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By Stefano Ceccotto, Eugenio Trussoni

"INTRODUCTION Contemporary city is made of layers. Physical structures layers (built fabric, residential, commercial industrial etc. ), infrastructural layers (below and above ground), “green” layers (parks and open spaces), and also informational layers, i.e. connections, links, between sectors of the city and other territories. The “city of layers” concept represents the exercise of “rebuilding the city” per each layer, highlighting those physical built structures that are functional to define a relation. For example, if consider the “connection” relation, the city is re-designed by considering only transportation built structures. The layer obtained in such fashion is hence the “transportation” layer, including below grade infrastructures (subways) and above grade lines (rail, bus, tramways etc.), as below shown in Figure 1.In this sense, the contemporary city is represented by separate constructs assembled together according to a specific functionality (e.g. “connection”). As a consequence, the relation between what is built underground, and the related above-ground development, can be perceived in his most evident appearance. What could happen within the contemporary city if the planning process would begin from below to above and not vice-versa?INTERACTION The question risen in the introduction is strategic when approaching the difficult task of designing (or re-designing) a multi-level organism like the contemporary city. Nowadays, the theme of integration between underground and at-grade master planning has become the subject of many urban renovation projects, where the design process has begun within the transportation layer, underground, and further developed by interacting with at-grade structures already existing or in phase of design.A series of case studies where below/above interaction plays a key role in the project will be further analyzed. Moreover, it is relevant to understand the mechanics of an urban transformation process that originates within the transportation layer and ends up with the design of entire sectors of the city. The Transit Oriented Development approach is a useful tool to clearly understand such transformation process. TOD has become, in particular in the last decade, one of the most effective tools for urban design, in order to solve simultaneously the many different instances related to transit planning, urban design and real estate market."

Jan 1, 2016

By A. E. Raddatz

The U.S. Department of the Interior, Bureau of Mines, is investigating methods for recovering tungsten from domestic resources. A calcine-quench-leach (CQL) technique was developed for the extraction of tungsten from the Golconda, Nevada, hot springs ores. The deposit contains disseminated tungsten, which cannot be beneficiated by conventional techniques and must be treated by hydrometallurgical methods. The CQL procedure consists of calcining the ore at 900° C for 3 hr, quenching in a solution containing 1.5 parts of NazCO3 and 1.5 parts of NaOH per part of WO3 in the ore and at a solution- to-ore ratio of 3 to 1, leaching at 200° C and at 250 psig for 3 hr, and filtering and washing the residue. A series of closed-circuit batch tests showed that 92 pct of the tungsten was extracted from a sample containing 2.32 pct WO3. The pregnant solution contained 11 q of W03/1.

Jan 1, 1982

By M. Misra

The dissolution of mercury during gold cyanidation is the cause of many environmental, health and processing problems. A study was undertaken to find a suitable reagent for the removal of mercury bearing complexes from the leach liquor. Removal of mercury from synthetic solutions and process water from a gold mine was investigated using sodium sulfide, sodium and potassium dimethyl dithiocarbamates as precipitating reagents. The results have shown that efficient mercury removal could be achieved by addition of potassium dimethyl dithiocarbamate (KDTC), by formation of stable mercury compounds. The resultant mercury-potassium dimethyl dithiocarbamate precipitates are stable under present plant operating conditions and do not have any deleterious effect on gold adsorption by activated carbon. Furthermore, it is also possible to stabilize the mercury in the heap during cyanidation by adding dimethyl dithiocarbomate.

