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By M Francoeur

Oct 12, 2022

By Paul J. Lewis

Estimation of the axial side shear resistance of drilled shaft rock sockets is directly related to the unconfined compressive strength of the bedrock. Commonly, the mean unconfined compressive strength value is calculated from a range of laboratory test results and is used to estimate the side shear of the bedrock. This paper presents the results from a full scale axial load test performed on an 8.5-feet-diameter drilled shaft rock socket, and compares measured side shear values to estimated values for two different rock strata. Measured side shear values correlated well with the design value calculated for the "strong" rock stratum, but did not correlate well with the design value calculated for the "weak" rock stratum. The mean unconfined compressive strength was used to calculate the side shear in both strata, but review of the laboratory data indicates that this value may not have been appropriate for the weak stratum due to a large variation in the laboratory test results. Also included in this paper is a discussion of the subsurface conditions, the laboratory test results, and the methodology used to design the drilled shaft rock sockets for axial and lateral resistance.

Jan 1, 2005

By Dianne C. Marozas

The U.S. Bureau of Mines is conducting research to evaluate the potential for developing an in situ leach mining process that will selectively extract manganese from oxide ores, leaving gangue relatively undisturbed. To accomplish this, a geochemical approach, based on deposit-specific information such as mineralogy and geology, is used to constrain the operating parameters of the system. Among the studies being conducted are (1) leaching experiments to define reaction mechanisms and kinetics, (2) detailed petrologic characterization at the microscopic scale to assess Mn distribution and leaching efficiencies, (3) deposit characterization and evaluation, and (4) development of potential Mn recovery schemes. Data from these studies are being used to develop engineering design information for an in situ mining process. Specific details of the Bureau's research project are discussed, including results obtained to date.

Jan 1, 1991

By Briggs H.

The illustrated device uses the principle that the lamp can burn with a smaller inlet passage if the air is rich in O2 and that the size of the inlet can be made a measure of O2 percentage. The appliance consists of an adjustable cut-off applied to the inlet of a safety lamp of the improved Gray pattern. Precision is assessed from tables of calibration tests in air contaminated with blackdamp of CO2:N2 composiiton 1:5.67 at temperatures of 40-70 degrees F. Results are presented of tests at St. Germain's colliery, of tests in air contaminated with pure CO2 and of air contaminated with both blackdamp and inflammable gas; published ranges in mine-air blackdamp compositions are tabulated as ranging from 90.06% N2 to 43.90% CO2. When firedamp is present at 1.25-2.5%, its content must first be estimated by means of the cap and a fifth of its value then deducted from the lamp reading for O2

Dec 1, 1916

When the mining and milling of 1100 copper orebody commenced at Mount Isa a satisfactory grade of copper concentrate was difficult to produce. The major concentrate contaminants were fine pyrite and silica, particularly in the minus 10 microns fraction. Studies of the 1100 orebody showed that much of the fine grained pyrite and a proportion of the silica present in the ore contained carbonaceous matter in the form of complete or partial rims and as internal carbon films disseminated throughout grains. The hydrophobic surface property of the carbonaceous material resulted in inherently flotable fine pyrite and siliceous particles.The addition of a 60:40 mixture of nigrosine and dextrine, initially to a prefloat concentrate of the inherently flotable carbonaceous material and finally to the total copper flotation feed, successfully controlled the flotation rates of the carbonaceous pyrite and silica. The objective of a 25 per cent Cu concentrate grade was then achieved without decreasing copper recovery.

