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By David J. Hatem

Tunnels and underground projects are inherently more risky than vertical projects, which typically utilize more conventional design and construction approaches and are undertaken in the context of relatively ascertained and defined conditions. On tunnel and under-ground projects, there are a host of special risk factors, including unknowns and uncertainties as to the physical and behavioral characteristics of the ground, the inextricable interdependence and necessary interaction of design decisions and construction means and methods with those ground conditions as well as the manner in which risks are allocated among project participants for un-anticipated subsurface conditions. Public-private partnerships (PPP) projects, in their own respects (and independent of any major subsurface component), pose significant risk for all private sector participants. The main driver of owners to procure projects using PPP is financial, as often all, or substantially all, of the design and construction risk are transferred to the private sector consortium, including the design-build (D-B) team. For a concerning number of those public owners, that risk transfer regime includes rather onerous and aggressive contractual terms that allocate to the private sector participants substantially all risks associated with the encountering of unanticipated subsurface conditions. These aggressive risk allocation provisions, while directly impacting project participants upstream of the consulting engineer, have an indirect and corresponding risk intensifying effect upon consulting engineer professional liability exposure. There are many factors that result in increased professional liability exposure for consulting engineers involved in PPP projects. The more prominent and prevalent of those factors fall into the following categories:

By G. Davis

It is well known that the anticipated mineral price at the start of a prospective mineral project can have an overwhelming effect on a property's ex ante value. However, possible price movements throughout the life of a project can also have an impact on this value. This paper demonstrates how different potential price paths can affect project value. When considering commodity price projections for mine valuations, it is thus necessary to estimate not only the expected commodity price at the start of the project, but also the manner in which that price is likely to fluctuate throughout the project's life.

Jan 1, 1995

By R. Jedrzejczak

Endako Mine is an open pit molybdenum mine located in the north central region of British Columbia, Canada, approximately 160 km. west of Prince George. Production for the latter part of 1992 is expected to average at 63,500 tonnes per day of which 27,000 tpd constitute the mill feed. This production is achieved with five 15 to 19 cu. yd. electric shovels, six Euclid R190 and two Unit Rig M120 diesel-electric haul trucks, and three 121;.1 inch electric rotary drills. There are three ore zones delineated into pit areas called the Endako, Denak East and Denak West. Present mill feed source is the South East stage of the Endako Pit while the stripping is carried out in the South Wall stage also of the Endako Pit. The mine high grade aggregate is reduced in the primary and secondary crushing circuits before processing in conventional RM/BM/flotation circuits. The majority of the Molybdenum Sulphide (MoS2) is roasted on site to produce technical grade Molybdenum Oxide (MoO3) while a portion is further refined and treated to yield a 99.9% pure Molybdenum Sulphide (MoS2) "Ultrapure" product.

Jan 1, 1993

By J. H. Dietz

The electric assist option for diesel-electric trucks can improve truck productivity while maintaining the inherent flexibility of a truck and shovel operation. In addition, the resulting cost reductions offer a rapid investment payback for many mine situations. A review of the present technology and performance experiences verify the projected benefits in productivity and operating cost. New technologies can further improve the productivity/cost scenario.

Jan 1, 1984

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 P. E. Damon

An arsenal of isotopic techniques is avail-able that can date the full range of hydrothermal ore deposits. The following are prerequisites for ideal results: (1) Careful collection of samples that are related to the event in a field and process context; (2) Optical examination of the component selected for dating to be sure that it has not been altered; (3) Careful preparation of a pure component of the sample selected for dating; (4) Precise and accurate measurement; (5) Knowledgeable interpretation of the data with reference to decay systematics, properties of the component analyzed as well as the field context and thermochemical environment of the ore process.

Jan 1, 1992

By E. Watkins, S. J. Schatzel, V. Gangrade, R. Kimutis, J. Addis, C. Hollerich

The recent shale gas revolution in the United States has led to the drilling of hundreds of unconventional shale gas wells in active and future coal reserves in traditional coal-mining regions of Pennsylvania, West Virginia, and Ohio. This paper summarizes the impact of a shale gas well breach on the mine ventilation system of an operating longwall panel. This study utilizes a 1:30 scaled Longwall Instrumented Aerodynamic Model (LIAM) to simulate a single-panel longwall operation. The LIAM will be utilized to identify flow pathways and distribution patterns of gas from breached gas well scenarios in an operating longwall in the Pittsburgh Coal Seam. Sulfur hexafluoride (SF6) tracer gas is utilized to simulate a breached gas well. Preliminary findings suggest that the breached gas is diluted to regulatory levels and does not accumulate in the mine entries or in the longwall gob when the longwall panel is adequately ventilated. Overall, this study characterizes the potential interaction between shale gas wells and the mine environment in the event of a gas well breach, which provides critical information to the industry and regulatory agencies for improving safety, health, and welfare of miners.

