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By C. W. Schultz

Earlier publications from The University of Alabama have indicated that column flotation performance is improved when operating at low pulp levels and when the feed is directed into the froth phase. To validate these early observations a series of tests were performed in which the position of the feed entry to the column and the pulp-froth interface were systematically varied. The optimum grade-recovery relationship was achieved with high feed entry (WA) of column height) and very low pulp levels (<10% of column height). The position of the pulp-froth interface appears to be the more critical variable. When operating in this mode (1. e. at low pulp levels) column flotation becomes. in reality. a froth separation process.

Jan 1, 1991

By J. A. Bartnik

Flocculation, the process of coagulation or coalescence of finely divided particles, is commonly used in separating fine solids from fluids. Forces disposing of the particles to flocculate include: ionic forces of attraction, secondary entropic forces, and magnetism. Magnetic flocculation is due to a physical magnetizing process which affects suspended ferromagnetic particles. Such particles, after exposure to magnetic fields strong enough to cause reorientation of the particles and alignment of the induced magnetic poles, tend strongly to retain this induced magnetism, as the magnetic retentivity of ferromagnetic particles is a linear function of its specific surface.1 Thus, because they become small magnets with high residual magnetism, the particles become and remain attracted to one another, forming large agglomerates. Fine magnetic particles close to domain size can exhibit energies of the magnetization of the order of 105 ergs/cm3,2 which is many times greater than the energy affected by chemical flocculents. Therefore magnetic flocculation can be used to agglomerate particles having surfaces ionized with like charges and only a minute quantity of ferromagnetic material will be necessary to develop sufficient force to overcome the repulsive ionic forces and hold together relatively large masses of fine solid agglomerates suspended in fluids. Since flocculation occurs after the fine suspension passes through a magnetic field generated by magnets surrounding a pipe section, the simplicity of the process and economic advantage makes magnetic flocculation very attractive.

Jan 1, 1971

By Mark Newton Lowry

In the garden of national problems recognized by the American public, imports of mineral products is a hardy perennial. Concern for the security of mineral supplies has preoccupied nations since the industrial revolution and the mechanization of warfare. Since 1973, Americans have also been sensitized to the potential economic costs of overseas mineral supply disruptions and the cartelization of foreign production. Though oil prices have plunged since 1981, the import dependency issue remains topical. Political turmoil in Southern Africa reminds us that mineral supply disruptions will occur in the future as they have in the past. Producers of iron and steel, copper, and refined petroleum products seek protection from imports on national security grounds. The Reagan administration is proposing sweeping changes in the management of the federal mineral stockpiles. s an enduring need to take stock of the mineral trade position of the United States. This article considers the changing role that the U.S. has played in the twentieth century in non-fuel minerals trade. We begin by enunciating some principles that are useful in analyzing this trade. The changing pattern of trade in the 1900-1969 period is then reviewed. There follows a more detailed analysis of mineral trade trends in the 1970-84 period. Some consideration is given in the final section to the significance of non-fuel mineral trade for the U.S. economy. THE ECONOMICS OF U.S. MINERAL TRADE The allocation of non-fuel mineral products in the United States has in this century been accomplished primarily through the market mechanism. Except where trade barriers have distorted price signals, this means that mineral supplies have been obtained from the least cost source, with little regard for their country of origin. Mineral prices facing U.S. firms are sensitive to shifts in the domestic supply and demand, but are also sensitive to economic conditions overseas. The balance of trade in each mineral product has depended on the amount that is profitably produced and consumed domestically at the world price. The nation has produced exactly as much as it has consumed only by chance. U.S. demand for non-fuel minerals is derived from the demand for manufactures, farm commodities, and other goods whose production requires mineral products as inputs. The demand for such goods can be quite volatile, and in most industries moves cyclically due to its sensitivity to the level of aggregate economic activity. The supply of mineral products depends on the cost of extracting and processing mineral raw materials. These costs do not vary greatly in the short run. Because of these attributes of mineral markets, U. S. trade in mineral products fluctuates considerably from year to year. Most of this volatility results from shifts in domestic and overseas demand and from changes in exchange rates and trade barriers. Longer run changes in the mineral trade pattern can also be discerned. These depend on secular trends in demand and in the cost of mineral extraction and processing at home and overseas. The United States was originally endowed with extensive reserves of an array of mineral-rich ores and fossil fuels. It is also a nation with an entrepreneurial climate and technological capability conducive to extracting and processing those reserves. Not surprisingly, it has at one time or another ranked among the world&apos;s leading producers of a great many mineral products. With a population that is large and an economy that is technologically advanced by world standards, the U.S. has also been a leading consumer of mineral products. Because of its voracious appetite, the bulk of mineral products produced domestically has traditionally been consumed domestically as well. Net exports have been sizable only in those industries in which the nation has enjoyed an extraordinary cost advantage. Depletion has gradually reduced the cost advantage that the U.S. mining industry once enjoyed. The economic conditions that encouraged early development of U.S. mineral resources have

