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By Robert H. Merrill

7.1-STABILITY OF SLOPES IN SOIL AND ROCK ROBERT H. MERRILL 7.1.1-DESIGN ANALYSIS APPROACHES The analyses of slopes in soil or rock can be made through application of soil- or rock-mechanics principles. In most cases, the material in the slope wall can easily be identified as either a soil or a rock. However, there will be instances where, because of unique characteristics, the soil may behave as a rock structure, or vice versa. By necessity, these unique cases must be identified through experience or critical observation by the engineer, because there are no definitive rules clearly establishing the differences. The most important step in a solution to a slope problem is to define it. Normally, once the problem is identified, a solution usually can be found or a reasonable estimate obtained. The design analysis of a slope wall implies an evaluation of the stresses or forces in the wall, and of the ability of the material in the wall to withstand them. Therefore, the factors influencing a design analysis can be divided into two categories: those which influence stresses, and those which influence the ability of the wall to withstand stress. For simplification, the latter is termed the strength of the soil or rock. Perhaps the basic difference between analyses for soils and those for rock is in the identification of the failure surface. Soils generally do not have an identifiable failure plane. However, some soil layers in a slope wall may have different strengths. A soil slope wall may consist of a thin layer of topsoil overlying a thick, uniform clay, or a topsoil over a gravel or other materials. Therefore, the soil generally does not have a potential plane of weakness that can be identified through observation. On the other hand, rocks normally contain planes of weakness in the form of fractures, faults, joints, bedding planes or other discontinuities weaker than the intact rock, which can be found through observation and/or tests upon rock samples. If the failure surface cannot be identified, the principles of soil mechanics should apply because, in soil mechanics, the failure surface usually is assumed. If it can be identified, then the principles of rock mechanics should apply. 7.1.2-ANALYSES OF STRESSES OR FORCES IN SLOPES All existing methods of soil-slope analysis are based upon interpetations of the Coulomb and Coulomb-Navier failure criteria, commonly termed the total-stress 2nd the effective-stress criteria (Sec. 6.1). The total-stress criterion may be illustrated by the diagram in Fig. 7-lA, which relates the total stress, S, to the cohesion, c: the normal stress, u, and the angle of internal friction, 9, by the expression

Jan 1, 1973

By D. -P. Georgescu

A native sulfur mineralization associated with pyrite and iron oxides containing 20% iron was quarried in Calimani Mountains, Oriental Carpathians. The wastes resulted from this exploitation activity, with a volume of 33 millions m3, were stored in four dumps while the wastes resulted from ore processing using flotation and the subsequent treatment were disposed of in a settlement pond. The investigations carried out in the entire mining area focused on the following two aspects: - the impact of environmental factors mainly on the hydrographic network; - the characterization all pollution sources, namely dumps, leachates and the quarry and the assessment of acidic drainage generation. The total sulfur content of the excavated ore was 3.8% while in dumps it ranged between 0.54 and 1.06%. Analysis of samples collected along the hydrographic network, draining the mining area, resulted in pH values ranging between 1.7 and 2.83 as well as high concentration of iron (4525 mg/L to 1.6 mg/L), copper (1.87 mg/L to 0.04 mg/L) and zinc (13.13 mg/L to 0.3 mg/L). Samples from the quarry, the dumps and the tailings pond were analyzed in order to deter-mine: - the maximum potential acidity (MPA); - the acid neutralization capacity (ANC); - the net acid production potential (NAPP).

