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By Jr. Flynn

The filtration process has long been utilized in the mining industry and typically associated with processes where clear solutions are required. One definition of filtration states that it is utilized to affect a more complete separation of liquid and solid phases than is possible with settling alone. The development of Diatomaceous Earth filter aids has added a new dimension to filtration technology in the mining industry. It makes possible the filtration of slimes with almost perfect clarity, and at rates that become economical.

Jan 1, 1980

By E. D. Attanasi, J. H. DeYoung

Several factors contributed to continued declines in mineral-exploration activity in the US in 1985. Low metal prices and, what appears to be worldwide chronic excess capacity in copper, molybdenum, lead, and uranium, have resulted in mineral-exploration expenditures remaining anemic. Economic recovery could result in a healthier mining industry and more cash flow to fund exploration. This is because general economic activity and US mining industry activity have historically been closely linked. However, as the worldwide economic recovery has expanded, the mining sector has continued its downward slide. New cuts in industry exploration budgets in 1985 shocked those who thought the exploration situation could not become worse. Some personnel and equipment had been redirected from base metals exploration to precious metals in the past few years. Last year, continued reductions in exploration sent many professionals out of the mining industry. Recent staff reductions or consolidations of operations were made by Noranda, Chevron, Molycorp, and other exploration companies. The latest data from the Society of Economic Geologists (SEG) summary of exploration statistics show that professional staff at year end in major US exploration companies (domestic and foreign operations) fell from 2355 in 1981 to 1868 in 1983 and 1277 in 1984. By the end of 1985, two economic trends were established that could improve the future profitability of mining and hence exploration. First, the price of crude oil began a decline. If sharply reduced energy prices increase worldwide economic expansion, the substantial excess capacity in some of the base metals industries could disappear, and prices could improve. Furthermore, if energy price declines reduce mining and processing costs significantly, metals may recapture some lost markets. The decline in oil revenues has already encouraged some oil-producing countries, such as Venezuela, to look toward development of mineral resources to earn foreign exchange for debt repayment. Second, the decline of the dollar by 21% during 1985 could also help US producers meet foreign competition. During 1985, industry restructuring continued as many oil companies sold off mining subsidiaries and minerals properties. Gold, silver in new discoveries Precious metals continued to dominate the announcement of new discoveries and exploration projects in 1985. A review of domestic exploration and development activities reported in several industry journals shows that 60% to 80% of these projects were directed primarily at precious metals, particularly gold. Base metals exploration activities frequently involved polymetallic deposits with gold or silver values. Because much of this exploration was done on identified targets (on-property exploration), the decrease in wildcat or grassroots (off-property) exploration may be more substantial than indicated by reductions in total exploration activity. Significant gold discoveries in 1985 included several in Nevada, among them the Genesis property of Newmont (near the Carlin mine), Goldfields' discovery of the Chimney deposit in Humboldt Co., and Freeport's discovery of two mineralized sites near Jerritt Canyon. Gold exploration continued to be focused in the western US and Alaska, but gold production starts at the Haile mine in South Carolina, and the Ropes mine in Michigan as well as Amselco's feasibility studies on deposits near Ridgeway, SC, are evidence that gold exploration is not limited to the West. The dominance of gold projects in exploration is not limited to the US, as demonstrated by gold dis¬coveries and exploration projects in Australia, Brazil, Canada, the Caribbean region, China, Guinea, Ivory Coast, South Africa, the South Pacific islands, and Thailand. From the standpoint of US metal miners, it is perplexing that worldwide exploration and development is also taking place in copper, zinc, tungsten, and other metals with depressed prices. During 1985, the US Geological Survey's efforts to map the sea floor of the Exclusive Economic Zone shifted from the Pacific Coast to the deep water areas of the Gulf of Mexico and to areas off the coast of Puerto Rico and the Virgin Islands. An atlas containing sea-floor maps of the west coast area was published as US Geological Survey Miscellaneous Investigations Series Map 1-1792. Results of the 1985 surveys are expected to be published by January 1987. Exploration trends - Statistical evidence Data from the SEG showed continued decline in the US mining industry's exploration expenditures through 1984. The share of US companies' domestic exploration expenditures directed toward base and precious metals has increased from 51% to 84% from 1980 to 1983 and to 86% in 1984. US mining companies spent about $0.67 of each exploration dollar in 1984 in the US. However, this represents an increase from earlier years. The 1983 data also show that firms spending more than $5 million on exploration accounted for 77% of exploration expenditures. Since 1981, the Bureau of Land Management (BLM) has been assembling data on claims and an-

