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By O. J. R. Baena, N. J. Zapata

In Colombia, more than 15 regions and around 100 municipalities develop gold mining at different scales, and these operations generate mining waste composed of processing fluids and crushed rock with metals and high silica content. Cement production requires clinker, gypsum and other corrective additives. Clinker results from the partial fusion of some minerals including silica. In this study is proposed to evaluate the effect of the use of mining tailings sands from gold mining in the manufacture of clinker. The proposed methodology will allow the characterization of the sands to manufacture a cement specimen and measure its physical and fire properties

Mar 2, 2022

By R. R. Klimpel

The use of chemical reagents in flotation has been studied in great detail, e.g. (1, 2, 3, 4). Important progress has been made on the understanding of surface chemistry concepts involved in flotation. However, such scientific studies are often very complex even for rather simple idealized systems. Therefore, the deve- lopment of predictive or quantitative tools for plant engineering evaluation is still in the evolutionary stages. Until further progress in fundamental work is achieved, the operating engineer is faced with semi-empirical physical testing of reagent changes on several sizes of the actual equipment under study to be confident of the economic viability of any change.

Jan 1, 1980

By B. Pesic

Northwest Alloys, a wholly owned subsidiary of Alcoa, produces magnesium from dolomite by reduction with ferro silicon and aluminum. This process produces alkaline by-products in quantities that allow their consideration for use as commercial by-products. Two such products are dicalcium silicate slag, Di-Cal, and magnesium oxide condensate, MgO. The alkaline properties of these materials offer acid neutralizing capability comparable to the traditionally used lime, therefore, warranting a study for their use in applications where the neutralization of acidic waters or process solutions is required, such as treatment of mine waters. In this ongoing study, three mine waters (Bunker Hill Mine, Berkeley Pit, and Blackbird Mine) were selected for treatment with Di-Cal and MgO. Lime was used as the background control. The solid precipitates were subsequently contacted with pure water at four different pH conditions for stability testing of prepared metal precipitates (expanded TCLP). It was found that neutralization with Di-Cal results in precipitates which are of equivalent to superior stability than those from lime treatment.

Jan 1, 1999

By and Heather E. Lawson, Mark K. Larson, Gabriel Walton

In this study, we evaluated the effects of different shapes and distribution densities of mineral grains in coal on failure mechanics using the numerical software 3DEC. The main aim of this study was to identify possible failure mechanisms influenced by mineral habit and frequency in coal. Exploring differences in failure mechanics associated with the mineral grains helped to determine the role of mineral character as a possible contributor to characterize burst-prone coals. To achieve the goal of this study, a series of numerical specimens were prepared in the 3DEC model as follows: first, the 3DEC modeling in conjunction with the DFNs (Discrete Fracture Networks) technique was performed to explicitly generate the discontinuities (i.e., cleats and bedding planes) in the numerical specimens based on the results of laboratory analyses. Then, the different realizations of mineral grains were embedded in the 3DEC model to simulate an unconfined compressive strength (UCS) test to assess the influence of the mineralogical characteristics on the UCS.

By Kenneth R. Krivanek

In recent years the widespread problems of air and water pollution generated by both population and industrial expansion have become a major public concern. Therefore, many municipalities are striving to achieve more efficient wastewater treatment processes so these wastewater's can be reintroduced into the waterways of our nation with little or no detrimental effects on the future beneficial use of that water. With this, improved treatment comes an ever increasing volume of wastewater sludge which must be disposed of in a manner of minimal impact on the environment. Furthermore, with demand for energy continually accelerating in this nation, our concern over high oil prices and our increasing dependency on foreign oil sources, there has been an ever growing interest in the largest energy source that are nation has, coal. However, surface mining of coal can cause many environmental problems when adequate precautions are not faithfully adhered to. These problems include water pollution from silt and/or clay erosion and acid runoff, produced by oxidation and hydrolysis of pyrite; i.e., FeS2 + 3/02 + H20 + FeSO4 + H2SO4. One method of wastewater sludge disposal which can utilize large volumes of sludge for a beneficial project that may not compound our environmental problems is spray irrigation, to either depleted farmland or to abandoned strip-mined soils. Sludge is characteristically high in organics, as well as having near neutral to alkaline pH properties. With these two qualities it possesses a potential for neutralizing acid strip mine spoils, which would enhance the establishment of a vegetative ground cover. Sludge can accomplish this by lowering the oxidation potential, reducing the solubility of iron and aluminum and by the chelation of metals, thereby

