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By V. Srivastava, T. Ghosh

The modeling and simulation of semiautogenous (SAG) mills have been widely used in the design and optimization of mill performance in terms of its power draw, processing capacity and product size distribution. However, these models are solved under steady approximation and do not provide any information on mill charge distribution in real time. 7KLVSDSHUDWWHPSWVWRFKDUDFWHUL]HPLOOFRQWHQWVE\VROYLQJ:KLWHQ¶V¿UVW RUGHUFRQWHQW EDVHGPRGHOLQWKH0$7/$% Simulink environment. The parameters in the model, such as breakage rate constant, discharge rate and appearance function, were estimated using process and design data collected from a gold mine operating in Alaska coupled with a nonlinear parameter estimation scheme. This model was then used to predict the dynamic responses of other key operational variables, such as mill power, bearing pressure, charge level and product size distribution. The transient response of mill behavior with respect to changes in feed size distribution, tonnage and mill feed water is also presented. This dynamic simulation approach can be used for practicing different control strategy and training purposes. The observed response of mentioned variables was validated using dynamic response data from the plant to encompass operational characteristics of SAG mill behavior.

By John F. Shea

When Dick Robbins asked me to give a keynote address, I felt it might be in order to review some of the practices and techniques used in tunneling and work up to some of the concepts now used to mine and construct tunnels. Needless to say, there have been many changes in tunneling technology and also many changes in the Safety Codes controling them. An example of this latter change was the fact that in 1931, my father excavated the Owyhee Tunnel No.5 with gas locomotives. He was able to do it because there was no natural gas in the rock and the ventilation system was designed to free the tunnel atmosphere from powder and exhaust fumes. Today OSHA rules would never permit gas locomotives underground, although there were no incidents on this particular project. One of my first tunnels, as Project Manager, was the Clear Creek Tunnel for the Bureau of Reclamation. Our method of handling muck was the Conway Muckers. This unit was a valuable improvement to the hand mucking of previous generations. The Conway was also used in our Navajo Project, in New Mexico. Unlike the Clear Creek project, where water was one of our main problems - up to 7,200 gallons per minute, at a pressure of 395 pounds per square inch - in the Navajo Tunnel, we had a mixed face which caused a major problem with our support system. In one of the Navajo Tunnels, there was a major cave-in, when the squeezing shale came in during an attempt to strengthen the support system. Although moving shale was not a constant problem, there were areas where the shale was five to six feet above the spring line.

Jan 1, 1976

By Lj. Obradovic

The aim of this paper is to study the feasibility of copper and gold recovery from the old flotation tailing dam at Bor, Serbia. Laboratory leaching experiments were carried out using a composite sample taken by drilling from 16 - 40 m depth. Different oxidation agents as FeCl3, Fe2(SO4)3 and H2O2 were used. An H2SO4 solution with a pH less than 3 was used for leaching. The influence of a number of parameters on the recovery of both elements as temperature, pH, duration of leaching and concentration of oxidation agents was also studied.

Jan 1, 2006

By Christina Dahnér, Kristina Jonsson, Savka Dineva

The iron-ore underground Kiirunavaara mine (Sweden) has been seismically active since 2008. In 2021 the production is on levels 1079 and 1108 m, at the deepest. The seismic activity has changed in character over time with one step change in 2015 when the number of large (ML>2) seismic events increased, and another one when the mine experienced a seismic event with Mw 4.2 in 2020. In 2017, the mine evaluated Hydraulic Fracturing (HF) as a possible mitigation technique for larger seismic events and a one-hole trial was performed. The trial proved promising, and it was decided to go forward with a large-scale trial covering an entire production area in the mine. The large-scale trial consists of 25 fracturing holes, 50 – 100 m long, running along 500 m out of the ~4500 m long orebody and spanning between production levels 1108 m and 1252 m. The fracturing process continued for a year, resulting in ~38,000 seismic events with −3.3<ML<1.4. The breakdown pressure varied between fractures in the same hole as well as between holes in the same area. Average breakdown pressure per hole was between 12 MPa and 50 MPa. The seismic response to HF in 2021 varied greatly from hole to hole and between fractures in the same hole. The variation in response could be related to the geological conditions and the infrastructure, such as large caving ore passes. In this paper some details about the experiments and broad preliminary analysis of the effect of the HF by using seismic source parameters of the induced seismic events are presented: 1) Distribution of seismic activity, 2) the ‘equivalent’ magnitudes for each hole calculated from the cumulative seismic energy and seismic potency released during the fracturing, compared with the local geological conditions; 3) the predominant failure mechanism of the seismic events caused by HF was defined. A difference in the behaviour between larger and smaller events was noticed, as ML>0 events seem to be compression type failures and ML<0 events seem to be related to slip on pre-existing structures. No seismic events related to creation of a new fracture have been identified yet.