Jan 5, 1986

By Keith E. Dyas, John Nelson, Ronald T. Johnson

GENERAL DESCRIPTION The Bruce mine of Cyprus Mines Corp. is located in Bagdad, AZ. The mining method used is open cut-and-fill. Of the annual production of 81 647 t (90,000 st), approximately 83% is taken from load-haul-dump (LHD) stopes and the balance from slusher stopes. All ore is produced from the area between the 1250 level and the 2300 level. The average travel time from the shaft pocket to the stope is approximately 5 min. GENERAL ORE BODY REQUIREMENTS AND LIMITATIONS Size, Shape, and Dip The Bruce ore body occurs in quartz-sericite schist with Dick rhyolite on the footwall and andesite on the hanging wall. Diabase dikes are found in the hanging wall; there is also a dike coming off the footwall and crosscutting the ore body. All of the rock types are of the Precambrian Yavapai series and have been subjected to regional metamorphism. A composite of the ore body is given in Fig. 1. The deposit is of massive sulfides occurring as a steeply dipping replacement body. On the upper levels the ore is veinlike with widths from 0.6 to 4.6 m (2 to 15 ft), dipping at 1.4 to 1.5 rad (80° to 85°). On the lower levels the ore is dipping from I to 1.2 rad (60° to 70°) with widths from 3 to 16.8 m (10 to 55 ft). The strike length varies between 107 to 183 m (350 to 600 ft). The rhyolite footwall generally has a knife-edge contact with the massive sulfides. The exceptions to this are the upper levels where there is a 1.5 to 3 m (5 to 10 ft) band of silicified sericite schist between the sulfides and the rhyolite. In the southern part of the ore body the hanging wall is tuffaceous andesite and andesite. In this area the contact is generally sharp and easy to follow. However, to the north there is a large chlorite schist zone that crosscuts the bedding and comes in contact with the massive sulfides. This is apparently due to hydrothermal alteration of the andesite. The chlorite schist is highly mineralized with chalcopyrite and pyrite and quite often forms economic pockets of ore. In the massive sulfides the chief ore minerals are sphalerite and chalcopyrite. Pyrite is the predominant sulfide with considerable pyrrhotite throughout. Bright arsenopyrite ouhedrons in fine grain massive sulfides are quite common. Occasionally small amounts of galena are seen, usually near the foot or hanging wall contacts. On rare occasions tennanite is associated with massive arsenopyrite. Minor amounts of quartz, calcite, and un¬replaced remnants of sericite schist occur, but essentially pyrite is the gangue in which the ore minerals occur. The ore values are in excess of 3.5% copper and 12.5% zinc with some silver and rare gold as byproducts. Ground Conditions The massive sulfides are generally self-supporting. One exception is in the 1850 stope where the ore body is 9 to 11 m (30 to 55 ft) wide and 152 m (500 ft) long. There are flat to shallow dipping slips and seams in the ore, creating extremely blocky ground. For support, old 25.4-mm (1-in.) hoist ropes were installed tensioned to 27 t (30 st), and then cement grouted over the entire length in longholes [14 to 15 in (40 to 50 ft) in length) drilled on 3-m (10-ft) centers from the level above. This has tied the formation together very successfully and virtually eliminated the blocky ground condition. Both the hanging wall and footwall are quite shaley in some areas. Reasons for Adopting Trackless Open Cut-and-Fill Methods First, any method other than open cut-and-fill would have caused too much dilution. The use of rubber-tired mining equipment in the pro¬duction stopes requires a footwall ramp. The inclines in ore will be mined out, so this ramp in the footwall will provide access to and from the stopes (Fig. 2). This incline is very expensive, but necessary to convert existing stopes to LHD mining. 'The final cost of ore mined by the LHD machines has not been determined. As of 1972, tons per manshift in the 2150 stope-the only one to complete a full cut-had increased from 7.58 t (8.36 st) to 12.83 t (14.14

