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By Richard H. Olson

Talc deposits in the Precambrian of southwestern Montana (Beaverhead and Madison Counties) are unique within the U. S. A. in that large bodies of tremolite-free talc can be open-pit mined. All known deposits are in pre-Beltian dolomite units. The origin is suspected to be metasomatic, with the siliceous component having been contributed by an intrusive Precambrian granite gneiss. Precambrian deformation was extreme and is characterized by multiple periods of tight isoclinal folding and the flowage of less competent rocks, rather than by faulting. Post- Precambrian folding has been relatively negligible; the characteristic Laramide structure is block-faulting developed along northwest-southeast trends. The talc is thought to have been formed in Precambrian time; the high-angle block-faults probably have no significance with regard to the formation of the talc, but do tend to complicate mining operations. Tremolite-free talc ore bodies with horizontal widths of more than 200 feet, vertical depths of several hundreds of feet, and strike-lengths of as much as one-half mile are known in the Ruby Range and the Gravelly Range. Where dolomite is interbedded with tremolite-free talc in the Gravelly Range, the scale of this relationship permits the use of conventional open-pit mining methods with subsequent upgrading by hand-sorting techniques. Underground mining has been used in the past, but all current Montana talc-mining operations are on the surface. The hand-sorted ore, some of which is shipped overseas, is finely ground or micronized in roller mills and fluid-energy mills. The products are distributed both nationwide and abroad.

Jan 1, 1975

By M. Deutsch, E. González, M. Williams

"There is uncertainty in ultimate pit limits due to geologic variation and unpredictable economic landscapes. In this work we show how this uncertainty affects the ultimate pit and how it can be analyzed to improve the mine planning process. A stochastic framework using geostatistical simulation and parametric analysis is used to model the effects of geologic and economic variation on ultimate pit limits and overall project economics. This analysis is made possible by a new, highly efficient pit optimization implementation which can be automated and set up to calculate ultimate pits for hundreds of different scenarios in a matter of hours. Quantifying ultimate pit uncertainty early in the mine planning process allows mining engineers to make informed decisions regarding infrastructure placement, and to mitigate the possibility of incurring substantial costs relocating critical mine facilities. INTRODUCTION The mining industry is increasingly concerned with the effects of risk and uncertainty. Uncertain prices, unpredictable global markets, and unknown foreign exchange rates can alter the economic viability of a mining project in substantial ways. This economic uncertainty is compounded by geologic uncertainty. The extent and quality of any given deposit cannot be fully measured and is not known before consequential decisions must be made. These two sources of uncertainty are responsible for the majority of deviation between what happens during operation and what was initially planned. Understanding and explicitly quantifying this uncertainty will lead to better decision making and allow mining engineers and investors to be aware of what may occur. It is unrealistic to believe that one model, estimated from sparse measurements, is enough to capture both geologic and economic uncertainty and allow for optimal decisions. The entire breadth of uncertainty should be considered, as both upside and downside risks have large impacts on the investment potential and operational efficiency of mining projects. The workflow presented here uses Monte Carlo simulation and parametric analysis together to explicitly analyze the breadth of geologic and economic uncertainty as it applies to ultimate pit calculation and long range mine planning."

Jan 1, 2015

By L. Adler

To properly analyze and apply mining equipment, a systematic, current, inclusive, and simple classification scheme is required. This paper provides such a classification for Roadheaders. This Roadheader classification is based on factors, such as the rock cutterhead, the boom type, and the chassis configuration. It first assigns Roadheaders as an equipment type within the larger group of Integrated Excavators. The Roadheader type is then delineated into the following subtypes: the standard, the extended boom, the tunnelers, and the miscellaneous. Next, these subtypes are devolved into kinds, and finally variants and attachments are considered. To resolve inconsistencies in characterizing the Roadheader, cross-referencing is employed within the classification scheme.

Jan 1, 1996

By H. Sevim

Long term production planning in open pit mines requires the determination of cutoff grade, mining and milling production rates, mining sequence, mine life, and ultimate pit limits. These variables interact in a circular fashion, that is, the value of a variable can not be determined without the knowledge of the value of the preceding variable in the circle. Therefore, a genuine solution to the problem necessitates simultaneous determination of the variables. Such a solution methodology, comprised of a group of heuristic algorithms and an unconventional dynamic programming algorithm, is described in this paper. The methodology is applied to a small size Western US gold deposit to illustrate its logic and capabilities.

