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By Jay C. Hanson

Various electrical and electromagnetic (EM) geophysical techniques are currently being evaluated by the U.S. Bureau of Mines for their effectiveness in the detection and monitoring of electrically conductive (1 to 5 S/m) lixiviant (leach solution) to depths of 600 m, either above or below the water table. These techniques include magnetotellurics (MT) , controlled source audiofrequency magnetotellurics (CSAMT), resistivity and focused resistivity, ground-penetrating radar (GPR), frequency-domain electromagnetics (FEM), and time-domain electromagnetics (TEM). Of these techniques, TEM may be the most effective, but CSAMT and focused resistivity also hold promise. Geophysical computer modeling of the borehole TEM technique was conducted based on an idealized geoelectric section (layered earth) with characteristics based on the Santa Cruz porphyry copper deposit near Cas a Grande, AZ. Layer resistivities and thicknesses were obtained from geophysical data and geologic logs available from the site. Modeling of borehole TEM in both preleach and during leach situations was conducted. Simulating the TEM method using computer modeling proved to be encouraging since there were substantial differences between leached and nonleached responses. The modeling does not prove the effectiveness of TEM in the field, but does indicate that detection of deep lixiviant zones is theoretically possible.

Jan 1, 1992

By Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By McLean E. J

Background The resources of the Gippsland Basin include not only the coal and oil for which it is well known, but also the tourism resource and the quality of life which it offers its residents and visitors. To manage this group of resources requires an understanding and ability to predict the consequences of possible developments. The water of the streams and estuaries as a key component as it is both a resource and the means for transporting wastes from one area to another. To aid in the resource planning process there is a need for models of the estuarine hydraulic processes. This paper describes an appropriate modelling technique. Resource use conflicts may arise from developments in the catchment upstream of the estuarine reach. For example the diversion of water for domestic and industrial use will change the velocity and salinity structure of the downstream estuary. In turn these changes will affect sediment distribution and deposition patterns and may impose stress on the biological communities and ultimately on the fisheries resources and water quality. The manager of an estuarine system may have expertise in ecology, hydraulics or another of the specialist disciplines involved, but commonly will not. The manager will identify needs for resource and development and the broad options required to satisfy them. The manager will use these studies as the basis for his/her selection of the option for execution. Thus a model for'use by the manager of an estuarine system must have the following properties: (i) The model must be sufficiently accurate to throw up all the likely options. (ii) The model must be capable of being run by the manager, interactively, to answer `what if' questions. This requirement implies a simple code andhardware limited to a personal computer or possibly a desk top work station. (iii) The model must be robust so that unrealistic input oes not generate apparently useful output, and no output is generated for cases where the model is not designed to give results. (iv) The model must be capable of being used as part of a modelling system comprising models of all the geographic and demographic components

Jan 1, 1992

By S. R. Titley

Results of regional analyses of precious metal habits in Arizona ores lead to interpretations of a fundamental ore control related to geographic location that corresponds with crustal contrasts. Measurements of isotopic and trace element characteristics of Laramide ore-related intrusions lead to interpretations of crustal derivation of apparent ore-related magmas. Interpreted regionally, the numerous kinds of Laramide ores, which include porphyry copper deposits of this southern cordilleran region appear to be phenomena of a specific crustal lithology characterized by a basement of Proterozoic turbidites and (an interpreted) lower crust of amphibolite. This association with a specific basement terrane may be extended in principle from the United states into Mexico where faulted offsets of this basement are similarly favorable to formation of Laramide porphyry ores -to the exclusion of adjacent terranes. Whereas plate tectonic mechanisms may have triggered evolution of these ores, it is hypothesized here that crustal setting and crustal composition are more profound influences of metallogenesis.

Jan 1, 1992

By A. Knoll, J. W. Beck, W. C. Brice, E. K. Lehmann

A cooperative study was undertaken in a neutral atmosphere by representatives of the environmental community, the mining industry and state government to identify and resolve environmental issues associated with base and precious metal mining before a commercial mining development is announced. The study included testing Minnesota's as-yet-untried nonferrous mining regulatory program using three hypothetical mining developments sited in environmentally sensitive areas where future mining could occur. Results include identification of critical paths for regulatory decision making, identification of particularly sensitive environmental issues that mill need continued deliberation before resolution and characterization of data necessary for environmental review and permitting decisions.