Jan 1, 1977

By Charles LeMoyne

The Cable belt Company has been building single flight conveyors for a number of years. The simple design concepts of this type conveyor, introduced over thirty years ago, when distances of one to two miles were considered major advances in technology, remain relatively unchanged. Conveyors that are 6 to 20 miles (9.0 to 32 kilometers) long are being built and are presently in operation through- out the free world. The Cable Belt conveyor is not conventional in its construction. Cable welt differs from conventional troughed idler conveyors in that the driving medium and carrying medium are separated. Motion is provided by two endless steel cables running the length of the conveyor. The cables are driven by a single drive unit incorporating a differential gear which insures identical cable linear speeds and equal tension in both cables at all times. The belting is located and supported by "V" shaped shoeforms moulded to the belt which form a wedging action. The friction between the belting and rope is sufficient to prevent slippage (See figure 01).

Jan 1, 1983

By James A. Curry

Table I identifies the maximum cost of the individual provisions with spoil disposal in Appalachia leading at $3.98 per ton, This was followed by deep mine subsidence control and monitoring at $1.66 per ton. At the request of the U.S. Department of Energy, the Bowser-Morner Testing Laboratories of Dayton, Ohio, evaluated Consol's cost estimates for 14 of the 21 regulatory provisions the company studied. It is interesting to note that Bowser-Morner concluded that Consol's estimates of costs were very conservative and that the actual costs will be substantially higher than what the company reported. In 1978 a joint committee of the National Coal Association and the American Mining Congress made estimates of cost impacts under 11 OSM permanent rules (see Table II). Six rules applied to mid-western strip mining were projected to cost $6.52 to $17.17 per ton. Five rules applied to mid-western strip mines showed costs ranging from $.91 to $6.11 per ton. Three rules applied to deep mines (regardless of region) were seen raising costs from $ .57 to $2.67 per ton. The joint committee reported trouble developing overall figures because member firms used widely different assumptions in calculating their costs. That same statement could no doubt be made when comparing most cost data available today.

Jan 1, 1980

By Lihong Zhou, DAVOOD BAHRAMI

A reliable and stable ventilation system is essential to the safe operation of underground mines. The stability of a mine ventilation system becomes extremely critical while responding to a fire incident since an unstable ventilation system will pose a risk of airflow reversal. The reversed airflow could bring the fire contaminants such as toxic gases and smoke unexpectedly to working areas. In the past few years, there has been a growing interest in the study of ventilation network stability using the concept of resistance sensitivity, which is described as an indicator of how the airflow in an airway is reacting to a resistance change of other airways. Several methods of calculating the resistance sensitivity in a mine ventilation network have been carried out by researchers and scholars around the world. However, the proposed methods heavily rely on a vast amount of mine ventilation simulations, which are very time consuming and computer-power intensive, especially for a large-scale mine ventilation network. In this paper, a derivative method calculating the resistance sensitivities with a single mine ventilation simulation has been developed and implemented into a mine fire simulation software, MFIRE. The results from the derivative method were verified against the results from a traditional method. The derivative method has been proven to be reliable and accurate.

Jun 7, 2022

By O. Tranbarger

In aging tunnels, wall and roof deterioration can eventually result in defects that must be detected and repaired to maintain safe structural conditions. In investigating tunnel defect conditions, a specialized FM radar system was developed with a programmable VHF and UHF operating sweep range for optimizing the penetration and measurement capabilities. The new FM radar technology was tested in two aging brick-lined tunnels in New York City. Test results showed that FM radar signals could penetrate eight courses of water-saturated brick and that the original steel liner outside the tunnel walls was intact.