Jan 1, 1995

By L. A. Price

With increased stripping ratios and with dwindling ore content, the mining fraternity is increasingly turning to larger and larger equipment for profitable open pit operations. The availability of higher horsepower prime movers and increased capacity electric transmissions using either wheel mounted or axle mounted traction motors makes a reality of single axle, rear dump trucks having 150 to 250 ton capacity. The size of electric loading shovels is inherently geared to the size of haulage equipment. To work effectively with this new generation of trucks, the Harnischfeger Corporation has introduced its P&H Model 2800 with a capacity of 20 to 25 cubic yards and a working weight of nearly 1,500,000 pounds. The Model 2800, depicted in Figure 1 loading a 200 ton truck, has many new electric and mechanical features designed to give excellent production and low cost operation. Chief among the new features is the ELECTRO TORQUE* control system. ELECTROTORQUE is a completely static, solid state electronic system supplying controlled power both to the armature and to the fields of the d.c. shovel drive motors. It eliminates many major electrical rotating machines and their attendant maintenance. The system was developed jointly by ASEA of Sweden and Harnischfeger Corporation.

Jan 1, 1969

By X. Cheng

The mechanism of cathodic decomposition of pyrrhotite was studied in deoxygenated solutions at natural, near neutral pH using potential and cyclic voltammetric measurements. Reaction products on pyrrhotite surfaces were examined by AES and XPS, and by analyzing the voltammograms for the electron balance of the reactions. Surface properties of the pyrrhotite/solution interface were characterized using ac impedance technique. The parameters of an equivalent circuit were determined by the nonlinear least squares fit (NLLSF) technique. The effect of cathodic polarization on floatability was investigated by micro-flotation tests. Possible implications to the flotation separation of chalcopyrite-pyrrhotite ores are discussed.

Jan 1, 1993

By F. Kitzinger

The possibility of increasing the efficiency of mineral processing plants by means of computer control has prompted metallurgists to examine their flowsheets more critically in order to develop practical control strategies. Control schemes in use to date generally rely on the automation of traditional and previously manually regulated control loops, for instance the addition of reagents to maintain a constant assay or a constant pH. This approach is predicated on the availability of well-established primary sensors such as pH electrodes or on-stream analyzers. Noranda Research Centre, in cooperation with Noranda Group concentrators, has developed a froth level monitor and a pulp density meter susceptible of application in this type of control. Although some of the basic principles on which they are based have been known for some time, their incorporation into the design of reliable, direct-reading instruments which can be interfaced with a computer, is be-lieved to be novel*.

Jan 1, 1977

By Marc E. Orman, Mark E. Smith

Regulatory and environmental concerns continue to broaden the range of mine wastes that must be capped with low permeabili­ty liner systems at closure. The mining industry has been a leader in developing liner technology for leach pads and tailings impoundments, but it is a newcomer to cap designs. Closure of waste piles, leach heaps and tailings require special design con­siderations. Factos such as differential settlement, surface ero­sion, veneer stability, vegetation and burrowing animals must be considered.

Jan 1, 1996

By R. D. Beard

Puerto Rico lies within the remnants of a deformed Cretaceous island arc system in the northeastern Caribbean. The Island can be divided into three broad geologic provinces: the Central Volcanic-Plutonic Province (Lower Cretaceous to middle Eocene), and the Northern and Southern Limestone Provinces (early Oligocene to middle Miocene). Known precious metal deposits are generally small and occur in veins and shear zones within Lower and Upper Cretaceous volcanic and plutonic rocks. Some Tertiary igneous rocks are also mineralized. Selected indications of disseminated lithology-controlled mineralization could represent larger deposits. Associated metals in some deposits include copper, zinc, and lead. At present, tax policies, population density, political outlook, and lack of proven significant precious metal deposits discourage the establishment of a metal mining industry.

Jan 1, 1993

By Charles L. Karr

Researchers at the University of Alabama in cooperation with the U.S. Bureau of Mines have developed adaptive process control systems in which genetic algorithms (GAS) are used to augment fuzzy logic controllers (FLCs). GAS are search algorithms that rapidly locate near-optimum solutions to a wide spectrum of problems by mimicking the search procedures of natural genetics. FLCs are rule based systems that efficiently manipulate a problem environment by modeling the "rule-of-thumb" strategy used in human decision making. GAS and FLCs can be combined to produce powerful, efficient, and robust adaptive control systems. To perform efficiently, such control systems require a control element to manipulate the problem environment, an analysis element to recognize changes in the problem environment, and a learning element to adjust to the changes in the problem environment. I" this paper, the details of an ongoing research effort to develop and implement an adaptive process control system for a column flotation unit are discussed.

