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By S. Utili

"The optimal profile of a rock slope under given geometry constraint is investigated by means of the upper bound method of limit analysis. The optimal condition corresponds to maximizing stability factor. It is assumed that rock failure condition is suitably described by the Hoek-Brown criterion. Genetic algorithm is applied for locating the optimal profile. The optimal profiles turn out to be concave profiles but there are heaps around the toes of the slopes. Compared with plane profiles, the percentage of increase in stability factor can reach up to nearly 50%. The key geometry parameters of the optimal profiles are provided for practical use. The new upper bound formulation is capable of computing the stability factors of slopes of any shape, thus the stability status of a slope under man-made excavation can be monitored during the whole construction period.INTRODUCTIONIn mining industry, man-made slopes are excavated to create working surfaces. It is important to optimize the slope profile in order to maximize slope stability under certain geometry constraint. For instance, when the height and width of an excavation are assigned, a plane profile AC (see in Fig. 1) is widely applied in engineering practice, but it has been proved not the best one in terms of safety (Utili & Nova, 2007; Cala, 2007). A vertical profile ABC is the one with least stability. Thus, it can be deduced that there is a profile within the domain of the rectangle ABCD providing the highest stability. Cala (2007) compared the difference of convex and concave profiles in stability using strength reduction technique. According to Cala (2007), circular concave slopes can increase the maximum slope inclination under given factor of safety. Besides, based on upper bound theory of limit analysis, Utili & Nova (2007) assumed a logarithmic spiral profile to prove it is more stable than a plane profile in terms of the stability factor. Although the above studies attempted to seek the best circular or logarithmic spiral profiles, none of them considered the arbitrary shape of the optimal profile and its contribution to enhance slope stability."

Jan 1, 2015

By David Mast, Amanda Foote, Mina Shinouda

The Michigan DOT’s I‑75 Modernization Project, Segment 3, is a 30-year, $1.2 Billion design-build-finance-maintain project in Southeast Michigan. The scope includes building a nearly 4-mile long, 14.5-foot ID stormwater storage tunnel. The tunnel and pump station are being built concurrent with new roads and bridges, requiring multiple levels of design and construction coordination. Underground risks include the poten‑ tial for encountering granular soils, groundwater, and explosive gases. The new tunnel will be mined by a new open-face TBM and lined with a one-pass steel-fiber-reinforced precast concrete segmental lining. Shaft construction began in early 2020 and tunnel mining in July 2020.

Jun 13, 2021

By M. Moats

Copper electrowinning operations have dramatically improved their ability to produce high quality copper at low costs over the past several decades. Even so, some fundamental knowledge is still lacking that could allow operations to run even more efficiently. For example, a rule of thumb exists that estimates a current efficiency loss of 2-3% per gram per liter of iron in the electrolyte. While several laboratory studies have been performed that demonstrate this rule of thumb is likely true, no definitive relationship exists. In this paper, the first steps in developing a definitive relationship are presented. The effective diffusivity of ferric ions in synthetic copper electrowinning solutions was measured using chronoamperometry and the Cottrell equation. The effective diffusivity of ferric ion was determined as a function of electrolyte concentration and temperature. Synthetic electrolytes were then used in laboratory-scaled copper electrowinning experiments, where relationships between current efficiency and solution composition were found to exist under stagnant conditions. Key words: Copper electrowinning, Current efficiency, Chronoamperometry, Ferric ions

Jan 1, 2009

By Xiaohong He, Qing Yu, Kaixiang Zhang, Rui Guo, Minghua Lin, Haoyu Miao

With the increasing depth of coal mining, the coal mine shaft traverses’ strata conditions become more and more complex. Shafts are often located in deep thick strata with unstable aquifers, and coal mining requires short-term rapid drainage of aquifers; the additional stress caused by aquifer water drainage is the direct cause of the shaft-lining failure. Over the years, many experts have conducted research on the shaft-lining damage caused by the consolidation and subsidence of the soil layer induced by the long-term drainage of the aquifer. On this basis, this paper conducts an in-depth study of the dynamic change of the pore water pressure of the aquifer in the short-term drainage and its influence on the response of shaft-lining strain and surface subsidence. The result shows that the Mandel effect of pore water pressure around the shaft-lining is obvious at the beginning of drainage, and the pore water pressure suddenly increases; the increase is independent of the drainage rate, which leads to the sudden increase of the shaft-lining strain value unrelated to the drainage rate. The result also shows that with the gradual dissipation of pore water pressure, the increase of shaft-lining strain is positively related to the drainage rate and negatively related to the drainage distance, and the variation trend of horizontal strain is greater than that of vertical strain, which appoints the main cause of shaft-lining damage.