Jan 1, 2005

By W. L. Wilson

This article could be entitled "The Rediscovery of the Windfall Mine," since it was originally discovered early in this century. The "Rediscovery" was made by personnel of Idaho Mining Corp. during the course of an investigation of the Windfall mine beginning in 1967. There had been historic production from the Windfall mine sporadically from 1908 until 1951 and there was present during much of this time a mill that vat leached crushed ore. Mining was underground to a depth of 91 m (300 ft). Prior to Idaho's activities, the mine had been inactive since the early 1950s. Idaho Mining Corp. was an "exploration company," privately owned and based in Reno, NV. The writer was at that time manager of exploration for Idaho Mining. The company held interests in the Cortez Gold mine, then being readied for production, and had conducted exploration for various mineral commodities in Nevada for several years. Idaho's attention was first directed to the Windfall mine in the Eureka District, Eureka County, Nevada (see Fig. 1, Nevada map) by a search of published geologic literature of the state of Nevada. An attempt was made to acquire a library consisting of all of the published geo-data for the state of Nevada as well as to obtain as much of the unpublished material as could be acquired. A study of these data, and in particular Tom Nolan's Professional Paper 406 (1962), indicated that the Windfall mine was anomalous for the Eureka District in that it contained deposits of disseminated gold. This source and other sources indicated that the Windfall had produced from underground operations approximately 59 kt (65,000 tons) grading 12.6 g/t (0.368 oz per ton) gold ore that was processed in a vat leaching operation and that the gold was "invisible" to the naked eye and could not be panned. It was ascertained that there were no active operations near the mine and a geologic reconnaissance was made and a few samples were taken to attempt to determine if the mineralization was indeed disseminated. The initial group of samples around the mine area averaged 1.25 ppm [11.5 g/t gold (0.036 oz per ton)] and the mineralization did appear to disseminate into the wallrock. The next step involved researching the ownership of property in the immediate area of the mine, and [ ] a property map was constructed that showed six or seven different ownerships of patented and unpatented claims, as well as some open ground, in the target area. Negotiations were commenced with the claim owners, ultimately resulting in the acquisition of all of the desired property, although some of

Jan 1, 1990

By E. F. Schnitzer, C. Lidstone, D. Cramer, P. J. Wampler

The River Island mining site is located at approximately river mile (RM) 15 on the Clackamas River, a large gravel-bed river in northwest Oregon. During major flooding in February 1996, rapid channel change occurred. The natural process of meander cutoff, slowed for several years by dike construction, was accelerated by erosion into gravel extraction ponds on the inside of a meander bend during the flood. In a matter of hours, the river cut off a meander and began flowing through a series of gravel pits located on the inside of the meander bend. The cutoff resulted in a reduction in reach length of approximately 1,100 m. Erosion by bed lowering, knick point retreat and lateral erosion of upstream river banks occurred quickly. Within two days of the peak flow, 3.5 hectares of land and 105,500 m3 of gravel were eroded from the river bank just above the cutoff location. Much of this gravel moved a short distance downstream into the excavation. Reach slope increased from 0.0022 to approximately 0.0035 in the cutoff reach. Between 1996 and 2003, the knick point from the meander cutoff has migrated 2,290 m upstream, resulting in increased bed load transport, incision, and local lowering of the water table. In 1993, prior to the meander cutoff, transects were surveyed in the River Island reach upstream of the cutoff location. Resurvey of these transects and aerial photo analysis indicates that 96% of the knick point migration occurred during the first winter following meander cutoff. Connection of the flowing river to the off-channel ponds has had minimal effect on water temperatures in the mainstem Clackamas River. It is likely that this minimal change in temperature will decrease as ponds are isolated from active river flow by gravel bar deposition. Fish net-ting in spring 2002, suggests that salmonid use of the pond in the spring is minimal. The most abundant native species netted were large-scale sucker and northern pikeminnow. The most abundant non-native species netted was brown bullhead. Early regulation by state and federal agencies did not adequately evaluate potential impacts to the river and the floodplain; nor did it evaluate future impacts related to geomorphic processes and sediment transport. New permit evaluation methods, currently implemented by both Oregon and Washington, incorporate 1) river dynamism through historic river migration analysis; 2) stability of human structures in light of river dynamics; and 3) sediment transport and its impact on channel stability and dynamics. The gravel pit capture at River Island highlights the potential risks of mining in an active secondary channel of a large gravel-bed river. Mining deeper than the depth of the adjacent channel, within the active migration zone, may increase off-site impacts. In locations where multiple gravel excavations are present within the meander zone, a comprehensive reclamation and restoration plan should be developed which provides long-term channel stability within the natural variability of the entire river reach.