Jan 1, 1982

By E. R. Pantos

US coal production increased 3% to a record 832 Mt (917 million st) in 1987, according to preliminary Energy Information Administration (EIA) data. Most of the increase was due to the unusually warm summer and the increased coal-fired electricity demand for air conditioning. Drought conditions in the Northwest lowered hydroelectric generation, contributing to the higher use of coal by electric utilities. However, excess production capacity and increased competition from natural gas added further downward pressure on delivered coal prices, continuing the declining price trend of the last several years. Coal production by region Appalachian coal production reached 402 Mt (443 million st) in 1987. This is about 3% more than in 1986 and just short of its 1984 peak. Virginia produced 7% more than its 1986 level, due to increased coal-based electricity demand. Smaller percentage increases were attained in eastern Kentucky, Pennsylvania, and West Virginia. Ohio and Alabama were the only major coal-producing states in Appalachia that produced less coal in 1987 than in the previous year. In the Interior region, 1987 coal production reached a record 182 Mt (201 million st), about 2% above 1986. Illinois is the largest coal-producing state in that region. Production there fell about 3.7%, primarily because of lowered demand at electric utility plants in Alabama and Tennessee. However, this was more than offset by production increases in western Kentucky, Texas, and Indiana. After falling slightly in 1986, coal production in the West resumed its upward trend to a record 248 Mt (273 million st). Wyoming is that region's dominant coal producer. It mined 7% more coal than in 1986. Wyoming's increase offset the 11% decline in New Mexico production and smaller declines in other Western states. Coal consumption and prices Domestic coal consumption reached a record 759 Mt (837 million st) in 1987. Most of the increase resulted from the unusually warm summer that led to higher than normal peak demands for electricity in the third quarter. Electric utility coal consumption was also boosted by the below-normal hydroelectric generation that resulted from low water levels in the Northwest. These factors more than offset the effects of increased nuclear power generation and competition from natural gas. As a result, coal provided 56.9% of electric utility generation in 1987, compared with 55.7% in 1986. Electric utilities consumed a record 651 Mt (718 million st) of coal. While electric utility coal consumption increased, the average cost of coal to utilities was down, from $1.58 per million Btu in 1986 to $1.52 in 1987. The average price of coal delivered to utilities in 1987 was $35.09/t ($31.84 per st), the lowest since 1981. Coal prices were held down by a glut of coal supplies and by a decline in the average price of natural gas to electric utilities. Coal consumption at coke plants in 1987 was 2.6% above the 1986's 32.5 Mt (36 million st). This increase reflects steel's recent resurgence. Coking coal demand, though, was reduced by the increased use of continuous casting and electric furnace technologies. The average price of coal delivered to coke plants fell from $56.02 to $51.35/t ($50.83 to $46.59 per st). Coal consumption in the industries other than coke plants amounted to 68.2 Mt (75.2 million st) in 1987, slightly less than in 1986. Coal lost part of its market share to natural gas, which was priced favorably relative to coal. The average price of coal delivered to manufacturing plants was at its lowest level of the current decade. It fell from $39.50/t in 1986 to $37.27/t ($35.84 to $33.81 per st). Residential and commercial coal consumption fell to 6.2 Mt (6.9 million st) that is 9.8% below 1986 and the lowest since 1980. This decline is also attributed to the relatively low price of natural gas in 1987. Coal stocks Coal consumers held 169 Mt (186 million st) of coal stocks at the end of 1987, 5.9% above the 1986 year-end level. Most of this increase was due to stockpiling by electric utilities in anticipation of a possible strike by the United Mine Workers of America early in 1988. Stocks at electric utilities increased to an estimated 154 Mt (171 million st) at the end of 1987, 5.6% higher than the previous year. This was much lower than 1984's stock buildup. Coke plants increased their coal stocks by 30% in 1987 to 3.5 Mt (3.9 million st), rebounding from the unusually low inventories of 1985 and 1986. Other industries increased their stocks slightly in 1987. Coal producers and distributors ended 1987 with 25 Mt (28 million

