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By Margaret Armstrong, Chris Roth

One advantage of kriging is that it provides both an estimate of the block or point grade, and an indication of the local precision via the kriging variance. If one assumes that the estimation errors are normally distributed, then confidence intervals for the grades can be calculated. But in mining, grades are rarely normally distributed; in general, they are skew. This is particularly true for precious metals. In this paper we study confidence intervals for variables with non-normal distributions. Using a non linear geostatistical technique, the grades are transformed into their normally distributed equivalents. Confidence intervals are obtained for these normal variables, and back transformed to give the corresponding confidence intervals for the grades, for either points or blocks. This approach is applied to gold data from the Witwatersrand basin in South Africa.

Jan 1, 1996

By Lyda W. Hersloff

As decommissioning of various radioactively contaminated facilities begins, the question of appropriate residual surface contamination becomes an issue. Surface contamination can result in exposure to people via inhalation, ingestion, and external radiation exposure, There is therefore the potential of exposure to workers involved in the dismantling of a facility as well as members of the general public acquiring salvageable equipment, tools, and building materials. The levels established as acceptable for unrestricted use by national and international organizations vary by as much as an order of magnitude for certain radioactive materials. The calculated doses associated with some acceptable contamination levels can be significant. The principle of ALARA, as low as reasonably achievable, is therefore a necessary element in establishing surface contamination levels for a specific site. Some components in evaluating site specific surface contamination levels for unrestricted use, especially removable contamination, include evaluations of the historical use of a facility, the mixtures of radioactive materials a&sociated with surface contamination, and resuspension factors for various materials.

Jan 1, 1991

By John G. Whellock

Over the last decade new constraints have emerged in the metallurgical industry which challenge the very basis of design and construction of smelters and refineries. The hackneyed designs of the past will not now serve the revised objectives of: - minimal cost of ownership - improved productivity - reduced energy consumption - greater flexibility in feed or product - minimized recycle loops and by-products - more stringent environmental control The impact of these constraints has been channeled constructively into process intensification - exemplified at the large scale by the introduction of flash smelting technology and at the smaller scale by the application of rotary process vessels and converters for augmented heat and mass transfer. The design of successful process plants depends on the understanding of the unit operations and their interactions which is the discipline of systems engineering. With the advent of increased process intensification the importance of a systems approach to process design and implementation becomes paramount. This paper describes the systems approach with specific reference to medium scale projects in the primary and secondary metallurgical industry.

Jan 1, 1985

By Fred H. Lightner

The feasibility evaluation of the Borealis project of Houston International Minerals Corporation (HIMCO) was initiated in October of 1980. The operation of the Borealis Mine and heap leaching plant began in late 1981. In order to achieve the rapid development schedule several items were necessary: 1) Pre-planning of environmental requirements and early study of key issues. 2) Adoption of conservative design criteria. 3) Coordination and cooperation between HIMCO and regulatory agencies. 4) Adoption of specialized engineering and construction procedures. 5) Careful evaluation of owner project management philosophy.

Jan 1, 1982

Zirconium chloride is of great commercial importance as starting materials for production of ZrO2, Zirconium metal and other Zirconium compounds from its main resources (Zircon Sands). The present study concerns with preparation of pure ZrO2 from Zircon by direct chlorination technique. Different parameters affecting the chlorination process are studied viz. carbon, chlorine flow rate temperature and time. The chlorination extent is determined from the loss in weight and chemical analysis of reaction products. The maximum chlorination extent -92% are achieved at 1100°C for 30 min. Zirconium oxide is produced from the collected zirconium tetrachloride either by calcination at 900°C or by hydrolysis in water in presence of RCI with a purity = 99%. Evaluations of the products of the process are investigated microscopically and by X-ray diffraction. The apparent activation energy of the chlorination of Zircon is determined to equal 36 kJ/mole.

