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By Ulrich Maidl, Marc Comulada, Janosch Stascheit

"INTRODUCTION Cohesive soils are notorious for causing clogging of the cutter head and the excavation chamber of tunnel boring machines (TBMs). While clogging leads to a drastic reduction in excavation performance, it further induces higher wear of tools and other parts of the cutter head and may even prevent a controlled support of the tunnel face and, thus, lead to face collapse and excess settlements or sinkholes. Employing well-balanced soil conditioning techniques, the clogging tendency can be significantly reduced. The monitoring and control of soil conditioning as well as the timely detection of potential clogging tendencies require a close monitoring of all relevant machine parameters and measurements. To this end, a reliable and powerful Process Controlling software that gathers all machine and process-related information is a prerequisite for successful mitigation of clogging-induced problems. The remainder of this contribution is organized as follows: First, a brief introduction to the Process Controlling system PROCON is given. Afterwards, the mechanisms and mitigation techniques of clogging are discussed. Finally, an example is given how Process Controlling has been employed to soil conditioning in a tunneling project with highly clogging soils.PROCESS CONTROLLING Being both the active part and a huge measuring device, the shield machine represents the core component in mechanized tunneling. This machine comprises a manifold of complex components and devices that require constant supervision and control and, thus, is equipped with a manifold of different sensors that provide a continuous monitoring of the state and condition of the machine (Maidl & Stascheit, 2014). If these data are put into the whole context of the tunneling process, they can provide insight to the assessment and optimization of the performance and to the prediction of potential risks and hazards such as, for example, the tendency of clogging of the cutter head."

Jan 1, 2016

By William R. Hess

Volcanic ash, although a little-used Kansas resource, is available in forty counties with estimated, reserves of more than 20 million tons. It was first produced in Kansas in the early 1900?s but not until the early 1920 is did it become an important abrasive material. Total production to date is estimated at 2 million tons, the major use being as an abrasive in scouring compounds and soaps, additional uses include ceramic glazes, an additive in cement, and a filler and stabilizer in hot mix asphalt for paving. Unrecorded tonnages have also been used in construction of black-top (macadam) roads. From 1916 through 1944, Kansas ranked first among the states in volcanic ash production; peak production was about 52, 000 tons in 1923. Since 1945, production has steadily declined, primarily because materials other than volcanic ash are now being used for abrasives; only two producers operated in 1964.

Jan 1, 1965

By A. Janwong

Ion exchange technology is becoming more prevalent for metal recovery from low concentration solutions. The products of ion exchange are typically a metal free stream (product stream) and a concentrated metal stream (byproduct). The metals in the concentrate stream are usually precipitated and returned to the process or discarded. The unique features of emew® technology enable metals to be recovered directly from the concentrated stream. The advantage of the IX-emew® combination is the ability to have two product streams: 1) clean metal free solution and 2) metal product for sale. In addition to recovering metals from solution, it is also possible to separate metals from each other and recover more than one metal product. In this paper, examples of IX-emew® combinations are detailed including the recovery of copper, nickel and cobalt from an industrial waste stream, recovery of nickel from a spent electroless nickel plating solution and recovery of cobalt from an hydroxide cake.

Feb 23, 2014

By R. Mittler

Over 100 saprolite samples from Turkey Hill Gold Mine, Lumpkin County, Georgia, were analyzed (-80 mesh) for As, Au, and Sb. Maximum values are 16.2 ppm As, 7.9 ppm Au, and 29.1 ppm Sb. Results show trace element content of saprolite varies with topography: ridge top samples show a pronounced decrease in Au and Sb, and to a lesser degree in As, whereas, slope and valley samples have anomalous Au and Sb concentrations, with no discernable pattern for As. Statistical analysis shows strong correlation between Au and Sb and none between Au and As. This study will serve as a model for gold exploration in deeply weathered terrains with variable relief.