Jan 1, 1998

By J. M. Smith, T. R. Horton, R. L. Blanchard, T. W. Fowler

INTRODUCTION Uranium mining operations release radioactive materials into both air and water and generate large quantities of solid wastes containing low levels of radioactive materials. Solid wastes produced by mining operations remain on the surface at many inactive mining sites in the Western United States. These mining effluents may present a potential health and environmental hazard. Therefore, Congress, in Section 114(c) of the Uranium Mill Tailings Radiation Control Act of 1978, instructed the Administrator of EPA to prepare a report identifying the location and potential health, safety, and environmental hazards of uranium mine wastes and to recommend a program to eliminate these hazards. Several facts and limitations helped shape the method and approach of the EPA study. Little information on uranium mines was available; measurement information that was available on uranium mine wastes was frequently influenced (biased) by nearby uranium mills; time and resources did not permit comprehensive field studies to provide additional data; and there are inherent variations between uranium mines and sites that complicate generic assessments of mine wastes. To accommodate these facts, the EPA developed conceptual models of uranium mines and made health and environmental projections from them. The models were based upon available data from the literature, supplemented with information from discussions with persons inside and outside the EPA, and by doing several short-term field studies in Texas, New Mexico, and Wyoming. When necessary, conservative (maximizing) assumptions were employed. This paper presents a brief account of a part of the EPA study dealing with the potential health and environmental effects caused by active surface and underground uranium mines. Airborne contaminants are emphasized, although solid and liquid effluents are also included. Due to the limited space, only the methods and parameters used and the results of the assessments will be presented here. Anyone interested in the source of the data used and the development of the parameters should refer to the EPA report (Blanchard et al., 1981). The occurrence and emissions of stable elements were included in the EPA report, however, due to space limitations and their apparent small impact, except for possibly at some specific mines, only radioactive sources will be included in this presentation. MODEL URANIUM MINES The model surface mine was located in the South Powder River Basin of Wyoming and the model underground mine was located in the Ambrosia Lake area of New Mexico. These are the prevalent type mines in those areas. The model mines were based on the average production parameters of the 63 open pit mines and the 256 underground mines that were operating in the United States in 1978 (Department of Energy, 1979) and on a report of an extensive study of open pit mines in Wyoming (Nielson et al., 1979). Information contained in environmental impact statements and in reports from federal and state agencies was also used. Parameters for the model mines are listed in Table 1. The surface mining scenario is that 7 pits are opened in the 17-year mine life with overburden from each successively mined pit used to backfill a previously completed pit, resulting in an equivalent of one pit of overburden (2.4 year production) stored on the surface. No backfilling is assumed at the underground mine. Overburden or waste rock, ore, and sub-ore are separated into separate piles that are either rectangular in shape with length twice the width or in the shape of a frustum of a regular cone. Both shapes have 45 degree sloping sides. To account for bulking, the volume of the material comprising the piles was considered to be 25% greater than the volume of material removed from the ground. It was assumed that dewatering was required at both mine sites. Wastewater discharge rates at the surface and underground mines were assumed to be 3.0 and 2.0 cu m per min, respectively. SOURCE TERMS The following radioactive contaminants at active uranium mines were assessed in the EPA report: 1. Radioactive particulates in a) wind suspended dust from waste rock (overburden) pile, sub-ore pile, ore stockpile, b) suspended dust from mining activities (rock breakage, loading and unloading ore and wastes), and c) vehicular dust, 2. Rn-222 emanation from waste rock (overburden) pile, sub-ore pile, ore stockpile, and mining activities, 3. Rn-222 emanation from mine surface areas, and 4. Radionuclides in wastewater discharged to land surface. Estimated average annual dust emissions (item 1 above) from the model mines are listed in Table 2. Emission factors and the assumptions used to estimate these dust emissions are described in detail in the EPA report. Radioactive source terms were computed for each of the sources; dust emissions were multiplied by the concentrations listed in Table 1

Jan 1, 1981

By S. M. Hsiung

Chain pillar design formula under weak roof condition was developed by statistically analyzing the results from the three dimensional finite element parametric analyses. The parameters such as mechanical properties of the roof and floor strata, overburden depth, panel width and length, and coal strength were incorporated in the formula. A conversion formula which transfers a rectangular chain pillar into a square chain pillar of equal strength is proposed. The influence of high in-situ horizontal stresses, which are often encountered in the coalfield, on chain pillar stability is also discussed.

