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By Neil S. Fishman

Tabular uranium ore in the Grants uranium region, New Mexico, occurs as tabular layers of a urano-organic mixture suspended within host sandstones of the Morrison Formation. The intimate urano-organic association points to the organic material as the main ore control. Petrographic evidence indicates that the organic material was postdepositionally introduced into the host sandstone, probably as humic acids; however, the mechanism by which these acids precipitated from solution remains uncertain. A model, the cation scavenging model, is proposed in this paper to explain humic acid precipitation. The model, supported by evidence from regional alteration studies of the host sandstones, proposes that cations responsible for humic acid precipitation were scavenged from framework grains which altered during passage of the humic-rich fluids through the host sandstone. This process, coupled with the affinity of organic molecules for each other, caused flocculation of humic acids into tabular zones. The precipitated humic substances then continued to concentrate uranium to form the orebodies. The cation scavenging model requires only one solution, the humic-bearing solution, in the precipitation process. All cations necessary for humic acid precipitation originated in the host sandstones. This model contrasts with a previously proposed model--the brine interface or two solution hypothesis--in which it was proposed that a cation-rich brine introduced into the host sandstones provided the cations necessary for humic acid precipitation. The brine hypothesis has several drawbacks, one of which is unrealistic hydrologic reconstructions necessary to accommodate mineralization at various stratigraphic horizons in the Morrison Formation. Moreover, no mineralogic evidence exists to suggest a brine occupied the host sandstones at the time of mineralization. The proposed cation scavenging model for humic acid precipitation not only readily accounts for humic acid precipitation, but also is consistent with geologic observations and regional alteration studies.

Jan 1, 2013

By Bill Cain, David F. Tsztoo, R. John Caulfield, D. Scott Kieffer

In 1994, the East Bay Municipal Utility District (EBMUD) commenced a system-wide Seismic Improvement Program to protect their facilities from catastrophic damage. A primary focus of this program has been on retrofitting the 75-year old Claremont Tunnel, which crosses the active Hayward Fault zone. A large earthquake on the Hayward Fault could generate enough right-lateral fault slip to effectively sever this important lifeline. The retrofit project involves construction of a new bypass tunnel through the Hayward Fault zone, together with systematic contact grouting and localized structural repair of the existing concrete liner. Several innovative design measures have been incorporated into the seismic retrofit design, including an oversized tunnel cross section, backfill concrete side drifts, seismic isolation of an internal structural pipe, and shear fuses in the final lining.

Jan 1, 2005

By R. Reddy Kallu

Prior to July 2007, the only accepted method by MSHA for evaluating the mine seal design and performance is the full-scale explosion tests conducted in the NIOSH?s Lake Lynn Experimental Mine (LLEM) for deeming a seal design suitable for use in U.S. coal mines. Since the new regulations came into effect use of these conventional full-scale explosion tests for evaluating mine seals for the new elevated design standards may not be practicable. Generation of such high explosion pressures in experimental mines is dangerous and may cause permanent damage to the testing facilities. Further, they require significant amount of time, labor and money. Considering these factors, there is a need to develop scientific methods for evaluation of new seal designs and for understanding the dynamic seal response. This paper tries to address the reinforced concrete (RC) seal design using the three dimensional finite element based explicit software ABAQUS. Full-scale explosion test data available from NIOSH?s LLEM on 20 psi reinforced concrete seal is used for validating the numerical models. Further in this paper, based on the results from the validation models, a reinforced concrete seal is designed for 120 psi design standard for typical entry dimensions.

Jan 1, 2009

By A. L. Martikainen

In fluctuating airflow, continuous air velocity recording is the most reliable method of air velocity measurement. It allows for fast recognition of changes and the calculation of long-term averages. Also, it enables the mine operator to identify when the airflow has decreased to a point requiring action. Using ultrasonic anemometers provides an accurate option for continuous air velocity monitoring. This paper provides information about the effect of common obstructions in underground mining on air velocity readings. Stationary and moving obstructions are used to represent workers and equipment that would cause discrepancies in measured airflow. Also, it is important to know how large of a sample size is required to ensure reasonable accuracy of results. Statistical analysis is used to evaluate the required sample size. The sampling procedure is further studied by comparing two different sample rates. The results show that obstructions provide noticeable differences in air velocity measurements. Also, movement of obstructions can be recognized from changes in results. Surprisingly small sample sizes provide reliable air velocity information. Standard sample rates are found to be suitable for the underground environment.