Jan 1, 1987

By P. R. Taylor

This investigation (Bowles, 1990) involves consideration of technology utilized by three separate fields of metallurgy and materials science: 1) The recovery of metals employing the use of solvent extraction, 2) The fabrication of materials using powder metallurgy, and 3) The use of composite materials in fabrication of engineering materials. The research considers each of the processes in order to realize the benefits of each. In light of the fact that materials have an intended use -it does seem plausible to simplify the process required between "mother earth" and final use. For instance, a primary copper producer that already employs a solvent extraction and electrowinning process could produce value added products directly. Part of the existing extractant flow could be diverted into a pressurized hydrogen stripping process in order to produce specialty composite powders. Innumerable methods have been employed for the recovery of metals; solvent extraction, the one considered in this study, was used due to the possibility of it providing a pure powdered metal. The use of solvent extraction in the recovery of metals has gained wide acceptance and its use proves beneficial in many applications (Ritchey and Ashbrook, 1984). Pressure hydrogen stripping of solvent extractants may provide the benefit of flowsheet simplification compared to conventional solvent extraction followed by electrowinning. It may also provide the benefit of direct production of high purity metal powder (Demopoulos and Distin, 1985).

Jan 1, 1992

By C. Alexander

Stillwater Mining Company is developing a second underground palladium and platinum mine approximately 21 km (13 miles) west of their existing Nye operation in south central Montana. A 5650 meter (18,550-foot) tunnel is required to gain access to the ore bearing horizon (J-M Reef). Access and primary mine development can be accelerated through the use of two 4.6 meter (15-foot) diameter tunnel boring machines (TBM). One TBM was purchased new while the other was purchased used. Machine specifications, site support facilities, portal/launch chamber construction, TBM assembly, startup and operation are discussed in this paper.

Jan 1, 1999

By Jack C. Haptonstall

The Tayoltita Unit of Minas de San Luis, S. A. is situated in an isolated corner of the state of Durango, Mexico. The ore deposits in the region were first worked by Indians, but by 1757 the Spaniards had discovered them, and the first systematic exploitation of the mines commenced. By the early 1900's most of the mines had been acquired by American interests, and the San Luis Mining Company was organized. The modern period of exploitation, uninterrupted for the last 74 years, began. In 1962 the company was fully "Mexicenized" in compliance with the modification of the mining law, and the name was changed to Minas de San Luis, S. A. Tayoltita continues as one of Mexico's most important silver and gold mines. The ore is extracted in en extensive underground operation, mining epithermal fissure veins by selective methods. The ore is milled and treated in an efficient counter-current cyanide plant, where 95 % of the silver and 96 % of the gold is recovered. Current annual bullion output is 55,000 kg (1.7 million troy oz) of silver and 1000 kg (31,000 troy oz) of gold from milling 165,000 try (181,900 stpy). Rough, 33-kg (1000-troy oz) bullion bars are smelted at the mine, shipped by air to Mazatlan, Sinaloa, and are thence sold to the Met- Mex Peñoles smelter in Torreon, Coahuila. Ore reserves, blocked by very conservative methods, are currently at 540,000 tons (595,000 st). Ore reserve grade is 425 g of silver and 6 g of gold per ton (12.4 troy oz Ag and 0.18 troy oz Au per st).

Jan 1, 1976

By R. C. Bunge

The success of a mineral separation is commonly assessed from the separation curve, a graph of the recoveries achieved versus the corresponding separator settings. Two values characterize the curve, first the "splitpoint" which is the separator setting that produces a recovery of 50%, and second a measure for the separation sharpness. The splitpoint represents the "mean" while the measure for the separation sharpness represents the "scatter". In modelling the performance of crossflow separations the mean particle behavior is calculated from the force equilibrium that determines the particle trajectory which leads to a deterministic model. The scatter is then represented by a stochastic model. This presentation discusses the modeling of a crossflow separation and some implications with separation theory. The model is shown to successfully predict the performance of a magnetogravimetric separator.