Jan 1, 1986

By Ming-yi Zhang, Zhong-nian Yang, Xiao-ming Guan, Quan-wei Liu

"In slurry balanced shield tunneling, how to ensure the safety of construction and to reduce the influence on the environment has arisen wide attention of scholars both at home and abroad. But now it is still in the stage of experience as to the instability mechanism of the slurry shield tunneling excavation and its stability analysis. Based on the large-diameter model tests and FLAC 3D, the effect of the different waterhead (non-water, 0.9m and 1.1m) on stability of excavation face of slurry balanced shield is investigated, and the stability mechanics is proposed. The results show that: waterhead heights play an important role on excavation face instability features of slurry balanced shield in sandy stratum, Regarding the different waterhead heights, the development mode of the excavation face instability features can be divided into non-water mode, lower-waterhead mode and higher-waterhead mode; soil arching is existed in the process of excavation face instability, the settlement of ground lags behind excavation face failure, the soil arching will block or eliminate the effects of ground settlement; excess pore water pressure need to be considered besides earth pressure and hydrostatic pressure when the supporting force is calculated. INTRODUCTION With the development of the society, for the cities all over the world, the exploitation of underground space has become an important measure to solve the problems about population, resources and environment and an important way to heal the city syndrome and implement the sustainable development strategy of city. Constructing shield tunnel with large diameter is the major trend for development of tunnel construction (Yin, 1999). Instability of excavation face caused by relief of shield soil stress is still one problem that needs to be solved (Xiang, 2001). How to reduce the effects of construction on surrounding environment? How to accurately determine the instability of shield excavation face and to effectively and reasonably select the supporting force? These are the crucial problems which need to be solved during shield construction."

Jan 1, 2016

By G. A. Dawe, E. G. Kelly

Because of the nature of the breakage in the Barmac vertical spindle impactor, the 80% reduction ratio is very small, so that when an energy efficiency is calculated from Bond&apos;s method, it appears to be very low. However, the product size distribution contains a high proportion of fines. It is argued that the production of these fines accounts for the high energy consumption, and Bond&apos;s method is modified to account for this, by considering the crusher to be, effectively, a number of smaller crushers in parallel, each having a different reduction ratio.

Jan 1, 1990

By J. Litsenberger, T. E. Marshall, L. Burke, R. Melville, A. T. Iannacchione

Excessive levels of horizontal stresses cause ground fall hazards in underground mines in the Appalachian Basin. At an underground stone mine in Pennsylvania, a modified stress control mine layout is reducing the hazardous conditions associated with excessive horizontal stresses. A microseismic monitoring system is in place to measure levels of rock stability and provide information on the effectiveness of the design technique. The microseismic data is supplemented with frequent and extensive mapping of roof falls and roof rock damage. Findings to date show that the stress control layout provides more stable conditions and thus a safer environment for the mine workers.

Jan 1, 2001

By R. J. Kolada

The ventilation systems of coal storage silos are normally capable of rapidly dispersing any accumulations of methane in the atmosphere above the coal pile surface. However, the results of an investigation which is presented in this report show that hazardous concentrations of methane can accumulate within the coal pile. Methane trapped within the coal pile is released into the atmosphere of the loading gallery when coal is discharged from a silo. If the methane released is of a flammable concentration it is necessary to ventilate the gallery to reduce the risk of an ignition. This report proposes a simple test, which, after further investigations may prove to be an effective method to calculate gallery ventilation requirements.

