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By Rolf Christiansson, Daniel Johansson, Urban Åkeson, Henrik Ittner, Mats Olsson

"This paper presents two recent studies on the extent of blast damage after excavation in crystalline rock. The Swedish Transport Administration and the Swedish Nuclear Fuel and Waste Management Company (SKB) are both under regulations to limit excavation damage during construction of tunnels. SKB is also required to limit the Excavation Damage Zone (EDZ), as this could be a potential flow path for radionuclides in the planned repository for spent nuclear fuel. Presented in this paper are investigations of blast damage from three tunnel sites, a road tunnel, an experimental tunnel in Äspö Hard Rock Laboratory and an underground subway depot. As expected the fractures resulting from the bottom charge are both longer and more frequent then those mapped in the column charge. The results show that the requirement to limit blast damage according to Swedish regulations was fulfilled for the column charge at the three studied sites.1 INTRODUCTION The Swedish Transport Administration (TRV) and The Swedish Nuclear Fuel and Waste Management Company (SKB) have both recently completed studies related the extent of blast damage from modern explosives after excavation. SKB studies focused on blast damage from pumpable emulsion explosives for underground construction (Ittner and Bouvin 2015) and hydraulic connectivity in the EDZ (Ericsson et al. 2015). TRV had a broader focus with different types of explosives including blasting for both road cuts and tunnelling with pumpable emulsion explosives. Investigations by means of geophysics were also conducted (Olsson et al. 2015). High demands on perimeter control and excavation damage is usually required for underground constructions with a long operation time, such as public tunnels for transport or underground repositories for nuclear waste. This paper presents the findings of recent Swedish studies and aims to discuss the topic in a broader context."

Jan 1, 2016

By C. T. Twort

As technology and economic conditions allow mines to operate at ever greater depths, increasing demands are placed on the environmental engineer to adjust the capacity of the installed mine . - refrigeration systems. At the same time the engineer must satisfy the changing legislation, which demands that developments are carried out in as an energy efficient and environmentally accept- able manner. Following the trends outlined above, this paper is written to give an overview of the current and potential future refrigeration technology available to the mining industry. The effects that may be produced by the adoption in mining applications of the new generation of 'green' refrigerants are examined both at the design stage and when considering the viability of retrofitting existing systems so that they comply with the Montreal Protocol. An introduction to the concept of Total Energy Warming Impact (TEWI) is provided, with an explanation of its use in optimising system design and performance, and its incorporation as part of an environmental audit strategy. The paper concludes with a discussion of innovative refrigeration techniques and the possible future developments in legislation.

Jan 1, 1997

By Lee S. Richardson

Silicon is usually considered to be a useful metallic alloying element. To be more truthful, it is not a metal at all, but a semiconductor, whose electrical resistance (when pure) is high and decreases with temperature. We will join the metallurgists, at least for this paper, and refer to it as a metal. In its commercially available form, silicon is metallic in appearance, brittle, with a density of 2.33, less than that of aluminum. Silicon dioxide or quartz has a high heat of formation, which not only makes the metal a useful reductant for other materials, but also makes it difficult to reduce from its ore. The melting point is 1412°C, slightly less than steel, but substantially higher than aluminum or cast iron. The alloys of silicon with iron, usually called ferrosilicons, have some unique advantages. The melting points of most alloys are substantially below those of iron or silicon (Fig. 1). The two major compounds formed (FeSi and FeSi2) help somewhat in the reduction of silicon by their energies of formation, but the influence of these phases on the mechanical properties is more important. Four major groups of alloys are made -- silicon metal (>95% silicon), 75-85% ferrosilicon, 50% ferrosilicon, and silvery pig iron (12-22% silicon). The alloys between 50 and 65% silicon and between 25 and 40% silicon are normally avoided because of structural instabilities, presumably of the two compounds, leading to disintegration of the alloys on cooling.

Jan 1, 1974

By Robert Semrad, J. Colin Anderson

INTRODUCTION Sulphur is a mineral which accounts for 0.05% of the earth's crust and may be found either in its elemental state or as a compound. References to sulphur production and consumption are found in early antiquity and international trade of sulphur from volcanic deposits in Sicily began in the 1880's. The supply of sulphur consists of two components: the first is production, and the second is inventory. HISTORICAL SUPPLY Production World sulphur production in 1984 was approximately 53.5 million metric tons, compared to the 1970 level of 42 million metric tons. Of this 11.5 million metric tons production increase, brimstone accounted for close to 90%. Production distribution in 1984 was 62% brimstone, 21% pyrites and 17% other forms, while in 1970 it was 55%, 28% and 17%, respectively. Brimstone Production is derived either from mining operations (Frasch, underground melting and native refined) or as a by-product from hydrocarbons. World production in 1984 exceeded 33 million metric tons, up approximately 10 million metric tons from the 1970 level. This increase was uniformly distributed throughout the world as shown in Table A.