Jan 1, 1984

By R. Masse, J. Chameaud, J. Lafuma, R. Perraud

Estimating the risk of lung cancers for workers in uranium mines and defining the resulting dose equivalent limits have been made possible thanks to work carried out in two scientific fields : physics and epidemiology. Theoretical calculations on the basis of physical models for the former and epidemiological surveys on the mortality of uranium miners from lung cancer for the latter. However, even though considerable work has been done in these two areas, the results obtained still remain controversial on several points. The radioactive and physical instability of the aerosols present in the atmosphere of the mines and the biological complexity of the human lung which even the most sophisticated physical models can reproduce only very schematically have often proved to be insurmountable difficulties for physicists, explaining the uncertainties which subsist concerning the dose delivered to the various parts of the respiratory tract from the air breathed by miners during their work. Epidemiological investigations on the other hand, in spite of the high quality of the surveys carried out, remain open to criticism, essentially because of the very approximative estimation of the individual occupational exposure to radon daughters. This is due to the fact that uncertainties arise from the measurement of radon gas if the state of equilibrium with the daughters is not accurately known or, if the active deposit is measured, to the fact that these measurements are insufficient in number. The controversies and discrepancies which subsist with regard to the evaluation of the level of risk, and in particular for low doses, can thus be understood. In addition, epidemiological surveys cannot dissociate the carcinogenic action of radon from the synergistic or potentiating actions of tabacco and of other pollutants present in uranium mine air. Animal experiments have been largely taken into account for evaluating the toxicity of various radionuclides. This type of experiment is necessary when human data do not exist and has provided us with much information. For instance, the relative biological effectiveness of the various types of radiation, the metabolism of radionuclides and the mechanisms of cancer induction have been approached and satisfactorily resolved in this way. Concerning radon and its daughters, however, animal experiments have been used very little even though it seems apparent that they should complement epidemiological studies. For instance, whereas doubt can be cast on the data obtained from human epidemiology because of the uncertainty concerning the individual exposure of miners, those drawn from experiments are indisputable because in this case the dose is as perfectly known as the effect. In addition, the effects of radon can experimentally be appreciated separately whereas in the surveys, they cannot be dissociated from the effects of the other pollutants in the mine. Finally, there are no other means of dealing with the mechanisms of cancer induction. In order to gain any useful knowledge from this method however, the experimental model must necessarily present certain methodological guarantees and the effects seen in the animals must enable a comparison with those which appear in man. For this reason we will present here the animal model we have been using for 15 years, and will give the results obtained and compare them with human data and made a synthesis. Finally the conclusions which can be drawn will be discussed as well as their limitations with respect to the protection of uranium miners. I - MATERIAL AND METHODS Male SPF Sprague-Dawley rats were used. At the onset of the inhalations they were around 3 months old. Their small size makes it possible to expose a large number of animals at the same time. Their life-span is long enough to be able to follow the evolution of the cancers and to estimate the latency time. Finally, they present the advantage of having a very low rate of spontaneous lung cancers (SANDERS, 1979). I.1 - Three inhalation techniques were used. 1.1.1. – [Inhalation of radon decay products.] The inhalation apparatus has been described previously (CHAMEAUD et al. 1971). The first experiments utilized a room of a half cubic meter linked to a source made up of high grade uranium ore. Later on, a large installation was built with a 10 m3 inhalation chamber making it possible to expose up to 500 rats at one time at radon concentrations ranging from 100 to 10 000 WL for variable lengths of time (1 to 10 hours per day). These concentrations are higher than those to which the miners are generally exposed, but in order for the cumulated doses in man and in animal to be similar and delivered for the same fraction of their respective life-spans, the ratio of the concentrations should be approximately that of the life-spans. The concentrations of radon and its daughters during the experiments were carefully controlled thanks to multiple samplings of radon gas associated with measurements of radon decay products. I.1.2 – [ The dust inhalation chamber] has already been described : it is a dust-loading chamber where the dust content remains constant during the experiment and can hold over 20 - 30 animals (PERRAUD et al, 1970). I.1.3 – [Tobacco inhalations] take place in a smoke box

Jan 1, 1981

By V. Nasri, S. Rashidi

The Baltimore Red Line Project is a proposed 22.7-km (14.1-mile) long east-west light rail transit (LRT) line envisioned to connect the areas of Woodlawn, Edmondson Village, West Baltimore, downtown Baltimore, Inner Harbor East, Fells Point, Canton and the Johns Hopkins Bayview Medical Center Campus. The Red Line LRT System has two tunnel segments - the Cooks Lane Tunnel (CLT) and the Downtown Tunnel (DTT). The CLT segment is roughly 1,920-m (6,300-ft) long. It commences at the west portal located at the highway ramp for I 70 (to be removed) and terminates at the east portal that is at the intersection of Edmondson Avenue (U.S. Route 40) and Glen Allen Drive. This segment of the project consists of the following construction components: approximately 1,458 m (4,786 ft) of tunnels, 143 m (469 ft) of cut-and-cover tunnel, and 318 m (1,045 ft) of retained cut (U) section. The approximate horizontal alignment for the Red Line LRT Project is shown in Fig. 1.