Mar 16, 2023

By J. W. Rutter, K. T. Aust

The migration of individual, large-angle grain boundaries has been studied as a function of tempereature and solute concentration in specimens of zone i.e filled lead containig very small additions of silver and of gold. Tile results are compared with various the-ories of grain boundary migration and with observations made prev.iorlsly of grain boundary migration in similar specimens of zone-refined lead containing tin additions. A previous investigation by the authors dealt with [he temperature dependence of grain boundary migration in bicrystals of zone-refined lead containing small additions of tin.' It was shown that tin additions as low as a few parts per million cause a large decrease in the grain boundary migration rate at any given temperature, as well as a marked increase in the temperature dependence of the migration rate. It was found that existing theories of grain boundary migration. based on the motion of dislocations. or upon the concept of atom transfer in groups across the boundary (group process theory). or upon the control of grain boundary motion by volume diffusion of impurity atonls along with the boundary. are incapable of accounting for the observations. The single process theory of grain boundary migration. which is an absolute reaction rate calculation based on the transfer ui atoms singly across the moving boundary, was found to predict the migration rate reasonably well for a number of boundaries whose motion was shown to be very little influenced by impurities, but not for boundaries whose illation was influenced markedly by impurities. It was concluded that the elementary process of grain boundary migration involves the activation of single atoms during transfer across the boundary. and that inadequate knowledge is available to permit the influence of impurities to be properly taken into account. The present study was initiated to check the validity of the above conclusions with other alloy systems, namely high-purity lead with small additions of silver and of gold. Both silver and gold diffuse faster. and with a lower activation energy of volume diffusion. than does tin in lead;' consequently, a study of the effects of silver and gold on grain boundary migration in high-purity lead offered a means of testing theories of boundary migration based on bulk diffusion of the solute (eg. ref. 3). In addition. it was hoped that the present work, in comparison with the results for tin in lead, would provide information concerning which factors are important in determin- ing the interaction between solute atoms and a grain boundary. EXPERIMENTAL PROCEDURE The preparation of bicrystals of zone-refined lead, with various silver or gold additions, was identical to that previously described for the lead-tin alloys.''4 Each bicrystal consisted of a striated crystal which was grown from the melt. and an adjacent striation-free crystal which was introduced by artificial nucleation and growth.''4 The striation or lineage substructure in the melt-grown crystal provided the driving force for grain boundary migration. During the preparation of striated single crystals by growth from the melt, it was found that silver or gold concentrations as low as 2 or 3 ppm by atoms were sufficient to cause formation of the hexagonal cell structure. which is due to the presence of impurity, during freezing. This structure is revealed on the solid-liquid interface by decanting the liquid during freezing. The hexagonal cell structure was observed previously4 in zone-refined lead crystals with tin contents above approximately 200 ppm by atoms. These concentrations of silver, gold, or tin are in agreement with the predicted amounts required for cell formation in lead,5'6 under the present conditions of freezing.4 The absence of cell structure at decanted interfaces, therefore, served as a useful indication that the silver or gold contents were less than 2 or 3 ppm by atoms in the specimens as grown. It was found that grain boundary migration occurred only very slowly when the solute content approached that necessary for cell formation. As a result, the present experiments were conducted with silver or gold additions less than 1 ppm by atoms. This impurity level is well within the solid solubility limits for silver and gold in lead.7 The annealing treatments, measurements of grain boundary velocities, and orientation determinations were carried out as described previously.' However. each bicrystal was also chemically polished in a solution consisting of 8 parts glacial acetic acid and 2

