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By F. E. Heuze, R. N. Nilson, R. J. Shaffer, R. P. Swif

As part of the Unconventional Gas Program at the Lawrence Livermore National Laboratory, we are developing a model that allows for time-dependent tracking of the fluid front and flow pressures during the quasi-static or dynamic fracturing of jointed rocks. Application of the model is directed towards both short fast fractures (as in tailored pulse loading) and long hydraulically induced fractures (massive hydraulic fracturing). The thrust of this research is to determine crack extension characteristics due to specific joint systems and fluid properties and to correlate pumping records with crack behavior in jointed systems.

Jan 1, 1986

By C. D. Wittreich

The results of an engineering study of fiber-reinforced cemented tailings are presented. These tests were conducted to evaluate the potential for using fibers to increase the strength of cemented tailings used as backfill for ground support in the undercut -and - fill mining method in a mine subject to high horizontal stresses and rock bursts. Stress-strain measurements indicate that fibers not only increase the peak compressive tensile and flexural strengths of cemented tailings, but limit reductions in residual strength following failure. Results also show the effect of water content, fiber type, fiber density, and curing time on strength.

Jan 1, 1987

By P. Brumit, L. Grady, R. Mitts, V. Holm

The Mesquite mine is a large, open pit, heap leach gold mine owned and operated by Gold Fields Operating Co.-Mesquite. The mine uses a fully integrated mine planning and reserve modeling software system developed at the mine. This system has recently been extended to include short-term mine planning, grade control, and daily production reporting. The grade control portion of the program uses a multiple indicator kriging (MIK) approach using the blast-hole spacing and exploration assays. The program permits ore control geologists and mine planning engineers to have immediate access to all the information.

Jan 1, 1991

By Harry C. Oussoren, James C. Miles

A new seven kilometer long subway line is being constructed through dense glacial soils under a major thoroughfare in Toronto. Eductor, deep well and vacuum wellpoint systems are being used to lower the water levels by as much as 16 metres for the construction of the twin tunnels and associated structures. The design and performance of the dewatering systems will be described. Unanticipated difficulties and their solution will be presented.

Jan 1, 1999

By R. L. Guerguerian

Critical fasteners are described as they apply to the specification, manufacture and assembly on large grinding mill bolted joints. The importance of adequate design methods, related joint diagrams and pivot analyses, with special emphasis on the quality of manufacturing and the tightening of procedures in the field, are discussed in an effort to ensure high availability plant operation.

Jan 1, 2003

By W. J. Pennstrom, J. R. Arnold

This paper focuses on solution-balance management around heap-leach operations. Experience has shown that increased leach recoveries can be achieved by utilizing various leach-solution recirculation techniques. The most prominent solution-recirculation technique is intermediate leaching. The net effect of intermediate leaching is to increase recovery plant performance by increasing solution concentration tenors, to increase metal recovery by increasing the total leach time and to decrease the overall capital expenditures required for metal-recovery facilities. The adverse effect on the flow of cash from increased metal inventories in the recirculating solutions is offset by increased metal recovery and lower operating costs per unit produced.

Jan 1, 2000

By John R. Turney

MARY KORPI: Harry Hinds will be filling in for John Turney today. Harry is an exception to the industry these days, in more ways than one. He has worked for the same mining company for 33 years. That is something very few of us can claim. He is currently metallurgical superintendent for Homestake Mining Company in Lead, South Dakota. Harry is also the envy of many of us as he will be retiring this year and working on lowering that handicap! Harry will be discussing the "Role of Consultants."

Jan 1, 1998

By Z. B. Yin, R. W. Bartlett, P. R. Taylor

Tube furnace experiments have been performed to evaluate the lime roasting of pyrite in air. The sulfur volatilized was measured over time. Variables studied included: form of lime, sodium sulfate additions, temperature, air flow rate, lime to pyrite weight ratio and pyrite particle size. It was found that more than 98% of the sulfur can be retained at a reactor temperature of 650°C, with a slight excess of calcium hydroxide. The roast products are primarily hematite and calcium sulfate.

Jan 1, 1990

By Cherie M. Tilley

Dynatec Mining Contractors (Dynatec) entered into a contract with Barrick Goldstrike Mines (Barrick) to develop the deep gold ore reserves at the Meikle Mine north of Carlin, Nevada. The Ventilation and Production Shafts were started in early 1994 and were completed in December, 1995. The mine development and mine construction programs were completed in November, 1996. This paper describes the Meikle Mine development program.

Jan 1, 1997

By Muammer Kaya, Derya Oz

The main objective of this study was to remove printing ink from waste newspaper and improve the de-inked paper brightness as close as the unprinted paper by bleaching agents. This paper summarizes results of laboratory investigation into the de-inkability of newsprint printed with offset printing. Different chemicals and process parameters were varied to assess the effect on the brightness and cleanliness. The operations involved in de-inking process are briefly described and some of the problems being encountered are discussed.

Jan 1, 1995

By R. M. Bowen

To help solve problems associated with the optimization of complex coal preparation systems, a mathematical model has been assembled which can simplify calculations pertaining to the core of the plant, i.e. the coal cleaning section. It uses algebraic expressions, derived by fitting hyperbolic equations to Mayer curves, to calculate optimum settings for a specified array of coal cleaning units and feeds. This is done without search procedures, and with usually only minor iteration of a simple calculation to specify optima within 0.02% of specified product ash contents. The key to the calculation is a relationship derived via the analytical geometry of conic sections facilitating easy application of the incremental ash theory of separations. The model has been assembled in a generalised form to cater for N processes in parallel, each giving M separations to produce P final products. Examples are given involving assessment of some complex circuit options.