Jan 1, 2011

By M. A. Reyes, J. Bickson, J. R. Srednicki

Federal laws mandate the presence of refuge alternatives (RAs) in underground coal mines and provide guidelines for harmful gas removal. After an explosion, harmful gases can follow survivors into an RA and can reach a deadly concentration. Investigators from the National Institute for Occupational Safety and Health (NIOSH) tested 12 ventilation system configurations (VSCs) to purge sulfur hexafluoride (SF6) tracer gas from a built-in-place (BIP) RA in the Experimental Mine in Bruceton, PA. Using a borehole air supply, tests were conducted with airflows of 750 and 1,000 standard cubic feet per minute (SCFM). Excluding a VSC where the air inlet was 1.98 m (78 in) from the air outlet, the results show that the time to purge the SF6 concentration from 1,000 parts per million (ppm) to 25 ppm ranged from 26 to 29 minutes for an airflow of 750 SCFM and ranged from 18 to 23 minutes for an airflow 1,000 SCFM. Mines can use this information to reduce purge time in case of a mine disaster and determine which VSC to avoid. INTRODUCTION After a fire or an explosion in an underground mine, the concentration of carbon monoxide can reach a fatal level. In a mine disaster, the main goal is to escape. However, if miners cannot escape, they have to migrate to a location to find refuge and, if possible, communication, and a borehole source for a fresh air supply. To ensure survival of the miners, Federal laws mandate the presence of a refuge alternative (RA) within 304.5 m (1,000 ft) of the nearest mining face. In addition, Code of Federal Regulations Title 30 CFR Section 7 sets the guidelines for personnel tracking, RAs, and the removal of noxious gases in underground coal mines (Mineral Resources, 30 CFR, 2014). Federal regulations define an RA as a protected, secure space with an isolated atmosphere and integrated components (Mineral Resources, 30 CFR, 2014). There are three types of RAs: portable metal RAs, portable tent-type RAs, and built-in-place (BIP) RAs. A BIP RA is constructed using masonry or other stoppings to create an isolated space in a mined-out area. Blast doors are installed in one or both of the stoppings for the miners to enter the RA. Furthermore, RAs must provide the following components: breathable air, food, water, air monitoring, and harmful gas removal. Federal regulations have emphasized the mandate for breathable air and harmful gas removal in the following words: “Purging or other effective procedures shall be provided for the airlock to dilute the carbon monoxide concentration to 25 ppm” (Mineral Resources, 30 CFR, 2014). The purpose of the mine ventilation system is to provide a sufficient quantity of air to the underground mine workings, to dilute methane and other contaminants, to maintain a suitable working environment, and to prevent accidents from happening (Cheng and Wei, 2014). In addition, the organic nature of coal amplifies risks from poisonous gases, explosions, and fires (Engström et al., 2018). If an underground coal mine ventilation system fails after an explosion, the concentration of toxic gases, most notably carbon monoxide, will increase. Carbon monoxide is dangerous because it creates tissue hypoxia by binding to hemoglobin (Özmen and Aksoy, 2015).

Jan 1, 2019

By Edward R. Mueller

As an alternative to a million dollar, sensor based, computer dispatching system, Cyprus Pima Mining Company has installed a home¬made analog computer. The device is used in conjunction with a standard radio-dispatching system; it is inexpensive and very simple to build and operate. It enables the dispatcher to make near opti¬mum dispatching decisions and to identify all off schedule haulage trucks. Since installation, Cyprus Pima has experienced significant increases in pit productivity.

Jan 1, 1977

By Delbert Hamilton, Christopher Snyder

In the last three years there have been four uncontrolled heating events in mines that have been attributed to the use of polyurethane foam as a void fill product. These heating events are due to the exothermic reaction that occurs during application of these polymeric products. These events led the Mine Safety and Health Administration to issue a safety alert on polyurethane products used in void filling and ground consolidation in mining, with the goal of educating the mining community about this potential hazard. This paper provides an overview of various types of polymeric products and best practices, the factors that contributed to the heating events, and case studies involving polymeric products.