Jan 1, 1985

By Vasiliki Founta, Andrew J. Whittle

"This paper describes the development of a 3D finite element model for predicting ground movements caused by construction of 7.1 m diameter twin bored tunnels for the Crossrail project in London using Earth Pressure Balance (EPB) machines. The model uses the commercial FE code, Plaxis 3D, to represent the face pressure, conical shield, grouting process and activation of precast segmental concrete lining systems through a set of boundary conditions that advance through the soil mass along a prescribed trajectory. Soil behavior is described using the Mohr-Coulomb soil model with input parameters calibrated from laboratory element tests. The analyses focus on the performance of the EPB tunneling machines in greenfield conditions beneath Hyde Park, where the tunneling occurs within deep layers of relatively uniform London Clay. The model predictions are in good agreement with surface and sub-surface vertical settlements measured at a well-instrumented section, but tend to overestimate the measured lateral displacements towards the tunnel. Ongoing studies are focused on the role of soil behavior and the approximations in FE model predictions of tunnel-induced ground deformations. Introduction Since their introduction in the 1970’s, closed-face Earth Pressure Balance (EPB) machines have become widely used for soft ground tunnel construction. The EPB design relies on a screw conveyor system to regulate the pressure of the excavated soil/spoil within the head chamber and hence control stability at the face of the machine. One of the key design issues in the application of EPB machines is to establish how control parameters, including the advance rate, face pressure and grouting processes (used to compensate for the tail void at the rear of the shield and to infill gaps between the precast lining rings and surrounding soil) affect and/or control the far-field ground movements. For closed-face systems, short-term deformations are associated with ground losses at the face, overcutting and ploughing of the shield and poor control of grouting in the tail void; while long-term deformations can occur due to consolidation and creep within the surrounding soil (and are closely connected to the seepage boundary conditions;e.g., Laver & Soga, 2012). The control parameters for advancing the EPB machine can have a significant effect on the magnitude and distribution of the far-field deformations. Therefore, analyses of the ground response to tunneling require accurate modeling of the soil stratigraphy and constitutive behavior as well as the construction process. Finite element (FE) methods have been used to simulate tunnel construction since the early 1980s, but only a few studies involved three-dimensional modelling of mechanized tunneling (e.g., Finno and Clough 1985; Bernat and Cambou 1999; Swoboda and Abu-Krisha 1999; Dias et.al. 2000; Melis et.al. 2002; Kasper and Meschke 2004; Möller 2006). In order to get a better understanding of the effect of the construction process and soil properties on the development of the ground deformations more comprehensive models of tunnel excavation and tunnel support are required in order to capture the 3D nature of mechanized tunneling and the effect of construction parameters such as advance rate, face and grout pressure."

Jan 1, 2016

By Hetland Donald L.

Regional Tertiary formations and basins of local sedimentation which contain uranium deposits west of the Rocky Mountains are mainly of Oligocene, Miocene, and Pliocene age (fig. 1). The host rocks have been derived mainly from intrusive and extrusive igneous rock. The major host formations which cover broad geographic areas include the Esmeralda, Truckee, Humboldt, Thousand Creeks, Payette, Panaca, Cedarville, Coso, and San Joaquin Formations. Local areas of Tertiary sedimentation containing uranium deposits occur near Yuma, Safford and Artillery Peak, Arizona; Dillon and Canyon Ferry, Montana; Spokane Indian Reservation and Pend Orielle River, Washington; Topaz Mountain, Utah; Stanley Basin, Idaho; and Sonora Pass, California. Uranium deposits in these sediments have been classified into five categories based on environment (fig. 2). They are: (1) Deposits in lake sediments consisting mainly of water-laid tuffs; (2) Deposits in lake sediments intruded by volcanic plugs; (3) Deposits in lake sediments interbedded with arkoses near batholiths; (4) Deposits in coarse volcanic sediments in local sedimentary basins; (5) Deposits in arkosic conglomerates in local sedimentary basins.