Jan 1, 1996

By Yuji Tsuneno, Yoshikazu Mikami, Yasuo Takeuchi

A new device was successfully developed in order to overcome the difficulty of drilling longer holes for anchors in soft soil bedrocks or swelling bedrocks, which is one of the major impediments to rapid excavation by NATM (New Austrian Tunnelling Method). With higher rotation (1200 - 1800 r.p.m.) and lower percussion energy (4 - 6 kg.m), the new drill has following advantages: (1) Applicability covers soils and medium hard rocks with the same drifter. (2) Longer hole (more than 9m) is achievable only with air flushing even in cohesive soils or rocks. (3) Better borehole stability is obtainable even in earth or in fissured rocks.

Jan 1, 1981

By L. Alan Weakly

The purpose of this paper is to present a viable method of reinforcing rock pillars by utilizing fully grouted reinforcing steel and a cement - fly ash mortar. Although the fully bonded bolt concept is not new as exemplified .by the present widespread use of resin bolts within United States mines and by the use of cement grouted reinforcing used as back pins in the Kiruna Iron Ore Mine in northern Sweden, (1)(2) the method of stabilizing mine pillars with fully bonded reinforcing is new. This method, called the "grout-rebar system", was first incorporated at St. Joe Minerals Corporation's Fletcher Mine in December of 1972. The system was used on an emergency basis before extensive research on the mechanics of the system could be completed. Since December of 1972, however, approximately 206 pillars have been reinforced at Fletcher and the system is currently being used on a regular basis at two other St. Joe mines and at two competitor mines in the area. Basically, this paper is a case study of the efforts, research and results of utilizing the grout-rebar system, on a selective basis, at the Fletcher Mine. In addition to information about the system, this paper will explain in detail the three rock mechanics instruments developed by St. Joe and used to measure and monitor rock movement to validate the grout-rebar system.

Jan 1, 1976

By A. Adhikari, P. Tukkaraja, S. Jayaraman Sridharan

Shafts are critical components of the mine ventilation systems and contribute significantly to the mine ventilation pressure. Estimation of shaft pressure losses is an important aspect of mine ventilation planning and shaft frictional pressure losses are extensively studies. Shock losses contributed by shaft buntons are estimated using the interference factor model developed half a century ago. This study aims to develop a better performing prediction model for shaft buntons using state of the art experiment and numerical data, and machine learning techniques. Results show that the present prediction model is performing poorly, and the prediction performance can be improved by incorporating additional predictor variables. The Artificial Neural Network standardized Machine Learning model developed in this study is able to predict the shaft bunton shock loss with high accuracy (R2 = 0.956).

Jun 25, 2023

By Raimo J. Leimala, Heimo U. A. Saarinen, Matti Seilo

Processes for hydrometallurgical treatment of crude nickel hydroxy carbonate and impure high grade ferronickel to produce cathode nickel and cobalt hydroxide are described. Outokumpu nickel refining process originally developed for nickel matte has been adapted to the mentioned new raw materials. Both new process routes contain the Outokumpu cobalt removal and nickel electrowinning stages but leaching and solution purification stages differ from the industrial process in operation in Harjavalta.

Jan 1, 1979

By Bernie W. Martin, Duncan MacLennan

Building a new tunnel to accommodate CN North America's needs for double stacked container traffic for the next 100 years presented new and unprecedented challenges. Innovative approaches to contracting, especially the Negotiated Compressed Process (NCP), TBM design, project management, and the regulatory and approval process, were all required to deliver a new tunnel to meet the needs of CN North America within the approved completion schedule of 39 months compared to a traditional approach of 45 to 48 months. The NCP resulted in trimming 6 to 9 months from the project schedule, at a great saving of direct and indirect costs. The Negotiated Compressed Process is an innovative formalized approach to risk sharing for complex infrastructure projects. Ads were placed in the international trade journals and a short list of "approved" contractors and suppliers was developed. The approval process for this international project involved contacts with over two hundred agencies, departments and interested stakeholders.

Jan 1, 1995

By P. R. Taylor

A cyclone reactor system for the partial reduction and melting of taconite concentrate fines has been engineered, designed and operated. A non-transferred arc plasma torch was employed as a heat source. Taconite fines, carbon monoxide, and carbon dioxide were fed axially into the reactor, while the plasma gas was introduced tangentially into the cyclone. The average reactor temperature was maintained at above 1673 K (1400 C), and reduction experiments were performed under various conditions. The influence of the following parameters on the reduction of taconite was investigated: carbon monoxide to carbon dioxide inlet feed ratio, carbon monoxide inlet partial pressure, and average reactor temperature. The interactions of the graphite lining with carbon dioxide and taconite were also studied.

