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By Joseph Goessling, Mark Kroncke, James Parkes

The I-35 Capital Expressway (CapEx) Central Drainage Tunnels will serve as a stormwater collection system for the forthcoming I-35 Capital Express Central reconstruction project through downtown Austin, Texas. The schematic level concept design included three tunnels, 10 to 14 ft ID, totaling 26,000 LF. Constructability reviews during design development indicated issues with the concept design including phasing of construction, conicts with future retaining walls, staging area concerns, and signicant mixed face tunneling. The design was updated to mitigate these risks. The revised design includes two tunnels, both 22-ft ID and totaling 33,000 LF, that will be mined almost entirely in rock.

Jun 23, 2024

Separation of dolomite from Florida phosphates was achieved by first conditioning the feed with fatty acid at pH 10 followed by reconditioning at pH 4 or below, before flotation. Observed selectivity of this two stage conditioning process was attributed to the amount as well as changes in the nature of the adsorbed collector species upon reconditioning. In this paper, bench scale flotation results of optimizing the major process parameters, such as reconditioning pH and collector dosage, for upgrading natural high dolomitic phosphate samples from Florida are discussed.

Jan 1, 1988

By A. D. Davis

A ground-water flow model was developed to simulate the post-mining recharge rate at the Belle Ayr surface coal mine in the Powder River Basin near Gillette, Wyoming. State regulations of Wyoming require that reclaimed lands should provide a rate of recharge that approximates the pre-mining rate. Steady-state calibration and transient simulations showed that the post-mining recharge rate in backfill is at least five centimeters per year, exceeding the original infiltration rate of 0.4 centimeters per year to shallow, overburden aquifers. Major reasons for the increase include the flat topography of reclaimed areas and decreased spoil density. It is expected that the backfill will disaggregate and settle over time, eventually resulting in a nearly constant recharge rate less than five centimeters per year but somewhat greater than the pre-mining rate.

Jan 1, 1995

By Z. Hajnal

Three years ago a research program was initiated at the University of Saskatchewan to develop seismic surveying techniques for use in the Precambrian geological environment. The success of the reflection method in many younger geological settings suggested that this is the technique which would be the most suitable for experimentation. A successful adaptation of this technique to the Shield environment would make mapping of rock formations possible to much greater depth than is possible at the present time with any other applied geophysical technique. This presentation attempts to illustrate the advances which have been made in this program and will provide some insight into future plans. The field investigations were limited to the Flin Flon basin near to the town of Flin Flon, Manitoba (Fig. 1). This area was chosen because the surface geology has been mapped in great detail and it is a very important base metal producing region. It is an ancient sedimentary basin with some characteristics similar to areas where the reflection method has been successful.

Jan 1, 1976

By O. A. Velasquez, A. R. Kumar

"Continuous miners are often equipped with a flooded-bed dust scrubber to clean the air from close to an active underground coal mining face. However, its impingement screen is prone to clogging due to an accumulation of dust, thereby lowering the scrubber’s efficiency and potentially exposing the mine workers to higher levels of dust. Fans can compensate for the increased resistance by varying their operating parameters, but the scrubber screen needs significant maintenance which leads to downtime. The authors have proposed a suitably sized Vortecone as an alternative to the conventional flooded-bed dust scrubber system. Water is used as the filter medium, which is replaced and recycled continuously. Preliminary CFD investigations of Vortecone scrubbers have indicated higher cleaning efficacies, especially in the respirable range. This paper presents the results including the flow characteristics and capture efficacies of a full-scale Vortecone. Multi-phase flows, including free-surface modeling and particle tracking methods, have been adopted. ACKNOWLEDGEMENT The authors acknowledge the National Institute for Occupational Safety and Health (NIOSH) for funding this research project. This research is being developed with the support of a NIOSH Grant 200-2014-59922- ‘Coal Mine Dust Mitigation through Novel Scrubber Development and Numerical Modeling’. The views expressed in this paper are those of the authors and do not necessarily reflect those of NIOSH. This project is aimed at designing novel and efficient scrubbing systems for underground mining operations. The authors acknowledge Dr. Thomas Novak of the Department of Mining Engineering, the University of Kentucky for his support and encouragement. The authors also thank Dr. Sunil Vytala, CFD engineer at Cradle CFD for his invaluable inputs to the numerical models.INTRODUCTION Continuous miners are the main production machines deployed in room and pillar mining operations. These miners extract coal by the shearing action of the wethead cutting drums. Strategically placed water sprays on the drum not only cool the bits extending their useful service life, they also suppress the dust at the point of generation itself. A flooded-bed dust-scrubber (Campbell, et al. 1983) is usually integrated onto the continuous miner to arrest dust from close to the active face. These fan-powered scrubbers have an impingement screen flooded with water, which also serves as the filter element. A demister downstream of the screen removes the excess water from the air cleaned. These conventional scrubbers have been found to be very effective in alleviation of respirable dust levels underground (Chao and De-sheng 2000) (Colinet, Reed and Potts 2013). However, the inefficiencies of the flooded-bed dust scrubbers arise out of their internal components. Depending on the mining conditions, the screen may be clogged by the accumulation of the trapped dust particles. The resistance of the scrubber system is increased reducing the airflow. The flooded-bed dust-scrubber system would, therefore, require frequent maintenance of the screen and the demister (Listak 2010). Since any maintenance needs to be carried out under supported roof, this leads to loss of availability of the equipment as well. In addition to this, the continuous miner operators could be exposed to elevated levels of dust when satisfactory airflow at the face is not achieved."

