Search Documents

By J. Nowak

Polish power industry is based on brown and hard coal combustion and transferring the heat into electric power. Over 99% of lignite is used as a fuel in power plants. Lignite is mined on in open pits. Therefore very deep (for example 300 m in Belchatow open pit) excavations having great volume are formed. Thus such type of mining has the impact on land degradation. In order to reduce this effect, at the earliest possible moment the cap rocks are dumped in the pit but at the safe distance from the mining face. Due to the big amounts of lignite delivered to the power plant, there are shortages of solids for filling the pit after completing the mining operations. Geotechnical properties of dumped combustion by-products depend on the lignite type, combustion technology and ashes haulage methods. The paper presents lignite combustion methods used in Poland and their impact on properties of ashes and methods of their transport determining the parameters of dumped wastes. Geotechnical, physical and chemical test results concerning transport and deposition of hydraulically active ashes from the Belchatów power plant are presented. The critical role of geotechnical properties in selecting the deposition technology and post mining management of open pit excavations was showed. The importance of filling the post-mining spaces for restoration the useful function of brown fields and for neutralization of negative effects of mining activity, was underlined.

Jan 1, 2006

By A. Shakoor, A. M. Hirt

The compressive strength of coal, and its variation within and between seams, was determined for four Pennsylvania coal seams (Pittsburgh, Sewickley, Upper Kittanning and Lower Kittanning). Large coal blocks were obtained from 12 coal mines (three mines per seam) and cut into 50-mm (2-in.) cubes using a low-speed saw. The cubes were tested for compressive strength, with the results used to compute actual pillar strength. Using the tributary area approach, the pillar stress was determined. The pillar stress and strength data were used to calculate the factor of safety against pillar crushing for each mine. The cube strength was also correlated with various physical and chemical coal properties (density, percent absorption, percent ash, percent sulfur and percent carbon) to see if any strong relationships exist. The coal's mean compressive strength varies from 9.1 MPa (1326 psi) in the Lower Kittanning seam to 37.8 MPa (5480 psi) in the Pittsburgh seam. Between different seams the pillar strength varies from 29.5 MPa to 48.1 MPa (4282 psi - 6981 psi). Although coal strength appears to be weakly related to carbon content, no relationship was found between compressive strength and other physical or chemical properties. Since the values for the safety factor against pillar crushing generally exceed the recommended value of two, the existing pillars are mostly overdesigned. This implies that an accurate assessment of coal compressive strength could result in the use of smaller pillars and, thus, increased coal production.

Jan 1, 1993

By Todor P. Stefanov

The thermal draught within ventilation networks of underground mines depends to a great extent on the shafts depths and degree of change of ventilating air density. When the topology and space orientation of a ventilation network are constant, the dynamics of thermal draught is determined mainly by the variations of the heat- and mass-transfer processes in the openings. This conclusion follows from the well known basic theoretical notions about the thermal draught-aerostatics and thermodynamics [1]. Quantitative evaluation about the influence of heat- and mass-transfer processes on dynamics of thermal draught could be made through: direct mine measurements, special experiments and with the aid of mathematical models. The first two methods produce sufficiently accurative results, however it is very difficult to perform such studies, particularly when these processes are evaluated within a large scope and multifactor aspects. Mathematical models of thermal draught allow to overcome easily these difficulties. The degree of accuracy of results, obtained by this method, depends to a great extent on the degree of approximation achieved by the model to the real heat- and mass-transfer processes. In this paper, with the aid of Bulgarian developed method, algorithm and computer program V WT-4 - for complex evaluation of ventilation parameters in active mine ventilation networks [2], the authors investigate some changes in the thermal draught. Basically, the method is an iterating evaluation of an open set of equations, which represents relationships between the following basic parameters of a mine ventilation network: [ ]

