Search Documents

By John Carson

Belt feeders are commonly used to meter the flow of bulk solids from bins and hoppers. If the interface between the hopper outlet and belt feeder is not designed correctly, flow from the bin may be severely compromised, resulting in problems of no-flow, segregation, flooding, etc. By knowing the flow characteristics of the bulk solid being handled and applying proven design techniques, such problems can be avoided. Relevant bulk solids flow characteristics are identified, along with measurement techniques. Design procedures for correcting problems with existing feeders as well as proper design of new feeders are presented, along with case histories of successful application of these procedures.

Jan 1, 2008

MULSIM/NL and La Model are displacement-discontinuity programs which have been used quite successfully in the past to provide detailed structural models of various single and multiple-seam mining situations. However, both of these programs required fairly complex details of the mine plan and topography to be manually input into the program, often taking several days of work. Recently, automatic mine and topographic grid generation capabilities have been added to the MULSIM/NL and La Model programs, reducing the input time requirements from days to hours. This paper discusses the algorithms used for the automatic grid generation and demonstrates the utility of the new capabilities with a case study.

Jan 1, 2003

By Paul M. Godlewski, Roberto J. Guardia

Hundreds of highway and rail transportation tunnels in North America have been rehabilitated in the last two decades. Tunnel rehabilitation is usually dictated by an owner’s need to extend the working life of the structure, but typically has the added benefit of increasing capacity (greater speed or increased clearance) and enhancing safety. Not only has rehabilitation proven to be an economical alternative to new tunneling, but it can be safely accomplished by working during short work “windows” without taking the tunnel out of service. This paper presents methodology for planning and designing of tunnel rehabilitation projects, and case histories illustrate successful excavation and support technologies.

Jan 1, 2003

On my arrival in New York after the Russian examinations John D. Ryan, president of Anaconda, asked me what my plans were. I told him I wanted to be useful somehow in the World War that we had entered while I was away, but I did not know how. Ryan and Thayer told me that the new American Air Corps was gathering a group of executives, most of them young, to go to France as Army officers to help with the industrial side of our aviation activities. This would include construction of military airports, maintenance, and supply for our rapidly growing Air Corps. They thought I might be accepted in this group of about 30. It seemed to be just what I wanted, and I put in my application at once. My application was accepted about three weeks later and I was told to come to Washington to take physical and other tests and to meet others of the group. I liked them. They were a cross section of competent American manufacturers, bankers, automobile executives, and merchants. I was the only miner. I had many discussions in the days in Washington with members of our organization and others I knew who were going into war service. Attitudes were very different from those 55 years later. There was no discussion as to whether war was right or wrong. We were in it and must do all we could to help. At the same time there was a holdover from the days when, at least for the elite, war was high adventure. Even the most high-minded did not then realize that war is a horrible form of wholesale murder and, in 1917, it would have been treason to suggest this. I had two weeks before our industrial group was to start work which gave me time for a hurried trip to Berkeley where Dorothy and I announced our engagement.

Jan 1, 1976

By R. P. King, M. K. McCarter, K. S. Free

Mine plans typically consider the profits and costs associated with extracting and processing minerals into marketable products. Interrelationships between mine and mill costs are often overlooked during the process of mine plan optimization. A simple and quick method for predicting milling costs for a given block would improve the planning process, especially if the procedure could be incorporated as part of routine ore grade analysis of drill core or cuttings. Incorporating milling costs as part of the mine planning process could improve overall optimization of the mine/mill combination. A method developed by the Utah Comminution Center (UCC) at the University of Utah provides a possible answer to the need for quick and reliable grinding cost estimation (King et al., 1996). Using results from single-particle impact tests, a work index, called the Utah Load Cell Work Index (ULCWI), is calculated. The potential for routine use of the new method is explored by comparing ULCWI values with corresponding Bond Work Index (BWI) values for eight mineral materials (Free, 2000).

Jan 1, 2004

By Mark Gershon

This paper describes an application of a new approach to mine planning and production scheduling in a gold mine. The technique, limited to use in open pit mines (but not limited to gold), has been described previously (Gershon, 1987). The-computer program used is the HOPS software, which has been described previously as well (Gershon, 1988). The mine is scheduled for the production of 8,000 blocks out of a mine having 25,000 blocks (50 x 50 x 10). The technique is based on the concept of inverted cones (Gershon, 1987). While it does not provide a true optimization of results, it does approximate the optimal situation. As opposed to most scheduling software that only serves as a computerized notepad for the scheduler, the use of this approach allows for a scheduling intelligence to be built into the software.