Jan 1, 2018

By W. G. Pariseau

Face and pillar bursts, bumps and bounces are violent failures that occur in underground coal mines in response to a complicated interplay of face and pillar geometry, seam depth, coal strength and moduli and interactions between roof, seam and floor strata. Additional complications arise from the presence of gas, mainly methane, and associated pressure and flow that vary with time and are further influenced by the rate of face advance. Numerical models provide a means of quantitatively accounting for the various complications of mining geometry, the stratigraphic column, mechanical properties, gas flow properties and associated interactions. A fully coupled hydromechanical finiteelement code, utAH4, serves the purpose well and allows study of the important interaction between stress concentration and gas pressure in determining safety and stability of the face during the advance of a longwall panel in a deep underground coal mine in central Utah. Face advance is relatively fast compared with gas flow and depressurization in coal seams of low gas permeability. Consequently, gas pressure is high at the face. When a longwall is stationary, depressurization occurs at the face, so effective stress and strength increase. thus, when gas flow at the face is high and requires a pause in face advance to bring gas concentration to an acceptable level, a second benefit occurs because of timely depressurization. However, quantitative analysis of a deep coal mine shows that regardless of gas pressure, high stress concentration is more likely to pose a threat to face and pillar wall stability.

Aug 1, 2013

By Kevin Andrews, SETAREH GHAYCHI AFROUZ

Ground control analysis and groundwater inflow assessments for underground coal mines require in-depth field investigations including, but not limited to, geological and geotechnical core logging, downhole geophysical logging, laboratory rock strength testing, and packer (Lugeon) testing. Field and laboratory data collection are time consuming and expensive, and an initial understanding of the expected trends among various geotechnical and hydrogeological parameters can assist with the planning and optimization of geotechnical characterization studies and grouting plans. In this study, a comprehensive database is analyzed, comprised of important rock mass characteristics (hydraulic conductivity, rock quality designation (RQD), and lithology) for coal-bearing rocks in the Central Appalachian Basin. Statistical analysis of the data is completed to establish an enhanced understanding of geotechnical and hydrogeological conditions expected to be encountered as underground coal mining passes near and beneath streams and rivers. The results of the study provide valuable reference material for the coal mining industry for completion of shaft installations, mine stream crossings, environmental assessments, and grouting and mine dewatering designs.

Jul 1, 2023

By P. C. Thakur

Horizontal drilling in coal mines is a relatively new technology. The earliest recorded drilling in the United States was done in 1952 at the Humphrey Mine of Consolidation Coal Company for degasification of coal seams. Spindler and Poundstone experimented with vertical and horizontal holes for eight years. They concluded in 1960 that horizontal drilling in advance of underground mining appeared to offer the most promising prospect (for degasification) but effective and extensive application would be dependent upon the ability to drill long holes, possibly 300-to 600 m, with reasonably precise directional control and within practical cost limits.(1) Mining Research Division of Continental Oil Company, the parent company of Consolidation Coal Company, began a research program in the early 1970's to achieve the above objective. The technology needed to drill nearly 300 m in advance of working faces was developed by 1975 and experiments on advance degasification with such deep holes began in 1976. Preliminary Its of this research have already been published.(2) To date nearly 4500 m of horizontal holes have been drilled for advance degasification and earlier results were reconfirmed. In summary, these are: 1) The greatest impact of these boreholes was felt in the face area where methane concentrations were reduced to nearly 0.3 percent in course of two to three months from original values of nearly 0.95 percent.