Jan 1, 1992

By Richard S. Kunter

Artech Recovery Systems, Inc has developed a low pressure and temperature? leach process called the "Cashman Process" to extract metals from arsenical flue dusts and residues and fix the arsenic in an environmentally stable form as ferric arsenate (scorodite). The process was pilot tested at Hazen Research in an integrated plant including continuous recycle from August 1989 to October 1989 during which several tons of flue dust were processed. Based on this pilot program, the process was deemed technically feasible and produced commercially salable products. Residues from this pilot program were subjected to a long-term stability test jointly designed by PTI environmental services and the USEPA. The process, its versatility, and the nature of the products is discussed in some detail.

Jan 1, 1992

By K. Cothern, S. Novack, D. A. Johnson, R. Borden, S. Pavlou

A procedure is presented for ranking hazardous waste sites for remedial decisions, and an example with application to mining waste sites is discussed. Typical contaminant concentrations are calculated from field data. Exposure indices that compare these measured concentrations with allowable limits are then computed. The limits are selected to protect both the health of humans (for both carcinogen and noncarcinogen effects) and the health of key organisms in the ecological food web. The additive exposure index for a site, defined as the sum of all contaminant-specific exposure indices, is then used in ranking the sites and assigning each a priority for remedial action. One key source of uncertainty in the process is the estimation of a typical site concentration from data that include values reported as "below certified reporting limit" (BCRL). This uncertainty is compounded in the additive exposure index and therefore may have a substantial effect on the assignment of remediation priority. A general approach is presented for incorporating consideration of BCRL data into uncertainty evaluation when assigning remediation priority designators to hazardous waste sites.

Jan 1, 1992

By N. P. Kripakov

This paper presents a brief overview of current bump mechanics theories and pillar design methodologies, and relates these concepts to experiences at two mines located in a north-central Utah coalfield where different pillar designs were used to control mountain bumps. Experiences gained at the first mine demonstrated the successful implementation of a two-entry, 9.8 m (32 ft)-wide, yield-pillar design. A U.S. Bureau of Mines field study quantified the timing of chain pillar yielding and resulting load transfer from the gateroad. In-mine pillar response, although apparently sensitive to site-specific conditions, compared favorably to estimates derived using two yield-pillar design methods. A second study conducted at another mine located in the same district, but subjected to different geologic conditions, documents the unsuccessful attempts to employ progressively narrower three-entry pillar designs based on successes achieved at the first mine site. This second mine never achieved a true yield-pillar design. Use of pillar widths ranging between 9.1 m (30 ft) and 27.4 m (90 ft) always resulted in violent bumps in the tailgate pillars. The pillars were either too large to yield, or too small to support peak operational loads. Hypothetical gateroad systems were evaluated using both analytical and empirical approaches for configurations comprised of two rows of conventional pillars, and systems incorporating both yield and abutment pillars. Analysis concluded that yield pillars less than 6.1 m (20 ft) wide and abutment pillars ranging between 30.5 m (100 ft) and 39.6 m (130 ft) square would be required to achieve a stable gateroad design. However, results of a field study conducted on a two-entry, 36.6 m (120 ft)-wide abutment pillar concluded that abutment pressures from the first panel overrode the pillar, and that a still larger pillar may be required to preclude bumps in the tailgate during second panel mining. Without the benefit of a demonstrated in-mine success, it is not clear which design would ensure elimination of gateroad bumps.

Jan 1, 1992

By J. Stachulak, M. Scobie

"This paper addresses the occurrence and indicated causes of conveyor fires in North American and European underground mines. Some significant convey or fires which have been experienced in recent years in Canadian hardrock mines are then reviewed. The nature of existing conveyor monitoring technology is considered in the context of such fire hazards. Experiences with new monitoring technology recently installed at several conveyor sites at Inca Ltd. mines are then reviewed.IntroductionFires associated with conveyors have long been recognized as a serious hazard in underground coal mines. Recently, however, there have been some significant conveyor fires in Canadian underground hardrock mines. These offer important evidence as to the nature and causes of potential hardrock mine fifes. They also warrant attention with a view to improving over-all mine design, ventilation and emergency preparedness.In addition, a new era in mine communications and monitoring technology has been entered which should offer improved capability to protect against such fires. This paper was motivated by the need to understand the causes and mechanisms of conveyor fires in order to improve their safety. This should be possible through implementing more effective monitoring systems, as well as improving conveyor design. Underground mines are becoming more intensively mechanized, with less human surveillance of equipment and a greater dependency on remote monitoring systems."