Jan 1, 1985

By Alper Kirmaci, Taghi Sherizadeh, Dogukan Guner, Samuel Nowak, Khaled Mohamed, Morgan Sears

Coal ribs present a major safety hazard in underground mines, and there is currently no unified approach for their design in the United States. To tackle this issue, this study investigated the stability of underground coal pillar ribs under development load. Utilizing over a thousand 3DEC models, a framework for calculating coal pillar rib rating (CPRR) was developed. A detailed step-by-step method was outlined for computing the CPRR based on a 3DEC analysis, which was then validated with various 3DEC models, demonstrating a strong correlation between the two models. The results demonstrated that the rib factor of safety (RibFOS) under development load is directly proportional to CPRR, coal mine roof rating (CMRR), and floor strength, and inversely proportional to the overburden depth and rib height. Moreover, a regression equation was formulated to predict the RibFOS based on the aforementioned parameters. Furthermore, empirical relationships were developed between the RibFOS and the applied primary rib support density (PRSD) in U.S. coal mines. To ease the calculations, a stand-alone application, Design of Rib Support (DORS), was developed. This application can be used to assess rib stability and easily calculate CPRR, RibFOS, and PRSD.

Jul 1, 2023

By D. W. Gillmore

Numerous orphaned strip mines and old refuse piles scar the landscape, contributing to stream pollution and degradation of the natural environment. Field experiments to reclaim acidic surface-mined spoil and refuse banks with fly ash from bituminous coal-fired powerplants were conducted at several sites in West Virginia. Fly ash served as a neutralizing agent and soil amendment, permitting vegetation of waste lands and disposal of large quantities of ash. Reclamation of land by this method is estimated to cost about $300 per acre of leveled site, depending upon the topography of the land and quality and availability of the fly ash.

Jan 1, 1972

By Timothy D. Gardner, Christopher Mark

Coal mines in the Illinois Basin have not engaged in pillar recovery for many decades. In large part, this is due to the exceptionally weak nature of much of the roof in the region. But, as room-and-pillar mining is conducted at greater depths, and larger pillars become necessary, recovering them becomes more attractive. Recently a western Kentucky coal mine became the first in recent times to successfully employ full pillar recovery. This paper describes the many challenges that were overcome during the process. From the beginning, the focus was on protecting the miners from roof instability, using cable bolts, mesh, mobile roof supports (MRS), and engineered final stumps. Two short test panels were extracted first, and the results were used to adjust the support pattern and mining sequence. Further adjustments were made based on subsequent experience. To date, seven panels have been recovered without a ground fall injury.

Jul 1, 2023

By M. C. Manderson

Phosphate rock is a naturally occurring mineral which, in upgraded form, is important to both agriculture and industry. Phosphate rock normally must be upgraded before it can be assimilated and used. Most of this upgrading is now carried out by chemical means, largely through the reaction of a strong inorganic acid (primarily sulfuric acid) with the phosphate rock to remove major impurities and to produce soluble phosphate. A less important but yet still commercially significant conversion method involves the thermal reduction of phosphate rock at high temperature in an electric furnace to produce elemental phosphorus. The elemental phosphorus is then converted to usable end products. This conversion route is a more costly method than the chemical route, but it has the advantage of being able to produce chemically pure phosphorus derivatives. On the other hand, the use of phosphate rock for agricultural application-primarily for use as a plant nutrient ingredient for fertilizer -does not require the same level of purity. As a consequence, the chemical method of phosphate rock upgrading is the predominant technique for producing phosphatic fertilizers.

Jan 1, 1977

By C. Vass, A. Noble

"The chemical treatment of mine-influenced waters is a longstanding environmental challenge for many coal operators, particularly in Central Appalachia. Mining conditions in this region present several unique obstacles to meeting NPDES effluent limits. Outlets are often located in remote areas with challenging terrain where conditions do not facilitate the implementation of large-scale commercial treatment systems. Furthermore, maintenance of these systems is often laborious, expensive, and time consuming. Many large mining complexes discharge water from numerous outlets, while using environmental technicians to assess the water quality and treatment regime multiple times per day. As an alternative solution, this paper describes the ongoing research and development of automated chemical treatment systems for mine water discharges. The current work explains the development of a bench-scale prototype that has been used to evaluate various monitoring, notification, and control strategies. Results from this testing are compared to present day practices to show the costs and benefits of implementing an automated treatment and monitoring program. INTRODUCTION Background The National Pollution Discharge Elimination System (NPDES), per Section 402 of the Clean Water Act, requires permitting of all point source discharges from coal mines. This program dictates that all water leaving a permitted boundary, whether it be process water or storm water, must leave through a monitored NPDES outlet. These permitted NPDES discharge points, also denoted outlets, outfalls or monitoring points, must meet a rigorous set of effluent limits to maintain compliance. Common effluent limits monitored by coal companies include but are not limited to iron, manganese, aluminum, total suspended solids (TSS), and pH. Raw mine water is often deficient in meeting these effluent limits, and as a result, various treatment processes are required to bring the water into compliance prior to environmental release. Depending on the mining and geologic conditions, water monitoring and treatment programs can constitute a significant operating cost for the mine operator. In Appalachia, acid mine drainage (AMD) constitutes one of the most significant and widespread water quality challenges that must be treated per NPDES guidelines. AMD is a general lowering of water pH that occurs when water and sulfide minerals interact within oxidizing conditions in coal and metal mining. Acid Rock Drainage (ARD) is a similar term that applies more generally to non-mining causes such as highway construction and other large-scale excavations. Today, mine influenced waters (MIW) is becoming more popular as the general term referring to all types of mining-induced water issues. AMD has been researched substantially over the last 30 years, with investigators studying various causal mechanisms and treatment strategies (e.g. Gazea, 1996; Ziemkiewicz, 1998; Skousen, 2000; Kleinmann, 2001; Johnson, 2003; Akcil, 2006; Kalin, 2006). This research has produced several pragmatic results, which provide numerous methods to predict, prevent, and treat AMD."