Jan 1, 1986

By S. J. Jung

The prime criteria in the design of underground openings with complicated geological structures is ground control. Stability of underground openings for deep mines is critical because incorrect orientation or geometry of shaft, stope, and accessways often results in the failure of openings due to high stress conditions. Current design procedures for complicated orientation and geometry of mines are rapidly becoming inadequate as mines are being developed. In this study, finite element method has been used with optimization criteria to design more stable and safe underground openings.

Jan 1, 1993

By D. H. Lynch

This paper is a general description of current Central Florida phosphate mining, beneficiation and product transportation. It is directed and believed to be of interest to engineers not familiar with this industry.

Jan 1, 1978

By Eric Jones, Leslie C. Thompson

Biological processes for cyanide detoxification in mine waste are receiving attention as an alternative to conventional chemical treatment options. Some of the advantages of biological treatment include: Low comparative treatment cost * Shorter treatment time * In Situ Treatment * Complete Detoxification - Ends long-term liability - Eliminates in-perpetuity monitoring - Natural Re-Vegetation potential Natural and non-toxic nutrients, by-products and process end-products Hecla Mining chose a bio-neutralization process developed by Pintail Systems, Inc. for cyanide detox in spent are and process solutions from heap leach operations at the Yellow Pine Unit. The Yellow Pine operation is located 50 air miles east of McCall, Idaho, in the Stibnite Mining District. This district is a historic mining district dating back to the early 1900's. During World War II, this district produced a majority of the antimony and tungsten the United States using for the war effort. More recently, the Stibnite district has been known for its gold production. Hecla Mining Company is based in Coeur d'Alene, Idaho, and is a leading domestic producer of precious metals and a major supplier of specialty aggregate and industrial minerals. Pintail Systems, Inc. is a company specializing in the development of biological treatment processes for mine waste remediation. PSI has offices in three states and a laboratory, pilot plant and field office in Aurora, Colorado

Jan 1, 1993

By M. E. Smith

Chile is the world's largest copper producer and as such sets the standard of practice in copper SX/EW design. The authors summarize the liner systems used at many of Chile's major copper producers both operating and planned. The evolution in the state of the art is also discussed, considering both economic factors and Chile's burgeoning environmentalism.

Jan 1, 1994

By G. M. Swinkels

It is generally accepted, that oxygen is a necessary reagent for the flotation of galena with xanthate. Recent measurements have shown (1) that under plant conditions oxygen may be in a short supply to the extent that it limits the rate of flotation. Thus, it becomes important to define the exact role of oxygen and establish a model for the rational design and control of flotation separations, involving oxygen as a reagent. All theories or, the flotation of galena assign oxygen the role of an oxidant. However, they disagree on a number of questions: 1) Is the galena or the xanthate being oxidized? 2) Is a lead dixanthate or dixanthogen the actual collector? 3) Is the oxidation process in which oxygen participates of a chemical or an electrochemical nature? The last question arises from the observation (2) that an anodic bias as well as oxygen will make a galena surface hydrophobic in the presence of xanthate. Theories which are based an the premise that the influence of oxygen is of an electrochemical nature offer elegant models of galena flotation. However, full advantage has not been taken of available electrochemical techniques to discriminate between theories and this is the area towards which this research has been directed (3).

Jan 1, 1970

By J. LeRoy Peterson

This paper presents some of the theoretical aspects as well as some results of actual plant operation of the Ty-Hukki Classifier. Dual classification steps within a unit vessel are achieved by controlled separation of the sand product under turbulant flow conditions, followed by further classification under strictly laminar flow conditions. Plant operation has shown some of the benefits of the superior sharpness of classification to be reduction of circulating load in grinding circuits, prevention of overgrinding, increase in mill feed rate and consequent reduction in cost per ton of ore.

Jan 1, 1966

By Bruce C. Trent

In order to effectively model subsidence caused by underground openings, a two-dimensional computer code has been developed which couples near- and far-field response. The near-field is simulated by a discrete element block code and a finite difference code represents the continuum region in the far-field. The explicit equations allow rapid and inexpensive solutions to geometries which may lead to subsidence. Two sample problems are presented which illustrate the important features of the code.