Apr 26, 2022

By L. Nahai

In an exchange of views with the Program Chairman for the Technical Session on Industrial Minerals and Investment in Foreign Countries, it was agreed that it would be more interesting to approach the problem of mineral investment in foreign countries in a more general framework and not confine it to industrial minerals. Therefore, this Bureau of Mines report is proposed to examine current attitudes toward investments in foreign mineral resources and restraints that they impose on investments necessary to assure supply for future global mineral needs.

Jan 1, 1976

By Philip Antunes, A. E. (Tony) Reschke

"INTRODUCTION Tunnel Boring Machine (TBM) operations require the injection of material into the annular tail voids as the machine advances ahead of the segmental concrete lining. This annular gap is created because the cutting diameter of the TBM has to be larger than the outer diameter of the concrete segments of the tunnel lining. Fundamentally, the two basic types of annular grout are thick, concrete like mortars and thin, mobile, two-component grouts. While some European countries seem to still favor the concrete like mortars, from a global perspective it is now the two-component type grouts that dominate the industry. Two-component type grouts are comprised of an “A” component grout (typically cement, flyash, bentonite and a retarder/stabilizer) and a “B” component accelerator (sodium silicate or water glass as it is sometimes known). They are thus sometimes referred to as A/B type or bi-component grouts and were pioneered by the Japanese over 30 years ago. They offer a host of operational benefits over thick mortars, such as reduced settlement (Feddema et. al., 2001), effective penetration of the void space, with less energy, and reduced strain on the segmented linings (Robinson et. al., 2007). Two-component grouts are highly mobile and can be pumped many kilometers. The use of a retarder/stabilizer can also extend the shelf life of the “A” component grout for several days while the early strength of the accelerated grout stabilizes the ground and supports the segmental liner almost immediately. The batch plants that prepare the two-component grouts use one of two possible mixing methods for preparing the “A” component grout. The simplest plants use paddle type mixers and numerous tunnels worldwide have been successfully grouted using this technology. However, a superior type of mixer is available, namely the high shear colloidal mixer. Keller Colcrete successfully pioneered the development of the colloidal mixer back in 1937 and for over 75 years colloidal mixers have been internationally recognised as the most efficient method of mixing cement based grouts (Houlsby, 1990). These mixers are used in grout preparation for radioactive waste encapsulation, hydro dam grout curtains, soilcrete jet grouting, soil nailing, and numerous other geotechnical applications. In tunnelling, these mixers are also used for ground treatment, compensation grouting and for the preparation of bentonite lubrication for pipejacking. It has been only within the last decade however that these high-shear colloidal mixers have been adapted for use in the preparation of two-component grouts."

Jan 1, 2016

By M. L. Klohn

The Felder ore deposit is a 5,000,000-pound uranium deposit in the South Texas Coastal Plain. It occurs in the basal sand of an Oakville Formation (Miocene) alluvial system. The host sand is a carbonate-rich arkose which contains virtually no carbonaceous debris and has been reduced by the local introduction of hydrogen sulfide. The ore lies well within the reduced zone and occurs as coffinite and uraninite that fill interstices and coat and replace grains. The overall geometric configuration of the ore is that of a winged, crescentic ore roll. Weak mineralization extends the wings of the ore roll and gives greater expression to the roll character. Departures from the shape are controlled by discontinuities in bed- ding and by proximity of the ore to the surface. Associated with the uranium is a broad halo of anomalous molybdenum. Subsidiary mineralized trends suggest a pre-existing up-dip position for the main roll. Oxidation from the surface largely destroyed this previous roll by solubilization of uranium. Uranium subsequently migrated into favorably reduced sand and reprecipitated at the present roll position.

Jan 1, 1970

By W. N. Hamilton

British Columbia is geologically favourable for a rich variety of industrial mineral occurrences. Some have been produced for years, others overlooked until recently. Major production occurs for asbestos, gypsum, limestone, magnesite, silica and sulfur; lesser production for a dozen others. For several of the minerals, potential is much greater than existing production. New production opportunities exist also for diamonds, niobium and REE minerals, fluorspar, kyanite, nepheline syenite, talc, and several others. Alberta, though geologically less diverse, also has many industrial minerals. Limestone, salt and sulfur have the major production; clay and shale, silica, sodium sulfate and a few others lesser production. Opportunities exist for expanded production, and for new production in heavy (Ti -Zr) minerals, formation brines (Ca-Mg-I-Li), and gypsum.

