, and includes the surrounding mine environment. The thermal simulations were performed using a validated commercial heat transfer prediction computer software. Additionally, a module of the software provided the capability to simultaneously model the thermophysiology of 23 unique humans contained within the mine shelter. The human thermal models accounted for the thermal interaction with the environment and provided a core temperature response prediction that can be used to evaluate survivability in heat stress situations (U.S. Army, 2003). The models can also be used to determine maximum occupancy in order to maintain safe temperature and humidity levels inside the shelter in specific mine environments, to optimize shelter size for maximum heat dissipation, or to simulate active cooling systems."

Jan 5, 2017

By Nikhil Dhawan, Sanjay Pindar

The limited lifespan, ever-growing demand, and significant lithium and cobalt content are responsible factors for the immediate recycling of discarded lithium-ion batteries. Discharged batteries were dismantled, segregated, and size reduced to recover cathode and anode material. The active cathode material comprises LiCoO2 (65.8%) and LiMn2O4 (34.2%) and was carbothermal reduced with recovered graphite in a microwave furnace followed by water leaching and magnetic separation. A Box Behnken statistical experimental design is used for process optimization. Both cobalt and manganese report to magnetic fraction, whereas graphite and lithium carbonate report to non-magnetic fraction and solution crystal respectively. The final product comprises of cobalt 73% and manganese of 14% with process yield of 36% and saturation magnetization of 76 emu/g.

May 16, 2020

By G. Gaidajis, K. Angelakoglou

The development of a tool for assessing the environmental sustainability of mining facilities is described in this study. The tool is based on the analysis of basic components of the examined system, i.e., the quantities of the incoming materials and outgoing wastes, their hazardousness and scarcity, the utilization of water and energy resources, and the biodiversity. The developed tool provides both qualitative and quantitative assessment of the environmental performance of a mining facility in a broad time scales (past-present-future) and is easily applicable from non environmental experts. Moreover, relative software is developed to further support the application of the methodology. The implementation of the tool is expected to lead to an improved understanding of the environmental performance of a mining facility and more importantly identify the areas of significant environmental concern. However, based on feedback from industries, a number of shortcomings of the approach have been identified so far and are presented, indicating further actions for the advancement of the proposed tool.

Jan 1, 2011