Mar 2, 2022

By Valerie Kollonitsch

Functional mineral pigments are used in large quantities in paint, paper, plastics, rubber, textiles, agriculture, and several other industries. U.S. consumption in 1969 is estimated at over 5 million tons a year, valued at nearly $150 million, as shown in Table 1. Originally extender pigments were employed only to lower cost. They were thought of merely as adulterants to replace more expensive prime pigments and binders. However, over the years their role has become better understood, and today their main functions are: - Increasing strength, stability, and service life. - Improving surface properties. - Enhancing application and processing properties. - Extending prime pigments. - Controlling viscosity and package stability - Lowering overall costs of the finished product. The principal minerals used as functional pigments are kaolin, ground calcium carbonate, talc, and asbestos. Other minerals include barytes, attapulgite, diatomite, mica, ground silica, wollastonite, and nepheline syenite. Several synthetic products, including precipitated calcium carbonate; precipitated, gel, and fumed silica; alumina trihydrate; and barium sulfate, compete with mineral products. They are more expensive, but often have more closely controlled particle size or other properties because they can be tailor-made according to the requirements. This paper covers only natural products selling for $10 or more a ton, approximately the lower limit for pigment grades. Data refer only to consumption in pigment applications. For example, such applications as filter aids for diatomite are not included. Key properties of the major mineral pigments are given in Table 2. It is important to note that these properties are primarily physical rather than chemical. In general, these products are sold to performance specifications for what they can do rather than on chemical composition specifications on what they contain.

Jan 1, 1969

By Russell Frith

The entire subject area of micro-seismic events due to stored strain energy, as distinct from gas-driven coal outbursts, can be readily sub-divided into firstly events with their energy source from within the coal seam (termed “bursts”) and secondly, event with their energy source outside of the coal seam in either the overburden and/or floor strata. The reason for sub-dividing micro-seismic events in this manner is that if the causation mechanisms and associated geotechnical conditions are materially different, then effective pre-mining predictions and subsequent operational controls may also differ. Attempting to explain a multitude of micro-seismic event types without consideration of varying source mechanisms will inevitably lead to inadequate causal explanations and effective controls.

By H. H. Hayden

The accident repeater-40 you have one at your mine? Unless your company is vastly different from most coal companies, you will find that a small percentage (11-12%) of your employees will have a large percentage (47-50%) of your accidents. When you find out that this is a fact, what do you do? First, you establish a set of guidelines that can be used in identifying the ?accident repeater?. Next, you determine the type of action necessary to improve work habits and safety performance of the accident repeater. With these two steps in mind, objectives are developed for an ?accident repeater? program.

Jan 1, 1984

By Wayne W. Murdy

Since 1993, Newmont Mining has been growing through the development 'q of three major foreign mining operations with a fourth under construction. The first project, Yanacocha in Peru, began operating in October 1993. This occurred at a time when political and business risk in that country was considered high. In 1995, Newmont began operating the Muruntau joint venture in Uzbekistan. It is the first mining project of its kind in the Confederation of Independent States (CIS). In early 1996, Newmont started operating the Minahasa Mine in Indonesia. In early 1997, Newmont began construction of a $1.9-billion project in Indonesia. The company is also completing a feasibility study with its partner for the development of a gold operation in Mexico. All of these projects have been considered "risky" by most standards. Newmont has been successful in all of them through risk mitigation programs. These programs include using strong and successful in-country partners, concentrating on developing a strong national workforce with minimal expatriate employees, using World Bank, European Bank for Reconstruction and Development (EBRD) and International Finance Corp. (IFC) financing and building and maintaining strong ties with host governments.