Jan 1, 1979

The National Institute for Occupational Safety and Health (NIOSH) conducted field tests to evaluate the effectiveness of a wet head continuous mining machine for reducing dust exposure for continuous miner operators. Wet head technology delivers water via sprays to the continuous miner?s cutter head as opposed to traditional standard sprays located on the boom and body of the mining machine. The sprays, positioned directly behind each bit on the cutterhead, deliver water at the point of attack, serving to cool the bits during mining to reduce the potential for frictional ignitions. The sprays also flood the coal with water to potentially suppress dust generation. Dust surveys were conducted at several mines to evaluate the wet head?s effectiveness to control respirable dust exposure at the continuous miner operator location and in the immediate return. Results show that the wet head miner generally improved air quality at both sampling locations to varying degrees in some, but not all, mines when compared to a continuous miner with a standard spray system.

Jan 1, 2010

By James A. Bloom

To operate the Morris Fork Preparation Plant with a closed water circuit has been an elusive goal for Union Carbide. The benefits of a closed circuit have never been questioned. The removal of fine solids from washery water makes possible the recirculation and reuse of the water. Heavy media drag tanks and other separating machines perform better and more consistently with washery essentially free of fine solids. Finally, the production of a clarified effluent makes unnecessary the sludge ponds usually associated with a coal preparation plant. Why then do I say elusive? Because, since plant design was completed in 1970 we have been in hot pursuit of an ever-growing fine solids problem. In four years the minus 28 mesh material in the plant feed has nearly doubled. The replacement of conventional sections with continuous mining machines has led to a lowering in size and quality of product from the mine. In addition, increasing emphasis underground on roadway clean-up has contributed to the fines problem.

Jan 1, 1975

By Jian Liu

The dissolubility of a natural sphalerite (ZnS) in the entire pH range was theoretically calculated, and its practical dissolution in an aqueous solution at different pH values in an inert environment, together with its surface properties after dissolution, was fully investigated. The results of the investigation indicate that the total concentration of Zn (CZnT) decreases significantly with the increase of pH value, while the pH value is set below 8; however, it reverses when the pH value reaches 8. Such a tendency is similar to that of the theoretical calculations, although the experimental CZnT were much higher than those of the theoretical calculations. The X-ray photoelectron spectroscopy (XPS) of the sphalerite surface after its dissolution under alkaline solution shows that a polysulfide (Sn 2-) surface layer with a binding energy (BE) value of 162.96-163.25 eV is present on the surface, and the percentage of Sn 2- increases significantly with an increase in pH value; the undissolved and dissolved sphalerites under the acidic solution have a negligible difference in S2p peaks. The surface S/Zn ratio of all dissolved sphalerites shows a marked Zn enrichment and S deficiency. An atomic force microscope (AFM) view of the sphalerite surface, after its dissolution under the alkaline solution at a pH of 12, shows that the surface is significantly different in morphology from that of the undissolved one.

May 1, 2012

By J. Kallioinen

Flotation of low grade Ni ores with serpentinite host rock tend to yield low recoveries of Ni With high MgO contents in the concentrate. The recovery can be enhanced by optimizing the sub-processes in the pulp and in the froth. The new OF-100 flotation cell has been designed to be adaptable to different feed fineness (Coarse, Fine). The losses can according the research conducted at Outokumpu's Hitura plant be substantially decreased by OF-100's new rotor and stator design and froth zone geometry. The froth residence time is used to adapt for feed particle size changes measured by the Outokumpu PSI- 200. Models for the behaviour of different particle Sizes in the sub-processes have been developed. The modified froth zone geometry and the capability of maintaining a froth of desired thickness allows efficient washing of the obtained concentrate producing low levels of MgO.