Jan 1, 1997

By Tuncel M. Yegulalp

In this paper we revisit the well known "Ultimate Pit Limit Problem" and suggest an alternative approach for fast and efficient solution. We follow the approach originally proposed by Johnson and Barnes (1988), but utilize the "Excess Scaling Algorithm" in solving the equivalent maximum flow problem. This algorithm provides significant increases in speed and reduction in memory requirements over the well known Labeling Algorithm of Ford and Fulkerson (1956), enabling one to solve large problems with relatively small computers. We present results of a series: of benchmark tests using this approach against the well known Lerchs Grossman algorithm as well as a brief description of the new algorithm.

Jan 1, 1992

By J. H. White

It is hypothesized that the Hotelling valuation principle (HVP) can determine the value of developed gold reserves using simple methods and easily obtainable data. This paper reports the results of an empirical test of this hypothesis. The model for the HVP is given by [V R=Cp-0(1) or V - CP-0' R(2)] where p = current spot price of gold per oz, [c] = average extraction cost of gold per oz, V = current market value of the gold in the ground (dollars) and R = gold reserves (oz). Using publicly available data from North American gold companies, we obtained data for V, R, p and c, and we ran a simple linear regression using Eq. (1) as the definition of the dependent and explanatory variables. By examining the value of the coefficients of the resulting regression equation, we can draw conclusions as to whether or not the HVP can be confidently used as an estimator of the value of developed gold reserves.

Jan 1, 1997

By Clive Wilson, Bruce Hutchison, Daniel N. Adams

Two three-lane highway tunnels, 700 and 2900 m long, make up the driven tunnels portion of Melbourne City Link. Tunnel construction, using design-construct delivery, commenced in May 1996. Construction required excavation through varying rock conditions; temporary support included ground freezing, pipe-spiling, steel sets, and rock bolts. Permanent support for the tunnels required both drained and undrained tunnel cross sections using unreinforced concrete. This paper reviews the construction methods, and highlights some of the not-so-standard designs developed while construction was underway.

Jan 1, 1999

By M. K. Quinn, R. D. Chaffins, A. W. Khair

This paper presents an analysis of the effects of topography on static and dynamic ground movements and severity of damage inflicted on surface structures. A typical site containing varying topographical features (i.e., mountains, hillsides, valleys, and flat bottom land) representing the northern Appalachin region was chosen for the study. Typical subsidence monitoring techniques were employed. Frequent measurements were made as the face advanced.

Jan 1, 1987

By Clifford J. Lewis

The role of calcareous minerals in that area of the environmental improvement program involving the control or elimination of sulfur oxide emissions is discussed, and a new concept in gas scrubbing, rendering possible the use of calcareous rocks more extensively for this purpose, is presented. Calcareous rocks are defined as the more common limestones, consisting essentially of calcium carbonate and magnesium carbonate. The effect of magnesium carbonate on the reaction rate of limestones and lime toward sulfur oxides in aqueous scrubbing systems is pointed out. The relative economics of lime- stone versus lime as aqueous scrubbing reagents for sulfur dioxide are indicated.

Jan 1, 1974

By L. W. Saperstein, MJ. Carlson

With the goal of improving the strength characteristics of pneumatically emplaced material used for localized subsidence control, the binding additives fly ash, bentonite, and portland cement were examined for their effect on the support capabilities of coal refuse. It was found that, within certain concentration ranges, all three offered some increase in the ultimate strength of the backfilling mixture. However, portland cement gave the greatest percentage increases. Selection of the appropriate backfilling mixture will allow for the most economical and efficient subsidence control when pneumatic stowing is employed.

Jan 1, 1990

By C. D. Harrison, G. S. Stallard

The 199O Clean Air Act Amendments specify national objectives for reducing sulfur dioxide emissions from coal fired power plants. System-wide reductions can be achieved by combining various emissions control technologies and allowances, or compliance credits, that can be purchased, sold or traded. As part of the Coal Quality Expert development project funded by the US Department of Energy and the Electric Power Research Institute (EPRI), Black & Veatch has developed an interactive computer tool, the Acid Rain Advisor (ARA). Through this program, integrated, system-wide compliance plans are generated by comparing the costs and emissions reduction benefits of emissions allowances and various SO2-control technologies (coal cleaning, fuel switching, scrubber retrofits, etc.)