Jan 1, 1969

By J. D. Allen

The Concord Mine Coal Preparation Plant of United States Steel Corporation, located near Bessemer, Alabama, began operations in June, 1950. The basic cleaning circuit consisted of a Chance Cone for cleaning the 2-inch x 3/8-inch fraction and concentrating tables for cleaning the minus 3/8-inch coal fraction. Dewatering of the final product was accomplished with 35-mesh vibrating screens. However, because Concord coal is very friable (Figure 1), 85 per cent passing three mesh and 25 per cent passing 28 mesh, there was a considerable amount of fines passing through the dewatering screens. To recover these fines, the dewatering screen effluent was sent to two 70-foot diameter hydro-separators with the underflow returning to the dewatering screens and the overflow going to a 175-foot diameter thickener for water clarification, (Figure 2). As might be expected, there was a considerable amount of recirculation of the minus 35-mesh coal in this system. This degraded the coal and led to higher moistures. It also resulted in a fines bleed-off of plant water and thickener underflow to a fine-coal settling pond. In 1961, vacuum filters were installed to supplement the screens and to recover the fine coal lost in the bleed-off. The above system resulted in a product moisture of about 20 per cent. Further reduction to approximately 11 per cent was accomplished by drainage from railroad cars during transit to the coke plant. Control of the moisture at unloading was poor because of variations in operating levels and railroad car availability, but since the Concord coal constituted a smaller percentage of the coal previously used at the coke plant, the high moisture and fluctuations did not seriously hamper coking operations.

Jan 1, 1966

By Qingwen Shi, Gang Xu, Shuwen Wang, Brijes Mishra

Pressure relief borehole is one of the most effective methods to treat coal burst in deep-buried coal seams. However, due to the large amount of randomly distributed fractures in the coal body and the varying stress environments in underground coal mines, there is no practical method to assess relief boreholes by far, which brings problems for borehole design and construction. This study focuses on the assessment of relief boreholes in a single driving entry wherein the impact of mining panels on relief boreholes is eliminated. A practical method, focusing on field monitoring of borehole deformation with a new device, is developed to evaluate the single driving entry’s relief boreholes. This method is applied to a Chinese coal mine. The application results showed that the convergence process of the boreholes showed a three-phase characteristic. Phase one involves the fastest deformation, reaching up to 8% in the first 3 to 4 days. Phase two lasts longer and converges more, reaching up to 30% in 4 months. Phase three stays balanced until the excavating face moves. The three-phase characteristic indicates that a large diameter of the borehole ensures relief efficiency because the borehole provides adequate space for deformation throughout its life span. In addition, it is verified that long boreholes and slow footage improve relief efficiency by providing adequate time for the boreholes to work. The application proposes that boreholes in the test coal mine need to be drilled larger and longer for optimization.

Oct 19, 2021

By M. F. Martin

Dewatering aids are chemicals which enhance the efficiency of mechanical dewatering equipment such as vacuum disc filters and centrifugal dryers. A new dewatering aid has been developed which significantly lowers the moisture content of the mineral concentrate and causes none of the undesirable side effects normally associated with dewatering aids. Highlights of product development from laboratory screening through field testing will be discussed.

Jan 1, 1985

By E. Rubenstein, V. Gangrade, K. V. Raj, M. L. Harris

Underground stone mine ventilation is characterized by large openings with low resistances. These mines primarily face three challenges: moving adequate volumes of air, controlling and directing the airflow, and planning ventilation systems that work well with production requirements. Given these challenges, this paper examines the data collected by the Mine Safety and Health Administration (MSHA) to determine the extent to which respirable crystalline silica (RCS) and diesel particulate matter (DPM) are an issue in underground stone mines. Out of 522 sampled mines, there were 108 personal samples exceeding the RCS Permissible Exposure Limit (PEL) during 2000–2020. DPM were more prevalent than RCS in these mines with 382 personal samples exceeding the DPM PEL out of the 929 mines sampled during 2002–2020. Dilution of DPM is usually the defining parameter for design of mine ventilation systems in largeopening underground stone mines. With this knowledge, focused attention can be directed to these mines so that appropriate prevention and mitigation techniques can be utilized to prevent stone miners’ exposure to RCS and DPM and subsequent respiratory diseases.

Mar 2, 2022

By Robert S. Saunders

Cast iron tubbing for two centuries was the only practical watertight shaft lining for deep waterbearing formations. However, since World War II composite welded steel and concrete lining has gained favor and today is often preferred. While tubbing may not be applicable in all cases, a good argument can still be made for this time-honored method. Watertight linings are complex structures designed to withstand both hydrostatic fluid pressure, non-uniform loading created by ground forces, and vertical bending caused by subsidence. Resulting stresses in the lining can be high. To date linings have been designed that withstand hydrostatic pressures as high as 1,500 psi. Watertight linings must be robust, constructed of the highest quality materials, and manufactured and installed with precision. Therefore, such linings are expensive. Today's ductile cast iron tubbing is greatly superior to gray iron formerly used for tubbing, and is stronger, and more resistant to corrosion than welded steel lining. Tubbing, unlike steel linings, can be installed in wet conditions and used to control water inflow and stabilize unconsolidated ground as the shaft is deepened. Steel lining requires absolutely dry conditions for welding, which often necessitates expensive ground freezing and a primary lining.