Jan 1, 1994

By R. A. Pimentel

Complying with reduced dust standards (i.e., less than 2.0 mg/m3) due to quartz levels that exceed 5 percent is presently a critical problem for many continuous mining sections. Results are presented of research which was performed to determine the factors causing high levels of respirable quartz dust and to identify the major contributors to operator exposure. It was found that the significant sources of quartz dust are the drilling of the roof and the mining of the roof, floor and rock bands. Both the miner and the bolter may be on a reduced standard, but compliance is easiest to achieve on the bolter for which improvements in maintenance and operator practices are usually sufficient. At the miner, the problem is more elusive. Research continues to identify operating and mining practices that contribute to the exposure..

Jan 1, 1985

By Taghi Sherizadeh, Kutay E. Karadeniz, Dogukan Guner, Samuel Nowak

Mine explosions are one of the most concerning risks related to underground coal mining, as a single gas explosion can cause injuries and fatalities among miners. Underground infrastructure seals and build-in-place (BIP) refuge alternatives (RAs) are employed to isolate an area from active workings to mitigate coal mining-related accident risks. They are designed to withstand blast pressures from a possible accidental detonation of the contained gas or a coal dust explosion. Crosscut seals and BIP RAs, typically consisting of steel-reinforced concrete, are prone to strong convergence and have a significant leakage potential due to high convergence damage near mined-out areas. The roof-to-floor convergence can change the structural integrity of these structures, and altered structural integrity can lead to less explosion resistance capability. Hence, a thorough analysis is needed to further understand their explosion response under various strata conditions.

Jul 1, 2023

By G. Wheeler

Epithermal gold exploration in the last decade has developed useful models for exploring new ore districts in Oregon. In Eastern Oregon, disseminated gold occurs in epithermal deposits that have been pervasively silicified and brecciated. Many gold prospects staked since 1980 are in fluvial and lacustrine sandstone and conglomerate deposits. Clay alteration products and disseminated pyrite may be present. Vein filling calcite and thin to thick quartz veins are common. Late stage quartz forms pseudomorphs after calcite in many deposits. Arsenic, mercury and gold are geochemically anomolous but silver is usually not. The epithermal deposits are located in part of the Deer Butte Formation or equivalent units. Exploration criteria include the presence of Deer Butte Formation or correlative units and NW structures cut by N-S basin and range structures.

Jan 1, 1987

By W. K. Wedge

The chemical composition of the Pennsylvanian Bethany Falls Limestone Member of the Swope Formation was investigated using optical emission spectroscopy and both flame and flameless atomic absorption spectroscopy. Elements determined were Ca, Mg, Fe, Mn, AI, Si, Na, K, P, Ti, Zn, Cd, Ni, Co, Cu, Pb, Cr, V, and Mo. Over 100 samples were collected from active quarries along a 320-km-long (200-mile) outcrop in northwestern Missouri. Intervals were sampled representing uniform lithology to determine vertical and lateral geochemical variation. The Bethany Falls Limestone is the most extensively quarried Pennsylvanian limestone in Missouri. In 1975, 42 active quarries produced almost 5.4 million tons (6 million st) of stone valued at over 15 million dollars.

Jan 1, 1977

By K. S. E. Forssberg, M. I. Hallin

In many cases, the reuse of process water in flotation plants is desirable both for plant operating reasons and for environmental protection. The main advantages are better housekeeping of fresh water and process chemicals together with the reduction of polluting species to the environment. There are however a number of problems involved in the use of recycled process water. The main problem is that recycling sometimes has a deterious effect on the process and can occur months after the start of water recycling. The Division of Mineral Processing of Luleå University of Technology has been conducting experiments on recycling of process water at various sulphide plants in Sweden for over ten years. The experiments have been carried out in pilot- and full industial scale, in collaboration with the mining companies operating the plants. Until 1988 investigations were carried out in four different sulphide plants. The objectives of the experiments were: first to document differences in the composition of the process water during recycling; secondly to investigate any changes in the pulp chemistry of the flotation circuits wich may be due to the influence of recycled water; and lastly to establish critical levels, if any. of the parameters measured. While conducting experiments of this kind several things have to be kept in mind. Normally, recycling is done by using tailings pond water as process water. This means that time effects are important, because of the time lag between water input in the tailings pond and the reclaim of that water back to the plant. As will be shown, the