Jan 1, 1961

By H. W. Davis, W. W. Adams, O. E. Kiessling

"Current economic problems frequently have focused attention upon the lack of adequate quantitative information indicating the relationship between human effort and output in various branches of the mineral industry. With the exception of complete records covering coal mining, only scattered information on the units of human energy required to produce a unit of raw material is available for most of the important industrial minerals. Fortunately a virtually complete statistical record is available covering this phase of the iron-ore mining industry.For many years iron-ore mining companies, whose interest in safety work is well-known, have reported annual data on employment to be used in the compilation of accident statistics. These data on hours of labor and other detailed employment information have been correlated with the statistics on production also reported annually by producers. The outstanding trends shown by this composite record for the 10-year period 1923-32 are included in the following discussion, supplemented by a summary table that presents the principal statistical background of the study. 5The substantial reduction in the number of men needed to produce the annual iron-ore requirements of the United States, as shown strikingly in the graphs, illustrates that in iron-ore production improvements in technology have been consistently winning a battle over the difficulties of nature. In 1923, for example, 41,294 men working 107,551,244 hours were required to produce 69,351,442 gross tons of merchantable ore, equivalent to an average output of 0.645 ton per man-hour. In 1929, however, only 30,763 men working 77,111,686 hours 'zero required to produce 73,027,720 tons of merchantable ore, equivalent to an average output of 0.947 ton per man-hour. Thus, from 1923 to 1929 the average number of men working decreased 25.5 percent and the total man-hours worked 28.3 percent, while the average output per man-hour increased 46.8 percent and total merchantable ore production 5.3 percent."

Feb 1, 1935

By L. J. Habegger

This paper considers the potential water quality impacts of future energy scenarios which project an approximate doubling of coal utilization from 1975 to 1985. The major impacts estimated for coal extraction are related to effluents from unregulated activities (reclaimed areas prior to stable vegetation) and pollutants (e.g., metals and ammonia). Where applicable, the EPA effluent guidelines to be in effect by 1983 reduce the impact of individual sources to low levels. For example, total suspended solids and acidic discharges are to be regulated to levels generally below recommended water quality standards for receiving streams. However, implementation of these guidelines, particularly for coal extraction, has not been demonstrated on a wide scale. Water quality is not expected to be a major constraining factor for increasing capacity of coal fired utility and industrial boilers. Water quality control has not been demonstrated on a commercial scale for coal conversion to synfuels, but adequate control technologies appear to be feasible.

Jan 1, 1978

By P. Rusin

Toxic substances in On solutions can retard biological leaching of copper sulfide dump ores. On solutions were analyzed for metals, organics, and chloride, and showed inhibitory concentrations of aluminum, manganese, and chloride. Inhibition of bacterial activity by the solid fraction of On solution, with and without the organic constituents, was evaluated. Toxicity to bacterial species was evaluated by monitoring bacterial numbers, pH, Eh, and rates of iron oxidation. The On solution solids were toxic at 50 -60% of their field concentration. Most of the toxicity of the On solution was due to the organic fraction. Different SX reagents show varying degrees of inhibition of T. ferrooxidans. Bacterial inhibitory effects of carriers and lixiviants used in the SX plant should be determined so that entrained SX reagents do not retard biological dump leach systems. The reagents used should be the most cost effective and the least toxic.

Jan 1, 1994

By Muhammad Zia-ur Rehman, Sajjad Ahmad Baig, Gao Lei Fu, Muhammad Mohsin, Sobia Naseem

The environmental sustainability is linked back to human sustainability; the sustainability development comprises the environment, society, and economics. This study mainly focused on mining sustainability and its impact on the environment of Pakistan. For measuring the level and environmental mining sustainability nature to Environmental Impact Assessment (EIA) of the world’s second largest salt mine “Khewra,” Folchi and Phillips environmental sustainability mathematics (PESM) models are applied. The results indicated that Khewra was deemed to be potentially sustainable for the environment and quality of salt. The results suggest the delicate balance of maintaining sustainability successfully, regarding the mining process in Pakistan which has been affecting the local environment and community so badly. The paper lays emphasis on the potential significance of the model’s application for the attainment of sustainable mining goal. This study is essential for researchers,

May 11, 2020

By Romeo Calderón

El presente trabajo describe los trabajados realizados en la Compañía minera Huarón con el objetivo de realizar la explotación de vetas muy angostas y sinuosas de potencias inferiores a 1.20 m. de un modo seguro, eficiente y económico, donde fue necesario resolver el problema de carguío y acarreo en tajeos inferiores a 1.20 m. empleando equipo LHD de 0.80 m. de ancho, fabricado especialmente para este fin.