Jan 1, 1986

By F. H. Muge

The problem of how to handle heterogeneous populations in an ore reserve global estimation arises in many geostatistical studies. In some cases it is possible to split data into different significant types of ore in such way that non-overlapping subpopulations are obtained, and a separate study is possible. In other cases the subpopulations are intermingled and a set of nested structures may model the spatial variability of the ore. Finally, one of the populations, consisting of a small proportion of high grade values of economical meaning, may disturb the structural analysis. In this paper, some methods are proposed to cope with these kind of problems and typical case studies are presented.

Jan 1, 1986

By J. Chappell

The Nuggety Gully prospect is located 170 km (106 miles) south- east of Port Hedland and 40 km (25 miles) northeast of Marble Bar in the Pilbara Region, Western Australia. The area is held under title by Esso Exploration and Production Australia, Inc. The prospect covers a significant, but currently uneconomic body of molybdenum and copper mineralization of porphyry style, associated with Archean high level acid intrusives intruding sediments and volcanics of a narrow east-west Archean greenstone belt. The Nuggety Gully intrusive rocks have been dated at 3.2 b.y. ± 117 (de Later, oral communication). The current resource estimate for the deposit is 102 Mt (1 12 million st) of 0.1 1 % Mo and 0.15% Cu.

Jan 1, 1991

By Antonieta Middea, Rupen Adamian, Fernando F. Lins

This work presents the results obtained with aggregation of fine talc (-19 m), a naturally hydrophobic mineral, in the presence of KC1 solutions. The classical DLVO theory describes well the aggregation of talc in dilute KC1 solutions. Beyond 1 M KCI we have found indications that a non-DLVO interparticles force is operative, say an hydration (repulsive) force. This structural force could be responsible for the unexpected re-dispersion of talc suspension. However, no repulsive force (depression) has been observed in salt flotation of talc at higher ionic strength, up to 3 MKCI.

Jan 1, 1995

By P. Riveros, A. Pratt, G. Deschênes

The effect of pyrite, pyrrhotite, chalcopyrite, realgar and arsenopyrite on gold dissolution in cyanide media was investigated. The cyanidation of synthetic gold ores, in the presence of various concentrations of sulphides, was studied under constant experimental conditions. A mineralogical analysis of the minerals was performed. The leaching kinetics were determined. The negative effect of sulphides on the gold dissolution rate varies with the sulphide mineral, and decreases according to the following order: realgar > pyrrhotite > chalcopyrite > pyrite > arsenopyrite. The chemical characterization of gold and sulphide minerals surfaces using X-ray photoelectron spectroscopy (XPS) was undertaken to identify the mechanisms involved. XPS analysis showed that a passivation layer of sulphides, arsenic or iron compounds may form on the gold surface as a result of the dissolution of the sulphide minerals.

Jan 1, 2002

By F. L. Wilke

Truck haulage costs form a major part of the total mining costs in hard rock open pit, mining operations. In order to minimize these costs one has to - determine the optimal truck fleet (type, size and number of trucks), and. simultaneously - determine the optimal organization of running the haulage system, i.e. especially select the optimal dispatching strategy in order to ensure maximal utilization of the trucks, and simultaneously - establish a reliable maintenance and servicing system to guarantee maximal availability.

Jan 1, 1982

By E. Sarris

Tailings dams are large-scale earth-fill embankments that are designed to contain mining wastes from ore dressing plants. Most commonly tailings dams are constructed in stages in order to keep up with the increasing volume of mine tailings. Staged construction using various methods (like up-stream, down-stream, and centerline) is generally considered as a very effective way to construct this kind of embankments. The present study is devoted to the investigation of the behavior and the stability of these geostructures under static conditions. In order to accomplish this task, elaborate two-dimensional numerical models are examined, utilizing the geotechnical finite-element code PLAXIS. Numerical analyses are conducted for all three types of tailings dams in order to obtain the potential modes of failure, while the corresponding factors of safety are determined by the shear strength reduction technique.

Jan 1, 2005

By Mayank Srivastava, Satya Harpalani

Production of methane is an inevitable consequence of mining coal. Although the number of mines practicing recovery of methane prior to, or during, coal mining is increasing, ventilation air methane (VAM) is still a significant source of methane addition in to atmosphere. Recent studies have shown that there are ways to recover the VAM energy, while simultaneously reducing the methane emission in to atmosphere. This paper discusses a case study, currently underway, to develop a technique to quantify the VAM emission from a mine. It also presents the different VAM utilization techniques and the suitability of one for the mine being studied. Finally, the paper summarizes the research issues that require further investigation.

Jan 1, 2005

By L. Laage, R. Greur, W. Pomroy

MFIRE is a mine ventilation and fire interaction computer simulation program. It allows transient state ventilation simulation and features mass based flow rates, natural ventilation, air recirculation, fan curve fitting, airflow reversal and product of combustion tracking. MFIRE was designed to accommodate the needs of the mining industry, for routine ventilation calculations and mine emergency planning. This paper describes recent work by the US Bureau of Mines and Michigan Technological University to improve MFIRE by incorporating humidity in the mass flow and heat exchange calculations, a data file preparation program, and variable reference density in the network calculations. Recent bug fixes are also discussed.

Jan 1, 1995

By Joe Maloney, Steve Shadow

Mining conditions at Cyprus Amax's Twentymile Coal Company (TCC) require the use of regenerative conveyors. Regenerative conveyors were first used in the Southwest Mine District and then in the challenging East Mine District. This paper will discuss the development and refinement of the equipment used to brake the regenerative conveyors.

Jan 1, 1998