Jan 1, 1989

By C. J. Dungey

INTRODUCTION The County of Cornwall is situated in the South Western extremity of England, see Fig. 1, and has for hundreds of years been an historical centre of mining activity. In the last century many thousands of Cornish miners emigrated to Canada, U.S.A., Australia and numerous other countries throughout the world to form the nucleii of mining industries in those lands. At present there are four active underground mines within the county, all mining tin, together with a relatively large china clay industry. All the operations are directly or indirectly associated with the three main granite intrusions, namely the Land's End Granite, the Carnmenellis Granite and the Bodmin Moor Granite. The report which follows relates to two mines, owned by the South Crafty Group of Companies, namely the South Crofty Mine itself and its smaller subsidiary, Wheal Pendarves. Both these mines are adjacent to the Carn Brea Granite ridge, see Fig. 2, which is an off-shoot of the main Carnmenellis Granite mass. The Carn Brea Granite has provided one of the most intensive areas of copper and tin mineralisation anywhere in the world. Many of the mines worked during the last two centuries and the early part of this century were situated close to the metamorphic aureole surrounding the granite intrusion. Both South Crofty and Wheal Pendarves have their shafts collared in the overlying slate, locally known as killas, but the major part of their workings are in the granite beneath. The ore bodies, or lodes, of both mines are generally steeply dipping and approximately one to four metres in width. They have been, and continue to be, worked by either back or under-hand stoping with the major level interval being approximately 37 metres. A feature of both stoping systems is that they require no back filling and in many cases the completed working areas have remained open for many years due to the competent wall rock conditions. The stoping operation necessitates having box-holes or draw points at regular intervals along the strike length at 4 to 7 metres centres; thus a stope some 50 metres long may typically have ten box-holes or draw points through which air can percolate into the empty stopes above. The granite country rock contains traces of uranium minerals, namely pitchblende or uraninite, and it is the decay of this uranium mineral which leads to the formation of the mobile radon gas which, together with its short lived daughters, may create a hazard. The presence of uranium minerals has long been known, but the quantities being so minute, it was not appreciated until some ten to fifteen years ago that these might present a hazard. The Mines and Quarries Inspectorate approached Management approximately ten years ago with a view to taking samples in areas of the mine that they felt might contain the highest concentrations of radon. Samples were thus taken in several areas of both mines, normally well away from working areas and where there was no through ventilation. The results of these initial tests were published by the National Radiological Protection Board in a paper entitled "Radon and Its Daughters in Various British Mines". The results of the initial surveys made it apparent that improved ventilation was the most important factor in reducing radon daughter concentrations within the mine atmosphere, with increased flow rates having three beneficial functions, viz. (1) To dilute radon daughter concentrations. (2) To prevent radon and its daughters reaching a state of equilibrium. It is not uncommon for radon and its daughters to have a disequilibrium factor of 1,000 in some uranium mines.

Jan 1, 1981

By Enrique Jelvez, Pierre Nancel-Penard

The traditional way of generating open-pit mine production schedules has several limitations. This work addresses the design and production-scheduling problem by considering minimum operational space requirements under a Direct Block Scheduling approach to generate extraction sequences that satisfy the operational space required. For this, traditional formulations were extended by including a new set of constraints that generate operating spaces for mining equipment to move and extract material. Then, a heuristic algorithm produces close to optimal practical pushbacks. This proposal was applied in a case study, and the results show its ability to generate practical production schedules without sacrificing expected return, obtaining differences in terms of Net Present Value (NPV) lower than 1% when compared to the traditional approach.

Jun 25, 2023

By J. E. Wennen

Screens serve several important functions in CIL and CIP processes for gold extraction. One important screen application known as interstage screening allows slurry to be continuously transfered through a series of CIL or CIP tanks while retaining activated carbon in the tank. In some cases, this has been accomplished by using airlifts to carry slurry containing activated carbon to an external screen which separates carbon as oversize and returns it to the tank by gravity. The undersize slurry advances to the subsequent tank. More recently this has been accomplished using launder screens and Kambalda type screens. These are essentially static screens that rely on air blasts or mechanical sweepers to clear carbon away from the screen surfaces.

Jan 1, 1998