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By J. R. Carr

A crucial concern when implementing computer algorithms for geostatistical analyses on microcomputers is speed of execution. Kriging, in particular, typically relies on a Gauss elimination algorithm to solve for weights. Because such an algorithm is required for each estimate, the solution for weights can result in very slow program execution speed on a microcomputer. One approach to enhancing the efficiency of Gauss elimination is demonstrated herein. The upper triangle plus diagonal of the intersample covariance matrix is used in a modified banded Gauss elimination algorithm. Results show that such an algorithm yields approximately a two-fold reduction in execution time for kriging when the number of nearest neighbors used for estimation is large.

Jan 1, 1990

By B. Das, D. D. Mishra, M. I. Ansari

Experiments conducted with a 75-mm-diem hydroryclone have shown it is possible to obtain an iron ore concentrate containing 60% Fe. 2.65% SiO2, and 4.0% Al2O3 from Barsua iron-ore washing-plant slimes. About 60% of the iron values are recovered from slimes containing approximately 49% Fe, 8.9% A1203 and 11% SiO2. The obtained products can be used in the sinter feed for iron and steel making. The key to achieving process success lies in establishing the correct cut point (d50) of the hydrocyclone through the manipulation of operating and design variables, such as spigot and vortex finder diameter, solids concentration and operating pressure. The cyclone efficiency is represented by the partition curve. The cyclone performance, evaluated mathematically from the reduced efficiency curve, is represented by the equation Y = 100[1 -exp(-axb)], where: •X = did 50, •Y = corrected of efficiency (%) and •a and b are constants.

Jan 1, 1994

By Michael J. Humenick

A laboratory experimental research project was conducted to evaluate the use of chlorine for the oxidative destruction of residual ammonia which may remain in ground water after in-situ uranium solution mining operations. The work tested the idea of the injection of high strength calcium hypochlorite solution into the mining zone to convert ammonia to nitrogen gas as a final clean-up process for ammonia removal from the ground water system. The paper details ammonia removal efficiency as a function of chlorine dose, reactant and product material balances, and how the concept may be used as a final ground water restoration process.

Jan 1, 1982

By V. de la Garza

The La Cienega Gold District is located at latitude 25°01'01"N and longitude 106°19'00"W, in the NW part of the State of Durango, Mexico. Ore deposits at The La Cienega District consist of a series of sub-parallel, NE-trending veins which cut andesitic and rhyolitic rocks that belong to both upper and lower tertiary volcanic sequences. The veins are vertical to steeply-depping structures which consist of quartz, generally containing gold-silver and less than ten percent lead, zinc and copper sulfide and sulfosalt minerals. Supergene enrichment is present on the upper parts of known oreshoots. Tertiary volcanic rocks of rhyolitic composition are the main host rocks of the gold-bearing quartz veins in the District. Gold productionc from the La Cienega orebody is scheduled to reach 100,000 ounces per year, becoming the largest gold-producing District in the Sierra Madre Occidental Province.