Jan 1, 1971

By G. Demi

The biggest chromium mineral processing plant in Albania is Bulqiza plant. It has been in operation for more than 20 years, treating low-grade chromium ores grade 20 ? 26 % Cr2O3 and producing chromium concentrates grade 48 ? 50 % Cr2O3. About 2 million tons of tailings with 13 % Cr2O3 content are stocked in a dam close to the plant. Mineral processing of low-grade chromium ores with less than 16% Cr2O3 content is unprofitable because the mining expenses are high comparing with the current market prices of chromium concentrate. Recycle and enrichment of existing tailings is profitable, because there are no underground mining expenses in this case and because that this kind of raw material does not need expenses operation of crushing and grinding. The existing plant is in operation for more than 8 years treating existing tailings as raw material. Grade of concentrate in the value 40 % Cr2O3 and Cr2O3 recovery in the value 30-35% in the plant are considered low. The main reason of low concentrate grade and recovery is high content of particles under 100 microns, the slimes, in raw material. In the paper is described the study carried out to improve enrichment of the tailings, as well as analyses of existing process, raw material and products. It is concluded that majority of lost is present in the slimes which are not separated in existing spiral separators and shaking tables. Basing in the study is composed the new flow sheet of recycling and concentration of the tailings to produce chromium concentrate grade 41 ? 42 % Cr2O3 and recovery 60 %, decreasing in this way the concentrate production cost two times. In the paper are presented the tests and results of concentration of particle size fraction under 100 microns, using gravimetric, magnetic and flotation methods, as well as equipment and machines suitable for slimes treatment and concentration.

Sep 1, 2012

By H. Bai, B. G. Thomas

"A three-dimensional finite difference model has been developed to study the liquid steel-argon bubble two-phase turbulent flow in continuous casting tundish nozzles. Experiments have been performed on a 0.4-scale water model to verify the computational model by comparing its prediction with velocity measurements using PIV (Particle Image Velocimetry) technology. The computational model was developed using CFX and then employed to investigate the effects of various casting process variables. A fast, simple inverse model to quantify relationships between those process variables was developed, based on interpolation of the numerical model results, using Bernoulli's Equation and advanced multivariable curve fitting methods. Predictions using this model compare well with plant measurements. The model has been applied to present trends and observations on the relationship between casting speed, tundish depth, slide gate opening, and argon gas injection rate. The results can also be used to predict .the theoretical steel flow rate through the nozzle, so that clogging conditions can be identified in the plant.IntroductionTundish nozzle geometry is one of the few variables that are both very influential on the casting process and relatively inexpensive to change. Designing an effective nozzle requires quantitative knowledge of the relationship between nozzle geometry and other process variables on the influential characteristics of the flow exiting the nozzle. This relationship depends on the flow pattern within the nozzle components. Most previous modeling studies of flow in the nozzle have focused on single-phase flow [1-4]. Argon injection into nozzle is an efficient and widely employed method to reduce nozzle clogging, even though the real working mechanism(s) are still not fully understood [5]. Argon injection may greatly affect the flow pattern in the nozzle, and subsequently in the mold. Therefore, two-phase flow modeling is needed to improve understanding of fluid flow in the nozzle."

Jan 1, 2000

By Kenneth E. Merklin

The heavy media process is now being used extensively throughout the world for the gravity concentration of a great number of different minerals. The process is a commercial adaptation of the heavy liquid procedure which has been used in laboratories for many years to separate mineral of different specific gravities. In the heavy media process, a suspension of finely divided particles in water is used to increase the apparent specific weight of the fluid to the desired separating point. The original heavy media process used sand, galena, pyrite and occasionally other materials as the solid constituent of the separating suspensions. As the process developed, the need for a more universal media meeting the following requirements was recognized: 1. High specific gravity. 2. Resistance to abrasion. 3. Resistance to corrosion, 4. Readily reduced to a suitable size consist for suspension in water. 5. Available in quantity at economical price levels. 6. Easy to recover by a simple method.

Jan 1, 1958

By Harvey W. Parker

The underground industry is challenged by many complex technical and non-technical issues and risks. The most obvious of these are the traditional technical issues that we usually try to address with risk management techniques. However, there are many other non-technical risks that our projects face on a daily basis which we often fail to fully recognize or appreciate. This paper addresses some of the less-technical broad-based risks in order to put them into perspective with the technical risks we face day to day in underground planning, design and construction. The good news is that Risk Management techniques are not always about bad things. For obvious reasons Risk Management is always thought of in terms of the ?downside? of risk (i.e., the identification and mitigation of things that can go wrong). On the contrary, there is an ?upside? of things that might go better than expected. Fortunately, if a deliberate effort is made, the same principles and techniques that our industry uses in Risk Management can be applied toward identifying and quantifying the Opportunities and Benefits that might occur. In this way, the process of conducting risk management programs can not only identify the downside risk but can be used to identify and direct projects to take advantage of the upside of uncertainty (i.e., Opportunities as they arise). This beneficial aspect of risk management programs will be highlighted in this paper together with the importance of the non-technical issues.