Jan 5, 1988

By Keith A. Yarborough

INTRODUCTION The National Park Service (NPS) conducted a research program from mid-1975 to early 1978 to measure alpha radiation levels in natural caves which it administers. Subsequently, a long-term management program was developed which has conducted routine monitoring of radiation levels and has computed employee exposure accumulations in certain NPS caves. The overall program: research and management; was undertaken to evaluate the possible health hazard to cave visitors, interpreters, researchers, maintenance personnel, concessions employees and other workers and to protect their health. The results of this work have been reported extensively elsewhere (see References 1 through 3, 5, 6, 9 through 13, and 14 through 26). This paper deals with the relation of radon gas and daughter produced radiation levels to the cave air flows which mobilize them. These flows are a function of interior cave and exterior ambient air temperatures and pressures and of the cave's geophysical configuration. The low-level, ionizing radiation is produced by minute concentrations of radon and thoron gases which emanate from within caves. Because of confinement, the radiation levels are often appreciably higher than in surface atmospheres. Subsequent radioactive disintegration of the gases into their ionized "daughter" products, which are particulates, permits distribution of the alpha radiation throughout a cave system. The extent and character of this distribution depends upon the particular cave and the air flows which it produces. Thus, the alpha radiation serves as a "tracer" to describe the flows. The flow analysis is divided into two parts: 1) A qualitative description with respect to the two basic geophysical cave types over both long-term (annual) and short-term (diurnal to weekly) periods. 2) A quantitative description of the unsteady, uniform and non-uniform, one-dimensional, incompressible motions for both influent and effluent air flow situations in both basic geophysical cave types. A part of the qualitative description presents "Special Measurement" data: Tsivoglou [vs.] Kusnetz working levels, Tsivoglou individual daughter levels and free ion concentrations, radon gas concentrations, and equilibrium ratios. A great deal of important work has been carried out by Mr. Bobby C. Carson, Cave Radiation Technician at Mammoth Cave National Park, Kentucky. He reports these findings later in this conference (Ref. 6). Some of his results have been used here to establish the cave air flow analysis. Other National Park Service personnel have made measurements at others of the caves for which data are reported here. All of this work and cooperation has been vital to the success of this research program. It is very much appreciated. THEORETICAL FLOW DESCRIPTION Previously reported research (See Ref's. 20, 21, 23 and 25) has established the qualitative relationship between the alpha radiation in caves and their natural air flows. The radiation serves as a representation of these air flows. Changes in radiation with time represent changes in the main forces which produce the air flows. The quantitative data have substantiated that [all caves in which the primary cause of air flow is due to temperature produced gravity (density) gradients and also having minimal man-made disturbances, experience seasonal variations in airborne alpha radiation. The radiation levels increase in summer but decrease in winter], based upon seasonal air movements through each cave system which occur naturally. Two general types of physical cave configurations which control the air flows have been identified as: 1. Those which go up into a hillside or mountainside: Type I ("Upside-down" = USD). 2. Those which go down into the earth; Type II ("Right-side-up" = RSU). These act to control the air flows seasonally. The summer increase in Type I caves is due to increased air flows, whereas in Type II caves it results from stagnation or reduced air flows. This seeming paradox is explained by the physics of the air flow regime in each cave type and has been detailed elsewhere [Ref's. (20), (22) through (25)]. It[ i] true, in general, that air flow decreases airborne radiation in the [immediate vicinity] in which it occurs. Any paradox results from subsequent distribution throughout the case as to [ how] the air moves through a cave [system] with respect to time and space. Exceptions to the cave air flow "rule" are: 1. Caves in which pressure gradients and pressure fluctuations [predominate] in producing the air flows. 2. Caves in which man-made effects and management practices are superimposed on the natural air flow regime. Man-made disturbances which can alter the natural cave air flows are tunnels, elevator shafts, bore holes, sealed and closed portals, etc. If these are not properly sealed, the natural air flows which they change will totally alter the distribution and seasonal variations of the alpha radiation levels. These exceptions may act separately or in combination.

Jan 1, 1981

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

2.1 INTRODUCTION When total extraction of an opening of sufficient size is reached in a horizontal coal seam, the roof strata in the overburden deform continuously to reach a new equilibrium condition. The severity of deformation decreases upward toward the surface. As the downward saggings of the strata propagate and reach the surface, there will be a depression zone on the surface directly above, but extending beyond the edges of the underground opening. This is the surface subsidence basin or surface subsidence trough. The surface subsidence basin is circular in plan view, if the coal seam is horizontal and the mined-out opening is square in shape. But it is rectangular with rounded corners or elliptical if the coal seam is horizontal and the mined-out opening is a long- and thin rectangle or a short-rectangular, respectively (Fig. 2.1). Most underground openings (e.g., longwall panel) assume rectangular shape when total extraction has been completed. Theoretically the edges of the subsidence basin are the points of zero subsidence. But it is difficult to exactly locate the points of zero subsidence. Therefore in practice the points with vertical subsidence of 0.4 in. (10 mm) are used. The final subsidence basin is that which exists long after the mining has been completed, because its magnitude and shape are quite different from the dynamic subsidence basin formed while the face is moving. 2.2 CHARACTERISTICS AND TYPES OF DEFORMATION IN THE FINAL SUBSIDENCE BASIN For a horizontal coal seam, every point in the subsidence basin moves toward the center of the basin. Subsidence is maximum at the center of the basin. Any cross-section that passes through the point of maximum subsidence and either parallel to AB or CD line (Fig. 2.1) is a major cross-section along which principal directions of surface movements occur. However among those infinite numbers of major cross-sections, two specific ones are of special significance, not only because the magnitudes of surface movements are the largest, but also because they are the most easily identifiable directions, i.e., one that is parallel to the faceline at the center of the basin (CD in Fig. 2.1) and' the other is that perpendicular to the faceline but parallel to the diction of face advance (AB in Fig. 2.1). Nearly all the subsidence data obtained in the US have been derived from these two cross-sections, although some cross- sections parallel to CD but near the edges of the panel have also been included. In addition to moving horizontally toward the center of the basin, every point in the basin also subsides vertically. The magnitude of subsidence increases toward the center of the basin. Therefore surface subsidence is a three-dimensional problem and should be treated so in all cases. On all the major cross-sections, only principal subsidence and principal displacement occur. Since subsidence and displacement vary continuously in every major cross-section, three additional deformation components are de- rived, i.e., slope, curvature, and strain. On all other non-major cross-sections on the other hand the five components are accompanied by two additional components, i.e., twisting and shear strain. The seven components of the surface movement are defined as follows (Fig. 2.2): 1. Subsidence, S. On any cross-section, the vertical component of the surface movement vector is called surface subsidence. It generally points downward. But sometimes it points upward in areas ahead of the faceline or beyond the edges of the opening. In such cases it is a surface heave which is usually less than 6 in. 2. Displacement, U. On any cross-section, the horizontal component of the surface movement vector is called surface horizontal displacement. It generally points toward the center of the subsidence basin. But in steep terrain, it moves along the downdip direction 3. Slope, i. On any cross-section, the difference in surface subsidence between the two end points of a line section divided by the horizontal distance between the two points is called the surface slope of the section. 4. Curvature, K. On any cross-section, the difference in surface slope between two adjacent line sections divided by the average length of the two line sections is called the surface curvature of those two line sections. There are two types of curvature: con- vex or positive curvature and concave or negative curvature. 5. Horizontal strain, e. On any cross-section, the difference in horizontal displacement between any two points divided by the distance between the two points is called horizontal strain. If the distance between the two points is lengthening, it is tensile strain with positive sign. Conversely, if it is shortening, it is compressive strain with negative sign 6. Twisting, T. On the surface of the subsidence basin, the difference in slope between two parallel line sections divided by the distance between the two line sections is called twisting. 7. Shear strain, y. Shear strain is the changes in internal angles of a square on the surface of the subsidence basin or on any major cross-section. It is the summation of the differences in incremental (or decremental) lengths between the two opposite sides divided by the original distance between the two opposite sides. More precisely, the surface deformation indices (i.e., slope, strain, curvature, twisting and shear) are defined by derivatives of surface movement components. For simplicity, the x- and y-axes of the cartesian coordinate system are set to be parallel and perpendicular to the cross-section of interest, respectively. In such a coordinate system, slope and curvature along x direction are the first and the second derivatives of the vertical components (S) of surface movement with respect to x, respectively, or i, = ds/dx and kx = d2s/dx2. Horizontal strain along x direction is the first derivative of the component along x direction of the horizontal displacement,

