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By Kenneth J. Edmiston

The objectives of this paper are: to review the current status of chloride leach processes for sulfide concentrates, to make an evaluation as to the applicability of chloride leaching for replacing pyrometallurgical processes and to comment on recent advances in construction materials. The paper does not delve in detail on process chemistry. Sufficient references are presented on each process to allow the interested researcher to obtain process chemistry details. GENERAL The fact that chloride oxidates can solubilize base metals from sulfide concentrates has been known since the 1880's. The work of Hoepfner in 1902 was particularly accurate for its time with regard to the chemistry of chloride solutions. Recent work has dealt with the understanding of chloride extraction thermodynamics by modelling the behavior of metal chloride complexes. In the last several years several excellent review articles and symposiums have been issued covering chloride chemistry (1 thru 6).

Jan 1, 1984

By John Carr

The tremendous growth in grinding mill size and horsepower during the '70s demanded advancements in gear cutting technology and equipment for the '80s. Computers are used as an aid in the design and selection of the mill drive system; sophisticated computer graphics are used to create manufacturing drawings; and a new generation of gear cutting machines are used to manufacture the gears. These new gear cutters can generate-cut gears over 40' (12.2 m) in diameter at an AGMA quality level exceeding the currenty acceptable standards. The precision of the resulting gear assures maximum tooth contact, which will result in longer gear set life.

Jan 1, 1981

By C. Zhou, J. Srednicki

Electronic systems have been increasingly used in underground mines to improve mine safety. These electronic systems emit electromagnetic (EM) energy which can adversely impact the performance of other electronic systems nearby and thus should be characterized. Researchers at the National Institute for Occupational Safety and Health (NIOSH) characterized the magnetic fields emitted from devices that can potentially interfere with the performance of proximity detection systems (PDSs) and compared the emission levels of these devices to the susceptibility of PDSs. In this paper, we present our measurement results pertaining to this effort. Particularly, magnetic fields emitted from the different orientations of a powered air purifying respirator (PAPR) and two lite trackers are evaluated based on the RE101 protocol specified in the MIL-STD-461G standard. The results show that both devices emit strong magnetic fields which strongly depend on the orientation of the devices. At some frequencies, the maximum emission levels from the two devices exceed both the emission limit given in MIL-STD-461G and the maximum magnetic fields that a PDS can withstand without a failure. The results and findings in this paper can help the mining industry better understand electromagnetic interference (EMI) underground and provide critical scientific data that support mining-specific recommendations to address EMI-related challenges.

Feb 1, 2023

By Edwin K. Maughan

The Rocky Mountain region contains part of the paleocontinental shelf that lay in Arizona and New Mexico through Utah, Colorado, and Wyoming into Montana and North Dakota. The shelf was bounded by the northeast-southwest-trending Transcontinental arch and the Cordilleran miogeocline in late Paleozoic and early Mesozoic time. Major tectonic features that affected middle Phanerozoic sediments on the shelf were the Big Snowy trough and Williston basin in the north and the ancestral Rocky Mountains in the central part of the region. The Zuni uplift and similar positive areas occurred along the axis of the Transcontinental arch in the southern part. The late Paleozoic and early Mesozoic sedimentary rocks record transgressive-regressive marine cycles in which the Cordilleran shelf and much of the adjacent craton were inundated by epeiric seas. Early in the Carboniferous, an epeiric sea covered most of the shelf. Greater topographic relief developed in Late Mississippian, was at a maximum in Middle Pennsylvanian, and then diminished through Permian and Triassic time. The development in the Pennsylvanian Period of horsts and grabens along northwest- trending faults on the northwest flank of the Transcontinental arch resulted in the ancestral Rocky Mountain system. The eastern part of the region was emergent by Middle Triassic, and the emergence lasted until Middle Jurassic, owing to uplift along the Transcontinental arch. During the early part of the Mesozoic, the sediments were dominantly terrigenous and were deposited mostly in shallow littoral marine environments shifting to continental. Most middle Phanerozoic structural elements within the area of the shelf are characterized by lineaments that have either an east-northeast or a conjugate north-northwest trend. The east-northeast lineaments closely parallel the northeast trend of the continental slope (miogeocline) in Nevada to southern Idaho. The conjugate set closely parallels the northwesterly continuation of the miogeocline north of an approximately right- angle bend in south-central Idaho. The northeasterly trending Transcontinental arch and the northwest-trending margin of the Canadian Shield are parallel structural elements with the north- east and northwest trends of the miogeocline. The rectangular lineament pattern on the shelf suggests a system of rectilinear fractures within the underlying Precambrian crystalline basement rocks that moved several times in the Phanerozoic in response to external forces applied against the continental crust. Movement of these blocks influenced erosion, deposition, and lithofacies of the sediments in middle Phanerozoic time. Zones of crustal weakness, represented by the lineaments bounding these blocks, probably were influential in localizing sedimentary mineral accumulations and petroleum deposits, as well as later igneous intrusions, volcanism, and emplacement of hydrothermal ores. Igneous activity in this region was rare during the middle Phanerozoic, but these conjugate fractures seem to have been avenues for later passage of hydrothermal solutions responsible for ore emplacement.