Jan 1, 1993

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION Variations of cut-and-fill stoping are the most com¬monly used methods for mining narrow, nearly vertical veins in the United States. These methods offer the best results for maximum recovery with minimum dilution of ore from veins that are irregular along either the strike or dip. The vein is developed along the strike length in 61 to 122-m (200 to 400-ft) blocks or stopes and vertical lifts of 48 to 61 m (160 to 200 ft). The level development is either on the vein or parallel to the vein with crosscuts intersecting the vein at right angles. Chutes, manways, and haulageways are established in the center of the stopes at the lower level of the ore block. Mining then proceeds by blasting down horizon¬tal cuts of the vein in both directions from the chutes. As the blasting continues to the outer limits of the stope, the broken ore is slushed into chutes. When a complete horizontal cut has been made, the service raise, including chutes, is raised to a height of a few feet from the back and the stope is filled with either sand fill or waste rock. Then the mining cycle is re¬peated until the stope reaches the level above. LEVEL DEVELOPMENT PRACTICES FOROVERHAND CUT-AND-FILL STOPING The two basic methods used are: the development of the haulage drift within the vein, or development of the haulage drift paralleling the vein in the foot or hang¬ing wall with crosscuts intersecting the vein perpendicu¬larly at 61 to 122-m (200 to 400-ft) intervals. The il¬lustrated methods of development show some of the variations which can be used to develop a stope block. Development for cut-and-fill stoping does not require the more elaborate schemes outlined for shrinkage or sublevel long-hole stoping. Many factors must be considered before deciding on a particular development plan and usually the nature of the vein or host rock will dictate which specific method to use. If the vein is relatively straight, then develop¬ment on the vein is feasible. Excessive ground pressures will necessitate the leaving of a sill pillar (Fig. la) and highly fractured or "heavy" ground will require timber¬ing (Fig. 1b). Development on the vein has the advan¬tage of reducing capital outlay and waste handling prob¬lems since the mined rock has value. But removal of the sill pillar is costly and time-consuming. Also, where no sill pillar is left, excessive timbering and subsequent level repair is a drawback. Development in either the footwall or hanging wall is the more common procedure and offers greater flexi¬bility in overall development of consecutive stoping blocks by partially disassociating the level development from stoping (Fig. 2). Chutes, manways, and service compartments com¬prise the next stage of development and are established in a variety of ways. They provide access to the stope, ventilation ducts, and muck removal. Several different development systems are in common use and average costs for each have been developed. Raise borers are used to establish ventilation and ac¬cess from level to level. They are normally reamed with 1.5 or 1.8-m (5 or 6-ft) cutterhead and may either be left bald or lined with a 1.2-m (4-ft) diam corrugated liner plate, depending upon ground conditions. The use of an Alimak raise climber is another effec¬tive method of driving a raise from level to level. The size usually is 2 m (7 ft) square. This will accommodate square-set timber which is later installed. This method of raising is not common, although it is a valuable tech¬nique especially when level spacing is several hundred feet.