Jan 1, 1992

By J. P. Ramsey

This is a description of the efforts of a research project intended to demonstrate methods of alleviating pollution from coal mine refuse piles and slurry lagoons. These are mainly derelict barren sites. Some are burning and some are vulnerable to wind erosion which causes air pollution. Some occupy valuable land near metropolitan areas. They are an integral part of the landscape of the Appalachian and Midwestern Coal Fields. They are important in the light of growing civic awareness of the great general problem of waste disposal and environmental improvement. In the V-shaped valleys of the Pocahontas Region, they continue to be piled higher and higher. In flatter topography, they tend to form broad, flat ridges. Some contain more metal forms than others and some have a minimum of metal, but weather to a fine talc, which chokes streams with a fine particle suspension. Most are burning or have burned, but burning or weathering, most all are sources of pollution to the atmosphere and to adjacent waterways. This demonstration project is being carried out at an abandoned mine near the town of Du Quoin in southern Illinois. It is jointly sponsored by the Truax-Traer Division of Consolidation Coal Company and by the Federal Water Pollution Control Administration of the Department of the Interior. The site area is a refuse pile and slurry lagoon, each of fifty acres. It is hoped that basic data from this study will be generally applicable to other sites and will provide a basis for rational and efficient engineering design of future reclamation projects. Most refuse piles have extremely long term capabilities to produce highly potent acidogenic oxidation products typifying the more serious aspects of acid mine drainage contamination. Numerous sites remain where the abandoned mine no longer discharges acid waters, but its associated refuse pile continues to generate significant quantities of acid and other oxidation products even after many years.