Jan 1, 1987

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 Randall E. Hughes, John F. Burst

This chapter describes the nature and occurrence of the principal clay minerals that are used as ceramic raw materials, explains how these raw materials are used to produce finished goods, and summarizes positive and negative trends that will affect future demand for raw materials and products in the ceramic industry. The term ceramics was derived from the ancient Greek keramikos (a clay jar). A ceramic product is a material that has been fired to at least 468.3°C (Mitchell, 1983). In addition to being one of our earliest manufacturing and construction materials, ceramic products are among the earliest records of civilization. The enduring significance of ceramics is shown by the fact that, even today, the manufacture of whitewares, brick and related red-fired wares, refractories, and engineered ceramics continues to be a major sector of the US economy. A wide range of materials can be made into ceramic products, although relatively few earth materials make up most of the ceramics in today&apos;s markets (Table 1). Most ceramic products are made from clay or a related material. The long history of clay use in the ceramics industry stems from its variable and sometimes unique physical and chemical properties, as well as its ubiquitous occurrence and relatively low cost. Clay is important to ceramics because of its plasticity, moldability and filterability, chemical content, color. refractoriness, solubility. corrosion resistance, electrical properties, and other properties that result from the essentially two dimensional morphology of the individual clay mineral platelets. Because of their basic relationships to the chemical and physical properties of clays, the chemical and mineralogical content have been the subject of continuous studies over the past few decades. Advances in knowledge about the chemical, mineralogical, and physical properties of clays are responsible for most of the advances in processing. The need to remove off-colored contaminants, minerals with low melting points, and soluble salts has resulted in beneficiation by wet processing methods such as water washing. Water washing is restricted to kaolins, although low cost methods of water washing have been extended more recently to ball clays in Europe. High intensity magnetic filtration and flotation technologies have noticeably improved the quality of kaolins and broadly expanded their use in the ceramics industry. In addition to products for construction (e.g., brick, tile, sewer pipe, field drain pipe, cement, fiberglass, roof granules, and paint) and manufacturing (e.g., refractories, kiln furniture, sanitary ware, pottery, and dinnerware), clays are used in calcined form as ceramic fillers, carriers, extenders, and grogs. Ceramics suppliers are under economic pressure in several of these product areas. Manufacture of refractories in America has declined as steel production has decreased. Similarly, dinnerware and tile production have declined because of foreign competition. Fortunately, new uses for clays,

Jan 1, 1994

By S. J. Schatzel, K. M. Ajayi, Z. Khademian

The integrity of unconventional shale gas well casings positioned in the abutment pillar of a longwall mine could be jeopardized by longwall-induced deformations. Under such scenarios, the surrounding fracture networks could provide pathways for gas flow into the mine creating safety concerns. To provide recommendations for developing guidelines that ensure a safe co-existence of longwall mining and unconventional shale gas production, this study evaluates the impact of parameters that could affect potential shale gas flow into the mine in the event of a casing breach using a discrete fracture network (DFN) model. These parameters are evaluated using a conceptualized DFN realization that is representative of the fractured zone in the overburden, and the range of parameter variations are within values validated with field measurements. The results show that a decrease in fracture aperture (potentially due to longwall-induced stress in the likely vicinity of the breach location) reduces the potential gas flow to the mine by a significantly higher proportion. A 50% decrease in the aperture of the fracture that directly transports the gas from the casing breach location reduces the gas flow to the mine by over 70%. Similarly, changes in the fracture water saturation level significantly affect the gas flow. In all cases, the potential gas flow to the mine is higher if the casing breach occurs at an increased gas well pressure. These findings provide critical information regarding the impact of each of the parameters associated with gas flow in the event of a shale gas casing breach near a longwall mine and could help towards the development of guidelines to ensure a safe coexistence of both industries.