Jan 1, 2008

By J. A. McLennan, J. M. Ortiz

Nickel laterite deposits are typically formed from tropically weathered mafic-to-ultramafic complexes. The resulting nickel concentration is found within soil horizons and is mineable with regular dozer units. At the time of mining, digging elevations are needed at selective mining units (SMUs) or representative dozer regions (RDRs). Moreover, for mine planning, the costs due to dilution and lost ore require mining elevations to be specified. A conditional simulation approach is used to calculate “optimum” RDR mining elevations. Multiple realizations of the ore base surface are simulated. For a single bottom surface realization, dilution and lost ore costs are calculated over the entire vertical extent of each RDR. The optimum mining elevation is the elevation where the lowest summed cost of “accepting dilution” and “wasting ore” occurs. The reported RDR dilution is the cost of mining the volume of waste located below the bottom surface and above the optimum mining elevation. The reported RDR lost ore is the cost of not mining the volume of ore above the bottom surface and below the optimum mining elevation. For all ore bottom surface realizations, optimum RDR mining elevations and their associated dilution and lost ore costs are calculated and compiled to represent production uncertainty.

Jan 1, 2006

By J. D. Appleton, J. Ridgway, K. B. Greally

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The results suggest that meaningful geochemical maps can be produced from very low-density surveys, and that existing data sets could perhaps be incorporated into such a map series with the use of a system such as Uniras software. There are still many problems to be resolved, however, including the compatibility of data derived from different analytical methods, and the precise methods to be employed will necessarily require international agreement. Sampling densities should be chosen on the basis of the scale of the geochemical and geological features to be distinguished and will vary from region to region. Reanalysis of selected samples from archives to increase the range of elements determined or to unify analytical methods is only likely to be effective if the original survey was at quite a low density

Jul 1, 1991

By M. G. Fleming, F. Warner, R. W. Boswell, M. J. Cahalan

The annual dinner of the Institution was held at the Savoy Hotel, London W.C.2, on 22 April, 1971. The President, Mr. M. J. Cahalan, was in the Chair; members and guests numbered 320. The toasts of The Queen and Queen Elizabeth The Queen Mother, Prince Philip The Duke of Edinburgh, The Prince of Wales, and the other Members of the Royal Family were proposed and loyally honoured. R.W. Boswell proposed the toast of the Institution of Mining and Metallurgy, the president responded, Professor M.G. Fleming proposed the toast of the guests and Sir Frederick Warner replied

Dec 1, 1971

By Armin W. Stuedlein, Youssef Bougataya

Early stage design of driven piles primarily relies on static analysis based on one or a combination of total and effective stress approaches, the latter known as the method to estimate axial capacity. A database of 85 piles driven in the Puget Sound Lowland region and monitored at End of Driving (EOD) and Beginning of Restrike (BOR) was compiled along with capacities estimated using the CAPWAP procedure. Established soil profiles based on borings with standard penetration tests (SPT), cone penetration tests, and geologic maps were matched with their corresponding unit shaft resistance profiles from the CAPWAP procedure and resulted in more than 1,200 observations. In this study, eight new models were developed to predict the coefficients at EOD and BOR, based on the corresponding USCS categorization. Each coefficient model is formulated using a three-parameter exponential function, calibrated to capture the profile of coefficients with depth. These models could benefit the designer by providing them with a simple, empirical model that accounts for soil type and setup in a smooth, continuous function with depth. A parallel analysis was performed to assess the accuracy and variability of the formulated prediction models to facilitate implementation in load and resistance factor design (LRFD). INTRODUCTION The design of the axial capacity of driven piles during the planning stages of a project is typically based on a static analysis approach. The goals of this approach are to predict the components of capacity, consisting of the shaft and toe bearing resistances, and to assess project concept feasibility and preliminary lengths. In most cases, this analysis is based on empirically-developed methods, such as the total stress method, also known as the method (Tomlinson 1987) or the effective stress method known as the method (Esrig and Kirby 1979; Fellenius 1991). Many other methods, such as those based on in-situ test results exist and rely on correlations of blow counts from the standard penetration test (SPT), and cone tip and sleeve friction resistance from the cone penetration test (CPT), to shaft and toe pile resistances (Schmertmann 1978; Meyerhof 1976; Nottingham and Schmertmann 1975; Nordlund 1963; Eslami and Fellenius, 1997; De Ruiter and Beringen 1979). Although these methods were generally developed using data from specific geological regions, they are often recommended in national design manuals (e.g., FHWA, Hannigan et al. 2006).