Jan 1, 1989

By E. Topuz, J. Mastoris

The problem of defining the optimum final limits of an open-pit mine has challenged the mining industry for the last three decades. The difficulty results mainly from the great number of variables involved and from the sheer computational effort required in real-life applications. An actual lignite deposit is used in this study to introduce and apply a new methodology that can be used as a basis for surface-mine design optimization. A geologic-reserves model of the deposit is first developed with the use of an integrated geostatistical-modeling package. The model is transformed into an economic one through the use of flexible objective function formulation(s). The final open-pit limits are then optimized using a competent commercial optimizer, and comparative-sensitivity analyses are performed to study the effect of some basic mining and economic parameters on the optimal pit design. The conclusions drawn can develop useful guidelines for decision making by the mine operator.

Jan 1, 1996

By Patrick G. Hill

This paper discusses safety protocols for Kiewit Construction’s Level (3) project. The Level (3) project will cover a majority of the United States, and literally thousands of site operations will be conducted over a wide geographic area under challenging conditions; rivers, roads and other features, both from the surface and often for great and from boring pits. Developing a progressive safety plan for fast-track linear projects using micro-trenching and directional boring techniques requires significant investigation, planning and evaluation. Safety protocols for inner duct installation, to be accomplished with extensive use of directional boring is an essential part of the safety plan for network construction. In light of the shear volume of work and the geographical extent of this project, in many different types of terrain, this paper will identify approaches to safety applicable to fast-track linear projects, whether surface or underground-based. Establishing a safety culture into all aspects of this operation will improve productivity and cut unnecessary expenses. This new approach involves continual improvement and evaluation of hazard analyses, inspection procedures and training.

Jan 1, 1999

By Michael Schultz, Gregory Sanders

The City of New Haven is proposing to construct Downtown Storm Sewer Infrastructure Improvement project to mitigate on-going stormwater flooding in the Long Wharf District. The proposed project includes a 200 cubic feet per second (cfs) stormwater pump station; and a 914 meter (3,000 linear feet) long tunnel segment with an internal diameter of 2.1 meters (84-inches). The tunnel alignment will cross under the Long Warf railyard and then continue parallel to the Vison Trail Route. This paper presents the local geology and subsurface conditions, as well as discusses the major project challenges and risks including construction in soft marine soils and encountering remnants of the former wharf.

Jun 13, 2021

By Dale C. Matthews

The Getchell Gold Hine is located about 40 miles northeast of Winnemucca, Nevada. Gold was discovered at the mine in 1934 and production was started in 1938 and ended in 1967 for its first phase of operation. Gold production during this period was about 800,000 ounces. In 1983, FirstHiss Gold Inc. purchased the property and initiated an exploration program that proved minable reserves of about 1,300,000 ounces of gold remained in the mine. During the exploration period, metallurgical testing was conducted to determine the most economical process that could be utilized for recovery of gold from the very refractory ore. After extensive investigation, pressure oxidation of the ore was selected, Engineering for the new plant commenced in 1987 and construction was completed in 1989 at a cost of about $87,400,000.00, not including financing cost.

Jan 1, 1990

By A. Smithson

It is generally accepted by British mining engineers that coal will continue to be worked by the. advancing or retreating longwall system for the foreseeable future. At the coal face, the emphasis will be on better machine utilization; increased equipment reliability; modular design and more standardization; remote control and monitoring; and a continuing drive to increase productivity and safety. Improvements at the face can be sustained only if there are corresponding improvements in efficiency elsewhere in the mine. Coal handling systems, for example, must be able to accept increased tonnages without creating bottlenecks. As workings move further from the shafts, the time taken to transport men and materials must be kept within reasonable limits. Development drivages must he on schedule to be ready for the planned opening of new faces, and face ends must keep up with faster moving faces.

Jan 8, 1981

By L. J. E. Hofer, L. F. Zeiler, D. A. Giardino

The Jones Trickett Ratio (JTR) is generally used in investigations of fires and explosions for the determination of the composition of the fuel. This paper takes a close look at the JTR and finds it unreliable and ambiguous for the determination of fuel composition. A new index is presented, termed the (H/C) Index which uniquely determines the fuel composition. The (H/C) Index is simple to use requiring only the results of a single gas analysis of the combustion products. Experimental data testing the (H/C) Index for methane, propane, ethylene and coal dust are given, showing that the Index unambiguously determines the composition of the fuel. The (H/C) Index is also applied to the gas analysis data of several mine fires, illustrating how the Index changes with the progression of the mine fire.

