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By Keith G. Wallace

Coal mine ventilation systems are often subject to high leakage rates. As a result, changes in airflow resistance will strongly affect the efficiency with which air is delivered to the working place. One major source of airflow resistance is the line brattice used to direct air from the last open crosscut to the working face. Because it is a great distance from the fan, the resistance of the line brattice can result in more overall leakage than an equivalent resistance closer to the fan. Substituting auxiliary fans for brattice eliminates this source of resistance, with improvements in system efficiency and cost. Also, in some mines, the leakage that leads to spontaneous combustion can be reduced. The benefits obtained by several different brattice and fan substitutions have been studied by Mine Ventilation Services, Inc., under contract to the Bureau of Mines. Changes in main fan duty were compared with additional costs associated with auxiliary fans. Results indicate that in some circumstances, considerable leakage reductions and cost savings are possible.

Jan 1, 1986

By W. G. Pariseau

This contribution focuses on the role of stress analysis for mine planning and the selection of suitable computer programs for the task with special emphasis on coal mine pillars. In this regard, barrier pillars that defend a set of five main entries at the Crandall Canyon coal mine in central Utah were formed during extensive longwall mining north and south of these main entries. Numerical analysis for ground control guided the mine planning and permitting. Retreat mining of pillars led to disastrous events August 6 and 16, 2007, with the loss of nine lives. A most difficult lesson taught by the Crandall Canyon tragedy is the need for education in the selection and use of computer programs for pillar design. Much of this contribution is taken from a report prepared for the Mine Safety and Health Administration (Gates, et al, 2008). Details appear in Appendix Q of the report (Pariseau, 2008). The Crandall Canyon mine is about 16 miles west of Huntington, Utah, in the Wasatch Plateau coal field. Geology of the Wasatch Plateau is described by Doelling (1972) as gently dipping Cretaceous sandstones, mudstones, coal seams, and shales. Joint systems are present in strata above and below coal seams where cleat systems are present as described by Hucka (1991). Several major fault systems transect the field and form grabens with 450- 760 m of drop. One such structure is Joes Valley fault that crosses the Crandall Canyon mine. Mines in the Wasatch Plateau are generally developed from outcrops in steep canyon walls. Overburden increases rapidly as mining progresses into the plateau; mining depth varies with topography between 450 and 600 m in the region of interest. A stratigraphic column derived from a borehole into the mine is shown in Figure 1. There are 11 layers in the column.

Jan 1, 2011

In the last four years, 2007~2010, 9 out of 24 metal/nonmetal underground mine fatalities were caused by ground fall across United States of America (Mine Safety & Health Administration, MSHA). To reduce or eliminate incidents/accidents caused by ground fall, this paper clarified how to design and select ground support based on different ground conditions, how to use mine ground support standards, what geotechnical engineers and underground operators should do to keep mine production free of ground failures.

Jan 1, 2012

By G. A. Johnson

Basic management principles will be discussed (as they apply to minerals education efforts), especially in light of the changing nature of volunteerism in today’s society. Also, the “minerals education tree” will be presented, along with public opinion / public policy realities.

Jan 1, 2001

By L. A. Weakly, D. A. Weiss, R. B. Crookston

A presentation of experience gained from using mechanical and conventional equipment for excavating shafts, raises, tunnels and other openings in various Colorado oil shale mining properties.

Jan 1, 1983

By G. V. Krishnan, L. Adler

A rock classification for drilling and boring is presented covering most equipment types and providing an estimation of the key parameters for operation, such as thrust and speed, and of performance such as penetration rate and bit life. Drilling and boring are significant and integral aspects of both the mining and heavy construction industries. Together these constitute over 20% of the G.N.P. Drilling and boring represent the most arduous mechanical processes performed in industry. Their misapplication quickly leads to equipment destruction, hazards, and to major delays. The classification is unified in two ways: 1) for a particular rock class several parameters can be estimated, 2) the classification integrates most excavating activities (i.e. digging, ripping and even blasting), and is derived from ground control. The rock classification provides a job property, based on fundamental and index properties, which yields quick and rough estimates of vital information. However it does not obviate the need for a more thorough analysis, and maintaining field records. BACKGROUND In order to adequately describe a drilling operation the conditions, activity, and equipment must be characterized. Of these the major independent variables are the conditions. Conditions focus on the geologic mass and also consider whether the site is surface or underground. The primary component of the geologic mass is the rock type, detailed below in Rock Characteristics. The other components