Jan 1, 2018

By H. J. Maguire

(Presented by invitation at a meeting of the Spokane Local Section, Feb. 17, 1912.) THOSE familiar with mill-practice understand the work required of an average bucket-elevator, but I wish to call special attention to the wear on the buckets. I have been studying in what manner the life and service of the bucket might be improved, and I feel that an adjustable lip, attachable to each bucket without the aid of rivets, will be of material advantage. For illustration, consider the feed-elevator of a typical mill in the Cur d'Alène district. The ore is carried by water in a launder from the feed-rolls and dumped in the "boot" of the elevator, directly in front of the ascending bucket. Middlings from the return-rolls are similarly handled. Under this condition the bucket not only carries the ore, but also picks it up, and this latter requirement determines the life and service of the bucket. It might be said that it would be better practice to convey the feed to the elevator and dump it directly into the bucket, but at one mill at which this plan was tried the results were disappointing and the rubber belt was badly worn. The wear of the bucket is confined to the lip and the corners which have to pick up the material. When the lip on a corner of a 7- by 12-in. malleable cast-iron bucket is worn down about 3 in., the bucket is of no further value as a carrier and has to be replaced. The worn bucket, containing about three¬quarters by weight of the metal of the original bucket, has a scrap value of about 10 per cent. of that of a new bucket. To the cost of the bucket, however, should be added the time-cost of replacing the old bucket by a new one. This time-cost is considerable when the loss per hour, to cease operating the mill, is about $200. It is out of the question to put lips on a bucket unless the latter was originally fitted with this device. For if it is attempted to fit lips upon buckets not originally provided with

Sep 1, 1912

By Herty, C. H.

Present-day interest in the question of "dirty steel" has arisen primarily from the increasingly rigid specifications on various grades of steel and from the growing conviction that non-metallic inclusions are the source of many of the difficulties in meeting these specifications. The importance of inclusions has unquestionably been over-emphasized in many cases, but on the other hand many unpublished instances could be recorded where all evidence pointed to inclusions as the primary cause for the failure of steel in rolling or in service. The solution of the problem of dirty steel is not a matter of a few years. There are almost numberless types of inclusions. They segregate in steel ingots in an entirely different manner from other impurities, and, at best, only a start has been made in developing correct analytical methods for their determination. Most of the writers in the field have expressed opinions rather than given facts, and so many variables enter into the manufacture of steel that a study of plant conditions is difficult unless definite facts on certain phases of the inclusion problem are available. This statement is not intended to convey the idea that little work has been done on this problem. On the other hand, the number of investigations has been large, but in most cases too many variables have been present to allow definite conclusions to be drawn. In the body of the text, reference to previous investigations is made at suitable points. Rather than burden the reader with a lengthy review of the literature on the general subject of inclusions, reference to the particular works pertinent to the subject matter of the bulletin has been discussed. Three excellent bibliographies b on the subject have been lately published: one by the Committee on