Jan 1, 2013

By E. J. Mayhew

Bentonite and newly discovered deposits of sepiolite, saponite, and hectorite are now being processed and marketed from the Amargosa Valley of Nevada. All of these deposits are large. The bentonite has been known for decades and is the whitest known. The only other sepiolite deposit is in Spain. The only other commercial hectorite deposit is at Hector, California. No other saponite deposit is known. All the components except bentonite are hydrous magnesium silicates. The bentonite is mixed layer Na-Ca. All the materials have characteristics unique to their locale and type, such as high yield point for drilling muds and liquid suspending agents. The sepiolite has geothermal stability. Figure 1.

Jan 1, 1979

"The seventh annual Mineral & Metallurgical Processing Division (MPD) student poster contest was held last February at the SME Annual Conference & Expo in Phoenix, AZ. A total of 21 students entered the poster competition. The students were required to submit one-page abstracts, which were reviewed by the judges, after which they prepared posters to display their work. A panel of judges went to each student and listened as the student explained his/her research in five minutes.The students worked hard at their research and then set aside time to complete all the necessary steps to enter the competition. Recognizing the effort required to participate, the MPD provided monetary rewards to all participants. First place received $1,000; second, $500; and third through seventh, $200. All remaining entrants received $100 each. The winners have their abstracts published in this issue of Mining & Metallurgical Processing. As in past years, there were separate levels of competition for undergraduates and graduates.Now for the winners:Graduate winnersJoseph Halt won first place for research on the use of additives to starch binders to create iron ore pellets. Vivek Agarwal received second for working on using solvent extraction to concentrate lanthanum. Jordan Rutledge placed third for utilizing tannins to depress calcite in fluorite flotation. Fourth through seventh places were Vu Truong, Jacob McDonald, Hunter Sceats and Doug Schriner.Undergraduate winnersLaura Nugent won first place for using high-frame-rate cameras to follow bubbles as they moved from the pulp to the froth in flotation cells. Taylor Graham earned a second-place finish by researching how to acid leach low-grade manganese carbonate.Although its cliché to say everyone’s a winner, everyone can benefit from attending the MPD Student Poster contest. All the students were able to display their work to potential future employers, and industry professionals could talk to the up-and-coming engineers. Next year, there will be another competition for more posters and networking, so get ready to attend.Thank you to all the students for participating; Lisa Schlink for chairing the session; the judges, Aaron Noble, Debra Switzer, Mohammad Rezaee, Nick Gow and Ren Bryce, for evaluating the abstracts and posters; and the MPD sponsors for supporting the competition. This has only been successful with the input of all three groups. Engineering iron ore pellets to reduce their dustinessJ.A. Halt and S.K. KawatraGraduate student and professor and chair, respectively, Department of Chemical Engineering,Michigan Technological University, Houghton, MI, USAIntroductionIron ore pellets are hard spheres made by agglomerating iron ore concentrate and binders. Pellets are the preferred ironbearing feed for blast furnace ironmaking. Starch has been proposed as a binder because it has good adhesive properties, does not contaminate pellets and is relatively cheap. However, starch binders typically lead to weak pellets with rough surfaces, and these can cause high levels of dust within process equipment and when pellets are handled and shipped (Halt and Kawatra, 2014). Our research shows that by adding a small quantity of other additives, pellets made with starch binders become smooth and strong. The newly designed binder leads to significantly lower levels of fines when pellets are handled."