Jan 1, 1992

By Edwin R. (Original by) Phelps

Surface mining refers to the process of removing the material (over- burden) overlying a coal seam and exposing the coal so that it can be loaded out and conveyed by trucks or other methods to the preparation plant or other facility. Surface mining has not always been important in the coal industry. In the early 1900s, almost all of the coal mined in the United States was mined by underground methods. In 1900, about 192 Mt (212 million st) of bituminous coal were mined and less than 1% was mined by surface methods. The development and use of larger equipment has allowed surface mining to gain prominence throughout the years. Table 1 shows the total production of coal by mining method in the United States for ten-year periods since 1920 and indicates the growth of surface-mined coal production. Surface mining will undoubtedly continue to account for a large percentage of the coal production in the US for many years because: 1) The capacity of surface mining excavators has continued to increase. Today, mining companies are using shovels (see Fig. 1) which are able to move up to 137.6 m3 (180 cu yd) in each bite and draglines (see Fig. 2) which move up to 168.2 m3 (220 cu yd) in each bucketful. 2) Increasing tonnage from the thick western coal seams is being produced by surface mining methods. 3) Surface mining has normally had lower costs and a better safety record than underground mining; 4) Surface mining normally recovers a- much higher percentage of the coal reserve than can be recovered by underground mining. 5) Some coal measures can best be extracted by surface mining [ ] methods because of geologic reasons such as the nature of the roof or bottom, thickness of the seam, multiple bedding, etc.

Jan 1, 1981

By R. Gradnik

The continuous need for infrastructure expansion forces the mining industry to develop underground structures into more sensitive and violent environments. When underground excavation enters into deep and high stress rock conditions, geotechnical designers find themselves faced with the difficult task of selecting a rock support system that will meet today's stringent requirements. Whatever support system is chosen, it is mandatory that potential rock movement be controlled. All this has intensified the development of safety systems and new, unique solutions which can enable construction companies to go both, further and deeper, without reducing the level of safety. To address these needs, Atlas Copco developed the Roofex® bolt, specifically designed to withstand large static and dynamic deformations under prespecified load conditions. The Roofex Rock Bolt acts as stiff support up to a designable load level before the sliding effect of the mechanical frictional system is triggered and allows highly controlled rock mass movement without loosing the support function.

Jan 1, 2011

By Reno H. Sales

The syngenetic, metamorphic water, and source bed concept theories of ore deposition proposed by Anton Gray, C, Lo Knight and others, to explain ores in sedimentary rocks, are challenged on the basis of a survey of the literature and personal observation, A hydrothermal origin for the Northern Rhodesian Copperbelt deposits is indicated by the presence of post-Roan age igneous rocks and post-gabbro mineralization, the wide distribution of ore in the various Lower Roan lithologic types, and the zoning of the copper-iron sulphlde minerals and minor elements The proposal by Gray and Knight that igneous rocks are not favorable as guides to nonferrous metal deposits, and Gray's hypothesis that the redistribution of connate waters and their dissolved metals by metamorphic processes was responsible for the emplacement of ores, are rejected as contrary to field evidence, The absence of exposed potential igneous source rocks is shown to be an invalid argument for the proponents of any syngenetic hypothesis, The common association of ore deposits with calc-alkaline intrusive rocks and their derivatives is, however, demonstrated to be convincing evidence that an exploration program based upon a magmatic theory of origin, would have found most of the important known non-ferrous metal deposits of the world, It is urged that prospecting be continued on the sound basis of accumulated knowledge of the lithologic and structural facts surrounding known ore deposits.

Jan 1, 1960

By İbrahim Alp, Emine Yoğurtcuoğlu

This article includes the application of roasting pretreatment by assisting the cyanidation process in the recovery of Au–Ag from Bolkardağ Gossan refractory ore and the characterization studies of the ore, roasting sample, and postcyanidation waste sample. While ore contained many metals along with gold and silver, the environment in which these metals were found was carbonate, sulfated, silicated, and iron oxide-containing deposits that have undergone oxidation. In mineralogical studies, there were Fe oxy/oxyhydroxides, Pb/Zn carbonates, and jarosite-bearing structures such as beudantite, calcite, dolomite, clay, and quartz in the ore. The sample used in the experiments was d80 = 29.6 μm, and the test parameters were determined by examining the TG analysis made to the ore. Preroasting experiments were carried out at a roasting temperature range of 200–800 °C, during a roasting period of 10.0 min. Three different samples were characterized by TG for temperature changes, FT-IR for bond structures and permeability, SEM/EDX for visual inspection of structural changes, and XRD Rietveld’s analysis for mineral % content differences. As a result of the cyanidation experiments carried out after the pretreatment, gold was recovered with 80–90% yields and silver with 40–48% yields, respectively.