Jan 1, 1992

By Mary Cocklan-Vendl

Regulatory processes associated with development of a world class lead-zinc mine, Red Dog Mine, in northwestern Alaska were reviewed and evaluated. Informal interviews with key project personnel, consultants, and agency field and permitting specialists provided perspective on the regulatory successes and failures of the project. Due to potential impacts to air quality, water quality, wetlands, and National Park lands, an Environmental Impact Statement was required. By developing a comprehensive baseline of information on the existing environment to aid in minimizing impacts during project siting/design and through regular coordination of evolving project plans with regulatory agencies, the mine developers were able to acquire necessary permits in a timely and cost effective manner. The only major exceptions occurred when inadequate information was collected on dispersal of airborne particulates, rates of surface water run-off, and groundwater quality. These deficiencies resulted in the need for design changes, unscheduled construction, additional environmental monitoring costs, and delays in issuance of the NPDES permit.

Jan 1, 1992

By G. A. Rowell, T. M. Barczak, J. C. Zelanko

The US Bureau of Mines conducted a multifaceted geomechanics research project at a bump-prone longwall coal mine in eastern Kentucky. This mine presented a unique opportunity to study coal mine bumps because the problem appeared to be confined to areas beneath a sandstone channel of limited areal extent. The Bureau's research plan sought to exploit the uniqueness of the site by monitoring strata behavior and longwall support reactions as the longwall face approached and passed beneath a sandstone channel. The study incorporated static pillar stress and strata deformation measurements, shield support leg pressure measurements and microseismic monitoring, as well as geologic mapping and the collection of observational data. Data collection was underway when a major coal bump occurred on the longwall face at the mine. Pillar behavior (load and deformation), shield loading and microseismic activity were monitored prior to, during and after the bump. Observations in the tailgate indicated that these pillars were failing prior to and following the face bump. Shield load data, evaluated in an effort to identify trends that could be used to forecast coal bumps, appear to provide a measure of the effectiveness of destressing operations conducted on the face (e.g. shot firing). Analyses of microseismic data revealed anomalous values associated with microseismic "energy" prior to the face bump. In addition, microseismic source-location data and underground observations provided some insight as to the sequence of pillar and face bumps.

Jan 1, 1992

By Linda K. Killoran

The U.S. Bureau of Mines has developed a prototype cross well acoustic logging system and complementary tomographic image reconstruction software for the detection and delineation of abandoned underground mines and associated subsidence failure in relatively shallow environments. The logging system uses a piezoelectric, cylindrical bender as an acoustic source. A triaxial accelerometer assembly, designed to be rigidly locked in the borehole, is the receiver portion of the logging system. Both the source and receiver probes operate at high frequencies, thus providing short wavelengths capable of resolving small features in most rock types. A modified van with a dual-drum wireline winch, 4-channel data acquisition system, power amplifiers, and waveform generator supports field operation of the logging system. A field study was conducted at a test site in San Antonio, Texas, to demonstrate the cross well acoustic logging system. The underlying rock at the test site is similar to stratified sediments in coal measures. First¬arrival travel times were interpreted by tomographic reconstruction of the velocity field in the two-dimensional cross section between the source and receiver boreholes. The resulting image correlates well with geological borehole logging data for the test site.

Jan 1, 1992

By G. Archer

ASARCO, a large and diverse producer of nonferrous metals, is involved primarily in the smelting and refining of lead and copper. Lead-antimony alloys, antimony trioxide, bismuth, cadmium oxide, selenium, tellurium, silver and gold are among products which result from processing by-products of smelting and refining. The complex mixture of concentrates at some smelters and the high impurity loads at some refineries result in various drosses, sludges, dusts and slags. In this paper, the complex interplant and intraplant transfer of by-products is addressed. These by-products result in an exchange of metals between the lead circuit and the copper circuit. Examples of the transfer of by-products and the prospects for the recycle of valuable products from wastes generated by customers and unrelated processors are also discussed.

