Search Documents

By Fred N. Kissell

This U.S. Bureau of Mines report is a guide for the control of air contaminants during tunnel construction. Topics discussed are calculating air quantity requirements, types of ventilation systems, planning ventilation systems, control of methane gas, control of dust, control of diesel emission, ventilation to remove blasting fumes, measuring airflow, and measuring gases. This report does not provide detailed design information, but seeks to answer practical questions on air contamination issues.

Jan 1, 1995

By M. J. Daly

Historically, engineers and scientists, particularly those involved in the coal-mining industry, have been slow to adopt statistical methods. However, the need to obtain the maximum information .from expensive exploration and development programmes, and the current focus on total quality management, have led to a change in perceptions if classical statistical and geostatistical methods and their application as planning tools. Some if the underlying issues associated with the generally poor communications between statisticians and engineers/physical scientists, which contribute to some if the misconceptions relating to statistical methods, are discussed The potentially profitable application if a number if statistical techniques in the fields if geological evaluation and mine planning! development is also reviewed, with specific reference to the coal industry.

Jan 1, 1995

By E. Burgos Cruz

The behaviour of S, N and P during refining of Fe-18 wt%Cr-10 wt%Ni with calcium carbide was investigated. The effects of the initial contents of C and N in the metal phase, as well as the supply method of calcium carbide to the melt on the removal degrees of S and P were evaluated. Heats were carried out at 1873K, in MgO crucibles, using a laboratory induction furnace. It was observed that simultaneously with S and P, N and O have also participated in the reactions. It seems that, in fact, O governs the behaviour of the other elements dissolved in the melt and that N is had to the removal of P with calcium carbide. It was also noticed that high C content in the metal phase have not altered the dephosphorization and desuffirization degrees, but that the supply of calcium carbide done by injection led to a lower dephosphorization degree than the one obtained by dumping it.

Jan 1, 1995

By A. Benchekroun

The phosphate mining industry is confronted everywhere in the world with financial difficulties and low prices which prohibit further investments and development of new mines even in regions with a comparative cost advantage (North America/ North Africa/ and Middle East). But old mines are being progressively exhausted/ and if no replacement mines come on stream in the near future/ we may soon find ourselves (around the year 2000) with a global annual production capacity of 160 million tonnes of marketable phosphate rock instead of the capacity of 200 million tonnes existing today. Unless prices improve/ phosphate rock/ a non-renewable resource and a vital commodity to world agriculture/ may turn to be in short supply to world fertilizer industry. Whatever the extent of recovery of fertilizer demand/ the expected decline of the production capacity during the 1990 I s is bound to cause the disappearance by the year 2000 of the important surplus characterizing today the supply/demand balance.

Jan 1, 1995

By Richard N. Snyder

In this system for connecting blasting caps to the initiation source, the need for a redundant design structure provides more reliable method of explosive initiation. This is accomplished by using a complete system starting at the blasting control, through the initiation line structure through the initiation line and connecting blocks to the blasting cap. The connecting structure between the initiation device and the blasting caps may be connecting blocks or other means.

Jan 1, 1995

By Eugene R. Palowitch

From the late 1880s to the present, the Appalachian region continues to be a dominant supplier of premium-quality coals. The region contains an estimated 93.4 Gt (102.7 billion st) of demonstrated reserves in Alabama, eastern Kentucky, Maryland, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. Therefore, Appalachia will remain a source of quality coals for the metallurgical, export and utility markets. Figure 1 shows the annual production of coal in Appalachia and nationally from 1970 through 1993 (Energy Information Administration, 1994). During that 23-year period, annual domestic coal production almost doubled. Coal production from Appalachia increased at an average annual rate of only 0.7%. Coal production remained essentially constant at about 409 Mt/a (450 million stpy). Thus, Appalachia's market share decreased from 69.8% in 1970 to 47.2% in 1993 - a drop of almost one-third (Energy Information Administration, 1994).

Jan 1, 1995

By E. R. Bauer

The ground control aspects and occupational safety concerns of extended depth-of-cut mining are presented in this U.S. Bureau of Mines (USBM) report. The scope of extended cut use and typical face operations while extracting extended cuts is reported. A comparative review of roof fall fatalities and a statistical analysis of accidents and injuries for both extended and nonextended cut mining is included. The views and opinions on extended cutting from a series of interviews with mine workers in five states are summarized. In addition, some of the problems and safety concerns of this extraction system are mentioned.