Jun 25, 2024

By Warren D. Stanford Stanford

Introduction The Sleeper mine is a near-surface gold mine located in a remote area 56 km (35 air miles) northwest of Winnemucca, NV (Fig. 1). The deposit was discovered in 1984 by an Amax exploration geologist. Favorable drilling results led to feasibility studies and metallurgical testwork. Final evaluation of the mine potential proceeded very quickly. The project received Amax board approval in July 1985. Eight months later, the process plant was fully operational. The first gold ($1 million) was shipped one month later, in March 1986. Total plant capital was $27 million. Payback was achieved in six months. The Sleeper mine was expected to produce 1.6 t (53,000 oz) of gold and 1.3 t (41,000 oz) of silver annually. However, the ore body exceeded all expectations. Production for the first 10 months of operation amounted to 4 t (128,000 oz) of gold and 2.9 t (94,000 oz) of silver. Direct cash operating costs are in the $1.77/g ($55 per oz) range. Amax is actively conducting exploration nearby for additional reserves to extend the mine's life. (See update on page 242.) Geology The Sleeper gold deposit is located on the northwestern flank of the Slumbering Hills and in the Awakening Mining District. Rocks exposed in the vicinity of the deposit are interbedded siltstones, sandstones, and limestones of Triassic age. They are overlain by latite lava flows and tuffs of Tertiary age. Dikes and sills of latite and andesite intrude the sedimentary rocks. Quaternary deposits of mostly sand with minor gravel and clay cover a pediment containing the gold deposit. The sedimentary and volcanic rock units have been transsected and offset by extensive north- northeast trending faults and less abundant northwest trending faults. Both fault systems fractured and prepared the ground for subsequent invasions of mineral-bearing hot spring geothermal waters. The hot spring systems produced widespread hydrothermal alteration and gold mineralization at silicified centers near feeder fault structures. The deposit is hosted by siltstone and latite that have been hydrothermally brecciated. The main breccia is elongated north-northeasterly. The hydrothermal breccia zones appear to dip steeply to the west. Gold mineralization consists of native gold and electrum deposited in two or more high-grade quartz-breccia veins. Lower grade gold mineralization occurs

Jan 4, 1987

By John Rushton

Surface mining, from ore extraction to processing, requires many types of equipment to obtain the final product. Mine equipment often includes shovels, drills and haul trucks. Ore processing equipment, including plants, mills and concentrators, are also part of surface mining operations. Surface mining operations emphasize production. Production is where the bills are paid and fortunes are made. However, there must be support to keep the equipment operational. To most production people, equipment maintenance is a necessary evil. Maintenance is not glamorous work. It is often neglected when praise is being passed around. It is easy to recognize higher production, greater capacities, faster cycle times or more loads hauled. But who cares if an engine is replaced in 12 hours instead of 48? The answer is, everyone should - from the hourly miner to the mine manager. Surface mining equipment needs constant maintenance work. It must be lubricated, components replaced, electrical problems repaired and other problems addressed. Repair work for any surface equipment takes time away from production. It costs money. Maintenance costs cannot be avoided. However, they can be minimized. Minewide communication should include operations cooperating with maintenance. Traditionally, operations resist surrendering equipment to maintenance if it can continue to produce. The rationale is, every load that can be hauled today is money in the bank. If the unit is taken down, the money is lost. This thinking is prevalent in many surface mining areas, including the mill. "Not on my shift," the operator thinks. "Let the next crew worry about it. The problem with this thinking is in probability and statistics. The longer equipment goes without maintenance work, the higher the probability of equipment failure. When the failure does occur, it is certain to cause the equipment to remain down longer than if the maintenance department had been allowed to take it down. Many mining operations have closed early in their lives because of poor maintenance practices. This has become the industry standard because substandard levels of performance are acceptable. Management believes it gets five to six hours of work from maintenance people during an eight-hour shift. Actually, the industry average is less than two hours of work per shift. Real productivity levels of less than one hour are not unusual. There are few exceptions. However, a daily work schedule (DWS) will increase productivity at many properties by 50% to 100%. A 200% improvement is not unusual. The DWS will work. Maintenance people are among the most intelligent and motivated people on the property. They deserve the chance to be productive. [ ] In preparing a DWS, management needs to understand two productivity principles - the productivity spread and the real maintenance workday.

Jan 1, 1997

By Juan J. Monsalve, Mario Karfakis, AMAN SONI, Nino Ripepi, Jim Hazzard

Pillar collapses are events that due to their severe consequences can be classified as high risk. The design of pillars in underground room-and-pillar operations should migrate to risk-based design approaches. The authors of this work proposed a risk-based pillar design methodology that integrates stochastic discrete element modeling for pillar strength estimation, and stochastic finite volume modeling (FVM) for stress estimation. This paper focuses on the stochastic FVM component for stress estimation. The mining and geomechanical aspects of a case study mine (CSM) are described and pillar stresses are estimated by using three approaches: (1) analytical solutions, (2) 2D finite element modeling, and (3) 3D finite volume modeling. This operation extracts a 30° dipping deposit, which makes current underground stone mine design guidelines inapplicable for this CSM. This work compares results from each stress estimation approach and discusses uses the point estimate method as a simplified stochastic approach to evaluate the effect of rock mass elastic properties variability on pillar stress distribution. Results from this work show that the three estimation approaches lead to different estimations, possibly, due to the wide range of assumptions each estimation approach considers. It was also determined that the horizontal to vertical stress ratio has a significant impact on pillar stress magnitude. Therefore, it is recommended to perform in situ stress measurements, or assume worst-case-scenario values to account and reduce uncertainty due to this parameter. The stochastic stress estimation approach used in this paper provides results that can integrate a risk-based pillar design framework.