Jan 1, 1957

By Veerendra Singh, NILAMADHABA SAHU, ARIJIT BISWAS

Manganese alloys are important raw materials for steelmaking. However, selective mining of high-grade manganese ore resources has resulted in a scarcity of these high-grade Mn ores (Mn: >42; Mn/Fe: >5). The present research work is carried out to explore a new smelting reduction process to produce high-Mn/Fe syntheticMn ore from low-grade ferruginous manganese ores. Representative samples of low-grade ores (Mn: 25–30%; Mn/Fe: ~1) were collected and smelting reduction studies were carried out using variable smelting power (20–30 kWh), carbon rate (10–20% of ore) and slag basicity (0.1–0.3) to produce high-MnO slag and manganese pig iron. Studies have shown that different-grade high-MnO slags (MnO: 38.57–58.24%; Mn/Fe: >15) and manganese pigs (Mn: 5.16–24%) can be produced at optimum process conditions. The high-MnO slag can be used as synthetic ore for the ferroalloy production process. The developed process is capable to effectively segregate the iron and manganese in the metal and slag, respectively. The optimum Mn and Fe separation (>95%) was achieved by smelting of 10 kg Mn ore batch in a 50-kVA electric arc furnace using 30 kWh smelting power and 0.16 kg of coke. The slag basicity was maintained at 0.3 and the optimum slag SiO2 was ~30%. The studies indicated that the upgrading of low-grade ferruginous manganese ores is a promising solution for achieving high-Mn/Fe-ratio synthetic ores for ferroalloy production. It can help the manganese alloy industry to overcome challenges associated with the scarcity of high-Mn/Fe-ratio Mn ores and efficient utilization of low-grade resources.

Aug 3, 2020

By A. J. Kwitowski

Remote control is usually associated with deep mine, continuous mining machines. This is because thin-seam operation precludes an onboard operator's compartment or the mine has approval to conduct extended cut mining. Using a tethered or radio-linked control box, the remote operator is typically situated 3 to 15 m (10 to 50 ft) from the working face. The operator receives direct operational cues through senses like vision, hearing and feel. Remote control is sometimes touted as a safety feature. However, this is not always true, as operators are not provided protection from roof and rib falls or being crushed between the machine and a rib. Remote control operators are also left exposed to dust and noise. Teleoperation described here is the computer-based, distant control of mining machinery from a protected operator compartment located out of the line-of-sight from the operational site. Video, sound and other sensory information are gathered through sensors and electronically transmitted to and displayed at the operator's location. The teleoperator responds to the information and makes decisions that are initiated by control devices (usually switches). These control commands are then electronically transmitted to the re¬mote machinery and the appropriate machine function(s) are carried out. Teleoperation increases the safety of mining machine operators as it removes them from the immediate vicinity of hazards. The US Bureau of Mines' involvement with teleoperation dates back to 1979. Following feasibility studies, a highwall milling system (HMS) was developed and tested. A deep, thin-seam, room-and-pillar system (TSRPS) has been designed and is currently being surface tested.

Jan 1, 1992

By R. G. Votteler, A. C. Brent

"The business performance of mining corporations in South Africa is adversely affected by the constantly increasing electricity costs. The most commonly used power sources are the national utility supplier via a grid connection, and on-site diesel generators. Previous research has identified the renewable sources of solar photovoltaic (PV), onshore wind, and geothermal energy in hybrid versions with current sources as possible opportunities to counteract rising electricity costs. To provide a clear understanding of the new, developing market of renewable energy sources, this research is divided into two papers. This first paper investigates the internal business structure of mining corporations in order to evaluate electricity generating sources. The multi-criteria decision analysis (MCDA) method is selected as the most suitable approach for this. The paper identifies the criteria used by mining corporations to evaluate possible electricity generation sources for self-generation by means of the corporations’ own investment. Four mining corporations with several mining locations were interviewed. The interviews revealed both new and identical evaluation criteria when the findings were compared to earlier MCDA adaptations analysed in the literature review. The second paper (Part 2) combines current knowledge about the external macroeconomic environment with the findings about the internal environment described here. MCDA is adapted in Part 2 and implemented to analyse and compare current to hybrid renewable sources from the perspective of mines. IntroductionMining corporations in South Africa are currently adversely affected by increasing electricity prices. Electricity is supplied mainly by Eskom1 and, especially in remote locations, by on-site diesel generators (Boyse et al., 2014). Electricity price increases, emanating from diesel price hikes and Eskom, have escalated the total operational expenditure on electricity by the largest mining corporations from 8% to 20% of total operating costs in the past seven years (EIUG, 2015). The reliability of electricity supplied by Eskom has decreased drastically (Govender, 2008), and the prices will increase annually by at least 13% until 2018 (Numbi et al., 2014; Eskom, 2015b). In addition, the South African government plans to introduce a carbon tax on greenhouse gas emissions (Alton et al., 2014)."