Jan 1, 1985

By Raymond Mancha

"Conventional" coal dryers really do not exist. What we really mean to say is that there are many and varied kinds of coal dryers -- and the "air handling problem" is really the only portion of it which has been approached for solution by conventional methods. It now appears that these conventional methods need supplementing by some new, relatively unconventional apparatus. In order to approach this matter with mutual understanding, here is a quick survey of the coal drying art. Figure #1 shows a McNally Pittsburgh Pulso Dryer, In the McNally Pulso Dryer, the coal is fed-onto the screen by a rotary feeder assuring even distribution of the coal. As the coal travels forward due to the action of the screen, it is subjected to a controlled pulsating flow of hot gases. T ese originate below the deck and are directed up through the moving bed of coal. Fines sifting through the deck are dried in the hopper below the screen as they fall through the hot gases to an evacuation screw. The coal remaining on the screen is dried to the desired degree when it reaches the discharge end. At this point, it is directed down into the evacuation screw to combine with the fines, or it may be discharged as a separate product. As the coal travel down the screen, it is subjected to intermittent upward currents of hot gases. These first distend the bed allowing the gases to come into intimate contact with the coal particles for rapid and efficient heat transfer. Then, as the flow of gas is cut off, the bed settles and the extreme fines sift through the screen preventing their being carried away into the exhaust system.

Jan 1, 1958

By J. C. Draper

The Duquesne Light Company and GAI Consultants, Inc. conducted a demonstration program aimed at establishing permanent vegetative cover directly on acidic, deep coal mine refuse. Several plots were treated with formulas varying in soil amendment application rates and plant species. Periodic monitoring of refuse chemistry has indicated when maintenance applications of seed and soil amendments were required. To establish drainage control, the site had to be regraded. The most successful formula was applied to the entire site. Specific treatment for acidic spots has been initiated. Results of the program indicate that adequate permanent vegetation has been established.

Jan 1, 1983

By Y. V. Vasylchuk

This paper presents an algorithm for optimizing the classification of surface mine material subject to excavating constraints. High-resolution expected profit models are input and optimized to classification maps subject to site-specific rectangular excavating constraints. This optimization problem defies traditional closed-form analytical solutions; a practical heuristic algorithm has been developed to quickly determine the optimal final destination for the material subject to realistic constraints. The optimization is fast and generates results that achieve up to 98–99% of the total expected profit achieved with free selection. This algorithm provides a fast viable option for practical application in short-term grade control and in managing multiple realizations in long-term resource estimation.

By A. J. Naldrett

Over the past six or seven years important new ideas have been developed concerning the origin of nickel sulfide deposits. To a large extent these have been stimulated by the major nickel discoveries of the Eastern Goldfields area of Western Australia (Woodall and Travis, 1969; Ewers and Hudson, 1972). Prior to these finds, the most important nickel camps were regarded as being associated exclusively with intrusive rocks such as the Nickel Irruptive at Sudbury or the intrusive peridotites at Thompson, rocks that were thought to have no close association with volcanism. Study of the Australian discoveries, coupled with work in South Africa (Viljoen and Viljoen, 1969) and Canada (Naldrett and Mason, 1968; Pyke, Naldrett and Eckstrand, 1973), has shown that volcanic rocks with true ultramafic compositions and extrusion temperatures of 1400 to 1600°C were a common feature during the Archean. Under certain circumstances economic concentrations of nickel sulfides have formed from these rocks, either settling to the base of their associated flows or accumulating in shallow intrusive feeders to the flows. The aim of this article is to show how these ultramafic rocks can be recognized, how the nickel deposits, if present, are likely to occur within them, and what special features characterize ore-bearing examples of the rocks.

Jan 1, 1975