Jan 1, 1994

By Robert F. Goss

OCAW appreciates the opportunity given to us by the sponsors of this Conference to present our position and policies on the issue of radiation hazards in mining. Our principal concern is the health impact that the mining of uranium has on our members. OCAW represents 1,500 underground uranium miners and more than 10,000 underground miners with 3,000 in the Rocky Mountain region. The U.S. Public Health Service has determined through mortality studies that the number one cause of death among uranium miners is lung cancer. It was also determined that exposure to radon daughters and mine dust correlates with the lung cancer experience of uranium miners. Data from the U.S. Mine Safety and Health Administration has also shown that not only uranium underground miners, but all underground miners, are exposed to radon daughters -- especially underground miners in the Rocky Mountain region. It is our position that any OCAW underground miner is at potential lung cancer risk. The dosages of radon daughters that our miners are exposed to are very many times the background levels of radon exposures in the communities where they live. We are also aware that cigarette smoking accelerates the onset of lung cancer; however, it has to be clear that the available scientific evidence shows that alpha radiation does initiate lung cancer and that cigarette smoke, as a recognized co-carcinogen, promotes cancer already initiated by radiation. It is true that cigarette smoke increases the risk of cancer significantly for miners exposed to radon, but nonsmoking miners have experienced lung cancer rates twice as high as the comparable members of the U.S. population. OCAW's position is that the occupational regulatory agencies should concentrate on the exposures that can be controlled; that is, occupational exposures rather than life-style exposures. Our Union has maintained a consistent posture in relation to carcinogens in the workplace -- that is, exposure to cancer-causing agents should be limited to the [lowest feasible level]. OCAW has interpreted lowest feasible level as the lower limit of detection of the collection and analytical method used to detect the carcinogen. Our posture is based on the available scientific information on carcinogenesis. We have asked the scientific community, many times, to provide us with safe levels of exposure to carcinogenic substances, including radon daughters. The answer has been: "We cannot determine levels of exposure low enough to assure that no cancer will occur." In short, there is not a "safe threshold" for any carcinogen. This statement does not come from one of the few so-called "pro-labor scientists," it comes from the National Cancer Institute and the National Institute for Occupational Safety and Health. I don't need to be a scientific sage, then, to conclude that the lowest level of exposure corresponds to the lowest risk of developing cancer. That is, then, our policy on exposure to carcinogens. It seems there has been an attempt to ignore the fact that lung cancer in uranium miners is the principal cause of death. Uranium miners are no exception from workers exposed to carcinogens. Our policy applies to them. Uranium miners should be exposed to the lowest feasible level of radon daughters and any decrease in the permissible exposure level is a decrease in their lung cancer risk. Accordingly, OCAW has petitioned the Department of Labor for a new permissible exposure limit to radon daughters in uranium mining, which lowers the current exposure standard from 4 Working Level Months (WLM) per year to 0.7 Working Level Months per year. We made our demand to the Department of Labor on April 20, 1980. We are still awaiting action from the Federal Government on our petition. OCAW is also very concerned with other important health impacts of uranium mining. We are concerned with a rate of disabling accidents and fatalities which is twice as high as the same rate in other underground mines, excluding coal. We are also concerned with the rate of respiratory disease fatalities among uranium miners which is almost four times the rate among a comparable U.S. population. We have expressed those concerns when the U.S. Senate proposed a Federal Compensation Act for uranium miners. That proposal, by Senator Dominici of New Mexico, found a quiet death in two Congressional sessions. In conclusion, our position on lung cancer induced by radon daughters is the same position we have taken with all other industrial carcinogens: The lower the exposure, the lower the risk. OCAW is demanding a drastic decrease of the permissible exposure limits. OCAW will never accept that a segment of our membership which mines uranium should take the lion's share of the risk while the uranium mining companies take all the benefits.

Jan 1, 1981

By A. J. Guse

The primary limiting factor for hoisting capacity from great depths is the self-weight of steel wire ropes. Steel wire ropes are very suitable for mine hoisting due to their high strength and durability, but have the negative characteristic of a low strength/weight ratio. Also, as hoisting depths increase, the service life of steel wire ropes decreases due to the higher stresses and physical effects on the ropes. The significantly higher strength/weight ratio of synthetic ropes offers the primary advantage of hoisting a larger payload with a similar size rope and hoisting plant. The beneficial properties of synthetic ropes could be used to improve the overall economics of deep underground mining both for new deep shaft projects and for existing mining operations expanding to deeper orebodies. A research and development program has been initiated to evaluate the suitability of a fully synthetic rope for the mine hoisting application.

Feb 23, 2014

By G. Johnston, P. K. Chatterjee, S. Holguin

Underground mine planning is largely manual and can demand considerable resources to generate a working plan and to perform limited tests of sensitivity to variations in geological and mining conditions. It is possible to use computer aided mine planning to automate many of the manual procedures to allow the planner to evaluate a number of layouts, extraction strategies, and schedules. his paper examines the simulation and scheduling of an under- ground coal mine operation through the-use of on- screen graphics. The simulation will provide a basis for predicting productivity and other relevant information over a specified number of shifts. The software developed is extremely user friendly and reduces the tedium of repetitive manual calculations inherent to mine planning and drafting to a minimum, thus offering considerable savings in an area that is widely recognized as extremely labor intensive.