Aug 21, 2023

By I. Mikov

Established in the 60-ies, the Zlatna Panega quarry is a cement raw materials quarry supplying 95% of the needs of the Zlatna Panega Cement Plant with limestone, marl and other silica-aluminates. The two major types of raw materials are formed by accordingly dipping strata of Upper Jurassic limestones and lower Cretaceous marls. Between them there is a ?transition-zone? or ?contact-zone? of a high-silica content layer, about 5-m thick, defined as ?flint? by investigations including spot sampling throughout the quarry. For many years this ?contact-zone? layer was neglected due its negligible thickness. Further, with the increasing demand on the quality of the raw materials feed to the Plant and the focus on variability of the chemical and mineralogical components, it was decided not to mine any of the parts of the quarry contaminated by this material, for about three years. The latter had an impact on the availability of operating benches that could result in a substantial decrease in the total recoverable re-serves of Zlatna Panega, particularly with respect to marls. There were considerations for resorting to a partial, selective excavation of the quarry pit with a reduced lifetime for the lime-stones and re-opening of an other (currently in-active) marl quarry at a distance of 6 Km from the Plant. The Quarry Team of the Zlatna Panega quarry was assigned to study the problem. The ?contact? layer was duly confirmed with systematic geological (including mineralogy) studies, statistical analysis of available data, surface sampling and shallow exploration drills, resulted into distinguishing a third type of reserves and their credible subsurface delineation by means of geological 3-D modeling and quarry design. A new quarry design was finally elaborated with a view of providing flexibility in mining, utilization of the total volume of all available reserves and maximizing the mine life of Zlatna Panega quarry. An industrial test took place in December 2005, by using the contaminated parts of the quarry (co-mining of the ?contact-zone? materials) at a contribution of 15-20% in the raw materials mix, as dictated by their contribution in the total recoverable resources of the quarry. The purpose was to investigate the viability of this solution ? in line with improved quarry planning ? without compromising the quality of cement production and the efficiency of Plant Operations. Results were overall successful.

Jan 1, 2006

By P. S. Hettinger

Land Application Discharge (LAD) is a useful method of disposing of waste water from mining operations and in certain climatic regimes, stormwater runoff. LAD systems function under the premise that metals, salts and nutrients in water are dispersed over a large area and are effectively assimilated into the soil profile. Depending on the soil structure, migration or mobilization of dissolved metals through the soil profile can be Substantially reduced. Land application of treated effluent from sewage lagoons or waste water plants was probably the first general use of land applied water. LAD has gained popularity with the mining industry as a means of disposing of waste water and process water. In addition, large volumes of snow meltwater and stormwater are often placed in storage in Montana during spring, and Land Application Discharge has shown to be an effective method for disposing of stormwater during the dry, summer season. LAD can also provide an alternative to recycling or treating waste water at on-site waste water treatment plant&. Application of stormwater or process water can result in little or no change to the background concentrations of metals in baseline water quality samples. One cautionary note about LAD: high salt concentrations and pH values are associated with process water from heap-leach facilities and are known to cause burning of local vegetation. Some pre-treatment of process water may be necessary to prevent such environmental problems.

Jan 1, 1994

By J. B. Yianatos

This paper addresses the impact on performance of column height (H), and column height to diameter (H/D) ratio by modelling the effect of HID on mixing and consequently on recovery and grade. Mineral recovery increases with increasing H/D ratio for a constant column volume and feed flowrate, while the concentrate grade decreases to a minor extent. Columns 10-15m in height with H/D-10 are well suited for feed rates 150-600 L/min. Maximum H/D is determined by the gas carrying capacity, an important consideration for pilot units where H/D?200.

Jan 1, 1987

Column flotation cells continue to gain acceptance in the coal industry for the treatment of high-ash streams containing clay slimes. Unfortunately, some industrial installations have failed to meet expectations due to improper scale-up, incorrect operation and poor ancillary circuit design. To overcome these problems, case studies have been conducted to fully define the capabilities of column cells for coal applications. These data have been used to develop generic engineering guidelines for column circuit design and operation. An economic analysis has also been conducted to illustrate the importance of key capital cost considerations. These analyses indicate that column cells are significantly more expensive than conventional machines, although this difference can be greatly reduced through the installation of very large-diameter columns.