Jan 1, 2016

By W. Missildine, J. K. Hrica, I. Benbourenane, T. J. Orr, J. L. Bellanca

Each year, haul truck accidents account for a large portion of mining injuries and fatalities. To better understand why these accidents continue to occur, researchers from the National Institute for Occupational Safety and Health (NIOSH) utilized a cognitive task analysis methodology to identify the user requirements of surface haul truck operators and assess differences in perceptions between operators, managers, health and safety professionals, trainers, and maintenance personnel. Additionally, researchers used the critical decision method to focus on better understanding the cognitive demands, decision-making, and problem solving during nonroutine incidents. The preliminary results of this study identify and explore themes within the broad categories of hazards, skills & expertise, and training and provide detailed accounts of nonroutine incidents such as near-misses, loss of control, and collisions. These accounts reveal insights into operator decision making and event progressions that can then be used to build more realistic training scenarios and address hidden hazards and root causes of these incidents. These results, along with potential solutions offered by study participants, can inform future research and help identify creative interventions that can be used by mine operators to address haul truck safety issues

Mar 2, 2022

By H. Dho

The role of sodium silicate in the anionic flotation of a Florida phosphate ore was investigated using laboratory continuous flotation tests, frothability tests and SEM observations. In the absence of sodium silicate, Ca++ promoted the unwanted activation of quartz by forming calcium bearing precipitates. The addition of sodium silicate enhanced the flotation efficiency through: (1) the removal of impurity minerals and calcium-bearing. precipitates from quartz surfaces by dispersion, (2) drier and more persistent froths stabilized by oily droplets containing calcium silicate precipitates, and (3) higher specific flotation rates of phosphate relative to quartz, leading to faster flotation rates and increased selectivity of separation.

Jan 1, 1990

By Burton H. Boyum

The paper generally reviews the iron ore occurrences and regional geology of Western Australia, but features in particular the mesa deposits of PJasic Materials - Cliffs International. Initial production is planned from a aeries of mesa deposits of Eocene-Oligocene age. The ore is oölitic to pisolitic goethite and hematite. Source of the iron in the mesa deposits is thought to be from the Precambrian iron-formations. The geology and occurrences of the mesa iron ore deposits are summarized and illustrated.

Jan 1, 1964

By J. A. Herbst

Until the past decade, the energy-size reduction relationship was the dominant form of mathematical model used in the description of tumbling mill grinding processes (1,2). Typically, in these models some single measure of product fineness (e.g. the 80% passing size, the size modules, the specific surface area) is chosen as the dependent variable and the energy input per unit mass of material being ground acts as the independent variable. In some instances these models have been useful for the correlation of experimental data, but, invariably, they have been found to be inadequate for meaningful process simulation. During the last decade considerable advances have been made in the development of phenomenological grinding models derived from population balance considerations (3-7). In these models a set of dependent variables is employed, corresponding to the set of mass fractions which constitute the product size distribution, and energy input is abandoned in favor of "time in the mill" as the independent variable. The phenomenological models have been shown to provide accurate simulations of the entire size distribution of ground products produced in batch (8-10), locked cycle(11)and steady and unsteady state, open and closed circuit continuous grinding(12,13).