Jan 1, 1969

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

10.1 I~RODUC1'ION In order to understand the effects of surface subsidence due to underground mining on the ground water hydrology, a brief introduction to the rate, direction, and general pattern of ground water movement in aquifers is necessary. Ground water movement in an aquifer is controlled by aquifer lithology, structure, permeability, water levels, topographic set¬ting, and pumping patterns (Sgambat et al., 1980). Fig. 10.1 shows an idealized flow pattern of ground water in a hilly terrain (Coe and Stowe, 1984). The hill is made up of a series of interbedded permeable aquifers (mostly sandstone) and confining units (mostly shale). Since sandstone is porous and permeable, ground water moves through it downward and laterally until it reaches the interbeddings of the confining unit immediately below. The ground water then moves laterally along the interbeddings, be¬cause the confining unit is less permeable, and comes out as springs on the surface at the intersection of the aquifer and the confining unit. If there is a ground water table in each aquifer, it is a perched water table (e.g., right side of Fig 10.1). On the other hand, if the ground water recharge is larger than can be drained out, the interbedded permeable aquifers and confining units will be filled with water and a ground water table will exist only at the uppermost permeable aquifer. This is the semi-perched water table (e.g., left side of Fig. 10.1). There are three ground water flow systems: shallow, interme¬diate, and deep. Shallow flow systems occur near the land surface and the surface drainage system. The flow depth ranges from a few to several hundreds of feet with a resident time of a few weeks to a few years after entry, depending on the permeability of the rock strata. In a shallow flow system, the drainage coincides with sur¬face run-off water divides. Intermediate flow systems occur in minor hills some distance away from surface drainage. The travel distance ranges from several hundreds to several thousands of feet, the travel time from several months to tens of years. These systems are less dependent on seasonal recharge or discharge. In deep flow systems, the ground water travels from thousands of feet to miles, and transfers between surface basins. The travel time ranges from several tens to several hundreds of years. The systems generally receive recharge over a large area on major mountains and dis¬charge into major stream systems. 10.2 CASE STUDIES There are two ways of monitoring water wells for studying the effects of dewatering due to underground mining, i.e., water level and piezometric level. The water level is the water elevation in a water well that has penetrated two or more aquifers. Thus it indi¬cates the combined flow of all the aquifers that the water well intersects during the time of measurement. The piezometric level is the level to which water rises in a piezometer cased to a specific aquifer, and coincides with the pressure level of water in that aquifer. Therefore piezometric level reflects the water condition in that particular aquifer to which it is confined, while the water level represents the total yield of a water well without regard to the source of water. For instance, if a water well intersects two aqui¬fers, and if the lower aquifer is affected by undermining and goes dry while the upper aquifer does not, the water level in the well will drop, but may never go dry. Under this condition, the data obtained by monitoring the water level do not indicate the true behavior of the individual aquifers, especially if they are located at widely separated heights. 10.2.1 WATER LEVEL EFFECTS The effects of underground mining on ground water flow have been the subject of many investigations (Booth, 1984; Coe and Stowe, 1984; Owili-Eger, 1983; Rauch et al., 1984). However, the problems are very complicated, as have been exemplified by the conflicting conclusions reached by various investigators in var¬ious case studies. The most dramatic examples were described by Coe and Stowe (1984). In the first case (Fig. 10.2), the coal seam was 5 ft thick with cover from 400 to 800 ft deep. The majority of water supplies came from a sandstone aquifer in most ridge tops. When the face of the Panel No. 3 passed under it, dug well WW-1, which was approximately 670 ft above the coal, went dry, while the water level in Borehole B- 1, which was located at the center of Panel No. 4 with the bottom reaching the coal seam, also dropped about 160 ft. In Panel No. 5, the developed spring DS-2, which originated from the surface of the sandstone/shale contact and was approximately 750 ft above the coal seam, stopped when the face passed under it. The water level in the dug well W-2, which was dug into the shale about 700 ft above the coal seam dropped about 22 ft, but the well did not go dry. Therefore, nearly every spring or well located above or near the active panels was affected by longwall mining. In the second mine (Fig. 10.3), the seam was 5 ft thick with cover from 200 to 400 ft thick. Dug well DW-2, the bottom of which was 35 ft deep and approximately 330 ft above the coal seam in a perched sandstone aquifer, went dry right after the longwall passed under it. Drilled well W-3, in the sandstone aquifer, about 220 ft above the coal seam, experienced a 75-ft drop in water level when the face was under it, but showed some re¬covery after the face had passed under it. Ponds P- I and P-2 were developed in shale bedrock and were spring fed. They were not affected by longwall mining. Pond P-3 was developed in the sand¬stone aquifer, and its water table showed some decline when the face passed under it. Spring ST-1, which originated from Pond P-1 and was fed from several tributary valleys, was affected by longwall mining, probably because it passed across the panel edges where tension cracks drained off the water. Although the overbur¬den in case 2 was about half of that in case 1, the majority of water resources were not affected by longwall mining. Coe and Stowe (1984) attributed this discrepancy to: (1) a higher percentage of clays, shales, and claystones, resulting in a lesser degree of inter¬connected fracturing, and (2) a less rugged topography resulting in a less localized ground water flow system. Therefore, in order to assess the effects of underground mining, the premining ground water flow patterns, topographical, lithological, and meterological conditions must be known. Booth (1984) also monitored the ground water effects of a longwall mine (Fig. 10.4) in a seam 5 ft thick and 300 to 800 ft deep. There were three major aquifers: Morgantown sandstone approximately 30 ft thick and 630 ft above the coal; Saltsburg sandstone of up to 50 ft in thickness and 520 ft above the coal; and

Jan 1, 1992

By P. Ollivier

A comparative study on potential refractory ore processing techniques was launched at the BRGM to enable exploitation of numerous small deposits of arsenopyrite and antimony sulphide ores.