Jan 1, 2016

By Cal D. Iles

Decreasing ore grades and increasing labor and material costs have seriously eroded the economic vitality of many mining operations. Coupled with global economic stagnation and recession in the early 1980&apos;s, these conditions have forced reevaluation of operating strategies and methodologies with the objective of remaining competitive in a world marketplace. A concept offering large potential benefits is hardrock portable crushing and conveying. Implementation of this system at Duval Corporation&apos;s Sierrita open pit copper-molybdenum mine (Figure 1) has significantly reduced mining costs, becoming a major part of Sierrita&apos;s cost reduction strategy. Located 48 km south of Tucson, Arizona, the 209 000 t/d property has one portable 60x89 gyratory ore-crusher in operation with tentative plans for two additional units.

Jan 1, 1985

By G. L. Brooke

At present, there are two known cobalt deposits in the 48 contiguous states. This paper is a brief description of one of these deposits. It is a Mississippi Valley type deposit, but somewhat atypical in that the metal of greater interest is cobalt as opposed to lead, zinc, and copper. The history and present work are outlined along with a discussion of the geology and mineralogy.

Jan 1, 1981

By Lucien Duckstein

The purpose of this paper is to give recommendations for utilization of water resources in a mining region, considering also water supply and environment; the case study of mining for coal and bauxite under the karstic aquifer of the Transdanubian mountain of Hungary is used to illustrate the approach, which consists in formulating a static multiobjective control model and solving it by compromise programming. The three activities of regional mineral resource exploitation, water supply and environmental protection are represented by different objectives which cannot be expressed in commensuerable units. Thus, a solution which is optimal for one objective is usually far from being optimal with respect to the other two objectives. As a result, we are not seeking an optimal solution for the conjunctive regional system, but a good compromise, trade-off or "satisfactum" (1), (2).

Jan 1, 1979

By Wendell E. Bearce

At the, Crescent Valley Mine of the Hanna Coal Company, several 10,000 ton unit trains of 41" x 0 strip coal are loaded per week during the lake season. This is accomplished without the use of any accumulation of prepared coal. A large raw coal pile is built up during the winter months adjacent to two truck dump bins. This is added to whenever trucks are coming in from the pits and trains are not being loaded. During the loading of trains, trucks from several pits dump into the truck hoppers and coal is also dozed in from the pile. At a rate up to 3200 tons per hour this coal is screened, the plus 6" hand picked, the plus 4" crushed, and&apos; all weighed and sampled as it goes directly to railroad cars being handled on two tracks by car retarders. With such an arrangement it is possible to exercise some control over coal quality, if it can be assessed rapidly. For instance, if the moisture rises to a level where it seems probable the BTU per pound will be reduced to the point where the contract calls for penalties, the trucks from, the wettest pit may be stopped, more or less coal may be moved in from the stockpile, or other measures taken to assure that the average BTU of the trainload will be satisfactory.

