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By Stephen R. Brown

The principles of quality management are well developed and, from a practical stand- point, thoroughly implemented in the process industries of Japan. Although these principles are now applied to the U.S. manufacturing industry, and as a result, the steel industry, they have been largely ignored in the non-ferrous and precious metals industries. This paper presents the concepts and practical approaches to implement a total quality management program. Contrary to the beliefs of many managers, such a program increases yields, recoveries and output while it decreases unit costs. In fact, quality management incorporating statistical process control will be an essential ingredient for metallurgical plants to effectively compete in the '90's.

Jan 1, 1991

By S. K. Singh, J. Shepherd

Feather-edging, a major source of injury and fatal accidents in Australia, South Africa and the United States, refers to a phenomenon in which the roof at the goaf edge falls, often suddenly, as a thin wafer of rock that overrides conventional timber breaker lines. The fall may adversely affect a working bord at a distance of 15 m (50ft) or more from the goaf edge. Feather-edging typically occurs in relatively massive, strong roof strata such as sandstone or conglomerate. This paper presents the results of a test in which a concentrated row of fully grouted bolts were used to prevent feather-edging in an Australian pillar- ("total-") extraction coal mine. The test demonstrated that the bolts could resist feather-edging.

Jan 1, 2000

By V 7. 0 / 300 dpi

In the last ten years the U.S. coal industry has experienced the collapse of several large silos. In addition, other problems such as extensive structural damage, small "live" capacities, inadequate feed rates, arching, coreholes, and particle segregation have been common to the industry. This paper explains the relationship between those problems and stored material properties, silo hopper configuration, silo structural design, and granular flowability. Methods of identifying, repairing, and/or modifying damaged silos, and designing new silos are given.

Jan 1, 1989

By Anis Farah, Khosrow Aref

Pull-out tests were conducted on cable bolts grouted with concrete, and cement paste. The influence of several parameters on the performance of these cables were studied under loading rates varying from very slow to relatively fast. These parameters include water-cement ratio, cable surface conditions, curing time and embedded length. In addition to being more economical, the results indicate that cables grouted with concrete have higher ductility and ultimate bond strength as compared to those with cement paste only.

Jan 1, 1986

By R. R. Tatiya

The selection of a mining method for a particular deposit must be based on certain technical and economic criteria. This can be interpreted as maximizing extraction and productivity while maintaining safe working conditions and minimum costs. The methodology developed here examines some of these aspects. The proposed methodology was tested on copper deposits that could be mined by underground stoping methods such as sublevel stoping, cut-and-fill stoping and their variants. In general, it provides a practical approach to both method selection and optimum stope design for base-metal deposits.

Jan 1, 1998

By O Gutsche, Fuerstenau D. W., R. Ravikumar

Six minerals and one ore, namely, barite, dolomite, galena, limestone, quartz, quartzite and taconite, were ground in single-particle comminution mode in a rigidly mounted roll mill with different levels of energy input. Grindabilities were determined from the median size of the self-preserving product size distributions, which was taken as a measure of the fineness of the ground material in an empirical energy-reduction ratio relationship. These values reflect the inherent resistance of the solids to mechanical size reduction that are least distorted by particle-particle interference effects, grinding characteristics, energy efficiency of the milling system employed and the extent of the fineness specified.

Jan 1, 1992

By K. Biswas

A finite-element algorithm was developed for an axisymmetric heat-transfer problem involving phase change. The finite-element treatment of the phase-change problem was dealt with by using the enthalpy method. The finite-element algorithm was subsequently applied to model the heat exchange between mine ventilation air and frozen ground in the presence of roof bolts in an underground mine with permafrost. This paper analyzes a single bolt in the problem domain with the convection boundaries at the roof level of the mine airway. A short-term study, comprising the evaluation of roof bolting (friction-anchored type), was conducted, and recommendations were made regarding the applicability of roof bolts as a support system for a given thermal condition.

Jan 1, 1996

By K. J. Stanaway

Syngenetic concentrations in clastic sediments of valuable mineral particles with specific gravities exceeding that of quartz constitute placer deposits. Two fundamentally different modes of concentration characterize "trap" and "bed" placer variants. Trap placers originate during sediment erosion or reworking. Bed placers form during episodes of sediment accumulation in a variety of depositional environments and lithofacies where mineral supply and fluid dynamics are favorable. Because trap placers are thin and generally limited in area, they rarely yield economic heavy-mineral deposits. They can become economically significant if they contain more valuable "heavies," such as gold, or if they occur within or very close to much larger but characteristically lower-grade bed placers.