Jan 1, 1993

By J. H. Fewings

The rapidly escalating capital costs for new projects, or extension of existing projects, has placed greater emphasis on maximum use of existing resources. Thus, when increased grinding capacity was required to achieve metal production from lead-zinc ores a number of alternate approaches were studied. The most cost effective way of achieving the required 5% increase in grinding circuit capacity was to install upgraded instrumentation and computer control of grinding - Fewings, Wickham and Wiseman (1). Once the computer installation cost had been borne by the financial returns from that project, other projects involving computer control were economically viable on an Incremental cost basis. These Included centralised control of tailings thickening and return circuit water distribution, centralised control of the crushing plant and use of the computer as a data processor for an on-stream analysis system for flotation slurries.

Jan 1, 1979

By André Vervoort, Jef Caers

Compound lognormal distributions serve as new generalized distribution laws for analyzing and estimating ore value distributions or related properties such as the average ore grade. These models are an alternative to the well known lognormal distribution. They are the translation of general geological constraints on the genesis of the deposit cumulated in suitable statistical properties. In this paper a maximum likelihood framework is established for estimating the parameters of such laws or parameter functions thereof. It is shown that under certain conditions maximum likelihood estimation is accurate and efficient in estimating the mean value even when relatively few samples are available. The method is based on a numerical maximization of the likelihood function of these models given the data. Confidence limits on these estimates are set up using resampling techniques such as the bootstrap. By this a complete methodology is presented for inference on ore grade distributions such as is shown in an example of gold data from the Merriespruit mine (South Africa) and the diamond size distribution of the Bougban deposit (Guinea).

Jan 1, 1996

By Patrick M. Hurley

The spreading-ridge, or accreting plate margin, is the primary conduit of metals delivered to the earth's surface. Isotope ratios of lead show primitive mantle values at these sites, indicating that this is true. We can use lead isotopes in any mineral deposit to indicate the degree to which the metal is "primitive" in the sense of having been uncontaminated with U-enriched crust or "crustal" in the sense that it has been cycling at the earth's surface since earlier times. The reason for this is that the upper continental crust has an enrichment in the ratio of U/Pb over that in the mantle, so that old continental leads have a larger radiogenic component. The primitive metals delivered to the surface at the spreading-ridge are transported on the oceanic plate until they reach a subduction zone. Here they become cycled in the "orogen". However, in this process the primitive metals are mixed with metals from the continent so that the average lead isotope ratios are between those in the mantle and the average upper continental crust. Subsequently a part of the metals in the orogen may become fixed in a new block of continent. However there are processes which continue to uplift and erode ancient continental regions so that there is a continuous feeding back of metals to the orogen. We have therefore a cycling of metals from the existing continental crust into the orogen where they are mixed with new contributions from the spreading ridge and mantle.

Jan 1, 1977

By H. Sevim

In long-term open pit production planning, a series of nested and maximum-value pits is usually generated first. These pits are then considered as possible pushbacks over a number of planning periods. To determine the best pushback in each planning period, the pits are evaluated for their technical and economical feasibilities under certain production constraints. Parameterization is a commonly used technique to generate a series of pits. In almost all cases, however, some of the consecutive pits generated by this technique are too far apart from each other. This is called the "gap" problem. It may make the entire pit series useless for production planning purposes. A new pit gener¬ating algorithm has been developed to overcome the gap problem. Through this algorithm, a series of nested maxi¬mum-value pits can be generated with a controllable size increment. The logic of the algorithm is illustrated through a small hypothetical case. Its capability of generating maximum-value pits that are as optimal as those generated by parameterization and its advantages over parameteriza¬tion are presented through an actual gold deposit case.

Jan 1, 1996

By H. Wesley Peirce

Arizona, in 1966, has continued to be the site of an extensive and intensive search for metallic mineral deposits. Over fifty separate entities--companies and individuals--have been actively engaged in mineral exploration programs, both large and small, in the Basin-and-Range portion of the State. Certainly, copper has been primarily responsible for the major efforts, although associated gold, silver, and molybdenum mineralization also has been important in the economic evaluation of potential copper deposits. It is not difficult to explain why the Basin-Range portion of Arizona is receiving such attention. Part of the story, undoubtedly familiar to most, can be illustrated by reference to three graphical presentations. For example, Figure 1 shows Arizona's annual copper production for the period 1955-1965, inclusive, and it demonstrates that new records of production have been accomplished in each of the past 6 years and in 9 of the last 11 years.