Jan 1, 1980

By D. M. Milne, H. H. Kanduth

INTRODUCTION The past few years has seen an increased interest in the determination of statistically valid properties of a rock mass. The increased use of computer modelling for the study of rock excavation behaviour has created a need for upper and lower statistical bounds for the properties of a rock mass being modelled. Obviously, to determine the statistical properties of a large volume of rock, many samples must be tested - an expensive proposition when using conventional testing facilities and procedures. As a result of high costs per sample, sufficient tests for statistically valid results are rarely done. In an effort to reduce both sample preparation and test facility costs, an instrument called the Bemek Advanced Rock Tester (BRT) was developed in Sweden. With a total weight of approx. 35 kg, the BRT is portable and sells at a small fraction of the cost of a conventional testing machine. It is comprised of a small 65 KN loading frame with attachments for a variety of tests (see Table 1) , a hand operated hydraulic pump, an electronic balancing unit and a programmable microprocessor. The microprocessor is capable of storing data, performing arithmetic operation on, and printing signals from, a transducer and two strain gauges. A detailed description of the apparatus is given by G. Swan et al. (1). The proposed test strategy involves first a 3-point flexure test on a notched core specimen, followed by a 4-point flexure test on the separated specimen halves. Finally, point load and Brazilian tests can be carried out on the quarter parts of the original specimen. Thus specimen preparation is kept to a minimum. These and other perceived advantages have prompted the purchase of this machine and an evaluation of its suitability to provide data on mechanical properties of intact rock for numerical modelling and rock mechanics design at Noranda's underground mines. Details of its performance evaluation and experiences with the unit are discussed in the following sections. [ ] INITIAL OPERATING EXPERIENCE During the commissioning stage the BRT had, or developed, a series of problems, some of which seriously affected its operation. Below are some examples. Poor documentation was the most serious problem encountered. Confusing instructions for the 4-point bend test installation and its microprocessor programing, as well as poor and ambiguous information on the calculation of gauge factors, are some of the difficulties which had to be overcome. Meehan~cal problems occurred, including failure of the hydraulic pump, as well as electronic difficulties with the microprocessor. Other problems with the printer, requiring its replaceqent, were fortunately covered under warranty.

Jan 1, 1986

By Lynn B. Hales, Randy Ynchausti

Expert systems are now being used effectively to streamline and improve the performance of supervisory computer control strategies. Their advantages have led to use in both batch and continuous applications. Expert systems in the context of real-time process control, will be defined and examples of their successful implementation in autogenous, semi-autogenous and ball mill grinding circuits will be discussed.

Jan 1, 1990

By C. Mermiris

Bauxite ores in Fokida belong to Parnassus-Giona zone and are found exclusively in limestone in two bauxite horizons, which are of great economic importance and with very unfavorable conditions for the reclamation process. The ore bodies are usually less than two million tones. They are in many cases encountered near the surface as a result of the erosion and are exploited either with open pit or underground methods. Mining activity, which dates back 70 years, causes many changes to the environment and most of all to vegetation and landscape. The first step to mining exploitation of bauxite ores is the selection of an underground or open pit method taking into consideration mostly economical and technical criteria. Open pit exploitation, which causes the most severe environmental consequences, is done with the method of vertical benches in hard rock with the use of explosives. The impacts on the landscape that result from the method of vertical benches are: ? The front of the excavation that is usually solid rock of the hanging wall (limestone). The height of the benches varies from 10 to 20 meters and the gradient of the final slope is designed to be around 65o, unless the rock is not so stable and the gradient is reduced accordingly.