Jan 1, 1993

By M. M. Botz

Cyanidation tailings disposed of in a surface impoundment experience a loss of cyanide due to natural attenuation, which frequently reduces the cyanide concentration to very low levels. Quantifying cyanide losses in terms of impoundment geometry, local weather conditions and feed-solution chemistry has been largely empirical in spite of the fact that, in many cases, mining operations rely on surface impoundments to reduce cyanide to below an internally regulated concentration or below an effluent limitation. To permit a quantitative evaluation of cyanide losses in an impoundment, a computer simulation was developed to estimate the losses of free, weak acid dissociable (WAD) and total cyanide due to dissociation, photolysis and volatilization. Results of the model are compared with data collected for a North American tailings impoundment in 1998.

Jan 1, 2000

By S. C. Gambrell

Support characteristics of in-cycle trusses are analyzed using a photoelastic model loaded by tightening a truss in the sequence normally used in an underground mine. Stresses in the roof at its center point and at the junction of the roof and rib are examined. Effects of zero tension and unequal tension in the inclined anchor rods are presented. Effects of simulated subsidence on stress in the roof surface and on tension in the separate truss members are examined. Conclusions are drawn relating to (1) the effects of tension in the inclined anchor rods on uplift and compressive stress parallel to the roof surface, (2) the effects of subsidence on stress in the roof surface, and (3) the effects of subsidence on tension in the truss members.

Jan 1, 1987

By M. M. Rajkovich, L. Adams, J. J. Zaluski, S. Gardner

In 1998, a group called Kentuckians for the Commonwealth filed an Administrative Petition with the Kentucky Natural Resources and Environmental Protection Cabinet to designate 8,903± hm2 (22,000± acres) on Black Mountain, which contains the state's highest point, as unsuitable for mining. A fast track legislative process was triggered that could have "taken" 91 Mt (100 million st) of coal reserves or, in the alternative, imposed severe restrictions on mining. Even with all parties represented by reasonable individuals, this process can be extremely cumbersome and expensive. The legal and technical preparation for this unusual hearing process as well as issues and strategies of the negotiated resolution are reviewed

Jan 1, 2002

By P. Somasundaran, C. C. Harris

The power consumption of stirred-media mills was studied using an approach developed from work on stirred reactors. Evaluated were the relationships of factors such as stirring speed and impeller and tank dimensions on the torque required to rotate disc and pin impellers immersed in dense particulate media. Data collected under carious experimental conditions were analyzed. The results were summarized and presented in the form of characteristic plots, general equations and dimensionless group correlations involving power and modified Reynolds numbers. Special attention was directed towards the rheological properties of the media, which was considered a non-Newtonian liquid, and hence the equation of power-law liquids was employed. A procedure for estimating the parameters of effective viscosity and scale-up guidelines (with respect to power consumption) are proposed.

Jan 1, 1996

By Joseph B. Alberts, David D. DiPonio, Francis B. Manning

From 1996 to 2001, Wayne County and 13 suburban Detroit communities constructed the Downriver Regional Storage and Transport System (DRSTS) to improve area water quality, protect public health and alleviate basement flooding. The project consisted of a 10-mile long storage and transport tunnel, a pump station at the existing wastewater treatment plant, 9 miles of relief sewers (6 in tunnel and 3 in open cut). The work was separated into 10 contracts. Due to hydraulic design requirements and other constraints, the tunnel profile was located generally 65 feet below ground surface within a soft to medium clay strata which skimmed along the top of a very dense glacial till “hardpan” overlaying bedrock. Boulders within the tunnel bore were recognized as a significant, but indeterminate risk. This paper presents a case history of the owner’s contracting strategy for risk assumption and management of the boulder impacts on the project. Actual conditions encountered during construction and contractual adjustments made to address problems are reviewed, and recommendations for future contracts are included.

Jan 1, 2003

By W. C. Patrick

The Spent Fuel Test-Climax (SFT-C) was con- ducted to evaluate the feasibility of retrievable deep geologic storage of commercially generated spent nuclear-reactor fuel assemblies. One of the primary aspects of the test was to measure the thermomechanical response of the rock mass to the extensive heating of a large volume of rock. Instrumentation was emplaced to measure stress changes, relative motion of the rock mass, and tunnel closures during three year of heating from thermally decaying heat sources, followed by a six month cooldown period. The calculations reported here were performed using the best available input parameters, thermal and mechanical properties, and power levels which were directly measured or inferred from measurements made during the test. This report documents the results of these calculations and compares the results with selected measurements made during heating and cooling of the SFT-C.