Jan 1, 2006

By M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed out of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferro-magnetic fluid was used as the separating medium. The separating density was changed by varying the intensity of the electromagnet. Both batch and continuous separations were made using 0.59x0.50 and 0.18x0.15 mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1996

By W. Dan Hausel

Archean supracrustal rocks of the South Pass greenstone belt of western Wyoming have been an important source of gold and iron ore. Actual gold production statistics are incom- plete although gold production estimates for the South Pass- Atlantic City district range from a low of 2.0 Mg (70,000 oz) (Koschmann and Bergendal, 1968) to a high of 9.8 Mg (327,000 oz) (Hausel, 1980). From 1962 to 1983 iron ore was also mined from the greenstone belt and production totaled more than 91 Mt (90 million It). The supracrustal rocks of the South Pass greenstone belt occur in a tightly folded synform bounded by Late Archean granite and granodiorite. The youngest of the Archean successions has a reported Rb-Sr isochron age of 2.8 b.y. (Stuckess, et al., 1985). Metamorphism of the supracrustals increases towards the flanks of the belt and is amphibolite-grade enclosing a small island of greenschist facies rocks. The supracrustal sequence consists of metasedimentary and metaigneous rocks that are divisible into four mappable units. The metasediments include metagraywacke, quartzite, pelitic schist, banded iron formation, metaconglomerate, and graphitic schist. Metavolcanics include metabasalt, meta-andesite, and ultramafic schist. These supracrustals have been intruded by mafic sills and dikes and tonalitic stocks and dikes. Two granite plutons and associated pegmatites intrude the supracrustals in the western portion of the belt, and the supracrustals exhibit both fault and intrusive contacts with granitic batholiths along the western and eastern margins. The northeastern flank of the Archean belt is unconformably over- lain by Paleozoic sediments, and the southern portion of the belt is onlaped by Tertiary sediments.

Jan 1, 1990

By Hemendra N. Kalia

Several attempts have been made in the past sixty or so years to commerciliaze the vast oil shale deposits of the United States of America. However, the industry has yet to become viable and economic. To date, it has not been possible to produce oil from the oil shales at a competitive price when compared to the oil produced from oilfields by conventional methods. However, the development work has been quite fruitful in furthering the art of thick bed mining and technology of in situ retorting. The in situ method has the potential of recovering oil from thick beds and the resource recovery potential is much greater than that from underground mining and surface retorting. In situ methods require that the shales/ marlstones be fragmented ' in place to induce adequate porosity and permeability to allow in situ' heating of the fragmented shales. This can be accomplished by using explosives. However, it has been found that the existing blasting systems, though very efficient, are somewhat lacking. The explosive become insensitive when shot in multiple vertical decks. They can also become insensitive when spaced horizontally at close proximity to other charges. Also, since the blasting is done in a very limited free face, this limits the delay time that can be allowed between charges. Consequently it is not always possible to predict the performance of the blasting system on a routine basis. Furthermore, since it is not possible to undertake secodary blasting, it is imperative that the blast design function properly. Recent, successful retorting by Occidental Petroleum Company of retorts seven and eight suggests that some of these problems may have been overcome. This paper addresses some aspects of in situ retorting and problems those have impeded the development of a viable oil shale industry in the U.S.A.

Jan 1, 1983

By Donald Babbitt

In 1971, during the planning and design stages of a $300 million expansion, the Iron Ore Company of Canada Ltd. through its Engineers, Canadian Bechtel Ltd., came out with a preliminary request for two (2) 10,000 LTPH belt conveyor scale systems. These Systems were to provide weighing accuracies within 2.5% of the iron ore pellets and concentrates in transit on two (2) 72" wide conveyors from the stockpiles to the ships. Each conveyor system would be fed by a rail mounted bucket wheel reclaimer, with the conveyed material moving directly to the ship loaders with no inter- mediate surge and/or storage bins between the stockpiles and the ships. The bucket wheel reclaimer discharge rates would vary from 0-9600 LTPH in cyclic periods, with the periods varying from 1-5 minutes - dependent on the level of the reclaim buckets in relation to the stockpile as well as the slewing rate of the reclaimer. There would be frequent interruptions for bucket wheel repositioning (laterally and vertically), changing ship holds, and trimming ship holds. These frequent zero flow conditions, approximately 500 per 150,000 ton ship, could last 1-5 minutes. In addition, the conveyors on which the scales were to be mounted would be over the water and subject to the wind and cold of Northern Quebec. These Systems would be in use 350 working days of the year and would load 30,000,000 LT/yr. (An average of 90,000/working day).