Jan 1, 1973

Fossil resin types occurring in the Hiawatha seam of the Wasatch Plateau coal field, Utah, have been separated according to color and their physical and chemical properties evaluated. These resin types were separated into four color fractions, yellow, amber, light brown, and dark brown. Each resin type has then been subjected to comprehensive spectroscopic examination and other physical methods of characterization. Included among the spectroscopic methods of characterization are FTIR and 13C NMR spectroscopy. Physical properties that have been measured include density, optical, and magnetic properties. These analyses reveal that the resins are distinct from other macerals, predominantly nonaromatic in nature with small amounts of oxygen functionalities and a low degree of unsaturation. The four resin types show distinct differences in certain physical and chemical properties such as density, hexane solubility, magnetic susceptibility, and aromaticity.

Jan 1, 1990

By R. S. C. Rogers

The present study examines the use of two vs. one stage of hydrocyclones in a pilot scale ball mill circuit. The approach used for doing this is based on computer simulation with mathematical models that explicitly account for the grinding mill/classification system interaction. Parameters for the ball mill model are obtained using a short-lived radioactive tracer method in open circuit tests of the study mill. The hydrocyclone model, based on the size selectivity concept, is developed and validated in standalone testing of the study hydrocyclones. Simulation procedures are validated through actual tests of the closed circuit grinding configurations of interest. Results of the evaluation indicate that two stages of hydrocyclones in the study circuit would improve classification, increase productivity and lead to more closely sized circuit products when compared to the conventional one stage hydrocyclone circuit. A computer simulation approach for comparing these circuit configurations in larger scale grinding circuits is also suggested.

Jan 1, 1981

By S. Acar

"In recent years the gold mining industry has been challenged by declining metal prices as well as having to treat ores that have low grades and are refractory in nature. Many factors must be considered when metallurgical studies are designed to develop process design criteria for these type of ores. These factors are mostly related to the mineralogical and chemical compositions of the ores, the geological setting of the deposit and how the ore/waste will be mined, such as whether openpit or underground, the mine schedule, and the mine fleet type and capacity. The purpose of this paper is to provide an experience-based practical approach to how to select and characterize test samples as well as devise process development metallurgical studies for both oxide and refractory gold ores, and to provide insight into some of the matters that might go wrong during the course of the studies. This paper is intended as both a guide for someone new to the field and also as a reminder for those familiar with the field. IntroductionThe recent decline in ore grades and metal prices have challenged mining companies to reduce capital and operating costs associated with developing new mineral resources. In some cases, metallurgical studies have been sacrificed to prevent cost overruns resulting in inadequate mineralogical, chemical and metallurgical characterization. Consequences have included longer construction schedules, higher initial and working capital, higher operating costs and less than desirable plant performance (Whincup, 2010; Torres, Chaves and Meech, 1999).Mineralogy, geology, mining type and sequence, and the metallurgy of an orebody will determine the process development metallurgical study requirements and eventual process plant design. Therefore, once the geologist has an early indication of a prospective orebody, geologists, metallurgists, mining engineers, and social and environmental responsibility scientists should convene and devise a plan on how to exploit the orebody economically (Lunt, Ritchie and Fleay, 1997).Geologists may find a prospective orebody solely based on grade. However, if the orebody cannot be mined and processed economically, then it is deemed not to be a deposit. An example of this could be a refractory gold deposit, either sulfidic, carbonaceous or siliceous refractory or any combination of those, that may not be mined and processed economically due to reasons such as the physical location of the deposit, depth of the ore lode, or social and environmental concerns. Therefore, an early collaboration between all disciplines must be established.Each orebody may have its own unique mineralogical, geological and chemical characteristics (Guresin et al., 2012). These unique characteristics should be effectively sampled to reduce risks associated with process design and engineering efforts for the process development metallurgical studies. If the sample or samples are not representative of these unique characteristics, then the studies performed will be pointless. The project metallurgist in charge of conducting metallurgical studies should also possess general geology, mineralogy and mine engineering knowledge. Recommended readings are a book on understanding mineral deposits by Misra (2000) and articles on heap leach development by Scheffel (2014a and 2014b)."