Jan 1, 2002

By Samantha Smith

Nautilus is completing the world's first environmental impact assessment (EIA) of seafloor mineral extraction and Nautilus has gained extensive experience conducting environmental studies in subsea environments. Nautilus is currently working on the Solwara 1 Project in the Bismarck Sea, Papua New Guinea, where high grade seafloor massive sulfide deposits lie at ~1600 m water depth. Conducting an EIA in the deep sea presents some interesting and exciting challenges. Seafloor studies commenced in December 2005 using a remotely operated vehicle (ROV) fitted out with highly specialized scientific equipment to conduct water quality, sediment, biological and oceanographic studies. During 2007 and 2008, Nautilus launched two two 30-day ROV programs dedicated to environmental baseline studies and during this campaign, over 550 biological, sediment and water samples were collected and over 20,000 seafloor observations were logged. On board specialists included an international team of experts in the field of deep sea marine science. Collaboration between industry and scientific research institutions allows data to be collected for the EIA but also provides an extraordinary opportunity for researchers to access sites that might otherwise remain unobtainable to science. This presentation will review the studies conducted as part of this exciting project. Keywords: Seafloor Massive Sulfides, Environmental Impact Assessment

Jan 1, 2008

By Philippe Dumont

Presentation of the project Underground civil works to be performed They include two single track running tunnels and a service tunnel of a length of fifty kilometers . Many cross adits (180 adits) : to link the tunnels (53 cross passages), to relieve air super pressure from one tunnel to the other (87 piston ducts), to install technical adits (40 electrical rooms). Two cross-overs located at one third of the whole length, allow trains to shunt from one tunnel to the other so as to ensure one way traffic in case of emergency. Pumping stations allow water to be collected at the lowest point and pumped out. 1 Main features of the tunnels 1.1 The service tunnel This 4.8 m inner diameter gallery allows During civil works - front probing operations of the geological layers encountered (front and vertical probes). - lateral soil grouting that may be necessary to facilitate the boring of the two running tunnels . During operations - Maintenance and safety vehicles traffic - Fresh air supply to running tunnels - Fire protection and drainage system - Electricity supply and control and communication. The service tunnel has been bored with a 5.72 meter external diameter Robbins TBM for the undersea section, and a MITSUBISHI TBM for the land section.

Jan 1, 1991

By Jean-Claude Bianchini, Paul Bauernfeind, Erwin Gartung

Introduction The city of Nuremberg, located in Bavaria in the Federal Republic of Germany, started building a subway in 1967. The construction operations began in a southern suburb, where no complications were encountered in the design and execution of the job. As the first subway line approached the downtown area of the city, the civil engineering challenges increased rapidly. Tunnels had to be excavated next to, or below precious historical buildings, and the work of the responsible engineers was closely watched by the public, who were very anxious about any damage to the existing beautiful old houses and churches. The job has been handled successfully to date in cooperation with the owner-designer, the geotechnical consultant and the contractors, who jointly went through a process of systematic learning and gathering of experience, and who developed a modern tunneling technique specifically tailored to the natural properties of the encountered ground conditions and the requirements of the city of Nuremberg. The application of scientific methods has been an important part of this development. Research into the geotechnical properties of the predominantly encountered soft Keuper sandstone, studies of the geomechanical performance of grout reinforced sand sections and finite element analyses of various tunnel problems for the prediction of displacements, for the assessment of stability, or

Jan 1, 1979

By P-M. Dupond, S. Lowrie, C. Tauziéde, Z. Pokryszka, A. D. Jones

A physical model has been developed to simulate the flows and mixing of gases in the waste of a longwall retreat coalface. The model is used in conjunction with computational modelling, and the distributions of permeability and gas emission in the model waste follow those in computer simulations (Pokryszka et al 1996). The physical model represents at 1170th scale a 200 m long, 3 m high coalface with a waste extending up to 280 m to the face start line. The model is tilted to the same seam slopes as the real face, e.g. 22° ascensional ventilation along the face and 7" slope to the dip. The purpose is to investigate the flow of three components: ventilation seepage flow through the waste; methane; and nitrogen injected to quell spontaneous combustion. A heavier-than-air surrogate gas (SF,) is used in place of methane, and therefore the model is inverted so that gas layers form along the 'roof". The main forces driving the flows in the waste (pressure gradients due to ventilation and the density difference of gas layers) are kept in proportion by appropriate scaling of the permeability. Calibration and validation used data from a coalface at a mine in the Lorraine coalfield. The model is now in operational use.