Jan 1, 2014

By R. D. Hagni

Pyrometallurgical products from lime roasting of refractory gold ores, pyrite, and arsenopyrite have been examined for their mineralogy, porosity, permeability, retention of contaminant sulfur and arsenic, and potential effectiveness of gold extraction. Cathodoluminescence microscopy, supplemented by X-ray diffraction and scanning electron microscopy-energy dispersive analysis study, has shown that the products phases have characteristic cathodoluminescence properties as follows: anhydrite (CaS04), deep blue; unreacted portlandite (Ca(OH)2), deep purple; oldhamite (CaS), light yellow to rarely pink or orange; a sulfur-rich, arsenic-poor phase, violet; an arsenic-rich, sulfur-poor phase, non-CL. Within the temperature range examined (400-850°C), hematite exhibits greater porosity and permeability at the intermediate roast temperatures of 600-650°C.

Jan 1, 1993

By C. D. Elifrits, N. B. Aughenbaugh

Introduction Federal and state laws enacted to regulate coal mining and the accompanying public concern about the adverse effects that mining might have on land use have focused much attention on the subsidence of the land surfaces over underground mines. Some questions asked are • Will abandoned mines subside in the future even though they have exhibited no surface adjustment to date? If so, when will subsidence take place? • Can a specific surface area be affected by subsi¬dence more than once? • What surface form will the subsidence feature take? • Is there any way to predict when subsidence will occur and end? An attempt is made here to address these questions insofar as it is possible with available data and experience of evaluation of subcritical extraction conditions. Mining that results in subsidence features can be classified as supercritical, subcritical, and critical with respect to the minimum span lengths of the worked-out rooms (Fig. 1). A complete basin will not develop fully immediately over subcritical conditions because the span lengths of the entries are less than the critical dimension (Wardell, 1983). Passageways, entries, and room-and-pillar panels are all included in the subcritical category. Because of the short span lengths, subcritical mining conditions tend to be stable over the life of the mine unless adverse geologic conditions exist (Gray et al., 1974; Dunrud, 1976). Various roof control and support procedures are employed to maintain entry stability during mining. Little information exists concerning the time factor of subsidence over areas of subcritical extraction. Data that have been collected relate to longwall mines, whereby the cavity sizes are designed large enough to induce caving behind the working faces so that complete subsidence at the surface occurs within a short period of time. The UK's National Coal Board (1975) has reduced the enormous amount of data it has collected to empirical correlations and has published these correlations in its Subsidence Engineers Handbook. The handbook states that "None of the foregoing remarks applies to pillar and stall working," with respect to the section discussing the time factor of subsidence caused by longwall mining (National Coal Board, 1975, p. 40). To understand and evaluate how time relates to subsidence above room-and-pillar mines, one must first recognize how mine cavities deteriorate and fail. The propagation of failure to the surface must then be studied, and, finally, the failures that are manifest at the surface in the form of depressions accompanied by both compressional and tensional movements must be investigated. Failure of mine cavities Any cavity beneath the earth's surface represents a condition of nonequilibrium and tends to close with time. Failure of cavities in a subcritical mine can be classified as failure of the roof, failure of the floor, failure of the supports (pillars, cribs), and elastic rebound of the rock. One mode of failure may dominate, but generally combinations of the four will occur. Also, initial instability of geologic materials and structural features and in situ stress may be unknown factors that can contribute to cavity failure. Roof failure is the most obvious opening stability problem in most operating mines. The bridging capabilities of the roof rock are dependent on the rock's material strength, geologic discontinuities, and reaction to humidity changes in the air of the mine. This type of failure may vary in magnitude from gradual flaking to massive roof falls. Mine floor instability can be manifest in the form of a general heave over a broad area or of individual pillar punching. The weaker and thicker the immediate floor material, the more prone a mine is to experience floor problems. Water seeping into an area can soften the underclay, reduce its bearing capacity, and precipitate failure of support for the overburden.