Jan 1, 2016

By J. O?Hanlon

The 4500 m3 blast furnace at the Redcar Works of ESC operates or, a burden of sinter and pellets, both materials being produced within the works. The early history of the furnace was given to the AIME Ironmaking Conference in 1981(1) when the burden was 65% superfluxed minter and 33% acid pellets. While ironmaking performance was adequate, it was felt that there were advantages to be gained by the use of fluxed pellets. For example, Kobe Steel had reported (2) that the rise of 30-50% dolomite fluxed pellets had enabled them to achieve better furnace permeability, higher gas utilisation, and enhanced ore/coke ratios. It appeared probable to BSC that the use of magnesia-bearing fluxed pellets would give a burden which had compatibility of softening and melting properties, i.e., fluxed sinter and dolomite pellets would result in a thinner cohesive zone because of closer matching of softening and melting temperatures, with consequential benefits on furnace stability and efficiency.

Jan 1, 1983

By F. Alsobrook

Industrial minerals are receiving increased attention by metals, coal and other companies seeking to diversify and stabilize earnings. Each industrial mineral has a unique set (and sub-sets) of business dynamics, however, and the diversity can present a bewildering maze to the corporate planner. Shrugging off this complexity and relying on serendipity for entry opportunities often results in unsuitable acquisitions. An effective alternative used in exploration can also be applied to strategic planning. By providing focus and direction, this flexible methodology can prevent wasting corporate resources on random pursuits and result in a quicker, more satisfactory achievement of diversification goals.

Jan 1, 1990

By A. Moharana

A massive slide at Bingham Canyon wiped out a side of the pit and covered the main haul road in and out of the pit. All pre-slide mine designs and schedules were no longer valid. New designs and schedules needed to be developed quickly to provide management with information regarding the immediate post-slide production potential and the time needed to ramp back up to full production. At the time of the slide, an effort was already underway to convert Bingham?s in-house Medium Term Scheduling Process to MineSight®?s Schedule Optimizer (MSSO). One of the main reasons for doing this was to reduce the time needed to produce Medium Term Schedules at Bingham, which involves a complex shovel-based scheduling approach with shovel productivities based on shovel type and the types of mining cuts to which the shovel is assigned over each planning period. The objective of the schedule was to maximize shovel usage, satisfy mill feed requirements of four SAG mills with variable milling rates, and have flexibility in setting truck constraints. This paper will describe how the new MSSO-based mine scheduling process met the challenge of producing new schedules for Bingham in a minimal amount of time.