Nov 1, 1982

By Alexandre Bonan

This paper reports the results of a kinetic study on the oxidation of free cyanide and Cu-cyanide complex ions with HO,. The variables and respective ranges studied were the following: [CN] total =10 - 500 mg/l; pH=10-11; (H2O2/CN) mole ratio = 1- 3; (Cu/CN) mole ratio = 0.10 - 0.25. The results were interpreted by a semi-empirical model that incorporates the useful oxidation reactions and the parallel alkaline decomposition of H2O2

Jan 1, 1994

By E. H. W. Hornbrook, P. W. B. Friske

Paper presented at the 28th International Geological Congress, Washington DC, July 1989 (International geochemical mapping sessions). The objective of the programme is to establish and maintain a nationally consistent geochemical drainage database. Towards this end systematic surveys have been conducted since 1973. To date more than 200 surveys have been completed to the required standards, representing 180 000 sites and covering about 2 100 000 km2 throughout Canada

Jun 13, 1905

By P. Thapliyal

The petroleum refining industry generates over a million tons of spent catalyst per year, containing valuable metals. Currently, these materials are recycled to smelting furnaces, but the fundamental mechanisms controlling the recovery processes are poorly understood. Furthermore, submerged injection of finely divided materials is potentially a means to obtain high recoveries of pay metals. In this study, a catalyst containing 10% Ni and 1% Co was injected into 45 kg heats of matte. A copper matte was chosen so that the nickel and cobalt recoveries were measurable. It was found that the recovery ranged from 40 to 700Al, increasing with catalyst feed rate, decreasing with catalyst particle size and decreasing with the oxygen content of the carrier gas. A mathematical model was developed to account for the results, and to permit extrapolation to nickel mattes. The industrial implications are discussed.

Jan 1, 1996

By L. M. Amaratunga, G. G. Hein, D. N. Yaschyshyn

Fine tailings produced in the milling process have traditionally been disposed of in tailings ponds. Attempts have been made to use these fine tailings in backfill, however, to date the majority of backfill operations have utilized only a small percentage of fines. The remaining fines are, therefore, being sent to tailings ponds creating a waste disposal and environmental problem. This disposal practice is even more acute in the gold milling industry where fine grinding, required for value liberation, results in the production of large quantities of fine tailings, of which a large percentage cannot be used in backfill. Through Cold-Bond Tailings Agglomeration (CBTA), these fine tailings can be agglomerated into pellets which can then be used as a coarse aggregate in back-fill. This paper presents the results of using these pellets to create an Agglomerated Tailings Paste Fill (ATPF) made entirely of fine gold mill tailings and cementing binders. Through this process, supplementary imported aggregates such as sand, gravel, rock-chips are not required while still maintaining adequate back fill strength. By using this CBTA technology, fine tailings are diverted from tailings ponds and becomes utilized as a value added resource in the form of aggregates for use in paste fill.

Jan 1, 1997

By Z Lubosik, S Prusek, M Plonka, B Syrek

"The most commonly used method of thick coal seam extraction in Polish deep mines is multislice longwall (MSL). In MSL stability of goaf in the roof as a result of previous extraction in upper slice is a major geotechnical consideration that must be managed.This paper outlines the results of a wide range of investigations carried out in three longwalls that were in operation in a multislice system using caving with additional fly ash goaf stowing. The longwalls were operated by Katowicki Holding Weglowy SA (KHWSA) in the Upper Silesian Coal Basin of Poland.Examinations were completed on the properties of goaf at the roof of longwalls ie measurements of strength parameters of the goaf material by means of a borehole hydraulic penetrometer, determination of the goaf condition by means of a borehole endoscope and laboratory testing of the caved rock. The results of underground examinations of the loading on yielding arches in the gate roads associated with these longwalls and measurements of vertical and horizontal convergence are also presented.CITATION:Prusek, S, Lubosik, Z, Plonka, M and Syrek, B, 2014. Multislice longwalling for thick seam extraction – properties of goaf in the roof and gate roads behaviour, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference, pp 359–366 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 5, 2014

By Leonard B. Rothfeld

For many years, pulverized coal (PC) boilers in utility power plants have been the dominant market for domestic coal. Today, two new coal utilization technologies challenge the PC boiler's dominance. Atmospheric fluidized bed combustion (AFBC) and "coal gasification/combined cycle" (GCC) stand on the verge of commercial demonstration in the utility environment at a scale of 100 MW. Developed over the past decade, these technologies respond to the demands for cleaner ways to burn coal and for more flexibility in fuel supply. In the near term, these are the "clean coal" technologies most likely to have a significant impact, because they are ready for commercial application. As for environmental acceptability, consider that just a few years ago one of the environmental slogans was "no coal in California." Indeed, the only large quantities of coal above ground in California at that time were in transit on the way to Asia. Today, thanks to new technology, we can point to two operational coal-burning plants in California and one in the works: * Cool Water GCC demonstration plant (100 MW) * California Portland Cement AFBC commercial cogeneration, near Riverside (190 000 lb/hr steam) * Energy Factors AFBC commercial cogeneration at Stockton, to be operational 1988 (44 MW)