Jan 1, 1993

By Georgios Kalamaras, Sebastiano Pelizza, Carlo Alessio

"This article describes, through the presentation of five cases-history, technological advances that the Authors together with Tunneling Contractors devised for coping with adverse geotechnical conditions. It is believed that by introducing these new elements in a method that has proven its value in Italy and abroad for the last 40 years, the umbrella arch method, due to its versatility and simplicity, can become a universal method for conventional tunneling in very poor ground conditions. After a description of common faults and mistakes in applying the method, 5 projects are presented which demonstrate that self-drilling pipes give excellent results in terms of performance a zero volume loss, while, function of the ground conditions the various grouting mixtures used, such as expansive jet-injected cement-base grouts and bi-component resins, extend the use of the umbrella-arch in variety of grounds even in presence of water-bearing lenses. The case-histories provide successful applications in different conditions.BASIC FEATURES OF UMBRELLA ARCH METHODThe umbrella arch method provides a short support of the tunnel vault just ahead of the excavation face. The method foresees the drilling and installation of peripheral, sub-horizontal steel pipes in the ground, followed by their grouting. The umbrella arch method is also known as forepoling, steel pipe umbrella, reinforced protective umbrella or simply “umbrella”. The umbrella arch method does not have a static function because the immediate stabilization of tunnel section is entrusted to the internal shell of steel ribs and shotcrete. The “umbrella” provides a pre-support of the excavation which has to be stable for an adequate length and duration permitting the installation of the next steel rib and shotcrete under conditions of safety (Figure 1).The umbrella-arch provides pre-reinforcement of poor ground around the tunnel perimeter in a simple and flexible manner that is adaptable to different ground conditions. In fact, it is possible to vary the number and length of pipes, the distance between them, their diameter and thickness as well as the overlapping length of two succeeding umbrella arches. The versatility of the umbrella arch technique allows its application to: clay deposits, granular alluvial deposits, moraine and debris materials even when containing large blocks, heavily jointed, foliated and tectonically disturbed rock masses."

Jan 1, 2016

By Larry D. Wayland

Almost 100 sedimentation ponds were conceptually designed for a large surface mining study area in northeast Texas. An approximate procedure was developed to economically estimate construction quantities in order to predict surface water control costs. This procedure utilized site-specific empirical relationships developed from detailed analyses on a representative number of proposed sedimentation ponds. Use of these equations provided earthwork volumes, and spillway pipe lengths. The procedure developed for this study is presented along with the results of a verification analysis.

Jan 1, 1983

By John R. Buzek

Thickeners are simply large tanks, usually circular in shape, which are designed to allow settling of solids and to operate with continuous overflow of clear water and underflow of thick pulp. The dimensions of the thickener are usually such that dewatering of very fine pulps may be accomplished while still 1 overflowing clear water. Some thickeners such as the Genter, Hardinge and Hydrotator types combine thickening with filtering2 while others such as the Dorr type are pure thickenersl,2,3. A schematic diagram of the traction type Dorr thickener is shown in Figure 1. This type is appropriate for tanks over 15 m (50 ft) in diameter. This tank employs a rotating raking mechanism which moves the settled material toward the central discharge. For this and other thickeners, it is common to have a shallow conical tank bottom in order to conform to the geometry of the raking mechanism, and it is often desirable to elevate the tank for ease of access to the product. When the tank does not rest on the ground, the forces resisted by the cone are large, and thick plates must be employed. The fabrication of these tanks requires temporary supports in order to erect the cone. A flat-bottomed tank could also be used because the settled material would soon form a hardened conical surface. However, because of the presence of large bending forces, even larger plate thicknesses are required than for the conical bottom. Significant cost savings often can be realized by the use of a scalloped-bottomed tank such as the one partially shown in Figure 2. The particular scalloped bottom discussed in this paper (and shown in the Figure) employs radial beams forming the outline of the cone-shaped bottom. These beams are supported directly by columns. Cone segments are hung between adjacent beams. The exact geometry of these segments depends upon the cone angle and radius, the number of radial beams, and their inclination. The geometry is chosen to satisfy certain clearance restraints and to utilize the material as efficiently as possible. The resulting thickness of these segments is significantly less than that of the

Jan 1, 1977

By Greg Bold, Mahmood Khwaja, Yuannian (Jerry) Wan, Michael S. Schultz, William Simcoe

Beaver Creek Clean River Project will satisfy the consent decree requirements by capturing and treating combined sewage overflows. The project consists of, approximately, 2,700 feet of 30-inch trenchless pipe installation, a new screening/disinfecting facility, an expansion of an existing diversion structure, and a 72-inch internal diameter, 530-foot long mined tunnel. The tunnel portions are being progressed as early release packages. This paper presents the geotechnical exploration program and the subsurface conditions encountered; interpretation of the geotechnical conditions; and, approach to developing stand-alone packages for the tunnels to mitigate construction and schedule risks and continue to advance the project.

Jun 13, 2021