Jan 1, 1992

By Associates

The headwaters of Skippers Creek and the Shotover River are reputed to be among the richest alluvial gold catchments in the world. This alluvial gold has no doubt been derived from reef systems similar to, and associated with, the Bullendale lodes. Physiographically the prospect covers steep ridges and deeply incised gullies between the Richardson Mountains in the west and the Harris Mountains in the east. Vegetation is mainly tussock with bush either side of Murdochs Creek. Access to the area is by metalled road to Skippers and then by 4WD track to Bullendale. Alternatively the prospect area can be reached by helicopter from Queenstown in around ten minutes.

Jan 1, 1992

By Ann G. Kim, Thomas R. Justin, John F. Miller

The U.S. Bureau of Mines applied its mine fire diagnostic method to an abandoned anthracite mine fire site in Carbondale, Lackawanna County, PA. The technique to locate fires in abandoned coal mines and coal refuse piles includes the determination of hydrocarbon concentrations in mine gases, the imposition of an underground gas flow direction, and use of a surface mapping method, to define heated and cold zones in underground coal strata. The heated zones at Carbondale were characterized by elevated methane concentrations. The results of 25 communication tests were analyzed to define 2 large (approximately 100 by 250 ft) and 5 small, isolated heated zones. An approximate correlation existed between the location of the heated zones and areas of anomalous snow melt. The correlation between the results of the diagnostic test and subsurface temperatures was not significant.

Jan 1, 1992

By W. E. Heinrichs, R. W. Davis

Introduction Cross borehole seismic tomography (CBST) is a geophysical technique that allows definition of the distribution of some physical rock property between two boreholes. The method is similar to the computer-assisted tomography (CAT) scans used by the medical industry. This paper describes the method, its applications and the developing trends in its use that interest the mining industry. The idea of using tomography in connection with geophysical methods for measuring rock properties between boreholes has been around for three or four decades. Until the advent of high-speed, large-capacity computers, the necessary calculations were too formidable for production use. Another factor in the development of the technique has been the refinement of a mathematical base to meet the needs of the medical industry. The geophysical applications have benefited from this refinement. An extensive discussion of the basic theory is given in Kak and Slaney (1988). CBST, although widely researched and written about, is still not extensively put to use in mining and engineering projects. Most real world examples in the literature have come from research carried out by government laboratories or by large companies. An exception is the regular use by Prospection Geophysique Francaise (Cottin et al., 1986) in damsite investigations. The Japanese appear to be doing extensive research and testing of CBST's uses in civil engineering projects (Saito et al., 1988). Canada is researching the use of the method in connection with nuclear waste site investigations (Wong et al., 1987). Finland has tested the method in connection with a foundation investigation for a nuclear power plant (Cosma et al., 1984). In the US, the US Bureau of Mines has taken an interest in using CBST as a means to enhance in situ mining operations (Tweeton, 1988). Major oil companies are examining the method as a tool in oil field development (Justice et al., 1989). Description of the method CBST involves placing a series of receivers down one borehole and recording transmissions from an energy source placed successively at a series of positions in another hole. The objective is to generate a dense network of seismic raypaths between the holes. The denser the network of raypaths, the better the features between the boreholes are resolved. Either seismic travel times or sine wave amplitudes are measured by the receivers. Analysis of travel times between boreholes develops a picture of rock velocities between the holes. Analysis of seismic wave amplitudes develops a picture of the distribution of energy transmission characteristics between the holes. These seismic properties can be used to define occurrences of fracture zones, lenticular sequences or other important geologic data not apparent from examination of the borehole logs. When longitudinal (compressional) and transverse (shear) waves are analyzed, the physical properties, such as elastic moduli, can also be mapped. When wave amplitudes are measured, rather extensive corrections to the data are necessary. There is some disagreement among researchers as to the feasibility of making some of the corrections. For this reason, this paper will concentrate primarily on travel time analysis. Wave amplitude analysis will be mentioned occasionally only in passing. This does not mean that amplitude analysis does not provide important data on rock parameters, only that for the present there are limitations on its uses. Vertical seismic profiling (VSP), extensively used in recent years in oil exploration, is similar to CBST. Instead of using two boreholes, however, the VSP method uses an array of seismic sources or detectors down one hole and an array of detectors or sources along the surface radiating outward from the hole. While adequate for determining vertical velocity distributions, the VSP method is not, by itself, suitable for most engineering or mining projects. Computer programs used to analyze the field data make use of the fact that the total travel time or change in signal amplitude between boreholes is described by Dines and Lytle (1979) as: [9k = f Rk f( x,Y) ds (1)] where gk = the total time or attenuation along the kth ray path,