Jan 1, 1987

By B. E. Davis

A problem that has continued to plague the Florida phosphate industry is the loss of coarse phosphate in the flotation circuit. Attempts to remedy this problem such as floating the coarse material (plus 425 µ m) in a separate circuit have resulted in limited success, but recovery is still not optimum. The Bureau of Mines is investigating ways to improve the recovery of coarse phosphate through improvements in the conditioning step. Studies to optimize conditioning parameters such as agitation energy, conditioning time, conditioner solids, and residual clay content have resulted in improved P2O5 recovery. Optimizing these and other conditioning parameters resulted in a rougher concentrate grading 30 pct P2O5 with a P2O5 recovery of 97 pct.

Jan 1, 1993

By C. Opoku-Ware, M. Kukay, P. Conrad, F. Inkoom, R. Pal

Researchers at Montana Tech are investigating the potential for developing trees tolerable to degraded un-reclaimed mine site tailings and soils as a solution to re-establishing long-term tree growth on those sites. This project involves growing tree seedlings from seeds planted in the degraded mine tailings and soils in which they will eventually be planted. The outcome of the project is expected to lead to a successful solution for re-establishing tree growth in degraded tailings and soils in Butte, Montana with minimal post-planting human intervention. Work conducted on the project to date has shown successful growth of seedlings in degraded tailings and soils. INTRODUCTION In an effort to improve Butte Area One natural resources, this research project is working to help restore tree growth in the Butte Priority Soils Operable Unit Boundary (BPSOU) (Opoku-Ware, et al 2018). Research by Blicker, et al (2003) found that, the BPSOU, which is part of the Silver Bow Creek/Butte Area National Priorities List (Superfund) Site within and near Butte, Montana has multiple historic mining sites situated entirely within the urban setting of Butte. Mine wastes and mill tailings, accumulated from over 100 years of gold, silver, and especially copper mining are dispersed throughout Butte, posing health risks to human and environmental receptors. Stabilization of tailings sites is needed to control fugitive dust, prevent run-off of toxic material resulting in subsequent sediment deposition in streams, reducing the volume of water seepage through acidic and heavy metal contaminated material, and improving land productivity and aesthetic values (Watkin and Watkin, 1982). If successful, the project will help restore water quality and maintain stream flow in Silver Bow Creek where it flows through Butte Area One. Trees native to Butte are being grown to seedlings in a greenhouse located on Montana Tech’s campus which will be planted in degraded soils located within the BPSOU. Growing trees is expected to help restore vegetative ground cover within the watershed contributing to stream flow in Silver Bow Creek. The trees will prevent soil and tailings from eroding and being deposited in Silver Bow Creek where they could degrade water quality and choke stream flow. The project combines research with tree seedling growth to provide a resource for Butte that could produce thousands of tree seedlings each year adapted to the harsh climate, soil, and tailings conditions that exist in the BPSOU where they will grow. It is anticipated that the trees developed by the project will have the capability for long-term survival and growth because they will be germinated and grown into seedlings in the degraded soils and tailings collected from the BPSOU where they will be planted. Soils and tailings collected for the project have been evaluated to determine if they lack nutrients or contain substances potentially toxic to the long-term growth and survival of the trees. Toxic levels of metals, high concentrations of soluble salts, extremes in pH, nutrient deficiencies and imbalances, surface crusting, high bulk density, low infiltration rates, high surface temperatures, low cation exchange capacity, restricted microbial activity, low water retention, harsh climatic conditions and surface particle movement are some of the traits of mine tailings sites that restrict revegetation efforts (Barth, 1986).