Jan 1, 1967

By Ron M. Canon, John M. Begovich

Chromatography, ion exchange, and other techniques based on the interaction of solutes with solid phases offer versatility, high resolution capabilities, and near-universal potential applicability for the separation of valuable constituents in liquid solutions. The expense associated with obtaining reasonable throughput for these separations has been the only, albeit overwhelming, obstacle preventing widescale use of these methods. Attempts to devise continuous (cheaper) systems have previously resulted in moving, or simulated moving, beds of resin with complicated valving and timing sequences. These disadvantages, plus technical problems associated with the disturbing effects of non-plug flow and reduced resolution of moving versus packed beds, severely limit applicability of these systems. Over the past decade a new device has been developed that overcomes many of these problems. It utilizes a slowly (less than one revolution per hour) rotating annular bed of sorbent material with fixed-feed inlet and product withdrawal points. Numerous units of various diameters and lengths have been fabricated and operated, and a parallel effort has developed a satisfactory theoretical treatment of the device. Several simple control systems have been incorporated to thoroughly demonstrate the simplicity of operation, even for multiple products and multiplecarrier flows. This device has been developed using several metal solutions and has demonstrated its power with some of the most difficult, including the zirconium-hafnium, separations. Design equations are available for sizing units based on simple laboratory data and have been tested for units as large as 18 in. in diameter.

Jan 1, 1985

By Ulf Marklund, Manfred Lindvall

Fighting the challenge of diminishing ore grades, low base metal prices and a changing pattern of ore supply, Boliden has now taken the second generation of the fully­autogenous grinding concept on stream, Using new design and a highly-developed process control system the benefits of conventional two stage autogenous grinding technology are obtained with a wide range of ore types. The APC grinding system has been developed further. A new design of the Boliden Pebble Extractor together with an advanced control strategy make the performance of the APC concept superior to all other grinding systems with any ore quality. The capacity and simplicity of the autogenous grinding concept is equivalent to the best SAG installations but the operational costs are up to 25 % lower than for SAG or other primary ball or rod mill systems. The concept is as flexible as conventional crushing and rod mill installations but investment and operating costs are of the order of 25 % lower. Also, from the metallurgical point of view, the different types of autogenous grinding system outperform all other comminution systems including SAG. From 1989 to 1991 four fully autogenous grinding sections have been installed at various concentrators at the Boliden company. Old crushing plants and rod and pebble grinding circuits have finally been replaced by highly productive and cost-efficient autogenous grinding equipment. Significant savings in operational costs have already been reported. Power consumption and maintenance costs have been reduced significantly. Productivity expressed as milled tonnes per operator has been improved. Metallurgical results have developed favourably.

Jan 1, 1992

By Heflin. L.

The Washington Metropolitan Area Transit Authority, WMATA, has constructed over 92 revenue miles of rapid transit facilities including some 14 miles of rock tunnel and 12 miles of earth tunnel. The system map is shown in Figure 1. During construction it is not unusual for contractor to encounter ground conditions resulting in major problems and extra cost. Problems such as major rockfalls and a "stuck" boring machine in squeezing rock are not unusual. In recent years, faced with additional tunnel construction projects, the Authority has sought newer tunneling methods which might be less costly. One new method which has been tried is NATM, the New Austrian Tunnel¬ing Method. NATM, which is applicable to both soft ground, mixed face and rock tunneling, relies on miners and comparatively small machines to excavate in conventional ways, but it is unique in its methods of obtaining "stand-up" time at the excavated face and its method of using shotcrete as an initial lining, frequently with a drainage system to reduce hydro-static pressure on the final lining. Lower costs result from use of a cast-in-place concrete liner, and from a reduction in the number of work operations at the mine heading which provides better daily production. WMATA has recently completed three twin bore tunnels constructed by NATM technology. The first was the Wheaton Tunnel and Section, followed by the tail track tunnel to total some 4200 linear feet cut through jointed rock up to 270 feet below ground surface, and the last was in soft ground at Fort Totten. A

Jan 1, 1993