Sep 24, 2022

By D. G. Kotlyar

Oxidized sulfide minerals, commonly formed by weathering, increasingly are becoming important resources as primary sulfide deposits are depleted. Oxidation, in general, reduces selectivity and recovery in flotation. The objective of this research was to determine the mechanisms of oxidation and collector adsorption in sulfide systems as a step towards developing improved technologies for beneficiation of oxidized sulfides. Data from microcell flotation tests are combined with electrochemical and spectrophotometric measurements. The adsorption of ethyl xanthate (EX) on oxidized sulfides was characterized using AC impedance techniques and correlated to flotation response. The floatability of chalcocite, chalcopyrite and pyrite was dependent on the extent of oxidation. Oxidation for 1?) d at 65? C inhibited flotation of chalcocite, and chalcopyrite even after the addition of a large amount (1 x 10') M) of collector. Heavily oxidized (27 d) chalcocite remained unfloatable. However, longer oxidation of pyrite and chalcopyrite restored the floatability. Oxidation resulted in an electrically resistive, nonporous surface layer.

Jan 1, 1993

By B. T. Field

Pyroprocessing systems range from low temperature dryers to high temperature reactors. The materials and process requirements cover a broad spectrum. It is not the intent of this paper to do a detailed examination of individual processes and equipment, since that can be found in a multitude of other sources; rather it is the intent of this paper to examine the key process variables and offer empirical guidelines to assist in a user?s overall evaluation.

Jan 1, 1998

By Eti Purwaningsih, Widi Astuti, Erik Prasetyo

Selective-reductive leaching of manganese from low-grade manganese ore using tannic acid as a reductant in acidic media was demonstrated by XRD, SEM-EDX characterization, and batch leaching studies at room temperature. The pH change in the liquid phase before and after leaching revealed that selectivity of manganese over iron was due to the hydrolysis of iron. The acidity in the liquid phase during leaching was dictated by two mechanisms: proton-consuming reaction (manganese oxide reduction by tannic acid) and proton-producing reaction (ferric ion reduction by tannic acid to produce ferrous ion). Based on the leaching studies, the more prevalent reaction between these two was determined by initial leaching conditions: tannic acid concentration, sulfuric acid concentration, liquid-solid ratio, temperatures, and agitation time. Kinetic studies revealed that maximum recovery was attained within 6-h agitation, which indicated a product layer diffusion process.

By William W. Edgerton

Establishing geotechnical baselines on soft ground projects that require the use of closed-face tunnel boring machines (TBMs) is difficult. It is hard to see the face when mining and the excavated material is combined and mixed, all of which makes baseline quantifications challenging. In an attempt to meet underlying objectives of minimizing bidder contingencies, allocating or sharing risks and paying for conditions only if they occur, nongeotechnical baselines (i.e., functional baselines) have been developed. These have been used on the District of Columbia Water and Sewer Authority?s Clean Rivers (DCCR) Blue Plains Tunnel (BPT) project. This article examines the development of such functional baselines and how they were implemented on the BPT project.

Jan 1, 2012

By K. Yatsunami

NKK has developed a new cold bonded pellet process. The features of this process are; 1) it is a continuous process with 10 hours curing. 2) Products can be used as materials for various metallurgical furnaces. 3) Various kinds of slag are used as binders if necessary. 4) The quality of products is excellent. The pilot plant completed in 1981 is now being successfully operated. We are also constructing a commercial plant at our Niigata works. We produced cold pellets containing carbon as material for ferroalloys (Si-Mn), by pilot plant and used them in furnaces. Consequently, considerable economic advantages were obtained.

Jan 1, 1984

By R. E. Mitchell

The environmental impact assessment (EIA) is the accepted method for evaluating proposed mining and other industrial projects to obtain regulatory approval and to help companies plan for responsible development. Another increasingly common evaluation system for proposed projects is the environmental, social and health impact assessment (ESHIA). An ESHIA differs from an EIA for its generally more comprehensive and inclusive approach to evaluating potential impacts, such as on public health, and other features such as an ecosystem services approach to assessing biophysical and community impacts. An ESHIA may also be required by certain lenders for financing major projects. In this paper, EIA standards for the province of Alberta, Canada are discussed and compared to ESHIA. It concludes with several recommendations for consideration.