Jan 1, 1975

By James S. Falcone

Soluble sodium silicate materials have well known applications in flotation for desliming, selective depression and corrosion control. Recent advances in the understanding of the complex polymeric nature of silicate solutions using NMR spectroscopy, combined with our studies of the effects of polymeric silicate anions on metal ion activities in solution, oxide mineral surface charges and surfactant adsorption on clays are related to beneficiation processes. The results of these studies indicate the sodium silicates can be used to cause a solution chemistry and particle surface charge characteristics favorable to enhanced effectiveness in typical ore beneficiation systems.

Jan 1, 1981

By John Todhunter

Longwall mining is certainly not new in the United States, having first been used in the late 1800's in Illinois, but the surging acceptance of the method is relatively new. The number of longwall installations in this country are nearly doubling annually as this method continues to prove itself as a coal producer's delight terms of operating cost, performance and safety. Since 1951, several longwall installations have been tried in Barnes and Tucker Company operations. Although all efforts actually proved that the system itself could be used in prevailing conditions, it was not until 1967 that a unit was put in use that proved competitive with regular mining equipment, both conventional and Continuous.

Jan 1, 1968

By R. P. Fischer

Traditionally, molybdenum and vanadium have been used chiefly as alloy metals in steel. They impart similar characteristics to most steels, and to some extent one can be substituted for the other. In the United States during the 1950's the production of steel increased about 5 percent, and the reported consumption of both of these alloy metals in steel increased some 40 percent. In Europe during the 1950's the production of steel in¬creased nearly 100 percent. Data on the actual consumption of these alloy metals in European steels are not available, but production and trade records show that the European supplies of molybdenum increased about 150 percent and those of vanadium about 350 percent during the 1950's. If most of the molybdenum supplies in Europe are being added to steel, as seems likely, then the European steel industry has nearly caught up with the United State in the rate of consumption of molybdenum in steel. The vanadium supplies, on the other hand, are puzzling--unless Europe is adding mach more vanadium to steel than is done in the United States, it seems reasonable to assume that other uses are consuming moderately large quantities of this metal or that appreciable amounts of it are being transshipped from Europe. To the extent that a changing volume of supply signifies a changing pattern of use, the increased demand for molybdenum and vanadium in Europe should be of interest to domestic producers and consumers of these metals.

Jan 1, 1964

By Dirk van Zvl

The design of cover systems for reclamation schemes in tailings requires estimation or determination of tailings materials properties such as compressibility, shear strength and consolidation characteristics. It is very difficult and expensive to obtain truly undisturbed tailings samples for laboratory testing. In situ testing methods have been developed for economically obtaining large amounts of information. Two of these methods are described, the piezocone and the flat plate dilatometer. Both of these methods provide a rapid means of detailed material identification in a nearly continuous fashion for the entire depth investigated. The equipment is described and typical data from a uranium tailings impoundment is presented. The results are compared and the advantages and disadvantages of these methods are discussed.