Feb 23, 2014

By Janet A. Johnson, T. B. Borak, K. J. Schiager

INTRODUCTION In the USA regulatory agencies have adopted standards which limit the allowable concentration of ore dust in underground uranium mines. The American Conference of Governmental Industrial Hygienists has recommended a threshold limit value for silica which has been incorporated by reference in federal regulations (30 CFR 57, 1980). The Nuclear Regulatory Commission (NRC) imposes a limit for unprocessed uranium ore dust for reducing the exposure to radioactive materials from inhalation (10 CFR 20, 1980). We have been unable to trace the origin of the NRC standard. Recently the ICRP has published recommendations concerning limits for intakes of radionuclides by workers (ICRP, 1979). We have used the ICRP methodology to compute the dose equivalent commitment to lung and bone from inhalation of insoluble ore dust particles. These values were used to derive air concentrations which would provide an acceptable risk for induction of cancer from occupational exposure. Results indicate that the new ICRP recommendations are more restrictive than the present NRC standard for radioactivity. The maximum allowable dust load in a uranium mine will depend on both the concentration of silica (% Si02) and the amount of radioactivity (% U308). We have combined these standards assuming complete independence of biological hazard to establish boundary conditions for which either silica or radioactivity is the dominating factor. Based on these results we present suggestions for analysis of ore dust to insure compliance with regulatory agencies. SILICA STANDARDS Silicosis, fibrotic lung disease produced by crystalline silica, was one of the earliest forms of occupational disease to be recognized. The pulmonary lesions caused by silica, silicotic nodules, consist of concentrically arranged bundles of collagen fibers. Fusion of these nodules results in progressive massive fibrosis causing alveolar changes which decrease ventillation and blood flow in the lungs. The current Threshold Limit Value (TLV) for mineral dusts is based on the concentration of free silica. The standard is expressed in three forms: (1) Particle count standard: TLV (mppcf) = 300/(% Si02 + 10) (mppcf = million particles per cubic foot) (2) Respirable dust mass standard: TLV (mg/m3 ) = 10/(% respirable Si02 + 2) (3) Total dust standard: TLV (mg/m3 ) = 30/(% Si02 + 3) The most commonly used form is the respirable mass standard. These curent values for silica are based primarily on epidemilogical studies of Vermont granite workers and other occupationally exposed workers. In the Vermont study no cases of silicosis were seen in individuals employed after dust control measures were initiated and whose subsequent exposure averaged less than 5 mppcf. The free silica concentration in the airborne dust to which these workers were exposed averaged 25%. A concentration of 10 mppcf of granite dust is considered equivalent to 0.1 mg/m3 quartz. The current respirable mass standard allows a maximum silica concentration of 0.1 mg/m3. NIOSH (1974) has recommended a reduction in the current TLV for respirable silica to 0.05 mg/m3 Si02. As with radiation standards, the TLV for mineral dusts is an upper limit for time weighted average exposure. It is recommended that dust concentrations be maintained as far below the TLV as current practices permit. RADIATION STANDARDS The present concentration limit for airborne natural uranium in ore dust prior to chemical separation is 75 µg of uranium per m3 of air ( 10 CFR 20, 1980) . This corresponds to 1.85 Bq/m3 (50 pCi/m3 ) of natural uranium, U-238, U-235 and U-234 and is equivalent to 3.7 Bq/m3 (100 pCi/m3 ) of gross alpha activity with radioactive equilibrium between the long-lived alpha progeny through Ra-226. The origin or basis for this standard is not known, but it presumably includes both chemical toxicity and risk from somatic radiation injury. Recently the International Commission on Radiological Protection (ICRP, 1977) has published recommendations concerning the objectives and criteria for limiting radiation exposures. This was followed b y a revision of the limits for intake of radionuclides by workers (ICRP, 1979; ICRP, 1980). The previous compilation of limits for internal emitters was published by ICRP Committee II in 1959 (ICRP, 1959). The latest version includes new methodlogy outlined in ICRP Publication 26 (ICRP, 1977) as well as extensive metabolic information