Jan 1, 1982

By W. C. Yates

Lack of visibility from large, open-pit haulage truck cabs has become a serious safety problem. Anaconda conducted a research program to develop a low cost system to alert haulage truck operators to small vehicles present in blind areas. Several systems were developed and tested. As open-pit haulage truck size has increased, so has the size of the blind areas. Mine utility vehicles, pickup trucks, and cars are concealed within these blind areas and become safety hazards. Figure 1 shows the typical blind areas of a 136 t (150-ton) haulage truck. The areas of greatest concern are at the rear center and front right corner of the truck. In these "no visibility" areas many small vehicles have been crushed by large haulage trucks at various mine sites. In most instances, the occupants escaped the vehicle before it was destroyed. But injuries and death have occurred. In most cases, the accidents were attributed to negligence or carelessness by the small vehicle driver. The limited visibility problem still exists, though, and a solution is needed. Initial Solution The usual plane mirror on the driver's side and the convex mirror on the right front of the haulage truck allow only limited rear visibility. The typical, right side convex mirror is generally small and difficult to locate at a glance. This convex mirror also presents an image that distorts distance perception. These mirrors are of¬ten broken and immediate replacement not demanded or made. The US Bureau of Mines, in a contract with M.B. Associates, San Ramon, CA, developed an improved visibility system. It consisted of a larger, left view mirror and unique, blind area viewer. The large 230 x 690 mm (9 x 27 in.) left mirror has a small convex spot mirror near the bottom. The entire unit can be quickly replaced if broken. The large size provides a full view of driver orientation features such as the rear tire and the top of the load bed. The right 300 x 410 mm (12 x 16 in.) mirror has a convex surface and is quite rugged. The 510 mm (20 in.) spherical radius presents the operator with some distance distortion, but objects in its view are easily seen. The "blind area viewer" consists of a modified fresnel lens that allows the driver to "look around the corner." Installation of three of these lenses on the front of each haulage truck is rec¬ommended for adequate blind area coverage. This system significantly increases an operator's field of view and allows viewing of objects within about 3 m (9.8 ft of the truck. Many open-pit mines are nor mounting on smaller vehicles a long whip with a flag and lamp or both. This increases vehicle visibility to haulage truck operators. The whip is permanently attached to the mine vehicle. It can also be magnetically attached to transient vehicles. The whip system. though, is inadequate for visibility in the critical rear and right front blind areas. Alternate Solutions All of these visibility aids as¬sume an attentive driver. In addi¬tion, areas such as the rear blinc, area are not covered. Based on the inadequacy of existing visibility systems, Anaconda made a com mitment to further the truck de¬tection technology. The best ap¬proach was considered to be ar active system. It would notify the haulage truck operator that an en¬croaching vehicle is present. Sev¬eral systems were considered, in¬cluding ultrasonics and elec¬tromagnetics. For the ultrasonic system, com mercial and in-house design were looked at. Designing an( building transducers with the spe cific beam shape to match the haulage truck blind spots re¬quired a major technological breakthrough. False alarms ap¬peared difficult to prevent en¬tirely. They were caused by pass¬ing, trailing, or leading vehicles a., well as nonthreatening objects. As a result of these problems, the ul¬trasonic technique was not pur sued. An alternative, an electro

Jan 7, 1982

By E. J. Harvey

The Ozarks has been called "a diamond in the rough". In this region streams have steep gradients, sparkling clear flows of cold water fed by many springs, and a wildness that is almost unique in the central part of the United States today. The Current River and its tributary, Jacks Fork, have been set aside for preservation by the National Park Service as a "Wild River" in the first park of its kind in the country. It is called the Ozark National Scenic Riverway. Similarly, responsibility for the preservation of the Eleven Point River has been assigned to the U. S. Forest Service. Protection of other streams in the Ozarks has been considered by State agencies. The hydrologic system of the Ozarks is a complex network of gaining and losing streams, caves, conduits, and large springs. Increased sewage loads derived from the growing towns and expanding tourist trade are a potential hazard; effluents may flow underground for long distances, polluting springs and wells. To add another dimension to the hydrologic picture a new lead industry is also flourishing in the Ozarks. Although the history of lead mining in the area goes back to 1701 (U. S. G. S., p. 43), the area has not seen a revitalization like the one that has been developing in the last 10 years; and the economic growth promises to continue indefinitely. Although this brings capital expenditures and wages into the area, it also brings potential hydrologic problems. Chemicals, wastes and other substances either stored on the surface or transported across it are subject to accidental spillage. In an area where these substances remain on the surface their effects are subject to surveillance. In the Ozarks, however, this may not be possible.