Jan 1, 1997

By M. D. Flavel, J. C. Motz, G. V. Jergensen

Introduction Compared to the gyratory crusher, the cone crusher is character¬ized by its higher speed and a flat crushing chamber design which is intended to give a high capacity and reduction ratio for materials suitable to this type of processing. The aim is to retain material longer in the crushing chamber to do more work on material as it is being processed. A concept of how a piece of stone might flow through a secondary crushing chamber is shown in Fig. 45. The number of times material will be nipped during crushing will depend on material size, friability, and the geometry of the crushing chamber as well as its speed and eccentric throw. Cone crushers are usually specified in terms of closed-side setting (CSS) and a given quantity of material passing a particular square-mesh screen size. A criterion of product passing closed-side setting is often available. This value will vary according to the particular crusher design and the details of its applica¬tion. Essentially, cone crushers can be classified into distinct types, depending on their duty. Crusher sizes for all duties are described by terms arising out of common industry usage, such as 3-ft, 7-ft, etc., which refer to the crushing-head (mantle) diameter. At present the range of sizes available varies from approximately 2 to 10 ft diam. Weights vary in the range of 5 to 200 tons, and connected horsepowers range from 10 through 700. There are so many variations that specifics should be obtained from machine manufacturers. The crushing chambers that are fitted to various machines are also often referred to by terms arising out of common usage, such as standard for secondary crushers, and short head for tertiary crush¬ers, which refer specifically to the Symons design. Also used are more specific but equally vague descriptions, such as coarse, intermedi¬ate, and fine chambers. Some manufacturers such as Allis-Chalmers with their Hydrocone crushers refer to the model number of the machine by the feed opening and the diameter of the mantle. For example, a Model 10-84 Hydrocone crusher has an 84-in. diam man¬tle, and is capable of accepting a 10-in. diam sphere at the feed point to the crushing chamber. Rexnord and Telsmith define crushing cavi¬ties in their capacity tables as feed openings at minimum recommended discharge settings (closed-side settings). Each practice offers guidelines which should be carefully defined for the specific crushing problem. The utilization of a cone crusher depends on how well it is controlled and the features of the circuit in which it operates. Normally, it will operate in the range of 75 to 85% of the peak capacity. It is likely that industry pressures will call for a standarized de¬ applied crushing power. Experience has shown that the crushing process is more controllable if certain reduction ratios are adhered to for each stage. Technically, this is defined as that size of feed (in. or mm) of which 80% will pass, divided by the size of the product (in. or mm) which 80% will pass. Secondary Crushers These are the cone crushers which accept suitable feed size material either prepared by a primary crusher or occurring naturally, and reduce it to a size suitable for marketing in one stage, or make feed for subsequent crushing or grinding stages. Secondary crushers have feed openings of 4 to 25 in. in the larger (7-ft) models down to a 2'/a to 4 in. in the smallest 24-in. models. Reduction ratios normally range between 3:1 and seldom more than 5:1. In the 7-ft models, the cone crusher typically makes a product all passing 2 in., but this is dependent on the machine design and properties of the material being treated. Secondary crushers most commonly operate in open circuit. They also are operated in closed circuit with a vibrating screen, depending upon product requirements and conditions where the reduction ratio does not cause excessive power draw and build-up of circulating load. Screening ahead of secondary crushers is generally recommended, especially where the feed contains more than 25% material smaller than the desired closed-side setting. Tertiary Crushers These are cone crushers that normally take secondary crusher product and reduce it to a marketable product or make it suitable for subsequent comminution steps. The reduction achieved is a func¬tion of the crusher design and the properties of the material to be treated. The reduction ratio is normally in the range between 1.5 and 2 to 1, and seldom more than 3 to 1. The tertiary crusher normally operates in closed circuit with a vibrating screen and makes a product smaller than all passing 'h or 5/8 in. Fine Crushers Sometimes these machines are called sand crushers and are called by various manufacturer brand names, such as Gyradisc, Hydrofine, V.F.C., and others. A cross section of a Symons Gyradisc crusher is shown in Fig. 46. Essentially, these crushers would be used in a fourth-stage crushing operation, but could be called on to reduce a screened feed size fraction from a secondary or primary crushing operation. This type of crusher normally receives feed no coarser than 1'h in. that is scalped of all over-sized material and operates in closed circuit with a vibrating screen. For average materials, typical product is '/e in. top size, although a -10 mesh product can be produced on those materials having suitable characteristics. The crusher is nor¬mally operated in a separate circuit from the main crushing plant because of the variations in output rates that are caused by varying physical properties in the feed. The reduction ratio is generally less than 2:1, and circulating loads are generally high. More interparticle crushing takes place in these machines than with conventional cone crushers and capacities can be more sensitive to changes in moisture content, feed size graduation, and other physical properties. Design Features For the various applications, crusher manufacturers normally have a range of crushers of different sizes and power ratings to select from.

Jan 1, 1985

By K. W. Morris

Of the fossil fuels used for power generation coal is by far the most variable and complex in its properties. A thorough review of the characteristics of the coal to be fired is essential before boiler design can begin. Major parameters such as heating value, moisture content and ash properties will determine not only the boiler size and configuration, but also the performance of the unit with respect to the thermal efficiency, particulate and gaseous emissions, and unit availability and reliability. An example of a review completed on a large low-rank coal deposit for a power plant will be described.