Jan 1, 1997

By C. J. Bise, D. A. Poukhovski

Hazard recognition and prevention of accidents are two components of the 30 CFR 48 training requirements, which are mandated for new miners and newly employed experienced miners. These components are also part of the annual refresher training course required of all miners. In these categories, instruction shall include the recognition and avoidance of hazards present in the mine and shall include a review of accidents and their causes. Unlike instruction preparation for fact-based material, program development for hazard recognition presents a particular challenge to safety-training specialists, because they are often limited in their ability to adequately gauge the level of awareness of the individual prior to training. Further, they must also assure that the training is relevant and presented in a thought-provoking manner. Computer-based instruction is particularly well suited for assisting trainers in developing hazard-recognition topics, because it can be used in pretraining and posttraining modes for assessment of training effectiveness, in addition to its use as a presentation tool. This article presents a recent approach, developed at The Pennsylvania State University, that applies the technology for the assessment and instruction of accident prevention through hazard recognition. The application is prepared for surface coal mines.

Jan 1, 1999

This paper provides a summary on the use of the POL YCOM high pressure grinding roll (HPGR) for increasing extraction in copper leaching. The energy-efficiency and significant hydrometa1lurgical benefits of the HPGR result in better acid-curing, higher solution application rates, improved copper extraction from various copper minerals and better recovery from high acid consuming ores. The HPGR's metallurgical features such as micro-fracturing, better liberation of disseminated and veinlet copper, increased oxygen and lixiviant penetration lead to higher copper extractions than achieved by conventional crushing. Flowsheet options, operational characteristics and applications for various copper ores are outlined.

Jan 1, 1996

By R. R. Klimpel

During the period of 1973-79, an extensive period of research and development was undertaken by Klimpel and coworkers (1980, 1981, 1982a, 1982b, 1983. 1984, 1987) on the identification of a commercially viable chemically assisted approach to improving the efficiency of the wet grinding of coals and ores in tumbling media mills. The emphasis of the previous publications just listed was on the engineering use implications of controlling-slurry viscosity (rheology) in laboratory and plant scale grinding devices. In this paper, some discussion and results pertaining to the actual chemical screening phase will be presented.

Jan 1, 1988

By Erik Westman, Benjamin Mirabile

"Ongoing research is being conducted to evaluate secondary support performance in longwall ventilation entries. In a three-entry longwall gateroad, secondary supports are applied in the #2 entry to maintain a functional airway for the entirety of second panel mining. This airway represents a pathway for contaminated mine air to travel from the longwall tailgate to the mine bleeder system. The ground response curve concept may be used as a design basis for selection of appropriate secondary support in these ventilation entries. Two types of secondary supports are monitored for load and convergence in this project. These monitored supports are pumpable crib supports and interlocking wood crib supports. To evaluate the effect of support density, two installation patterns are monitored for each support type. Both a single-row, protected airway pattern and double-row, full entry support pattern are monitored for each support type. Load and displacement data is collected for all support patterns as second panel mining retreats past instrumentation sites. Data is collected for approximately 200-feet inby the second panel face or as long as safely possible. Load and convergence data collected will be used to calibrate numerical models that will simulate ground response curves for the #2 entry inby the second panel face.INTRODUCTIONWhen a bleeder ventilation system is used, the #2 entry of a three-entry longwall gateroad system is designed to function as a pathway for contaminated air from a longwall face to the bleeder system during second panel mining. The #2 entry is subject to substantial ground movement and loading during its function as an air course because it is a single entry between two longwall gobs. Secondary support is regularly applied in this entry to maintain air course functionality during second panel mining.Research on performance and design of secondary supports has been conducted extensively over the last 30 years (Barczak and Gearhart, 1993; Barczak and Gearhart, 1994; Mucho, Barczak, and Dolinar, 1999). This research has focused heavily on the application of secondary support in longwall tailgate, with little research on the application of secondary support in bleeders or other ventilation entries (Mirabile and Westman, 2018). Secondary supports in #2 entry are likely to experience similar loading and ground movement as those applied in the tailgate entry. However, the designed lifespan of the mine entry and the definition of acceptable ground conditions differs from mine entries where more extensive research has been conducted."