Jan 1, 1979

By Larry Diaz

A single stage ball mill-cyclone circuit was extensively tested for its reactions to step changes in three controllable variables: feed rate, water to cyclones, and water to the ball mill. A series of carefully designed tests are to be carried out in order to determine relationships between the various ball mill and cyclone parameters. Cyclone overflow particle size distribution is to be continuously monitored during the tests using an ultrasonic device. Other circuit variables that are to be measured and recorded are feed rate, ball mill mass flow, cyclone feed and overflow densities, cyclone feed sump level, water flows, etc. Once the circuit performance is defined, two types of grinding circuit control systems will be evaluated: (a) mass flow-based; (b) particle size- based. Results obtained by each approach in terms of feed rate and cyclone overflow size distributions are discussed. The high sensitivity of continuous particle size measurements to grinding circuit disturbances is emphasized.

Jan 1, 1971

By R. Vergunst, E. A. Devuyst, G. Robbins

By the middle of 1989 Inco will have applied its patented cyanide removal technology to seventeen commercial operations. Removal of cyanide from CIL slurry tailings is applied at Equity Silver and Inco's new 1.200 mtpd mill at Inco/Golden Knight. Detoxification of CIP tailings is carried out by Colosseum California (3.600 mtpd), Canamax's Ketza River (360 mtpd) and Westmin's Silbak Premier (2000 tpd) operations. Repulped tailings from Merrill-Crowe flowsheets are treated at Total Erikson's Mount Skukum (300 mtpd) and Skyline's Johnny Mountain (200 mtpd) mills and barren bleed at Inco/Queenston's McBean mill (500 mtpd). Lynngold's MacLellan mill (1800 mtpd) and ERG (40.000 mtpd) treat pond supernatant water. Plating shop cyanide effluents are decyanized at Kuntz Electroplating and two other plating shops in Ontario. Details regarding some of the above operations are given. Operating and capital cost estimates for various treatment options are discussed.

Jan 1, 1989

By X. Yin

Surface force measurements based on atomic force microscopy (AFM) are used to describe the wettability of surfaces, specifically kaolinite basal plane surfaces at a high resolution. The kaolinite particles (~500 nm) were ordered with either the silica tetrahedral face exposed or the alumina octahedral face exposed, and surface force measurements were made between a hydrophobic diamond-like-carbon (DLC) tip and the kaolinite faces at pH 4, which is around the isoelectric point of the DLC tip. Under these conditions, the effect of electrostatic interaction should be eliminated and only van der Waals interactions and hydrophobic-hydrophobic interactions are expected to contribute to the surface force. The wettabilities of the surfaces were determined from the magnitude of the surface force. Wettabilities of the kaolinite basal planes thus determined were compared with the corresponding wettabilities of talc and mica surfaces, which are well-known to be naturally hydrophobic, and hydrophilic surfaces, respectively. The results reveal that the silica tetrahedral face of kaolinte has a modest level of hydrophobicity, which may be due to the lack of hydrogen bonding sites. In contrast, the alumina octahedral face showed no hydrophobicity, since a layer of surface hydroxyl groups is present at the alumina face, resulting in a relatively strong interaction between this surface and water molecules. It is expected that, with a better understanding of the surface properties of kaolinite, further improvements in flotation separations and dewatering may be achieved.

Feb 1, 2012

By Douglas M. Smith

The town of Tayoltita, Durango is located at the bottom of the 2000 m. deep Rio Piaxtla canyon on the axis of the rugged Sierra Madre Occidental mountain range. Throughout most of the year access to the town is restricted to travel by mule or STOL aircraft. Silver and gold have been produced from epithermal veins in the north side of the canyon since 1757. During the last seventy-three years more than 4,588,000 kg. of silver and 76,322 kg. of gold have been produced from approximately 6,000,000 metric tons of ore. The Tayoltita mine is developed within a fault block bounded by normal faults which strike north-northwest and have opposing dips. A thickness of at least 1300 meters of late Cretaceous or early Tertiary volcanic rocks is exposed in the mine. These range in composition from andesite to rhyolite. Andesite predominates in the upper 750 meters of the section. The volcanic rocks were passively intruded by quartz-monzonite and andesite stocks during middle (?) Tertiary time. Mineralization spatially and temporally (?) related to the stocks occurs along the east boundary fault and in intersecting footwall fissures which strike east-west and northeast. Ore was deposited over a vertical range of up to 600 m. prior to tilting of the volcanic rocks 35 to 45° to the east. With few exceptions, the ore bodies are found within the lower 400 to 500 m. of the andesite. Argentite (acanthite), stromeyerite, jalpaite, electrum and native silver are the principal ore minerals. They occur in gangue composed of one or more of the following: quartz, calcite, bustamite, adularia, chlorite, and albite. Base-metal sulfides make up less than 1.5 percent by weight of the ore.