Jan 1, 1981

By R. T. Torrie, J. R. Mernagh, D. B. Chambers

l, INTRODUCTION Uranium mine and mill workers are exposed to external gamma and beta radiation fields from radioactive ore. In the past the average uranium content of ores mined in the United States and Canada ranged from about 0.1% to 1.0% U308 with pockets of much higher grade ore. Holiday (1973) reported that radiation surveys in the U.S. uranium mines found mean gamma "radiation rates ranged from 0.20 to 0.70 mrem/h. Such radiation rates cause relatively insignificant exposures." Others also concluded that the external gamma radiation fields associated with uranium mining did not result in significant worker exposures (Federal Radiation Council, 1967; Simpson, S.D. [et al], 1959) Gamma exposure levels in most modern-day Canadian uranium mines are reported to be low with average annual exposures estimated to be less than 1 rem/a (Frost, S.E. [et al], 1981). However, two developments are taking place which affect the potential significance of external radiation fields in the uranium mining environment. The first development stems from the most recent system of dose limitation developed by the ICRP which is intended to limit the workers' overall risk from exposure to ionizing radiation through the adoption of a sum rule (ICRP 26, 1977) which combines external and internal radiation exposures. In the case of exposure to radon daughters the sum rule will have the effect of reducing the annual exposure limit below the recommended limit by an amount that depends on external radiation and other sources of internal exposure such as the inhalation of ore dust (ICRP 1980). The Atomic Energy Control Board of Canada (AECB) is reviewing this subject and is expected to produce its recommendations shortly. Irrespective of the form of the sum rule eventually adopted by the AECB, it is clear that the net effect of the sum rule will be a collective reduction of the individual dose limits for individual exposure pathways. The second factor is the increasing development of high grade uranium deposits in Northern Saskatchewan. Some of these ore bodies have an average ore grade of 1% to 5% U308 or greater. Since the potential external radiation fields increase in proportion to the ore grade, it is apparent that increased effort in radiation protection planning is required in order to develop safe yet workable methods for mining and milling such ores. This paper is intended to provide information which can be of assistance in the formulation and development of a mining and milling plan. The principal focus of the paper is source identification and the design of radiation protection measures to limit external gamma radiation exposure. The exposure of workers to external beta radiation fields is also discussed. The paper is organized as follows: - Section 2 deals with source characterization. - Section 3 discusses the effects of finite source size and distance (i.e. geometry effects). - Section 4 presents selected data that are useful in evaluating shielding requirements. - Section 5 discusses the potential beta radiation fields. - Section 6 discusses practical data requirements for worker exposure scenarios. - Section 7 presents a variety of work exposure calculations. - Section 8 is a summary of this paper. 2. SOURCE CHARACTERIZATION This section develops the basic formulae for estimating the fluxes and doses from external gamma radiation. The calculation of the radiation flux due to a distributed source (i.e. a linear, area or volume source) as a function of distance assumes that any distributed source can be treated as a summation of point sources. [ ] Uranium ore contains radionuclides from both the decay chains of U-238 and U-235. In this paper the radioactive daughters are assumed to be in secular equilibrium with the uranium parent. (If natural thorium were present in the ore in significant quantities, the gamma rays originating from Th-232 would have to be added to the gamma rays from the uranium series). In all, there are over 50 separate gamma rays (as well as alpha and beta particles) emitted from the U-238 and U-235 radioactive decay series (USHEW 1970). The total

Jan 1, 1981

By R. M. Tyson

Sulfides present in the troctolitic and footwall rocks are placed into one of three major zones (hornfels, cloud, and basal) on the basis of their stratigraphic position and mineralogy. Hornfels sulfides, enriched in Fe, represent remobilized sedimentary sulfide. Sulfides from the Cloud Zone are probably magmatic and are enriched in PGE, Cu, Ni, and Ag. The basal sulfides, composing most of the ore, resulted from contamination of the magma by remobilized sedimentary sulfide. The basal sulfides exhibit a differentiation trend in their mineralogy and chemistry. PGE, Cu, and Ag are enriched with increasing differentiation which is attributed to fractionation within an immiscible sulfide liquid.

Jan 1, 1986

By MARK J. VANARELLI

Estimating groundwater inflows in rock deep tunnels is critical to the safety of personnel constructing the tunnel and the cost of construction. This paper presents two case studies for estimating steady-state groundwater inflows into deep rock tunnels. The case studies included the Chattahoochee and Nancy Creek tunnels. In this paper, statistical methods were applied to packer test data obtained from exploratory borings during geotechnical site investigations. A semi-empirical procedure was utilized for estimating groundwater inflows into these deep rock tunnels. It is the most widely used method/procedure in the tunnel industry. The Chattahoochee and Nancy Creek tunnels are deep rock tunnels which exhibit radial flow conditions. For the radial flow condition, a statistical analysis presented in this paper indicates that the semi-empirical procedure works well; however, variations in the procedure and/or an insufficient amount of testing could lead to underestimations of the inflow quantities. Packer test data plotted in histograms were observed in all cases to be log-normally distributed for the radial flow condition. Modeling using Monte Carlo simulations was observed to be an effective tool for removing irregularities in the distribution of the data and incorporating high-end permeability data to derive reasonable groundwater inflow estimates. This paper is based on the PhD thesis entitled “Improvements to the Current State of the Practice in Steady-State, Groundwater Inflow Estimates into Rock Tunnels based on the Application of Statistical Analysis Methods of Packer Test Data obtained from Exploratory Borings During Geotechnical Site Investigations.”

Oct 9, 2020