Jan 1, 1983

By D. Tolgyesi, L. P. Gignac

Mine development has evolved in the past 15 years from a human-paced system using hand-held drills and track-bound equipment to a mechanized system using specialized equipment for each component of the development cycle. In most Canadian hard-rock mines, face advance is achieved by the following sequential activities: drilling, explosive loading, mucking and ground support. The state-of-the-art for each work element is reviewed and methods for performance estimates proposed. The entire development system and its production capabilities are considered based on equipment reliabilities, spare units, haulage distances, and muck bay spacing. The effect of the number of working faces on the system's performance will also be analyzed. Manuscript not received in time for publication.

Jan 1, 1983

By C. A. Pryor

The aggregates industry is the largest minerals industry in the United States producing over 2.6 billion metric tons of crushed stone, sand and gravel annually. Approximately 5% of that production is fine material, passing a 75-micron mesh sieve. Of that amount, about 77% is not sold and represents one of the major industry issues. The material accumulates in stockpiles and settling ponds having an operational and economic impact on the site’s bottom line. Many factors cause this material to be produced: from blasting and processing techniques all the way to end use specifications.

Jan 1, 2002

By V. B. Achanti

Laboratory studies were carried out at West Virginia University to investigate the rock fragmentation mechanism by continuous miners using an automated rotary cutting simulator. The primary factors influencing the: fragmentation process were found to be: bit spacing, bit geometry, depth of cut, and cutting drum rotational speed. This paper presents the influence of these parameters in achieving optimum energy consumption and minimizing dust generation during rock fragmentation process. Three bits were used simultaneously on Indiana limestone while the bit tip angle was varied from 60° to 90°. Bit spacing was varied from 2.54 cm (1 in.) to 5.08 cm (2 in.) while the cutting process was assessed for varying cutting depths. Respirable dust generated during the course of the experiments was analyzed utilizing cascade impactors. Assessment of these parameters has led to a better understanding of the cutting mechanism by continuous miners in terms of energy consumption and dust generation.

Jan 1, 1997

By Peter Jackson

Over a quarter of a century ago a New Zealand physicist suggested the possibility of detecting coal seam discontinuities by a seismic method carried out underground in the mine workings (Evison 1955). Twenty years ago initial experiments were performed in Germany (Krey 1963). Since then research has continued, notably in Britain and Germany, in order to provide a reliable fault and washout detection system. The National Coal Board of Great Britain has now carried out more than 250 surveys in Britain, France and Australia. The first NCB survey in the U.S., a successful application of the technique to an Ohio coal seam, will be described and the strengths and limitations of the method explained.

Jan 1, 1984

By P. R. Taylor

Three refractory gold concentrates have been tested to evaluate the effect of roasting with hydrated lime followed by cyanidation. The results indicate that it may be possible to roast in such a manner as to contain nearly all of the sulfur, arsenic and antimony in the roaster calcine. Cyanidation results indicate that the gold recoveries are greater than 80% for all three concentrates.

Jan 1, 1993

By Yoshihiro Kawarabata

INTRODUCTION With only about 30% of Japan's entire population served by sewer systems at the end of 1980, extensive sewerage construction programs have been implemented. As major sewer networks in large cities are near completion, construction of smaller sewer networks in less populated areas and branch sewers in urban areas is on the rise, where a demand for sewer tunnels of 600mm to 1500mm diameter is very heavy. The pipe jacking technique, usually employed to excavate such small diameter tunnels, therefore has become the subject of further technological development and sophistication to cope with the increasing volume of construction. At the 1979 RETC, the state of the art on the slurry shield tunneling method at that time was reported. This paper is a follow up to the last paper and discusses a newly developed boulder crushing equipment and automatic pipe jacking system for the slurry shield method and their application. Such technological advancement as high-degree mechanization and automation will significantly improve tunneling operations in response to the aging society to come. Through application of the technique on so called factory automation, this is a step towards field automation for the construction industry.

Jan 1, 1983

By O. M. S. Rodrigues

The kaolinite presence in bauxite ores increases caustic soda consumption during the digestion step in the Bayer process. Depending on the kaolinite content, the utilization of the ore in the Bayer process may be unfeasible. This investigation addressed the variables involved in kaolinite flotation through microflotation experiments in a Hallimond tube and zeta potential determinations. The tests were performed with a pure sample of kaolinite (96%). Five collectors were tested: Duomeen T (DT), cetyl pyridinium chloride (CPC), cetyltrimethylammonium bromide (CTAB), dodecylamine (DDA) and Flotigam EDA (EDA). Four of them performed well as collectors, at a concentration of 1x10-4 mol/L: CPC, CTAB, DDA and EDA. The kaolinite isoelectric point (IEP) was determined at pH = 4.6. The IEP was shifted towards higher pH values in the collectors? presence, indicating specific adsorption onto the mineral surface.

Jan 1, 2011