Jan 1, 1999

By J. A. Organiscak

The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has recently studied several redirected scrubber discharge configurations in its full-scale continuous miner gallery for both dust and gas control when using an exhaust face ventilation system. Dust and gas measurements around the continuous mining machine in the laboratory showed that the conventional scrubber discharge directed outby the face with a 12.2-m (40-ft) exhaust curtain setback appeared to be one of the better configurations for controlling both dust and gas. Redirecting all the air towards the face equally up both sides of the machine increased both the dust and gas concentrations around the machine. When all the air was redirected towards the face on the off-curtain side of the machine, gas accumulations tended to be reduced at the face at the expense of increased dust levels in the return and on the curtain side of the mining machine. A 6.1-m (20-ft) exhaust curtain setback without the scrubber operating resulted in the lowest dust levels around the continuous mining machine, but this configuration resulted in some of the highest levels of dust in the return and gas on the off-curtain side of the mining face. Two field studies showed some similarities to the laboratory findings, with elevated dust levels at the rear corners of the continuous miner when all the scrubber exhaust was redirected towards the face either up the off-tubing side or equally up both sides of the mining machine.

Feb 23, 2014

By Felicia F. Peng

The plant data were collected from three streams around a dense medium drum for coarse coal cleaning operated at various volumetric ratio of medium-to-feed. The effect of the volumetric ratio of medium-to-feed (MF) and particle sizes on the performance criteria, g50 and Ep, of the dense medium drum. These measured data were adjusted and calculated for the yields and balanced relative density distributions by mass balanced method based on the statistic principle. These balanced data were then used to formulate the mathematical models of the separation distribution curves for the various feed size intervals. The correlation equations for the g50 and Ep as the function of inverse of the feed size, and MF and total throughput were established. A numerical algorithm utilizing the Secant method, based on the root searching principle, was developed for yield optimization and simulation of dense medium drum separation to improve the separation efficiency and hence the product yield. The relationships between the direct ash content and relative density of the particles in feed and the products were established and incorporated into the numerical algorithm for predicting the product quality.

Jan 1, 1996

By H. P. Cole

A team of researchers at the University of Kentucky, working under a USBM contract, developed over 65 simulation exercises for teaching and testing problem-solving and decision-making skills to miners and mining engineers. These skills involve both improving judgment and decision making in mine emergencies and enhancing the learning of real-world engineering design principles. The exercises are ideally suited for either latent image format or for computer-aided instruction. Exercise features are summarized, the structure and field testing of typical exercises described, and sample frames of individual exercises presented. Empirical data are summarized that describe the effectiveness of using these short, time-efficient performance tasks that simulate real problems and that provide immediate corrective feedback for teaching and testing critical skills. I

Jan 1, 1991

By W. A. Haley

Wheel loaders became important bulk materials handling tools in the early fifties. As they grew in stature, productivity, reliability, and acceptance, the demand for larger, more rugged machines evolved. In the early sixties, the introduction of a 6-yard model by a major equipment manufacturer led quickly to widespread experimenting and rapid worldwide acceptance in loading blasted rock in stone quarries and smaller metal mines. As the wheel loaders grew in popularity for shot rock loading, larger models, 12- to 15-yard size were developed and saw widespread use by 1970. In the past 20 years, at most quarries and small to medium size mines, most cable operated power shovels have been replaced by large wheel loaders and more recently, hydraulic excavators as the primary loading tool. Wheel loaders larger than the 15-yard class are not used widely. Until about 1970, very few overburden haulage trucks were used in domestic coal mines. About that time, many states started enforcing stringent mine relcamation regulations and in 1977, even more stringent federal legislation was passed. These controls brought about drastic changes in coal surface mining methods in the mountainous areas of Appalachia, in smaller midwestern mines and in the large mines of the western states. Basically, simple material casting methods were replaced at most eastern mines by "haul-back" and "mountain top mining" methods using controlled placement of overburden as it is removed from the coal. These methods dictated much more extensive use of loaders/ shovels and trucks to the point that most coal mining in those areas is now by loader/shovel trucks methods. And those areas have become the home of the country's largest population of large wheel loaders and trucks in the 35- to 85-ton size class with a trend to even larger trucks and shovels. To maintain equal production or provide for growth, the new methods have caused a sharp increase in machine intensity to the extent that at some mines, up to three times as many machines were required to mine a million tons of coal in the late seventies as compared to the machine needs in the sixties. Mining costs and coal prices also took a big jump in the mid-seventies, paralleling the drastic price increases in oil and other forms of energy.

Jan 1, 1984