Jan 1, 1988

By Steve Trussell, William H. Langer

"Arizona aggregate (sand, gravel and crushed stone) producers enjoyed more than a half a century of nearly constant growth in demand for aggregates. Approximately 80 percent of the aggregate produced in Arizona is sand and gravel, and 20 percent is crushed stone (U.S. Geological Survey, 2015). Figure 1 shows the generalized distribution of potential sources of sand and gravel (yellow) and potential sources of crushed stone (other colors described below). Black dots show locations of aggregate operations.Sand and gravel commonly is produced from modern river channels and terraces although some alluvial fans and high-level paleo-river terraces also serve as aggregate resources. The gravel clasts are a mix of rock types that reflect the types of rock in the source area of the rivers. Generally processed river gravels meet stringent specifications for highend uses.Crushed stone, which makes up about 20 percent of production, primarily comes from a variety of metamorphic rocks and light-colored intrusive igneous rocks such as granite (brown areas), dark colored extrusive igneous rocks such as basalt and scoria (rust colored areas), and carbonate rocks such as limestone or dolostone (green areas). Carbonate rocks are also used in the manufacture of cement and lime.Construction and aggregate production in ArizonaBecause aggregate producers have limited facilities for storing product, stockpile changes are insignificant compared to production. Therefore, demand or consumption of aggregate in Arizona is considered to be equal to production. Production figures used in this paper reflect shipments, sales or marketable production, including aggregate used by producers to make readymix concrete and asphalt. Production figures were reported by the U.S. Bureau of Mines from 1950 until 1995 and by the U.S. Geological Survey (USGS) since then. Production figures are reported voluntarily, and major operators are the primary source for these figures. Because many smaller operators do not report their production, the figures are conservative values that provide an approximation of aggregates production activity."

Jan 1, 2015

By V. R. Bovino

In the early 80's, the cover of a major weekly magazine proclaimed the "Death of Mining." A few years ago, mining conventions, similar to this, around the country sported the theme, "The Survival of Mining." Today, the SME announces that "Mining is Alive." Being part of an industry that is simply alive is not very exciting. We can do better! Our challenge must be to flourish, blossom, maximize our potential and expand our horizons. The pace of rejuvenating this industry is still woefully inadequate. The new generation of mining industry leaders recognizes the urgent need for bold operational changes?changes in the way we deal with our employees? changes in the way we achieve productivity? and changes in the way we reward our employees for productivity.

Jan 1, 1991

By J. W. Leonard

By using physical and chemical method to increase the bulk density of newly mined coal, the productivity of a mine can be significantly increased. Greater amounts of coal can be placed in fixed volume shuttle car by increasing bulk density. This can increase mine productivity by about 15%. Small, easy to achieve changes in mining operations are required to obtain the increased productivity. This article deals with chemical methods used to increase coal bulk density, the results and discussion are based on experiments performed in the laboratory.

Jan 1, 1992

By S. K. Palm

Volatility is a fact of life in the mining industry. Prices of and demand for mineral products are among the most volatile of those for any product. The volatility of these markets wreaks havoc on both corporate management and the personal lives of mining people. Yet, until recently, it has been difficult to assess the impact of volatility on business strategy. This paper discusses how mining firms can profit from market volatility through an operations strategy that stresses operating flexibility. The foundation for our strategy analysis is the observation that a mine is analogous to a stock option. Techniques based on those developed to value stock options have recently been extended to the field of mine valuation. The insights provided by option pricing are very valuable in the development of mine operating strategy.

Jan 1, 1986

By George J. Bujtor, Anthony K. Scott, Haddon F. King

In 1982, the result of a 3-year study was published as "A Guide to the Understanding of Ore Reserve Estimation". The principal conclusions were that computation formed only part, and perhaps not the most important part, of an estimate and that the estimate should recognize that geological, mining engineering and metallurgical judgements formed an essential part of the eventual result. Subsequent expectation/realization studies of several mines have produced case histories which form the principal basis of the paper. These imply that geology is even a larger factor than thought earlier.

Jan 1, 1992

By D. M. Steelman

Digital systems have been employed in industry as an aid in process evaluation and control for about 20 years. The earlier systems were quite simple and did little more than periodically scan a multitude of process variables, perhaps comparing them to alarm limits, and print out the results. As time passed, the needs of industry and the imagination of process engineers became more demanding. Rather than perform only alarm checking and logging, operating guides were generated to help the operator gain optimum performance from the process. Eventually, systems were entrusted with the job of manipulating the set points of the local analog control loops in a (DDAC) digitally directed analog control mode. Today digital systems are used to gather all-the process information, including both analog and digital variables; to make the necessary data manipulations; and to control the process end elements in a (DDC) direct digital control mode. During these years of transition from the very simplest systems to the complex systems of today, the demands upon the system engineer have been every increasing. The process engineer has required, among other things, more computational ability at high speeds, faster input and output rates, greater flexibility, better communication facilities (man-machine interface), (process oriented software), and finally, greater reliability at lower cost.