Jan 1, 2019

By Karel Rössler, Petr Vítek

"The Ejpovice tunnels in Czech Republic were built by EPBM in soft Clyashale, and in weathered profile with low soil overburden. The segmented liner at the cross-passage openings required support, which would not interfere with the EPBM clearance envelope during the scheduled pull back of the EPBM through both tunnel tubes. For that reason support frames or radial bolting could not be used. Steel rods inserted into the neighboring segments during the ring assembly, and later grouted were tested and realized as an innovative solution. The paper presents practical experience gained with the segmented liner support during cross-passages construction. INTRODUCTION An innovative solution using the grouted dowels was developed and realized for sixteen cross-passage openings of the twin Ejpovice Tunnels, whose construction was part of the railway track Rokycany – Plzen modernization. The following paper described practical experience gained with the innovative support of cross-passage openings, which was realized by short steel dowels grouted within the segments of the EPBM segmented liner. The paper is a continuation of the paper published in WTC 2015, which described the design aspects of the grouted dowels support, while the following paper concentrated on the production, and the performance of the dowel support observed during the breakout for the cross-passages openings. The connection by grouted dowels was patented by Metrostav, a.s. Company THE EJPOVICE TUNNELS CONSTRUCTION The Ejpovice tunnels construction started in 2013. The start of the high speed train operation through the tunnels was planned for 2018. The project was funded by the state government with the support of European Union funds of up to 70%.The tunnels were excavated with one EPBM (Earth Pressure Balanced Machine) with the external diameter of 9.89 m. The segmental liner inner diameter was 8.7 m, and thickness of 0.4 m. First, the South tunnel tube was excavated from the East portal, then the EPBM was pulled back through the South tunnel, and the excavation was started from the same portal for the North tube. After the South tube was freed from the EPBM excavation operations the cross-passage construction started. Due to the short time schedule, in the North tube the cross-passage construction started while the tunnel was still under construction. Therefore, the cross-passage construction was performed concurrently with the segments transportation, and with the EPBM pull-back through the tunnel. There were 8 cross-passages along the tunnels with a maximum distance of about 500 m, Fig.1."

Jan 1, 2016

By Siyu Song, Yanhong Wang, Guohua Gu, Linbo Huang

In this study, the effect of cations, Na+ and Mg2+, in saline water on copper flotation in the presence of calcium bentonite was investigated. It was found that as the concentration of NaCl was increased, the copper recovery initially decreased and then increased to above 99%, while the copper grade initially increased and then decreased. In contrast, as the concentration ofMgCl2 was increased, the copper recovery continuously increased, while the copper grade continuously decreased. The variation of copper recovery and grade was mainly attributed to the synergistic effect of pulp rheology and flotation solution chemistry. The underpinning mechanisms are the compressing electrical double layer and ion-exchange interaction between saline water and bentonite, which occur at the same time. Using salinewater slightly affected the pulp rheologywith a decrease in copper recovery at low NaCl concentration. Increasing the concentration of cations in saline water might even facilitate the flowing out of exchangeable cations, especially divalent cations, from the interlayer space of bentonite to the solution, resulting in the decrease of copper grade at high salt concentration.

Sep 10, 2020

By Roberto Fustos, Gonzalo Nelis, Víctor Sanhueza, René Gómez

Hang-ups are a challenging operational problem in block caving mines. They interrupt ore flow and imply hang-up removal activities, which take time, increase operational costs, and involve safety risks for workers. In block caving, the number of hangup events of mechanical arches that appear in the drawbell could be decreased if the drawbell geometry is adequately designed based on the expected rock fragmentation. Here, we compile and analyze hang-ups reported in several block caving mines to evaluate the impact of drawbell geometry, rock size, and vertical load on hang-up frequency at the mine scale. Results show that the ratios between drawbell length and d80 (dL/d80), between drawbell width and d80 (dW/d80), between drawbell volume and rock volume (VDB/VP), and vertical stress are critical parameters that define hang-up frequency. These findings confirm previous experimental studies, where a decrease in hang-up events is associated with an increase in these ratios. Additionally, these outcomes are used in a support vector machine algorithm to define categories of hang-up frequency. The results of this classification algorithm are presented in diagrams, which can be used to estimate the hang-up frequency in block caving projects.