Jan 1, 1986

By J. F. Dresser

Managing environmental compliance at a complex facility has the potential to bring a high degree of personal and professional satisfaction to both the corporation and the individuals responsible for day-to-day operations. The decade of the 1990's, however, has seen the emergence of a nationwide trend of aggressive federal and state civil and criminal enforcement for environmental violations. This trend, spearheaded by the U.S. Department of Justice (DOJ) and the U.S. Environmental Protection Agency's (EPA) Office of Enforcement, has the potential to place the corporation, its corporate officers, and compliance personnel at collective professional risk, as well as a growing tendency to place accountability on individuals. Management of environmental compliance has been anecdotally compared to a shooting gallery at a carnival, with the following exception: At the shooting gallery, successfully hitting nine out of ten targets usually brings a reward and recognition of shooting skill; hitting nine out of ten environmental compliance expectations not only brings agency consternation and negative publicity, but the "gallery" will likely shoot back with stiff fines and possible criminal allegations. Faced with the challenges of the new environmental compliance shooting gallery, corporations and professionals are often left asking themselves, "How do we (or more appropriately, can we) win at this game?" This paper examines recent federal enforcement statistics and offers several suggestions for coping with the responsibility of managing environmental compliance in the 1990's.

Jan 1, 1992

By John G. Reid

Geologists, employed by the Australian Company, Metals Exploration Limited, discovered nickel laterite enrichment at Greenvale in 1967. A joint venture was arranged with the Freeport Minerals Company who had gained early experience with nickel laterite ores when building and operating the Nicaro and Moa Bay Treatment Plants in Cuba. A 5 tonne/day Pilot Plant at the Freeport research facilities at Belle Chasse, Louisiana, verified the amenability of the ore to treatment by the reduction and ammonia-ammonium carbonate leaching process used at Nicaro. A 5 800 tonne/day Treatment Plant was constructed on the coast at Yabulu, North Queensland. This paper describes the ore body, the mining operation and the stages of treatment required to produce nickel oxide products and a mixed nickel/cobalt sulphide product at Yabulu.

Jan 1, 1979

By J. W. Jang, J. J. Moore, I. Iwasaki

The wear behaviors of grinding media with different chemical composition and microstructures in wet grinding of a quartz-pyrrhotite mixture were investigated under various environments. The marked ball wear tests showed that the wear rate could be minimized by a suitable combination of martensite and ferrite within the same ball. A ball composed solely of hard martensite exhibited increased wear under an oxygen environment, while balls composed of both soft ferrite together with hard martensite exhibited decreased wear due presumably to the difference in their passivation behaviors. The galvanic interaction between the two phases as well as among these phases and an electroactive mineral were investigated through electrochemical measurements under abrasive condition in a slurry. The rates of formation of passive film controlled the corrosion currents of the high chromium steel media. Corrosive wear and its effect on flotation are discussed using the passivation kinetics model thereby developed.

Jan 1, 1990

By J. Willison

Over the past decade, the coal mining industry has faced the difficult task of remaining profitable in the midst of declining market prices. Historically, the industry has been quite capable of meeting this challenge by various means. As total costs to mine and market coal continue to increase, new methods of tackling the problem must be implemented. Studies have shown that although many options exist to influence both inby and outby costs, the greatest potential remains in addressing costs at the coal face. Mining operations can positively effect a change in their profitability by either reducing costs, or by increasing production to in turn lower their net cost per man-hour. Original equipment manufacturers can play a key role in both options through the introduction of new technology that permits higher extraction rates, as well as other advantages leading to lower cost coal. A leading advancement over the past 30 – 40 year period has been the advent of progressively higher voltages to operate the mining equipment. This advance enables higher power transmission for a given cable size, operation at lower amperages resulting in less voltage fluctuation, and reduced heat on the cable and electrical components.

Jan 1, 2003

By M. G. Bakker, D. D. Murphy, D. R. Spears

The US Bureau of Mines studied the mechanism of shear flocculation of silica with stearic acid. At pH 6 and 12, shear flocculation of silica was not observed with the addition of up to 4.5 x 10-4 M (5 lb/st) stearic acid. However, in the presence of 0.1 M NaCl at pH 6, shear-flocculation was observed at stearic acid concentrations = 10-4 M (22.5 lb/st). Adsorption of stearic acid on silica was studied using stearic acids spin-labeled with a doxyl group. The presence of the spin-labeling group did not greatly affect the shear flocculation properties of stearic acid. Adsorption of labeled stearic acid on silica was measured as a function of surfactant concentration with electron paramagnetic resonance (EPR) spectroscopy and gas chromatography (GC). The GC results indicated that the stearic acid was predominately adsorbed on the surface at concentrations above 10-4 M. From the EPR spectra, the formation of aggregates of stearic acid was apparent at concentrations of approximately 10-5 M (22.5 lb/st). The results are discussed in terms of a possible mechanism for shear flocculation.

Jan 1, 1995

By Michael L. Nave

Belt Conveyors are an important method for transportation of bulk materials in the mining industry. The control of the application of the starting torque from the belt drive system to the belt fabric affects the performance, life cost, and reliability of the conveyor. This paper examines applications of each starting method within the coal mining industry.

Jan 1, 1993