Jan 1, 1995

By M A. Etheridge

The evolution of economic precious metal and copper-gold deposits in high-level igneous terranes is dependent on very efficient fluid focussing. This is most readily achieved by contemporaneous deformation, igneous intrusion and hydrothermal activity. Mineralisation in these environments generally occurs in fault and fault-vein arrays developed in the cover sedimentary and volcanics sequences above older regional scale fault systems. Such reactivated fault systems are particularly prone to developing tile complex fracture arrays, extreme local dilation and dramatic increases in permeability that are necessary to efficiently focus hydrothermal fluid and produce large mineral deposits. The arc systems of tilePacific rim are typically structurally and tectonically complex. At any given period in the evolution of an arc system, it may be dominated by extensional, compressional or strike-slip deformation. Indeed, it is common for the tectonic environment to change repeatedly through the development of a single arc segment. As a result, structures formed in one tectonic environment are commonly complexly reactivated in quite different environments later in arc evolution. These complexly reactivated structures have greater potential to localise extreme fracturing, dilation and fluid flux than primary structures. Application of this knowledge to practical exploration requires an understanding of the primary geometry of the controlling fault systems, the fault movements during reactivation, intrusion and mineralisation, and the consequent location and geometry of dilational sites. Simple 2D lineament analysis and targeting on lineament intersections does not suffice. Chemical processes that results from structurally focussed fluid flow may also contribute to permeability enhancement and further enhance fluid flux. Two main types of chemical feedback are important. The first involves selective dissolution of minerals during alteration and tile consequent production of increased porosity and permeability. The second occurs where alteration changes the mechanical properties of tile rock mass, especially where it leads to a greater propensity for fracture (eg by silification). In near-surface environments (< ~1 km), geomorphic processes complement fault systems in focussing fluid flow to develop sub-horizontal bodies of mineralisation, such as the giant Ladolam gold deposit (>42 million ounces of gold).   Along with classification schemes which stress crustal level, host rocks and alteration assemblages, the styles of high level 'epithermal' and reated deposits must also be considered in respect of their controlling co-active fault structures. Such structural understanding, combined with understanding of tile chemical processes involved (eg host rock reactivity), provides a major tool for exploration particularly in terrains obscured by deep weathering. Geological interpretation based on integration of field mapping with magnetic, radiometric and other remotely sensed imagery provides a powerful complementary tool to the traditional geochemical and geophysical targeting techniques. Timely and effective geological input is capable of reducing exploration risk and providing a more cost-effective basis for drilling and development. Examples of deposits associated with fault reactivation in extensional, compressional and strike-slip settings within arc systems are discussed in this context.

Jan 1, 1995

By K. Reipas

"Westmin Resources Ltd. operates the 3300 TPD H-W underground copper/zinc mine on Vancouver Island. Ore storage underground is handled in a 6000 tonne coarse ore bin and a 3000 tonne fine ore bin. Both of these bins have experienced significant wear since excavation and construction in 1985. Wear problems have included both deteriorating rock walls as well as worn out steel liners and concrete at the discharge points from the bins. Extensive rehabilitation work was completed in 1993.The basis o/this paper is the rehabilitation work done on the coarse ore bin. The design and installation of ground control measures are discussed. The bin access methods used to allow the work to proceed quickly and safely are also presented. This involved the use of a Tekfoam safety bulkhead to protect workers.IntroductionMine DescriptionThe H-W mine was commissioned in 1985. Mine access is by vertical shaft with most production areas at a depth of about 500 m. Host rocks are composed of andesite and rhyolite. Mine capacity of 3300 tonnes per day is achieved mainly by longhole open stoping methods, complemented by room and pillar mining. Metals recovered from the massive sulphide ore are copper, zinc, gold, and silver. Mineable reserves at January I, 1994 were 9.7 million tonnes."

Jan 1, 1995

By D Linn Coursen

In the proposed method, the charges are elongated and arranged in one or more arrays. The orientation of each charge in an array, its velocity of propagation of explosion, and the velocity of propagation of vibration in the formation are such that, at an outlying location where vibration is to be reduced, the onset of vibration from explosion of the first negligibly small increment of each charge arrives a finite time before that from explosion of the last negligibly small increment of that charge. The charges of each array are fired in accurately-timed sequence, with the times between initiations chosen so that, at the outlying location, the onset of vibration from explosion of the last small increment of each charge, except the last charge, arrives a negligibly small increment of time before the onset of vibration from explosion of the first negligibly small increment of the succeeding charge. With such timing, vibration may be reduced at the widest range of locations by tilting the boreholes so that the terminal end of each charge is directly above or below the terminal end of the succeeding charge.