Jan 1, 1984

By A. Juganda, Jr. Bogin, S. A. Lolon, J. F. Brune, J. W. Grubb

"A longwall gob is mainly filled with broken rocks from the collapsed roof and becomes a porous medium where explosive methane-air mixtures can accumulate. In bleeder ventilation systems, this mixture can migrate out of the gob into the longwall face and other active areas in the mine during barometric or ventilation-induced pressure changes. When external pressures change, the gob does not perceive this disturbance instantly but with a delay due to air flow resistance in the porous gob material. The delay of gob response to outside pressure changes increases the pressure differential across the gob and may cause an outflow of explosive air mixtures from the gob into the adjacent bleeder entries. With computational fluid dynamics (CFD) modeling, researchers at the Colorado School of Mines have evaluated the impact of gob pressure fluctuations on the outgassing of the explosive gas zones (EGZs), the magnitudes and rates of pressure changes, the volumes as well as the potentials location of outgassing if it occurs. INTRODUCTION The air pressure field in underground mines is controlled by many factors such as operating fan settings, ventilation controls, surface atmospheric conditions, and other local events that can intermittently disturb mine pressure, including blasting, roof falls, or inundations. Mine fan settings are rarely changed. Mine atmospheric pressure fluctuations due to adjustments in ventilation controls occur more often during the mining process. Atmospheric conditions and barometric pressures can generate fluctuations in mine pressure on a large scale. Atmospheric pressures change regularly every day but can fluctuate abruptly and become increasingly hazardous in adverse weather conditions. Investigations conducted in coal mines in the United States, Australia, Poland, and South Africa observed higher methane emissions from the gob during periods of falling atmospheric pressures, which led to mine explosions (McIntosh, 1957; Boyer, 1964; Kissell et al., 1973; Fauconnier, 1992; Belle, 2014; Wasilewski, 2014; Lolon et al., 2015). Falling external pressures are understood to cause potential outflow of explosive mixtures from the gob, while rising pressures may push fresh air into the gob. This phenomenon is widely known as gob breathing. The actual processes that trigger gob breathing are not fully understood, nor are the parameters that contribute to the process. Other major events such as roof falls or fan failures can also change the pressure conditions in the mine. In contrast to atmospheric pressure changes, these events can change mine pressures much more rapidly or immediately. TIME LAG AND GOB BREATHING CONCEPT In a bleeder ventilation system, the pressure in the gob is designed to be lower than that of the headgate entries and the longwall face. Air from the gob and gate entries flows towards the tailgate-bleeder returns. When the external pressures are disturbed, this designed pressure arrangement may change, potentially resulting in increased outflow from or inflow into the gob."

Jan 1, 2017

By S. C. O?Brien

This paper develops the procedure for simulating the special locked-cycle Work Index laboratory test using the kinetic parameters obtained by conducting standard size-mass balance (SMB) grinding tests and presents the results for three materials - quartz, a taconite iron ore and a bituminous coal. It was found that the WI could be determined by simulation; however, if a material breaks abnormally, a full description of its abnormal breakage is necessary. It was also found that the sensitivity of the WI test procedure to the sieving process and the estimating of the 80% passing size of the sieve undersize is sufficient to question the practice of quoting a WI to two or more decimal places. Finally, if a material grinds abnormally in the Work Index mill, then the WI test should not be conducted.

Jan 1, 1987

By Carl E. Williams

Several years ago it was decided that ASARCO was in need of a good mine scheduling program to complete the computerized open pit mine planning package that was being used on new prospects and operating properties. A trial and error approach was being used to schedule a mine on a year by year basis, but this was time-consuming and far from offering an optimum solution l. Due to the magnitude of time and expertise required to develop such a sophisticated computer program, it was decided to search outside of the company for one already developed and available for purchase, This proved fruitless and therefore proposals were requested from consulting firms that had the expertise to develop such a program. Out of the five firms that submitted proposals, the one chosen was Systems Control, Inc., (S.C.I.) of Palo Alto, California. S.C.I. was selected because it was felt that they offered the greatest capability in the mathematical solution of complex problems. But due to their lack of mining expertise, a cooperative venture was developed whereby ASARCO would supply this mining knowledge. The selection of this vendor, the formulation of the contract and specifications, and the development of the computer program required about 3 years to accomplish.