Jan 1, 1987

By G. Viramontes-Gamboa, A. Encinas-Oropesa, S. Velázquez-Roque, L. A. Ibarra-Bracamontes

Some industrially relevant applications for pyrite nano/micro-particles have been proposed in the literature, such as the catalysis of chalcopyrite leaching, the removal of As(III), As(V) and Cr(VI) from solution, as photovoltaic devices, and others. Even though pyrite can be recovered from solution by flotation, for some applications it may be beneficial to provide pyrite with magnetic properties. In this work, a methodology to synthesize magnetic shell/core composites made of pyrite as the shell and either natural or synthetic magnetite as the core is presented. The size of the magnetic composite may range from tenths to hundreds of microns. The synthesis is basically made by stoichiometrically mixing iron nano/micro-particles with sulfur microparticles with magnetite particles, and bringing the mixture in an oxygen free atmosphere from 200 to 300 °C for 4 h. The composites were characterized by optical microscopy, Scanning Electron Microscopy and X-Ray diffraction.

Jan 1, 2014

By F. T. Davis

Many contributors have added to the fund of knowledge in the basic sciences related to mineral dressing during the past year. During 1964, the French edition of the Proceedings of the VIth International Mineral Processing Congress together with discussions was printed. Also, complete Preprints of papers delivered at the VIIth IMPC were published in September1. Over a third of the papers presented at VIIth IMPC dealt with fundamentals. COMMINUTION It has been postulated by Ponceleta that flaws need not exist before a stress is applied but rather the flaws are created at the tip of a propagating crack at a stress well below the theoretical breaking stress.

Jan 2, 1965

By M S. Henderson, R D. Alorro, L G. Dyer

An alternative leaching system for rare earth element recovery from monazite is under development. The initial stage utilises oxalic acid to convert the rare earth phosphate into an oxalate salt through dissolution and reprecipitation and it is the efficiency of this stage that governs the overall recovery achieved. It has previously been proposed that lixiviant consumption is the primary limitation in this process. This work further investigates a range of conditions in an attempt to further elucidate the factors influencing the achievable conversion in this stage. It has been shown that the pH may be governed by multiple reactions both consuming and producing acid (thus the mild change over time). The importance of proper mixing and potential to operate at lower temperature with only moderate impact on kinetics has also been demonstrated. Staged/sequential leaching is more effective in fresh solution as opposed to restoring the lixiviant concentration with subsequent reagent addition, suggesting some impact of solution composition. However, contrary to previous findings, subjecting the leach residue to fresh solution resulted in significant decline in leach rate and overall dissolution. This may be because a greater proportion of conversion was achieved in stage 1 in this work than in previous investigation. This may indicate that eventual passivation or the presence of some more refractory REE minerals limits dissolution. Iron dissolution was relatively consistent upon exposure to fresh solution, displaying the ability of the solution to continue to leach the goethite component of the concentrate.

Aug 24, 2022

By Stanley Kesler

The first of two initial 650-mw units of the Paradise Steam Station, located on the banks of the Green River in the south-central portion of the western Kentucky coal basin, is scheduled for operation in late fall of 1962. Location of the site is shown on the map of figure 1. This plant will be the eighth, large-capacity,, modern station built by TVA in a series starting with Johnsonville, operated first in 1951. During that period of 10 years,, unit sizes have increased from a capability of 125 mw to 500 mw at the recently completed Widows Creek Unit 7 addition and at Paradise to 650 mw. This new unit will take its place in a power system that serves an area of some 80,000; square miles with a present installed capacity of over 12,000 mw. Upon completion of the Paradise units and other additional hydro and steam units presently under construction, the system capacity will have reached over 15,000 mw. Projected load estimates indicate that this system will provide a margin' of slightly under 10 percent of dependable capacity above peak demand at that tire. One Paradise 650-mw unit at that time will represent approximately 4 percent of the total system installed capacity.

Jan 1, 1962