Jan 1, 1974

By Louis D. Murino

Compared to coal or many metals industries, talc must be considered a small, specialty market catering to niches and dependent primarily on the physical attributes of the mined and processed mineral rather than the chemical attributes with copper, lead or uranium concentrate, the primary objective is the percent metal that ultimately is refined by the smelter, as opposed to the brightness, particle size distribution, trace impurities or morphology. The latter constitute the important determinants of where, how and why talc and similar industrial minerals are used. This paper addresses the talc market-place: where it is, how much of a market there is, who the producers are, available capacity, market growth, and marketing techniques.

Jan 1, 1984

By Charles H. Ricker

Simulation models have been widely used to analyze the operations and characteristics of a variety of systems. Such models mimmick a projected reality by analyzing the interaction of the events, transactions, and facilities which combine to make up the system. The models are structured as a computer representation of the system components and their logical, precedence and timing relationships. The operation of the system is then simulated over some finite time interval to gather analytical and staistical data. This paper presents a method whereby bulk handling systems, either actual or proposed, may be analyzed by means of simulation models to project the enconomic consequences which may be expected from the system over some future time interval. An example is given to illustrate the construction of bulk handling simulation models, the derivation of performance data, and the analysis of the information with an eye to effective decision making.

Jan 1, 1974

By Rolph Linder

It is generally known and accepted that the efficiency of the blast furnace process, expressed by the symbols specific production and coke consumption, is influenced by a large number of variables connected to the type of burden, the alloy contents of the produced iron and the conditions of production as composition and preheating of the blast, the furnace heat losses and the possible use of fuels added on the tuyere level. It is furthermore obvious, that the coke consumption of the process will be influenced by specific production which could be said to be the result of two counter-acting influences. With high production, realized through intensive blowing, the passage time of the ore through the furnace is shortened leading to a decrease of the indirect reduction taking place in the upper part of the shaft within the temperature range of 300 to 1000°C. Simultaneously the external heat losses (constant in time) will be smaller calculated on each ton of iron and the resulting change in coke consumption will be the effect of both those influences. It is certainly of interest to be able to predetermine the effect of those variables before a change in the production practice is carried out.

Jan 1, 1964

By B. Howerton, M. M. Matlock, D. A. Atwood

In the Gold-Cyanide Process (GCP) the cyanide anions act to solubilize the gold and silver present in the ore, and mercury as well. The resulting mercury and cyanide rich effluent are serious health and environmental problems. Currently, there is no mercury treatment from the ore leach solution since there are no precipitating agents or other technologies which can be used effectively in the pH ~ 10solutions. Recently, however, we have developed a new chelate ligand that is impervious to this level of pH and it can be used to precipitate Hg from NaCN solutions. On an actual sample taken from an active gold mine the chelate selectively reduced the mercury level from 34.5 ppm to 0.008 ppm within 15 minutes. Importantly, the gold and silver levels remained unchanged throughout this process. Thus, the environmental impact of Hg released in the GCP can be drastically reduced. Moreover, with a mercury treatment technology now available it may be possible to change, or reinvent, the entire GCP process.

Jan 1, 2003

By J. R. Hindman

The vermiculite review arrived too late for the June issue. In 1992, production of commercial vermiculite in the United States increased 1 % to 170 kt (187,000 st), according to the US Bureau of Mines. The estimated value of vermiculite concentrate was $13.6 million, yielding an average value of $80/t ($72.50/st). Vermiculite is used in several physical forms. Use of the thermally exfoliated product include light weight aggregates, horticultural growth media, thermal insulation applications and absorbents for spill control and liquid waste containment. The untreated commercial concentrates are used as intumescent fillers in plaster board, gaskets and paints. Several chemically modified vermiculite products include clay-sized dispersions and granules for treating flue gas. South Africa was the only major foreign source of vermiculite used in the United States. It exported about 40 kt (44,000 st) to the United States last year. In 1992, Palabora Mining Co. began processing vermiculite in a new beneficiation mill at Phalabowra. It produced about 164 kt (181,000 st). Minor sources of foreign vermiculite concentrates consumed in the United States included about 140 kt (154,000 st) from China. Brazil also exports some concentrate to the United States.

Jan 1, 1993