Jan 1, 1998

By Donald D. Gullickson

The entire system is built around pre-designed and pre-engineered modules which are assembled to meet the metallurgical and production parameters of the project. The carbon vessels are the key to the flexibility of the system. The vessels are made of a coated mild steel, which allows the carbon vessels to be used in the adsorption, desorption and acid wash cycles. In the adsorption mode, the solution is pumped up-flow through four (4) vessels in series at 250 gpm fluidizing the carbon bed. When the carbon in the lead vessel is loaded, it is disconnected from the adsorption circuit via rubber hoses with quick-disconnect fittings. The second vessel is then made the lead vessel and a stripped carbon vessel is added to the end of the adsorption circuit.

Jan 1, 1998

By E. Topuz

Productivity is the most important determinant in the economics of underground coal mining operations. Lower labor productivity increases labor requirements per ton. This, in turn, increases the unit cost of production. Intensive labor requirements may also affect miner injuries and fatalities by increasing man-hours of exposure necessary to produce a given amount of coal.

Jan 1, 1988

By Carmel Bofinger, Maureen E. Hassall, David Cliff, Eric Stemn

e Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

By B. Hearn, O&apos

Falconbridge, Ltd. operates six mines (the strathcona, Fraser, Lockerby, Onaping, East and Kidd Creek) in the Sudbury and Timmins districts of northern Ontario (Fig. 1). These mines vary in depth to approximately 1500m and experience a wide variety of ground conditions. Problems of greatest concern include rockbursting, backfill pillar stability, wall and pillar stability, and the use of cable anchors. A study was initiated approximately two years ago to identify how numerical models could aid in the examination and possible understanding or solution of these problems. This paper discusses the use of numerical models at Falconbridge and describes a case history of their use in examination of rockbursting at the Strathcona Mine.

Jan 1, 1988

By C. E. Brechtel

Bench cut-and-fill stopes with heights between 85 and 105 ft are being excavated in the lower levels of the B-NEATH Zone. Estimates of pillar strength and pillar loading indicated a high probability of pillar failure. Some changes in mining practice were made to minimize impacts of pillar failure and a rock mechanics instrumentation program was employed to monitor stability during mining of the first stopes. Limited pillar failure, in the form of destressing, was observed in the initial stopes; however, global stability during mining was good. Instrumentation data indicated that predictions of pillar strength and stress were quite close to field results.

Jan 1, 1989

The Mesquite mine is being operated by Gold Fields Operating Co.-Mesquite, a subsidiary of Gold Fields Mining Corp. The mine Is located in southeastern California about 56 km (35 miles) east of the farming community of Brawley, California. The mine has been in commercial production since early 1986 and Is a conventional open pit mine developed on 6.1 m (20 foot) benches. The gold is recovered by heap leach using permanent heaps built in multiple 6.1 m (20 foot) lifts. This year's gold production will be in the range of 5,600 kg (180,000 troy ounces). Current ore production is about 18,140 tonnes (20,000 tons) per day while the total tons mined Is averaging 65,000 tonnes (72,000 tons) per day. The climate at the mine is extremely arid with rainfall of 7.6 cm (3 inches) per year. From early May until late October daytime temperatures generally exceed 37.8 degrees Celsius (100 degrees Fahrenheit) and can be as high as 37.9 degrees Celsius (120 degrees Fahrenheit).

Jan 1, 1989

By Allan Neal, Jess W. Smith

FirstMiss Gold Inc., formerly FRM Minerals, Inc., is heap leaching gold from difficult, low grade ores at the Getchell Gold Mine in Humboldt County, Nevada. A two-thousand ton per day facility is leaching material from waste dumps from old operations and from small, satellite deposits around the main orebody. A three-thousand ton per day pressure oxidation mill is under construction to treat sulphide gold ores in the main deposit. The Getchell gold deposit occurs in a wide fault zone in carbonaceous, calcareous sediments and intrusive rocks. Intense clay alteration is typical within the mineralized zones. Silicification is a less dominant alteration phase within the ore. Gold in the upper oxide portion of the deposit occurs both in a free state which is leachable and complexed in fine disseminated pyrite which is not leachable. Gold in the lower sulphide portion of the deposit is almost entirely complexed in pyrite. Abundant arsenic sulphides and variable amounts of remobilized carbon are associated with the gold mineralization throughout the deposit. The waste dump material being heap leached was derived from the upper portions of the gold deposit. The dumps contain high quantitites of fines, clays and sulphides of iron, arsenic and other trace elements. No stockpiling of low grade materials was attempted during the old mining operations, therefore, the dump material is highly variable and unpredictable. A sample of representative material from one dump contained the following:

Jan 1, 1998

By J. Libaude

The Changement mine in French Guyana has, since 1983, processed gold ore by classical gravity methods. A large part of the gold is in the form of very small, free or enclosed grains. Recovery by gravity methods is thus limited (25-30%) and the present plant produces about 40,000 t annually of auriferous waste assaying about 6 git. The company therefore decided to retreat the waste by heap cyanidation. After laboratory tests which showed the feasibility of the method, a pilot test was set up on site. An experimental 3000 t heap, composed of waste of 0-8 mm grain size, was laid out by bucket loader on an impermeable pad covered by PVC and geotextile cloth. The upper layer of the heap was reworked by mechanical shovel to break up the area that had been compacted by the passage of the loader so as to restore adequate permeability.

Jan 1, 1998

By A. T. Yu

Once exploration is complete, "winning" of the ore can be viewed as fundamentally a bulk handling proposition. Whether it is to strip, break, size, extract, load, haul, or even process, the success of each of these phases will depend upon how effectively one can utilize-the methods and tools that are available in bulk handling. Since as much as 30 to 60% of the total delivered price of raw materials can be attributed to handling and shipping (ref. 1), this expenditure may spell the success or failure of an entire mining venture. In fact, it has become increasingly evident that handling and shipping are so intimately associated with mining that only when they are duly considered throughout the mine-to -smelter master plan as an integral part of a total system can an optimum operation be expected and the most economical ton of ore obtained, this total systems approach should not only take in handling and haulage in and out of the mine, but also storage and transfer at the terminals (ref. 2,3,t), including ship and barge loading and unloading which are likewise a major consideration (ref. 5). Much has been developed during the past century in bulk handling, particularly in its expanding use in the mining industry. In view of the major role bulk handling has played and will continue to play in mining, in commemorating AIME's centennial, this paper will attempt to outline the state-of-the-art at this three-quarter point of the 20th century - one that is marked by its industrial revolution and rapidly accelerating technological advances. Bulk handling systems Although many developments in bulk handling are worth noting. The most significant during the past three-quarters of a century are: the total systems approach to solving problems, automation, the increase in speed and capacity.

Jan 1, 1971

By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

"The Vermilion range extends from the vicinity of Tower to and beyond the ""international boundary, crossing into Canada at the eastern end of Hunter's Island. Merchantable bodies of ore have been discovered at but two localities along this extent, at Tower and at Ely, twenty-one miles east.The iron bearing formation of this range occupies the lowest position geologically of any of the Lake Superior iron formations, being placed by Van Rise and Clements in the Archean, as shown from the following succession:Lower Huronian Intrusive granites, granite porphyries, dolerites, and lamprophyresKnife Lake slatesAgawa formation (iron-bearing) Ogishke conglomerate(Unconformity.)ArcheanIntrusive granites, granite porphyries, and some greenstonesSoudan formation (the iron-bearing formation). (Minor unconformity.)Ely greenstone, an ellipsoidally parted basic igneous and largely volcanic rock The ores of the Vermilion series occur in the Soudan formation (the Agawa iron bearing rocks are not of commercial importance).At the Minnesota mine at Soudan the ore is a dense, hard hematite, occurring in irregular connected and disconnected lense shaped bodies in the jasper, which is intricately infolded in the ellipsoidal greenstone or green schists, so called on account of a characteristic ellipsoidal parting. The strike is about east and west and the dip approximately vertical, with a westerly pitch. The underground workings at this mine are some 4,500 feet in extent east and west, and over 1,500 feet in depth. The structure here is probably the most complex in the Lake Superior iron districts. Above the iron bearing formation, geologically, comes the basal conglomerate of the Lower Huronian, carrying large boulders and Masses of the iron bearing rocks."

Jan 1, 1920

By Randall E. Brown

Irrigation simulates a climate change so that crops can be grown that otherwise would not thrive. The abundant sunshine and warm weather of many arid regions induces a rate of growth in excess of that in cooler, moister regions. Hence, the arid part of eastern Washington, traversed by the Columbia River, is admirably suited to irrigation. The Pasco Basin lies in south-central Washington at the south end of the Columbia Basin Irrigation Project of the U.S. Bureau of Reclamation. The Basin, because it lies in the rain shadow of the Cascade Mountains, receives only 6 to 10 inches of precipitation a year with somewhat greater amounts, commonly as snow, on the higher hills. Recent extremes included 3 inches of precipitation from August 1967 to August 1968, and 12 inches in the succeeding "12 months. Most of the precipitation falls during winter. If it were to fall in summer or were evenly distributed throughout the year, evaporation rates probably would produce a true desert.

Jan 1, 1971