Jan 1, 2019

By D. Zaharaki

The optimisation of geopolymer synthesis was studied bymixing low Ca electric arc ferronickel slag with kaolinite, sodium silicate solution, sodium hydroxide pellets and water. The pulp was heated at low temperatures and left for curing at room temperature. Through statistical analysis it was shown that the factors with the most statistically significant effects on the compressive strength of the produced geopolymers are slag particle size and aging period. XRD and FTIR studies provide useful information regarding the progress of geopolymerisation mechanisms. Finally, studies regarding the durability and structural integrity of the produced geopolymers were also carried out.

Jan 1, 2006

By Debbie Nakamura, Daniel Tempelis, John E. Shamma

The Metropolitan Water District of Southern California established a Board of Consultants to assist them in administering the design and construction of the Inland Feeder Program tunnels. The Board acts as an expert review body for the owner, looking at key issues that can potentially impact the success of the program. The use of the Board evolved over the life of the project, and its composition was modified to better address the needs of the owner, and the Program requirements. The experience, function, and value of such a board is analyzed and discussed in this paper.

Jan 1, 2003

By D. R. Zeni

Today's mine development requires the safe, expedient and economical construction of vertical shafts for both ventilation and access. This construction must be accomplished within diverse ground conditions. Advancements in large-diameter shaft drilling have led to many exceptional mechanical refinements in shaft-drilling technology. The author traces the history of the equipment and methods employed by the large-diameter shaft-drilling industry and explores the likely paths of future development. Case histories that illustrate the adaptability of shaft drilling as a versatile tool for advanced, worldwide mining operations are cited. Safety, scheduling, costs, environmental impacts and capabilities are discussed.

Jan 1, 1996

By B. Day, L. Elinson

There is general agreement among those involved in occupational and public health that work-related diseases are under-diagnosed and under-reported. Highmark is particularly well positioned to carry out industry health analysis as it provides medical insurance for approximately three quarters of the insured population of Western Pennsylvania including some of the areas largest employers. The purpose of this study is to gain a more accurate understanding of the mining industry rates of respiratory diseases that maybe occupationally related and identify those inflated respiratory disease and hearing loss rates. Conditions examined included COPD, asthma, and pneumoconiosis.

Jan 1, 2004

By R. A. Haney

The Mine Safety and Health Administration (MSHA) has conducted studies both in coal and non-coal mines to evaluate methods for sampling diesel particulates in underground mines. The agency is investigating size separation techniques to distinguish between diesel particulate and respirable coal mine dust. Additionally, ashing techniques have been used to distinguish diesel particulate from mineral dust in metal and non-metal mines. As part of these studies, personal exposures to diesel particulate for various mining occupations have been measured. This paper describes the measurement techniques and summarizes the exposure levels for various underground mining operations.

Jan 1, 1993

By Dennis Ortega, Rich Kramer

After several operational improvements to FMC's Westvaco Mine Longwall, an ergonomic and operational bottleneck resulted at the mobile belt tail/rigid conveyor junction. Ergonomic hazards, cutting time losses, and spillage problems near the belt tail were identified and targeted for improvement. FMC Westvaco, consulting with FMC Material Handling Division, corrected the bottleneck using an expandable/retractable conveyor system to fill the gap between the mobile belt tail and the rigid conveyor structure. This paper explains the operational expectations, defined before; the challenges, encountered during; and the real outcomes, measured after the installation of an expandable/retractable conveyor system.

Jan 1, 2002