Jan 1, 1967

By W. G. Fischer

Trona ore at the Westvaco mine of FMC Corporation has been obtained by room- and-pillar methods since the mine began operation. The flat-lying, 10-foot bed of trona, Na2CO3 NaHCO3 2H2O, is covered by 1500 feet of weak shale and sandstone. Extraction of pillars on the retreat quite often throws large amounts of weight onto development workings. Weak shales in the roof and floor fail rapidly and the mine ribs slough to such an extent that mining often becomes very difficult. When this occurs efficiency goes down, costs go up, and the risk to men and machinery increases greatly. Difficult mining conditions in the early 60&apos;s forced a re-evaluation of all presently known mining techniques in bedded deposits. Many room-and-pillar mining plans&apos; were compared with the system in use at that time, but none of them offered a better solution to the roof control problem. Longwall techniques were seriously considered, but machinery was not available that would cut the hard trona seam and still maintain the productivity obtained from room-and-pillar sections. Roof cones troy in the longwall methods appeared to be more satisfactory than that found in room-and--pillar techniques. It was therefore felt that a new technique using the longwall principle and based on rock mechanics should be tried rather than previously known pillaring methods.

Jan 1, 1966

By J. E. Murphy, Y. Topkaya, R. E. Johnson, B. R. Palmer, D. K. Dysinger, R. B. Bhappu, A. E. Clark

The U.S. Bureau of Mines utilized a central composite experimental design to investigate leaching kinetics of pure chalcopyrite in the sulfuric acid-oxygen system. The six factors studied were oxygen pressures of 150, 300 and 450 PSI, leach temperatures of 35O, 65O, and 95O C, oxygen-to-chalcopyrite mass ratios of 0.5, 1.0 and 1.5, leach times of 8, 16 and 24 hours, initial acid strengths of 0.6, 1.2 and 1.8 g H,SO,/g chalcopyrite and pyrite to chalcopyrite mass ratios of 0, 1, and 2. Chemical analysis and oxygen consumption measurements indicatedthat leaching occurs through three consecutive reactions. Temperature was the primary determinant of leach rate and solution acidity was the primary determinant of oxygen consumption, sulfur oxidation, and activation energy.

Jan 1, 1993

By Yuting Xue, Gamal Rashed, Zoheir Khademian, Connor Brown, Khaled Mohamed

Ground falls in U.S. underground coal mines can lead to significant consequences, including loss of life, injuries, damaged equipment, and production stoppage. Improving the safety of the workplace is of utmost importance for mine workers and the U.S. economy. The Mine Safety and Health Administration (MSHA) accident/injury/illness dataset provides short narratives for reported incidents, including ground-falls. The main objective of this study is to develop a framework that includes: 1) utilizing machine learning algorithms to categorize ground-fall incidents from narratives based on the main cause of the occurrence and 2) demonstrating an example of a user-friendly visualization to display injury/fatality trends from narratives in U.S. coal mines between 1983 and 2021. The developed framework was tested on a subset of the data and achieved an average F1-score of 96% in categorizing the incidents. The outcome will help identify areas requiring additional research and innovative solutions to reduce severe occupational hazards.

Feb 1, 2024

By Sotiris Psomas, Colin M. Eddie

"Steel Fibre Reinforced Concrete (SFRC) Segmental Tunnel Linings have successfully been used for over 20 years in the UK and have been adopted in a number of high profile projects such as High Speed 1, Crossrail, Thames Tideway, as well as High Speed 2. Tunnel linings and especially SFRC design are not covered in the Eurocodes. This shortage of SFRC tunnel design rules seems to be partially addressed by several international publications. However, in the UK, the ‘design-assisted by testing’ (DAT) approach has also been adopted. The Paper discusses the UK’s best design practice and focuses on the DAT methodology as applied in the case of the 6.9km (4.3miles), 7.8m (25.6 feet) ID Lining for the £635million Lee Tunnel Project. The design approach, the full scale testing at the Building Research Establishment (BRE), and the construction innovations are presented. This experience will be transferred to the £4billion Thames Tideway Tunnel.INTRODUCTIONSteel Fibre Reinforced Concrete (SFRC) has been used for Tunnel segments for more than 20 years. The first application of SFRC in the UK was for the Heathrow Baggage tunnel (1994). Since then significant size tunnels have been designed and constructed, such as the Jubilee Line (1999) High Speed 1 (CTRL, 2006), Crossrail (2014), Lee Tunnel (2014) and the scheduled 25km Thames Tideway (‘Super Sewer’) and High Speed 2 rail tunnels. However one the main obstacles in achieving streamlined design and improving efficiency are the lack of appropriate design guidelines for SFRC tunnel segments. This issue will – to some extent – be addressed by a number of current documents on tunnel FRC design either being produced by BSi (PAS8810, expected 2016), ACI (544.R) and ITAtech (Design Guideline PCFRC, 2015) in an effort to advance the design of SFRC and take into consideration the recent developments in Steel and Macro-Synthetic FRC technology."

Jan 1, 2016