Oct 15, 2022

The US Bureau of Mines' dictionary of mining terms defines productivity as "the efficiency with which economic resources (men, material, and machines) are employed to produce goods and services." Or, the relationship between the physical outputs and the physical inputs used to produce those outputs. As demand for mine materials dropped, mining companies and equipment manufacturers discovered that ratios between the inputs and the final products were disproportionate to the profits realized. Some companies are fighting for survival. The US, while still the most productive country in the world in absolute terms, is looking over its shoulder as other industrialized nations continue to exceed its yearly productive growth rate. According to John Belcher, Jr., of the American Productivity Center in Houston, TX, the US has seen a steady decrease in productivity growth since the mid-1960s. During the post World War II period, the US labor productivity growth rate was 3.2% annually. The slowdown began in 1965 and by the mid-1970s, the country's annual growth rate was 1%. By 1978, labor productivity growth ceased to gain at all and from 1978 to 1980 a 2% decline occurred. Solutions to the productivity decrease are increasing product prices or improving productivity. By increasing prices, though, the producer runs the risk of pricing himself out of the competitive market. To maintain an acceptable profit level, prices must increase proportionately higher than required to offset production cost increases, Belcher says. Many companies are turning to in-house productivity improvement programs as an answer to increased costs and declining profits. These programs are geared toward management commitment and employee awareness of what productivity means. Companies are finding ways of measuring productivity levels in financial reporting, budgeting, and planning. Organizational teams have been formed to coordinate activities and oversee product management, and improve productivity of materials and capital investments. This special issue of Mining Engineering examines productivity in the mining industry. First, there are articles about various, and different, factors that affect productivity in each of ME's five main readership areas - exploration, mining, processing, coal, and industrial minerals. There is also a look at mining industry productivity from the manufacturer's view. The next section of this special issue is devoted to some topics that affect all areas and sectors of mining: research, management practices, computers, maintenance, and energy management. Then follows case studies in exploration, coal, and iron and steel. These studies provide examples of practices and strategies used by companies and operations to boost productivity.

Jan 11, 1983

By Ronald E. Feltman

Most engineering firms engaged in the design and manufacture of milling components and systems have established, through the years, a relatively well defined system design procedure. The process design engineer has at his disposal several alternative approaches to the successful completion of this task. Unfortunately, while these alternatives, at first glance, appear to be rather straight Forward, any attempt to implement them into a fully integrated commuter design program becomes increasingly more complex when one addresses himself to the problem in total. This paper summarizes Kennedy Van Saun's approach to the solution of this problem through a planned system design. Following the problem definition and discussion, a detailed analysis and system design synthesis is presented; the major aim here being to provide a system design which may be programmed and run on a relatively inexpensive computer installation such as the IBM 1130 system currently in use at Kennedy Van Saun. A summary section is also included, which Provides a general outline guide to the program systems design of equipment which, while quite different from milling system functionally, nevertheless lends itself to the approach used in this paper.

Jan 1, 1969

By Aladar B. Dory

INTRODUCTION Anyone familiar with the problems of hardrock mining will agree that the majority of the serious dangers present in mining are quite visible and obvious to any person reasonably familiar with the profession. Having unsecured, unscaled back over ones head, gives one a very good chance of ending up under a caved in mass of rock. Staying too close to a blast gives one almost a certainty of being hit by a flying rock. Too little oxygen in the air will very quickly lead to loss of consciousness and death. One walks only so much over deep, unsecured openings before he falls into them. It is because of this clear visibility of the conventional health and safety hazards that mining regulations in almost all jurisdictions world-wide are a more or less comprehensive collection of "shalls" and "must nots" of good common sense. When basic rules of common sense safe working practices are at stake, there is little room for dialogue and compromise. The mine inspector is then observing, during his inspection, how well the mine follows these common sense rules. RADIATION AS A HIDDEN DANGER Radiation in mines is a risk, the impact of which does not demonstrate itself immediately. It is first of all a potential risk. Two individuals exposed to identical radiation will almost certainly be effected differently, if at all. This is certainly true of exposures and doses one might encounter in the mines today. We hear very often the phrase: "there is very little known about the effects of radiation". It is one of the most misused and misunderstood half-true statements. I would doubt that there is any other carcinogen whose effects have been studied as extensively as the health effects of radiation. Where the statement is correct is regarding the knowledge of the quantitative assessment of the risk of low level radiation exposures. The reason for this uncertainty is that the magnitude of their health effect is very close to the health effects of natural radiation, cosmic radiation and the effects of other carcinogens such as industrial pollution, hydrocarbons from cars and other chemicals we have grown accustomed to using. As far as lung cancer is concerned, the effects of wide use of tobacco probably outperforms any other single substance. All this having been said, the bottom line is still unchanged. Radiation exposure, in most cases mainly radon daughter exposure, was and still is one of the health hazards of uranium mining and as such has to be controlled to the best of our ability. Various jurisdictions have adopted different approaches to the control of radiation exposures of uranium minemill workers. The following sections of this presentation will attempt to explain the regulatory approach taken in Canada. THE CANADIAN REGULATORY PHILOSOPHY As indicated earlier, the health effects of low level radiation are quantitatively not yet defined and no proven threshold of radiation exposure exists. The Atomic Energy Control Board's (the Board's) regulatory system is based on the basic assumption that there is no absolutely safe limit of radiation exposure below which there are no health effects. Theoretically we should therefore strive to reach zero exposure. It is obvious that this objective cannot be reached in real life. The objective of the regulatory process therefore has to be to achieve radiation exposures of the workers that are as low as reasonably achievable, social and economic factors taken into account. This, of course, is the internationally acclaimed ALARA principle put forward by the International Commission on Radiological Protection (ICRP). To avoid any misunderstanding it is worth emphasizing that the ALARA principle is applied to achieve exposures below the regulatory limits which must not be exceeded in normal operation of any nuclear facility including uranium mines and mills. The present regulatory limits for radiation exposures of atomic radiation workers are based on the recommendations of the ICRP and they are almost universally accepted. They should ensure that the risk from radiation exposure is not greater than the risk associated with working in a comparatively safe industry. Basically, there could be two extreme approaches to the regulation of uranium mining and milling. One extreme approach is to develop very extensive and detailed regulations and requirements covering all aspects of radiation protection. This is a somewhat autocratic approach to the regulatory process. This approach has two very serious shortcomings. If detailed requirements are set in regulations, due to the great variations of actual conditions at various mine-mill facilities, they have to be set as a compromise between the desirable requirements and those which could be met by practically all facilities. This approach takes away from the management of the facilities the initiative to strive for improved conditions. Requirements are spelled out in clear, understandable targets and the only worry of the management is to comply with these targets. One of the basic duties of management is to manage the operations in the most effective way with the maximum health and safety of the workers in mind.