Jan 1, 1992

By David T. Bunney

In .December of 1987, International Mill Service, Inc. signed an exclusive licensing agreement with Tetronics Research & Development Co. Limited of Faringdon, Oxfordshire., England to commercialize plasma technology which had been demonstrated in an EAF dust processing application. The intent of the process is to reduce and volatize the zinc, lead and cadmium oxides inherent in EAF dust and collect these elements as metals in an ISP (Imperial Smelting Process) zinc splash condenser, and to render the resultant slag an inert, non-hazardous material. With these objectives in mind, IMS started commissioning facilities in 1989 at Florida Steel in Jackson, Tennessee and Nucor-Yamato Steel in Armorel, Arkansas. This paper will address the commercial development and progress of the technology at these two installations. Process Description In the EAF steelmaking process typically the off gas stream is cleaned by some form of baghouse. The particulate collected is known as Electric Arc Furnace dust and has been designated by the U.S. EPA as hazardous waste number K061, once it leaves the collection system. This designation was given to the material due to the high toxic concentrations of lead and cadmium (nickel and chromium for stainless EAF dusts) inherent in the dust. IMS' method of operation is to locate the facilities on the client mill's property adjacent to the baghouse. The dust is transported directly to IMS via a closed conveyance system. This method enables the technology to be an additional processing step in the steelmaking process. Once the dust has been transported to the IMS facility, it is fed, metered and mixed mechanically in the feed conveyance system with a carbon reductant (typically coke breeze). The carbon reductant is approximately 10% of the dust feed rate. This mixture passes through the feed system and enters the furnace

Jan 1, 1992

The STATE MINERAL SUMMARIES publication provides estimated data and summaries of mineral activities at the State level for 1991. Most of the estimates are based on nine months data. Individual State summaries are published separately as State Mineral Industry Surveys and copies can be obtained from the appropriate State mineral officer or Bureau field office specified in each State summary.

Jan 1, 1992

By S. M. Matthews

The magnitude and orientation of the in situ stressfield has been determined as a key factor in controlling the stability of openings for both coal mine development and extraction. Monitoring of roadway and pillar behaviour in conjunction with numerical analysis has identified specific stress control measures that have been successfully applied to improve productivity in underground coal mining operations. The influence of the major horizontal stressfield on the stability of openings has been identified at a wide range of sites including mines in Australia, Britain, the USA, New Zealand and Japan. Stress mapping, stress measurement and stress monitoring techniques have been applied to define the in situ stress regime and, together with the correlation of measurements of rock deformation and rock reinforcement behaviour, has enabled appropriate stress control measures to be developed. Stress control measures for development headings have required the selection of roadway orientation, roadway sequencing, reinforcement density and pillar size. The monitoring of behaviour at a range of trial sites has confirmed significant improvements in development stability. Stress control measures for longwall extraction have required rational selection of longwall orientation and extraction direction. Where a mine layout design incorporating the optimum longwall layout design has not been possible, the use of sacrificial roadways has been successfully applied to protect key roadways from stress concentration effects. Comprehensive in situ monitoring of behaviour has been carried out to confirm the mechanisms involved.

Jan 1, 1992

By Aspinall T. O, Just G. D

Computer software systems have been developed to assist in a wide range of specific mine planning and scheduling applications. In selecting appropriate systems for any mining operation it is apparent that certain features have particular advantages for each mine site. The ideal solution to this problem is to select a range of systems which best relate to sections of each mining operation. This approach raises potential data linking difficulties where output from one system is incompatible with input requirements for other systems. A study at the University of Queensland investigated the problems related to the integration of a number of mine planning and scheduling software systems. The project used data from large scale coal strip mining operations in Central Queensland. Two major computer packages used extensively in the study were the SURPAC mine planning and XPAC mine scheduling systems. Dragline and truck and shovel operations were analysed in the project. Results of the work have been directly applied at the mine site to assist current strip design by effectively automating the design procedure. This enabled sensitivity studies to determine the effects of changing dragline working levels and varying pit dimensions. Coal blending studies and procedures to optimise operations have been investigated using linear programming within a spreadsheet software application. Output from the SURPAC and XPAC programs was directly linked to the linear program for this analysis. The simulation program GPSS/PC was also used in a similar manner to assess optimisation parameters.

Jan 1, 1992