Jan 1, 1969

By E. E. Maurer

Kerr-McGee has operated the Ambrosia Lake uranium mill since startup in 1958. Tonnage milled per day has varied from 3500-7000 tons. The mill capacity is currently rated at 7000 tons per day. The process consists of two parallel circuits following crushing and sampling, \\lhich include open circuit rod mill grinding, sulfuric acid leach, cyclone classification, and counter-current washing circuits of sand classifiers and slime thickeners. Pregnant solution is clarified and polished by precoat pressure leaf filters prior to amine solvent extraction. Yellowcake is precipitated from the pregnant strip solution with ammonia, filtered and dried.

Jan 1, 1972

By J. L. Vanderbeek

Investigations have been conducted at Chino Mines Company into the effect that SAG mill recycle material (critical size) exerts on SAG mill throughput and specific energy requirements. Tests were conducted on the laboratory, pilot, and plant scales, to evaluate the merits of alternative treatment options. Removing critical size material from the SAG mill circuit has been shown to improve new feed rates by 34% with a reduction in specific energy (kWh/ton) of 33%. Test results obtained to date are presented.

Jan 1, 1985

By Charles H. McGuirk

The Port of Conneaut, the largest bulk material handling and storage facility on the Great Lakes, is using the latest electronic and visual testing devices to augment and enhance its well established computerized preventive maintenance system. The results of this comprehensive program have been impressive. The remaining life of components can be accurately forcast, and replacement can be programmed around operations, resulting in a significant improvement in system availability and reduced costs for the dock operator and its customers.

Jan 1, 1983

By R. A. Allwes

In-plane bending and torsion tests were conducted on full-scale masonry walls to evaluate three post-reinforcement designs. The designs were developed to minimize longwall mine subsidence damage to existing residential masonry foundations. The bending tests show that vertical and horizontal post tensioned tendons significantly increase the resistance of a masonry wall' to in-plane bending. The torsion tests reveal that post tensioned tendons increase a masonry wall's limit of deformation but do not increase its torsional stiffness. The torsion tests also show that the masonry units minimally contribute to the torsional stiffness of a masonry wall.

Jan 1, 1995

By Tatiana Kotrikova, Steven Kolarz, Alan Kolodne, James Parkes, Matthew Goff

The WMATA Yellow Line is the section of steel segmentally lined tunnels that have experienced leakage and significant corrosion in isolated areas. A three part rehabilitation design has been developed for curtain grouting, structural repairs, and corrosion protection to provide continued performance. As WMATA’s first Construction-Manager-at-Risk (CMAR) project, the design development benefitted from collaboration with the Contractor through the final design development process. Rehabilitation work started in Fall 2022 and will be completed by late Spring 2023. Details of the project, the remediation design, and the process and benefits of the CMAR approach in the design development are presented.

Jun 13, 2023

By J. S. Chung

As part of ongoing deep-ocean mining research, hydraulic transport systems as well as status of deep-ocean mining systems are reviewed in the aspects of manganese nodules and crusts from 800-6,000-m depth. The emphasis of the investigation of hydraulic transport is placed on the shape effect of particles on the pressure gradients and flowrates. Series of tests are being conducted to study the lift characteristics of a 2-phase vertically upward hydraulic transport of 2 types of small solid particles in a PVC pipe of 1-in (2.54 cm) diameter: irregular-shaped silica sands and equivalent spherical glass beads. Pressure drops and mass as well as volumetric flow rates were measured by electromagnetic (EM) flowmeter and mass flowmeter. The particle sizes used are 8-10 mesh. The results in turbulent flow range of 104 < Re < 105 show that pressure gradients or friction factors are smaller for the spherical beads than the sands. The larger the concentration of the particles are, the larger the pressure gradients become. The larger the particle concentration is, the less the effect of particle shape on pressure gradients becomes. The shape effect is greater for the minimum particle transport velocities than for the settling velocities.

Jan 1, 1999

By J. B. Hiskey, P. H. Qi

Activated carbon loaded with gold from different halide solutions was characterized by thermal analysis (TA) techniques. The mechanism of gold uptake by carbon varies from predominately adsorption for gold iodide to predominately reduction for gold chloride. Thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements confirm the existence of adsorbed gold-halide species within the micropore structure of carbon. These results suggest that the ratio of reduced to adsorbed gold increases for gold halides in the following order: Au-I < Au-Br < Au-Cl. In the case of Au-I, TA results for the loaded carbon were compared with pure compounds of 12, Aul and Aul3.

Jan 1, 1998