Jan 1, 1995

By Guiseppe Bonifazi

This work applies the definition of "separation function" already introduced in the paper presented at the XVIII IMPC. This 'function" (defined for a certain size distribution after comminution of an ore) refers to the recovery distribution of a mineralogical species in a product made up of all the particles having at least a given content of that species. Many tests would be required to determine the liberation function for each mineralogical species, particularly for complex ores. Several stages of comminution would need to be examined and the mineralogical composition of the particles of each grain size class would need to be analyzed for each process step. A quick and dirty method is shown for obtaining the "separation function". It is based on the processing of data from topological maps of polished and/or thin representative sections of ore. By superimposing grids of different sizes over these maps and with appropriate combinations of mesh sizes, it is possible to simulate the grain size distributions linked to different stages of comminution and then evaluate the mineralogical composition of each grain. The procedure is carried out full automatically and can simulate a complete treatment circuit, imposing cut-off grades for the products at each separation phase. It is also possible to predict the results of treatment processes that involve grinding phases. The procedure has been successfully applied to complex ores containing several useful components.

Jan 1, 1995

By A. I. Kogut

Impurity minerals in fluorspar ores and concentrates from a deposit in Southern Africa have been studied by reflected light, transmitted light, and cathodoluminescence microscopy. The principal impurities are quartz, calcite, aegirine, apatite, ankerite, magnetite, goethite, and synchysite [Ca(La,Ce,Nd)(CO3)2F]. Cathodoluminescence microscopy was found to be very useful in studying the character of the fluorite and especially for recognizing the presence of apatite and calcite impurities. Fluorite exhibits blue, calcite shows yellow, and apatite has white, light purple, and pink cathodoluminescence. The cathodoluminescent character of apatite varies with its geological environment and position in the orebody. The results of this microscopic study show that phosphorus present in fluorite concentrates occurs principally in binary locked apatite-fluorite particles. Successive fluorite cleaner concentrates contain progressively smaller amounts of locked apatite-fluorite particles. Free apatite has been effectively partitioned to the final tailings.

Jan 1, 1995

By Y. C. Guan

The cementation of gold on to copper and zinc in ammoniacal solutions has been studied using rotating disc electrodes. The cathodic reduction of aurous ammine was studied on a gold rotating disc electrode and the anodic dissolution of copper and zinc was studied in the absence of aurous ammine. The cementation rate was found to be a first order with respect to the concentration of aurous ammine and to be proportional to the square root of the disc rotating speed. Based on the results obtained, it was concluded that the cementation reaction was controlled by mass transfer of aurous ammine to the reaction surface under the experimental conditions.

Jan 1, 1995

By Denby B

The ever increasing demand on land use has led to large areas of land being considered for development, which because of past mining activities are covered by substantial depths of fill materials. This paper examines the problem faced with the development of land infilled with open cast mining backfill, in predicting the behaviour of the fill upon development. To be able to design foundations suitable to withstand the movements that occur within open cast backfills or design a backfilling operation that produces land suitable for a proposed after development, a means of predicting backfill settlement is required. Factors critical to this prediction are the timing of backfilling operations, the compactive state of the backfill and the inundation of the backfill. The analysis of a considerable quantity of data collected from the monitoring of backfilling operations and backfill movement at a range of open cast coal sites located within the UK has given the authors a better understanding of how open cast backfills behave in terms of long-term creep settlement, collapse settlement and how these are effected by backfill scheduling. This knowledge has been encoded into a program running under Microsoft Windows that enables a user to make settlement predictions for a point, a given section or area or for the whole site. Differential settlements, critical to any development design, can also be determined between any two points taking into consideration the heterogeneous nature of open cast backfills. The program was tested with data from an open cast coal site in the UK. Compaction monitoring during the placement of the backfill material enabled a model of the backfill to be constructed taking into account backfill properties and scheduling. This model, taken as input into the program, enabled future backfill settlement predictions to be made. A comparison is given between these results and actual settlements obtained from a short-term settlement monitoring scheme.