Jan 1, 1983

By D. R. Hack

Increased consumption of concrete in the Pacific Northwest has pushed aggregate resource development pressure from urban areas west of the Cascade Range to rural areas east of the Cascades. Some recent development has focused on barge and rail accessible off-reservation Indian allotments that are exempt from state and county regulations. These lands have their own unique set of challenges, especially when Federal and Tribal governments have conflicting goals and attitudes pertaining to resource development. This paper discusses issues of leasing, reclamation, Federal vs. Tribal authority, cultural resources, and the history of allotment.

Jan 1, 2002

By R. Graeme, J. Komadina

Gold Fields acquired an option to purchase the Cerro Corona Project, located in Hualgayoc, Cajamarca Department, Perú, in December 2003. In January 2006, the option was taken up and the transaction closed. During the intervening months, Project development occurred against the backdrop of a Presidential election, increasing national social activism and environmental regulation, rapidly escalating operating and capital costs, as well as unprecedented demand for engineering and technical skills. Project “Lessons Learned” are outlined and discussed in the context of an evolving strategy.

Jan 1, 2007

By Ben Sosewitz

The subject of rapid excavation tunneling is one that is extremely important to the people in the Metropolitan area of Chicago. My personal observation is that it is also extremely important to the urban communities around the U.S., to many local and state governments, and to the public officials who are deeply concerned about state affairs and taxes. The Metropolitan Chicago area is in fact, (as are 40 other major urban areas in the U.S.) confronted at the present time with a very serious combined sewer overflow, drainage and pollution problem which accounts for an estimated 40% of the pollutional load on its waterway system. In response to this the District has to date spent some seven millions of dollars in an attempt to find the most economical solution available for the elimination of this problem. This study included extensive investigations of the geological strata, the quantity and quality of storm runoff to be dealt with, and the various methods of storage and treatment available. It has considered solving the overflow problem by a concept involving a series of tunnels, rock tunnels, shafts and storage areas which will collect, retain and subsequently treat that portion of the combined sewer overflow which can be handled in the most cost-effective and economical way, consistent with following the federal and state standards - with which we at the present time agree in principle.

Jan 1, 1997

By Robert G. Woolery

Union Carbide_ began looking seriously at heap leaching in 1971. At that time some 1.6 million tons of mineral averaging 0.040% U308 were stockpiled at various sites around the Gas Hills, Wyoming, uranium facility. Several alternatives for economically exploiting these reserves were considered and heap leaching seemed the most attractive. At the time, Western Nuclear Inc. was operating a heap leach project nearby in which the low-grade ore was leached with sulfuric acid, the product liquor treated in an on-site solvent extraction circuit, and the stripped product liquor re-acidified and recycled. They were most generous in allowing us to visit their site, answering our questions, and were helpful in discussing the problems associated with heap leaching. They confirmed our belief that, it was possible to operate a heap leach profitably on material too low grade for. conventional milling. Based largely on what we had learned from Western Nuclear's experience, a program was set up involving a laboratory study to determine the characteristics of the mineral stockpiles as related to heap leaching and to conduct a pilot heap leach adjoining our Gas Hills mill. Basically, the pilot heap construction and leach procedure were similar to those described in the literature(1,2) with certain modifications to permit detailed monitoring of the operation. In May, '1972, the decision was made to construct a test heap. The UCC plant at Gas Hills, Wyoming was selected as the most appropriate site for the follow¬ing reasons:

Jan 1, 1977

By Bryan Ulrich

Knight Piésold and Co. hosted its annual roundtable discussion on March 17, 2011 at the Stockman Hotel and Casino in Elko, NV. The theme for Roundtable 2011 was, ?High density tailings, paste, and filtered tailings,? although the topic may well have been subtitled, ?Don?t prematurely rule out any technologies before they are given their day in court.? Bryan Ulrich, Knight Piésold?s local representative, as well as Tom Kerr from Knight Piésold?s office in Denver, CO, were on hand to help facilitate the discussion. Ulrich and Kerr are senior vice president and president of Knight Piésold?s U.S. practice, respectively. The event played host to more than 30 attendees from several western states. Attendees included personnel from a dozen mining properties and various corporate offices. There were also attendees from manufacturing and specialist consulting firms who have been providing services to various high-density tailings, paste and filtered tailings operations worldwide. It may be noted that the term ?filtered tailings? is used in this discussion. Alternative terms, such as ?dry stack? or ?dewatered tailings,? should be avoided whenever possible, as such terms tend to give a false sense about the nature of the material since these materials typically still retain a significant amount of moisture.

Jan 1, 2011

What decision making tools and methods are available to a project owner when there is no clear differentiator between construction alternatives? A team led by a joint venture of Parsons Brinckerhoff and PGH Wong Engineering (PB/Wong) has been providing preliminary engineering services to the San Francisco Municipal Transportation Agency (SFMTA). The SFMTA and PB/Wong team developed several alternative construction methods for the tunnels and stations of the San Francisco Central Subway Project, none of which could be judged clearly better than another using traditional approaches and metrics. The team employed a risk assessment and analysis frame-works as a means of comparative analysis, drawing upon the knowledge of industry experts in the geotechnical, tunneling and construction fields to assist in the effort. This paper presents the approach and results of a cost and schedule risk analysis for two such analyses designed to answer two different questions regarding the advisability of different construction approaches. These assessments paved the way for key decision making in the preliminary engineering phase of the project and formed the foundation for continuing risk management efforts on the project. The focus of this paper is primarily the first two stages of risk management?identification and assessment?and some of the organizational dynamic issues that arise in such efforts.

By J. A. Rusnak, M. M. Gadde, S. S. Peng

In situ stresses are one of the key inputs to a successful underground excavation design. Because of the complex mechanisms involved in arriving at the current state of stress at a point in the Earth’s crust, often the only reliable way of estimating in situ stresses is by actual measurement. In the United States coal mines, overcoring relief method is by far the most popular technique used for estimating the virgin stress field. Typically, for stress measurement with overcoring, a vertical borehole is drilled into the roof or floor of an underground coal mine opening to a certain distance and change in borehole diameter is monitored at multiple points along the length of the hole when this borehole is overcored. For the measured stresses to represent the pre-mining stress field, the measurement points should be located beyond the influence zone of the mine opening. Actual data from several US coal mines have been collected to check if the measured stresses by overcoring represent true in situ stresses. The data indicate that most of the stress measurements were within the excavation influence zone. A three-dimensional numerical modeling methodology was applied to one of the collected cases to correct the measured stresses for the excavation influence. The modeling approach demonstrated the usefulness of integrating numerical modeling into a stress measurement program to estimate ‘true’ in situ stresses.

Jan 1, 2006

By Robert E. Kirby

The potash mine and refinery of AMAX Chemical Corporation is located 26 miles east of Carlsbad on the north end of the potash producing areas. This property was developed between 1949-1952 and production of muriate began in August 1952. Two shafts, located 400 feet apart, were sunk to the ore zone 900 feet below the surface. A 15-foot diameter ore hoisting shaft equipped with a 1000-ton ore pocket, crusher and automatic skip loading equipment plus a 20-foot diameter service shaft with a curtain wall for exhausting air were provided. Sylvinite production to date has been from the first ore zone, stratigraphically, the lowest of ten identified mineralized zones in the salt section. This first ore zone has been the top producer of Muriate of Potash over the years. In our area we do have some very marginal mineralization in the third ore zone some 35 feet above the first. We have not mined from this seam as yet but we are investigating the economics very closely with access slopes and an experimental mining panel. Our ore seam is generally flat lying but does have local gentle rolling with grades from 2% to 5%. The mine was designed and developed from the beginning with conventional mining practices and rail haulage from the mining section to the ore pocket. As mining progressed in the early years, production increased from less than one million tons annually to a maximum of 3,935,000 tons in 1964. Efficiency also kept pace with the increasing production and continually improved until the efficiency of the production crews reached an average of 100.3 tons per manshift in 1964.