Jan 1, 1973

By E. Watkins, S. J. Schatzel, V. Gangrade, K. M. Ajayi, Z. Khademian

Longwall-induced deformations could jeopardize the mechanical integrity of shale gas well casings positioned in the abutment pillar of a longwall mine. The in situ and induced fracture networks surrounding the gas well could provide pathways for gas flow into the mine creating safety concerns. Hence, this study by the National Institute for Occupational Safety and Health (NIOSH) develops a discrete fracture network (DFN) model to characterize the fractures in the overburden based on geomechanical analyses of mining-induced fracture apertures at a study site in southwestern Pennsylvania. The apertures from the geomechanical model are used to develop a stochastic DFN model of the site in fracture flow code (FFC). Multiple realizations of the stochastic DFN model that replicate potential fracture geometries are simulated, and the fracture permeability is compared with field measurements. A maximum field measurement of 5.03 × 10− 12 m2 (5080 mD) and 3.82 × 10− 13 m2 (386 mD) was estimated over the abutment pillar at the Sewickley and Uniontown horizon, respectively. The results show that the average permeabilities from the DFN model agree closely with the field measurements. In addition, the comparison of all the field measurements and 100 DFN realizations show the model is representative of field conditions. These findings provide critical information regarding fracture characteristics in the overburden, which will further be used to predict potential shale gas flow to the mine in the event of a casing breach for an unconventional gas well.

Jun 17, 2022

By George A. Desborough

Marine black shales of Paleozoic age in the Western United States that exceed 10 weight percent organic carbon contain as much as 5,000 ppm vanadium, 1,000 ppm molybdenum, 1,300 ppm nickel, 600 ppm cobalt, 16 ppm silver, 7,000 ppm chromium, 18,000 ppm zinc, 280 ppm cadmium, and 350 ppm selenium. Depositional settings include: (1) continental-rise and marginal-ocean basins, (2) continental-shelf and foreland basins, and (3) cratonic-platform embayments. Most of these metalliferous organic-rich shales have not been examined for resources because of rapid weathering and poor exposures which preclude easy sampling of unoxidized rock necessary to determine actual concentration and residence of indigenous metals. Generally, the marine black shales of Paleozoic age in the Western United States are richer in metals than marine Paleozoic black shales in the Eastern United States.

Jan 1, 1982

By J. R. Hunter

The present is rooted in the past. This is particularly true in the case of mining operations. Coal mining in the United Kingdom is considered an old Industry comprising today 246 Coal Mines many of which have worked coal reserves in their locality for over 100 years. More than half the current producing mines lie in the Yorkshire and Midlands coalfields. They are in the oldest age group and produce 70% of the Industry's output. Some 50% of the remaining U.K. workable reserves amounting to approximately 98,000 million tons are still available to these regions. Fig. 1 Over the past two decades a gradual erosion of demand for coal in the U.K. has virtually halved the Industry's capacity. The number of Mines has reduced by 53% during the past 10 years. Productivity has increased by some 42% mainly through improvements in the central coalfields which has enabled costs to remain broadly competitive with oil.

Jan 1, 1976

By Daniel H. White

Block caving, unlike most other conventional forms of mining relies principally on the natural forces within the rock mass to fragment and transport the ore. Obviously, not every orebody can be satisfactorily mined by block caving. In the early stages of mine planning an attempt should be made to assess the benefits of the block caving system relative to others, and develop a reasonable mining concept that may be used to provide preliminary information to mine planners and financial specialists. It is the intention of this paper to outline some basic geotechnical parameters that are essential to: 1) Assessing the feasibility of block caving an orebody and 2) Providing semidetailed information relative to mine design based on drill hole and other data.

Jan 1, 1979

By K. F. Unrug

The research work reported in in this paper deals with the monitoring of roof behavior in a drift mine located in Eastern Kentucky operating in the Coalburg Seam. The thickness of the seam at the monitoring site ranges between 9 and 10 feet with the immediate roof changing from sandstone to shale then back to sandstone. Shale thickness varies between 0 and 2.5 feet. The characteristics of the immediate shaly roof were monitored with 38 dynamometers which were set up in three survey lines to cover the entire range of shale distribution. The dynamometers are capable of providing accurate load readings in the range of +/- 5 pounds. To closely observe the contribution of moisture toward roof deterioration the dynamometers were set up in intake and neutral airways. A television borescoping camera was used in conjunction with the dynamo- metric instrumentations at pre- determined observation holes to physically observe and record the separation process of the shale and sandstone stratum with respect to time. Monitoring took place between January 1985 through January 1986 in order to cover a full cycle of dry and wet mine conditions associated with the seasonal changes. Analysis of the data show a trend of roof deterioration induced by condensation and eventual penetration of moisture within the immediate roof bedding planes, leading to rapid disintegration of the mine roof.

Jan 1, 1986