Jan 1, 1995

By Gülhan Özbayoglu, Yusuf Ziya Akgök

The effect of cooling rate on the flotation behaviour of copper slags of flash smelter plant in Samsun was investigated. Fresh molten slag was solidified in laboratory scale in three different ways. All the samples were characterized by chemical and mineralogical analyses. The chemical analyses showed that samples prepared from fresh slag had 0.9 to 1 % Cu with 40 % Fe and 30 to 32 % SO2. Old pit slag samples contained between 1 to 3% copper. Microphotographs showed that rapidly cooled slags showed fine size distributions, e.g. the copper grains in granulated slag had sizes in 1-2 microns. On the other hand, the size of copper grains in slowly cooled slags increased above 40 microns. Flotation tests carried out by using potassium amyl xanthate and Flotanol-C showed that slowly cooled slag reduced the copper losses in the tailing and improved the grade of concentrate. Under the light of laboratory investigation, the pit dimensions of Samsun Plant have been modified which resulted in a pronounced improvement of the grade and recovery of concentrate produced at Samsun slag flotation circuit.

Jan 1, 1995

By P. C. O. Chukabarah

Many aerodynamic and thermodynamic properties (such as temperature, pressure, velocity and density) vary widely, and in random spatial and temporal manner for a given underground mine environment. Such variabilities are seldom evaluated statistically, even though the relevant theories and principles are both available and feasible. The main purpose of this paper is to introduce the methodology for applying aerostatistics to the analysis of multiple fan systems in mine aerology/ventilation. Pertinent data were obtained from a small multi-level European coal mine. Results confirmed that aerostatistical methodologies are computationally more efficient. Being grounded in solid engineering statistical theories, they can be used to analyze networked parameters in mine environmental engineering.

Jan 1, 1995

By Richard Hogg, Heechan Cho

Investigations of long-time grinding of fine quartz (to about 80% passing 0.35 pm) in a 0.6 liter stirred-media mill are described. Breakage rates and primary breakage distributions have been determined based on extensive characterization of the ground products by laser scattering/diffraction and gas adsorption. The results indicate that, while there is qualitative similarity between the breakage parameters for ultrafine and conventional (coarse) grinding, there are important, quantitative differences. In particular, it is found that primary breakage distributions become significantly narrower in the submicron sizes. The trend can be described using double-truncated log-normal distributions in which both a maximum (breaking) size and a grind limit are specified. The breakage distributions become progressively narrower as the size being broken becomes finer. Breakage rates follow a typical, consistent pattern in which the rate decreases with size according to a simple power law. Further decrease in the rates seems to occur after very long grinding times when the entire mill contents become finer than about 1µm. The effect is explained as a result of changes in the rate/size relationship in the submicron range.

Jan 1, 1995

The Golden Cross mine is situated in a sensitive environmental setting on the North Island of New Zealand, about 150 kilometres south-east of Auckland and about 8 kilometres NW of Waihi. The mine is situated in dipping topography, with volcanic ashes making up soils, fault zones running through the area, and rainfall of about 3m per year on average. Water management is the most demanding environmental challenge on site, and a comprehensive programme has been put in place to address tailings deposition, long term tailings storage, and water treatment during and after operations.

Jan 1, 1995

By E. L. Gillenwater

Coal mine planning has three distinct decision levels: (1) decisions made at the upper level of management that determine production requirements for specific mines, (2) decisions made at the middle management level, the mine level, that determine how the mine satisfies its production requirements, and (3) decisions made at the operating level of management, the sectional level, that determine the sequencing of machine movements at the face. In this paper, the underground production scheduling problem is formulated in multi-stages using the Hierarchical Production Planning (HPP) approach. Two linear programming HPP models for accomplishing decisions at the first two levels are developed. Both models address the aggregate production planning process. The Mine Production Scheduling (MPS) model permits determination of monthly production and inventory levels. The Section Production Scheduling (SPS) model incorporates a quality blending requirement into the determination of weekly sectional production and inventory levels.

Jan 1, 1995

By R. J. Kriek, J. J. Cruywagen, W. J. Engelbrecht

Selective photo reduction, using the semiconductor TiO2 under UV irradiation, has been investigated as a possible recovery and/or separation method for the PGM's rhodium, palladium and platinum. The effect of pH value and concentration of the sacrificial reducing agent (ethanol) on the rate of reduction of Rh (III), Pd (II) and Pt(IV) ions have been determined separately for these ions as well as for some mixtures. Conditions favourable for the reduction and adsorption (or precipitation) on TiO2 have been established. It has been found that already deposited Pt or Pd metal promotes reduction of Rh (III) ions at a pH value where it would not otherwise be reduced. A method for the separation of a mixture comprising Rh (III), Pd(II) and Pt (IV), based on photo reduction and adsorption on the TiO2, is proposed.

Jan 1, 1995