Jan 1, 1970

By Carol A. Hill

Native sulfur occurs with barite, celestite, and bioepigenetic calcite in the Culberson, Pokorny , and Leonard Minerals deposits, Delaware basin. The sulfur in these deposits, in "castile" masses, and in deposits of the Fort S tockton district have 6 34s values between +9 and -15. Native sulfur in the caves of the Guadalupe Mountains is somewhat lighter [(634s = -15 to -25)]. Barite in the Culberson, Leonard Minerals, and Comanche Creek sulfur deposits have 63% values of +35 to +73; celestite in the Culberson and Leonard Minerals occurrences have values of +38 and +36, respectively, and 87Sr/86Sr values of 0.707808 and 0.708138, respectively. Barite associated with sulfide, deposits, Guadalupe Mountains, have [634s] values of +41 to +62. Barite at Seven aeart Gap, Apache Mountains, is somewhat less enriched in heavy sulfur [(634s = +14 to +37)].

Jan 1, 1992

By Jonathan K. Hrica, CASSANDRA L. HOEBBEL, Jennica L. Bellanca

Accidents involving powered haulage and mobile equipment like haul trucks are a major safety concern in the U.S. mining industry. They account for more than 50 percent of surface mine fatalities each year [1]. A recent National Institute for Occupational Safety and Health (NIOSH) analysis of 91 fatal incidents identified loss of vehicle control and situational awareness as key contributors [2]. However, the first-hand perspectives of operators are often missing, emphasizing the need for deeper insights into operators’ decisionmaking, lessons learned, sensory cues and mental strategies used during near-miss events. The findings in this analysis will help inform the development of training and safety solutions to prevent or reduce haul truck accidents.

May 1, 2025

By D. P. Bryan

The identification and-develop¬ment of new construction aggregate resources, the most common mineral mined, is an essential need in this country's growing urban areas. In developing an aggregate exploration program, a thorough geological identification of all potential aggregate resources in an area is still of primary importance but other factors have also to be considered. These include physical properties, end product application, transportation and mining costs, and local government regulations including zoning. The present major aggregate producers are most likely to develop these future resources and are in the best position to initiate comprehensive exploration programs.

Jan 1, 1987

By Robert Stefanko

The most perplexing problem that has confronted mining engineers since the dawn of mining has been strata control. For the purposes of this paper, strata control will be defined as control of ground in the immediate area surrounding the, mine opening. To prevent movement of the surrounding strata into underground mine openings, miners have traditionally relied upon some type of artificial supports placed within the openings and located in a manner determined by trial and error from previous experience. Without the means to measure changes of stress in the supports and within the mine structure itself, an evaluation of the efficiency of the supports and mining system was impossible. Strata control thus remained an art with very little application of science. During recent years a revolution has occurred in mining. The modern mining engineer is contented no longer-with trial and error methods but is utilizing all the technological information at his command to obtain a solution to this age old problem. However, serious problems have arisen due to the lack of certain basic knowledge in three important areas: 1, The original stress distribution within the earth strata prior to mining. 2, Redistribution and concentration of the original stresses with mining activity. 3. The properties of rock that are significant in failure and its prevention.

Jan 1, 1960

By Harold F. Yde

Hydraulic tailings fill in the Butte deep level mines was based upon studies made in 1958 by the Anaconda Company Mining Research Department, which published Bulletin No. 35, entitled "Hydraulic Stope Filling". Since then, many things have changed. At the time of the Research Departments study, dry mine tailings were hauled by rail cars from the Anaconda tailings ponds, twenty-five miles distant, to the underground mines' tailings fill plants at the Leonard Anselmo, and Mt. Con Mines. Now, with the installation of the new Weed Concentrator in Butte, tailings is delivered by pipeline to a cyclone at the Kelley Shaft, and stope filling has become more highly automated and streamlined. Presently, mill tailings at approximately thirty percent solids by weight, is pumped from the concentrator, eight thousand feet horizontally and upward, to the Kelley Fill Plant, where they are dewatered and deslimed by three Krebs Model D20B Cyclones, which discharge the material into the cased and grouted mine delivery bore holes at desired densities up to seventy percent solids. The vertical boreholes and four-inch rubber lined Victaulic pipe carry the material downward to horizontal distribution lines, which in turn tap into the stops-filling, three inch, unlined steel Victaulic pipelines. The slurry may travel several thousand feet before it finally discharges into the stope, where it lends support to the mined-out area.

Jan 1, 1969