Jan 1, 1981

By Robert P. King

In April, 1975 the Colorado School of Mines began monitoring rock mass response associated with a long- wall shield demonstration project near Raton, New Mexico. This project was sponsored by the U. S. Bureau of Mines (DOE) and performed at Kaiser Steel Corporation's York Canyon Mine. Two of the results of the intensive instrumentation effort are the empirical subsidence and horizontal strain models presented herein. These models are based on data gathered during mining three adjacent longwall panels (4N, 5N and 6N). A total of 251 permanent surveying monuments were monitored over the three-panel area. Lines of monuments were oriented along panel centerlines, perpendicular to centerlines and diagonal (45O) to centerlines. Active monuments were monitored twice a week, with less frequent monitoring of stable or slow moving monuments. Primary subsidence monitoring equipment consisted of an AGA Geometer Model 75 and a Wild T-2 Theodolite with -a Wild-Sercel DI-3S distomat.

Jan 1, 1979

By Edward K. E. ] [Williams

Conditioning is any treatment of an ore with or without reagents which affect its floatability. While it can start in crushing or grinding circuits and continue into the flotation circuit, conditioning will refer here only to reagent treatment in an agitated tank designed for the purpose. Such treatment is often unnecessary with sulphide ores and collectors or with amines,* but it has long been recognized as essential with fatty acid collectors in the flotation of non-sulphide minerals, The requirements can be extremely variable, depending upon ore alteration, the presence or absence of slimes, and 1 the minerals to be separated. The study described here was concerned with the recovery of oxidized molybdenum minerals from an ore containing the element in both sulphide and oxidized form. Flotation of the iron minerals with which the oxidized molybdenum was associated was the basis for the process. Recovery and optimum concentrate grade without desliming depended upon a twenty to thirty minute conditioning of the pulp with flotation reagents at forty to fifty percent solids and at high turbulence. The objective in the study was the determination of design and operating criteria for conditioners in order to permit scaling-up of the results without repeating the entire study on a larger scale.

Jan 1, 1968

By J. S. Walker

Public Law 95-87 enacted by Congress in 1977 and subsequent regulations require coal mine operators to predict the effects of mining on the environment prior to the start of mining. Prediction of the effects of mining on the local groundwater system is a difficult task due to its complex nature and the lack of detailed published information. An investigation of water level fluctuations in five we1 1s positioned over three consecutively mined longwall panels was initiated in conjunction with an intensive subsidence monitoring program. The purpose of this work was to provide detailed information which could be used to predict certain hydrologic effects of longwall mining in the Northern Appalachian Coal Region. The results of this case study indicate that water level fluct- uations in the local ground-water system above longwall panels is associated with subsidence and that the static water level will generally re- establish at or near the pre-mining elevation after mining is completed.

Jan 1, 1986