Jan 1, 1974

In the present study, we have investigated the conditions for the formation of bubble clusters and the effect of well-defined agitation on the stability of clusters. A specially designed cell was used in which bubble clusters could be formed at the surface of a porous block in a fluidized bed of relatively coarse hydrophobic silica particles. The clusters then rose through a flow field of known turbulent characteristics. The size of the clusters before and after passing through the turbulent zone were measured using a high speed camera. The influence of shear rate on the deformation of the bubble clusters was investigated. The results showed that the Kolmogarov microscale was much smaller than the maximum cluster size, suggesting that the breakage of the clusters was mainly due to interaction with clusters in the inertial convection sub-range.

Jan 1, 2009

By R. Tamblyn

Vertically stirred media mills are a highly effective low-footprint solution for the ultrafine grinding of industrial minerals. This work investigates the effect of media density on flow patterns within the mill. Direct irradiation of a media particle leads to decay through positron emission, consequently forming two anti-parallel gamma rays, which allow for the real time tracking of particle position. Grinding media of the same size, but with a range of specific gravities are followed using this method, and the effect on the flow within the mill is revealed. The technique is seen to be an effective method to highlight the velocity profiles within the mill, as well as the zones where grinding is less efficient ? areas of relatively low velocity and high residence time. The changing media is seen to effect the overall flow patterns within the mill, having consequential effects on the efficiency of the grind.

Jan 1, 2009

By T. S. Bomar, C. J. Wood

Heavy media cyclones (HMCs) are efficient, high-tonnage devices suitable for upgrading run-of-mine coal in the 50 to 0.5 mm size range. Unfortunately, industrial HMC circuits are often not optimized due to problems such as incorrect operating pressures, poor feed distribution, excessive media contamination, mismatched components, and improper density control. To avoid these problems, operating guidelines have been provided in this article that are useful for optimizing the performance of HMC circuits. The validity of these guidelines has been assessed by means of density tracer tests carried out at several coal preparation plants.

Jan 1, 2002

By P. Somasundaran

Three major types of solution chemical equilibria involving flotagents (Le. flotation reagents such as collectors, frothers and modifiers), minerals and solution play a crucial role in determining the behavior of complex flotation systems. Minerals of phosphates (apatite and francolite), tungsten (wolframite and scheelite) and associated carbonates (calcite and dolomite) are sparingly soluble in aqueous solution and form dissolved mineral species in bulk solution. Such dissolved species interact with mineral solids, often resulting in surface conversion of the minerals. In addition, they can interact with various flotagents and lead to surface or bulk precipitation and loss of selectivity in the flotation. Relevant solution equilibria of such sparingly soluble minerals and their interactions with oleic acid and structurally modified reagents were determined in this study using a multi-pronged experimental approach. Methods to manipulate and control the solution chemical equilibria and thus achieve selectivity in flotation systems are discussed.

Jan 1, 1990

By R. L. Grayson

In 1995, Congress abolished the Bureau of Mines in the Department of Interior but preserved the safety and health research functions being performed at the Pittsburgh and Spokane Research Centers. These functions were transitionally housed in the Department of Energy before permanently merging with the National Institute for Occupational Safety and Health (NIOSH), Department of Health and Human Services, in October 1996. Since the merger of the former Bureau with NIOSH, there has been an active evaluation of ongoing research activities, significant interaction with stakeholders, and the development of a process leading to "data informed" priority setting. This presentation will review current surveillance information concerning the level of injury and disease from mining work and will discuss how research priorities are evolving to improve the contribution of research to the prevention of injury and disease.

Jan 1, 1998

By W. Randall, Robert M. Leary

Twin 1250 m (4100 ft.) long highway tunnels through Cumberland Mountain near Middlesboro, Kentucky are planned to be completed in the early 1990's. The tunnels will be excavated in sandstones, limestones, and shales, dipping at 35 to 50 degrees and striking nearly perpendicular to the tunnel alignment. In 1985-86 a pilot tunnel was excavated as a crown drift along the alignment of the southbound tunnel. The benefits of the pilot tunnel in reducing uncertainties for main tunnel construction are discussed. The cost-benefits of the pilot tunnel are examined in view of estimated main tunnel costs.

Jan 1, 1987