Mar 2, 2022

By P. S. Hettinger

Land Application Discharge (LAD) is a useful method of disposing of waste water from mining operations and in certain climatic regimes, stormwater runoff. LAD systems function under the premise that metals, salts and nutrients in water are dispersed over a large area and are effectively assimilated into the soil profile. Depending on the soil structure, migration or mobilization of dissolved metals through the soil profile can be Substantially reduced. Land application of treated effluent from sewage lagoons or waste water plants was probably the first general use of land applied water. LAD has gained popularity with the mining industry as a means of disposing of waste water and process water. In addition, large volumes of snow meltwater and stormwater are often placed in storage in Montana during spring, and Land Application Discharge has shown to be an effective method for disposing of stormwater during the dry, summer season. LAD can also provide an alternative to recycling or treating waste water at on-site waste water treatment plant&. Application of stormwater or process water can result in little or no change to the background concentrations of metals in baseline water quality samples. One cautionary note about LAD: high salt concentrations and pH values are associated with process water from heap-leach facilities and are known to cause burning of local vegetation. Some pre-treatment of process water may be necessary to prevent such environmental problems.

Jan 1, 1994

By L. L. Newman, K. D. Ferguson

Traditional methods for mine waste management produces two waste streams and the construction of separate disposal facilities. Tailings impoundment design is usually controlled by physical stability problems. Alternatively. the waste rock offers high stability characteristics but hydraulic properties that create ideal conditions for oxidation. The problem of oxidation is significantly reduced for tailings due to a fine texture that augments water saturation. This paper introduces concepts for the co-disposal of tailings with waste rock and evaluates the physical behaviour of an integrated waste system. &apos;he potential benefits of co-disposal are shown for a typical mine such as Equity Silver.

Jan 1, 2000

By Jamal Rostami, Tala Tahernia

TBM utilization rate is a component of machine performance prediction and critical for developing a reliable estimate of the construction completion time and cost of the tunnel. Estimation of the utilization rate involves identifying and quantifying the time dedicated to each activity in a tunneling jobsite. Ring building is a common activity in TBM tunneling and takes a large amount of tunnel excavation time when using shielded TBMs. This paper concentrates on the effect of tunnel diameter on the duration of downtimes related to ring building and examines the impact of machine diameter on downtimes. For this purpose, the dependency of segment installation time to segment configuration, and also the diameter of the tunnel was investigated. Furthermore, the ring building time for four tunnels with different sizes of diameters and a variety of ring arrangement were analyzed and the relationship between TBM diameter and segment installation time and consequently TBM utilization was evaluated.

Jun 13, 2021

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

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

Jul 1, 2023

By Chester R. McKee, Amar C. Bumb, Kohei Kawakita

Unlike many other heavy metals, gold can be profitably mined in small operations because of the prices. One mining technique that seems ideally suited for small deposits of gold and for certain large, lowgrade oxidized disseminated deposits is solution mining. Solution mining generally requires lower capital investment and operating costs than conventional mining and milling and is safer and less degrading to the environment. Although gold has long been recovered by cyanide leaching following conventional milling, solution mining as discussed here gained momentum only in the past two decades, during which time alternative lixiviants instead of cyanide have been researched. Chamberlain and Pojar (1981) classified solution mining systems used today as three types, namely heap, dump, and in-situ leaching.

Jan 1, 1990

By Roger P. Ashley

The main problem in geochemical exploration for gold ore bodies in the 40 km2 hydrothermally altered area at Goldfield is to decide which of the many silicified ledges exposed are most likely to yield deposits with additional subsurface exploration. We conclude that the most efficient way to search for exploration targets is to collect rock samples from the ledges and analyze for the following elements in decreasing order of priority: gold, lead and silver, bismuth, and mercury. These elements form relict hypogene aureoles restricted to the ledges and are not appreciably redistributed during supergene leaching.