Jan 1, 2012

The Cadia Mine is located 25kms South West of Orange in the central west of New South Wales (NSW), Australia (Figure 1). Orange is a major regional centre with a population of 35,000 people. Cadia has a history of mining and exploration dating back to 1851 and shortly after the first Australian gold rush at Ophir, north of Orange. Newcrest Mining commenced an exploration program at Cadia Hill in 1992. This identified a substantial zone of copper and gold mineralization. Subsequent resource definition drilling defined an orebody with a mineable reserve of 200 million tonnes of ore with an average gold grade of 0.74g/t and 0.17\ copper. A full feasibility study commenced in 1994, approvals to proceed with development were granted in September 1996 and the processing plant was commissioned in July 1998. The project came in on budget at A$440 million and on time, 24 months from design to construction. The estimated operating cost at the time of commissioning was A$8.85/t of mill feed.

Jan 1, 1999

By T. Resende, J. Sismour

"Signs in underground mines are subject to variable airflow, which carries dust and moisture. Dust buildup reduces their visibility, hampering production efficiency and safety. Underground workers commonly must stop to clean signs in order to gauge their location, or find critical supplies or services. There are currently a variety of coating products, including dust and water repellants, available on the market that have the potential to reduce dust accumulation on sign surfaces. This paper describes a preliminary study to determine their effectiveness. The study involved a practical testing protocol using a trickle rock duster and samples cut from a clean, used road sign. Product effectiveness, under both dry and wet conditions, was evaluated based on photographic evidence by comparing changes in sign luminosity after a period of rock dust application. By analyzing the frequency of different pixel luminosities on the dust-covered samples, both uniformity of dust coverage and the total amount of accumulation was assessed. Results indicate that at least one product may reduce the amount of dust buildup on sign surfaces and increase visibility. INTRODUCTION In all underground mines, visibility of signage is critical. Signs inform miners of their location, direction toward escape routes, and location of supplies. Over time, sign surfaces can collect dust and can eventually become unreadable. The rate of dust accumulation on surfaces is often particularly high in coal mines, where both mining (e.g., cutting and drilling) and rock dusting activities can contribute significant amounts of dust to the airways. Several factors may contribute to dust buildup on sign surfaces. First, basic principles of fluid and particle flow are at play. When a fluid travels past a stationary surface, the velocity of the fluid at the surface boundary is zero. If a very small dust particle moving with air collides with a surface, it does not immediately fall off since the air velocity is zero at the sign surface. (This is the same reason that dust can collect on a rotating ceiling fan.) Further, once the collision occurs, other mechanisms may help keep the particle there – including friction that resists particle falling due to gravity, and adhesive forces due to humidity and/or static charges the particle and others already on the surface. Currently, the most common way to deal with reduced sign visibility due to dust buildup is for mine personnel (e.g., a compliance foreman, supply worker) to periodically clean sign surfaces – usually just by wiping them with a cloth. As a regular activity, this solution is inefficient; in cases of emergencies, it can also pose unnecessary risks. Application of an off-the-shelf coating to sign surfaces may represent a simple yet effective way to reduce the rate of dust accumulation. There are currently a variety of products on the market that may be suitable for this purpose, including dust and water repellants."

Jan 1, 2017

By D. Gove

All mining operations using trucks have a common need to properly match the number and size of hauling units (trucks. wagons. scrapers. etc.) to a loading unit (wheel loader. hydraulic shovel/excavator, cable shovel. push tractor. etc.) to provide the best possible fleet match. Optimizing fleet match minimizes the cost per unit of material moved by that fleet. As haul conditions change (haul length. grade. or rolling resistance), there may be need to adjust the number of trucks to maintain the optimum fleet match. Fleet Production and Cost is a tool which, among other things, can be used to optimize the truck-loader match.

Jan 1, 1994

By Paul D. Bybee

The Freeport Sulphur Company operates four sulphur mines in the coastal marsh area-03 South Louisiana. Employing the Frasch process of mining, approximately 13-million gallons of water per day is heated to a mining temperature of 325°F and is injected into the sulphur bearing formations of the four mines. A volume of cold waste water, roughly equal to the Input, is removed from the formations and presents a disposal problem. Two additional mines are currently being developed and will increase the disposal volume by an additional 5-million gallons per day. Although these properties are in a relatively small area, geographically speaking, as shown in Figure 1, they each represent a separate disposal problem with the treatment methods designed for the individual mine.

Jan 1, 1959