Jan 1, 2017

By Grey CA

Any economic evaluation of a lead-zinc mining project requires the estimation of net revenue per tonne of concentrate at the "mine gate". The value at the mine gate equals the Net Smelter Return minus all realisation costs. The paper develops a simple predictive model for Net Smelter Return based on metal prices.

Jan 1, 1990

By M. B. Kime

"A set of experimental batch leaching tests studied the effect of pH, time, temperature, and stirring speed on the relative Cu, Co, Ni, and Fe leaching yields of an oxidized copper-cobalt ore sample in an aqueous hydrochloric acid solution. The results were statistically analyzed and modelled using the structural equation modelling method. Models showed that Cu, Co, and Ni leaching yields were strong functions of the leaching time and leaching temperature, whereas the Fe leaching yield depended on the leaching temperature, stirring speed, and pH. Under optimum leaching conditions yields were 99.8% Cu, 82.4% Co, 91.3% Ni, and 30.6% Fe.RÉSUMÉ Une série d’essais expérimentaux de lixiviation en bâchée ont été menés pour étudier l’effet du pH, de la durée d’attaque, de la température et de la vitesse de brassage sur les rendements relatifs de lixiviation du cuivre (Cu), du cobalt (Co), du nickel (Ni) et du fer (Fe) d’un échantillon de minerai de cuivre-cobalt oxydé dans une solution aqueuse d’acide chlorhydrique. Les résultats ont été analysés et modélisés statistiquement à l’aide de la méthode de modélisation par équation structurelle (SEM, de l’anglais structural equation modelling). Les modèles ont montré que les rendements de lixiviation du Cu, du Co et du Ni dépendaient énormément de la durée d’attaque et de la température de la lixiviation ; le rendement de lixiviation du Fe, quant à lui, dépendait de la température de la lixiviation, de la vitesse de brassage et du pH. Dans des conditions optimales de lixiviation, les rendements étaient de 99,8 % pour le Cu, de 82,4 % pour le Co, de 91,3 % pour le Ni et de 30,6 % pour le Fe. INTRODUCTIONThe Katanga province in the Democratic Republic of Congo hosts the northwestern part of the Central African Copperbelt. This region abounds with large, rich deposits of sulfide and oxidized copper-cobalt ores. In general, the main valuable minerals present are malachite (CuCO3Cu(OH)2) and heterogenite (CoO(OH)). Common impurities found in heterogenite are Cu, Ni, Si, Al, Mn, and Fe. The substitution of Co by other cations (e.g., Cu, Ni, and Fe) has an influence on the crystallinity of heterogenite (Deliens, 1974). In general, well-crystallized varieties of heterogenite have lower impurity contents, whereas amorphous heterogenite types usually contain more impurities (Thys et al., 2009). Further, in heterogenite, Co can occur in the 2+ and 3+ oxidation states. The gangue generally consists of quartz (SiO2), talc (Mg3Si4O10(OH)2), kaolinite (SiO2·Al2O3·2H2O), limonite (Fe2O3·3H2O), and goethite (FeO(OH)). Oxidized copper-cobalt ores are often treated by hydrometallurgical methods, whereas sulfide ores are often treated by flotation or pyrometallurgy, depending on their grades. Hydrometallurgical methods typically entail selectively dissolving the metals of interest (Cu, Co, and Ni) in aqueous solutions (leaching), transferring the dissolved metals to an organic solution, and retransferring these to a second aqueous solution (solvent extraction). Copper and nickel are readily dissolved in an acidic aqueous media. In contrast, cobalt is difficult to dissolve, especially if it is present in the third oxidation state; however, this species becomes soluble after it is reduced to Co2+ (Mwema, Mpoyo, & Kafumbila, 2002; Kime & Makgoale, 2016)."

Jan 1, 2017