Jan 1, 1978

By A. Bhagavatula, M. Rezaee, M. J. Kiser, R. Q. Honaker

"A field study of the coal preparation plant fleet in the eastern United States was undertaken to determine if quantify of rare earth elements (REEs) present in the product streams are large enough to justify further concentration. Representative composite samples were taken from the clean product, coarse refuse, and fine refuse streams from 20 coal preparation plants. Each stream was then separated into various size and density classes and analyzed for ash and REE contents. The large database showed that coarse refuse contained the largest amount of REEs, although the ratio of heavy to light REEs was greater for the clean coal products. The concentration of REEs was also compared to that typically seen in the earth’s crust. This enrichment ratio ranged from approximately 1.5 to more than 4.0 as the ash content varied. The database also showed that a linear correlation existed between La and Ce for many REEs of interest, although there were several notable exceptions for some of the high-value REEs. INTRODUCTION Worldwide energy demand is expected to grow by as much as 37% by 2040 according to the International Energy Agency (2014). This growth, coupled with a decrease of the reliance on coal to generate energy, means that it is more important than ever for countries to secure the materials necessary to meet its energy projections. For the United States, the U.S. Energy Information Administration (EIA) predicts that total domestic electricity use will increase roughly 25%, from 3,836x109 kWh in 2013 to 4,797x109 kWh in 2040 (EIA, 2015). In the EIA’s reference case, coal’s contribution to electricity generation drops from 39% in 2013 to 34% in 2040. On the other hand, renewables share of electricity generation grows from 13% to 18% for the reference case. Compared to its current state, renewable energy electricity production is predicted to grow as little as 50% to as much as 121% over this time period, depending on the economic case being examined. This growth will largely be seen in the wind and solar sectors (EIA, 2015). The focus on viable renewable energy resources will be crucial to the future of fueling American growth. Many of the renewable energy technologies, such as wind turbines and photovoltaic films, rely on materials and supply chains outside of the United States. The lack of a reliable and low-cost domestic supply could pose a threat to the growth of the renewable energy markets in the United States. This potential vulnerability recently led the United States Department of Energy (DOE) to create a Critical Materials Strategy Report. In this report, 15 elements were identified as critical for the continued growth of the renewable energy market. Eight of these elements were rare earth elements (REEs). Five REEs (dysprosium, neodymium, terbium, yttrium and europium) were identified as highly critical and vulnerable to shortages (Bauer et al., 2012)."

Jan 1, 2016

By J. W. Jang, I. Iwasaki

Introduction Grinding ball wear in wet grinding is due to a complex combination of abrasion, corrosion, impact and their interactions. The ball charge is continually falling from a height greater than half of the ball mill&apos;s diameter, and contact is made with ore particles or other balls. Abrasive wear occurs through penetration and plowing of media materials from the ball surface by hard ore particles (Gangopadhyay and Moore, 1985). Electrochemical interactions between the abraded and unabraded areas of the ball surfaces, as well as between the grinding media and the minerals, occur in grinding mill pulps (Adam et al., 1986). The wear depends on the media composition, the hardness and the corrosive/abrasive characteristics of the slurry. The marked-ball-wear test method was used to evaluate the performance of grinding media under nitrogen and oxygen atmospheres. Also, the wear mode was studied by observing the grinding media surface under a scanning electron microscope. In general, grinding media of high hardness and high chromium contents were found to have better corrosive wear resistance than those of low hardness and low chromium contents (Jang, Iwasaki and Moore, 1988). The purpose of this investigation was to determine the size distribution and the shape of wear debris in a study of the wear rates and wear behaviors of grinding balls. Experimental Materials The grinding ball alloys used in this investigation were: •martensitic stainless steel (MSS; 0.96% C and 16.2% Cr), •high-carbon, low-alloy steel (HCLA; 0.89% C and 0.53% Cr), and •mild steel (MS; 0.22% C and 0.09% Cr). The mineral used in this study was synthetic corundum, because it was on hand and contained no magnetic impurities. Debris A 203- mm (8-in.) diam porcelain mill was used for grinding the corundum. The mill charge consisted of: •1200 g of 12-grit synthetic corundum, •770 mL of 0.05 mole/L Na2SO4 (61% solids), and •125 steel balls of nominally 25-mm (1-in.) diam. To minimize the debris corrosion, nitrogen was introduced into the mill. Grinding with MSS, HCLA-steel or MS balls was conducted for 2 hr at 51 rpm. The grinding time using the MS ball was varied from 0.5 hr to 2 hr in an attempt to study the debris amount and shape as a function of time. The debris was collected with a hand magnet from the ground slurry and separated from the corundum particles using a Davis magnetic tube. After the separation, the debris particles were immediately washed with acetone and then filtered and dried. Debris size analysis Buckbee-Mears 3-in.-diam, micro-mesh sieves and an electromagnetic shaker were used for determining the debris size distribution. In sieving, isopropyl alcohol was used. The debris fraction collected from each sieve was washed with acetone, dried and then weighed on an analytical balance. [ ]

Jan 1, 1993

By Jan Jekielek

Increasing capacity of bulk material handling systems creates difficult problems for accurate in-line material weight measurements. At the same time increasing system complexity and growing user demands call for more measurements. Precision in-line weight measurements for bulk materials are usually accomplished by application of conveyor belt scales. Belt scale accuracies listed by scale vendors are applicable for ideal situations with suitable conveyor design, belt scale location and calibration means. This paper attempts to provide designers and users with simple means to evaluate belt scale accuracy for practical scale installations. Based on known mathematical models simplified formulas for measurement errors are derived and discussed. These formulas allow for simple determination of achievable accuracy for alternative scale installations on the conveyor, conveyor designs, etc.

Jan 1, 1979