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By B. Beatty

Discussion by B. Beatty This is a response to M.J. Hrebar's paper, which tracks in detail the highly productive stripping capabilities of modern large bulldozers at two separate installations. It proves the old adage "economies of scale" and quantifies the advantage of being able to move large loads of dirt over comparatively short haul distances by sliding rather than carrying the load. This discussion examines whether a bulldozer is the most efficient way of using this geotechnical principle. Case 1 - Study eastern US: Contour coal stripping application The energy consumption for the Case 1 mining method (eastern US contour stripping operation) shows the D11 averaged 117 L (31 gal) of diesel fuel per scheduled hour, and produced 333.3 bank m3 (436 bank cu yd) per scheduled hour (0.351 L/m3). Assuming 1 L (0.26 gal) of diesel fuel contains 10.4 kW-hr of energy, the unit expenditure of fuel energy for Case 1 Study was 3.66 kWh/m3. Another way of shifting this material is by using an overburden slusher (OS), as shown in Fig. 1. The OS as shown in Fig. I. The OS is electrically powered and consists of a manned low wall winch (LW ), a remote controlled (radio telemetry) highwall winch (HW) and a hoe. The winches operate to pull the hoe back and forth across the pit. The hoe carries load in the forward direction ahead of a rear mounted blade and returns empty. A spreadsheet (Lotus 123) simulation package, BOSSIM, models the OS operation on a load by load basis over a wide range of pit configurations. The geometry shown in Fig. 2 of the paper was modeled using BOSSI M and the results are summarized in Table1. Table 1 shows a LW with 150 kW (200 hp) and a HW of 120 kW (160 hp) installed power, towing a 15-m3 (19-cu yd) hoe, would accomplish the Case 1 stripping task at about the same scheduled stripping rate (D11=333 m3/hr or 433 cu yd/ hour, OS=342 m3/hr or 447 cu yd/ hour). It was assumed the winches in this equipment have an electromechanical efficiency of 90%. This gives an average electrical energy expenditure rate of 151 kW-hr, and a unit energy expenditure level of 0.44 kWhr/m-3(0.57 cu yd/kWh)-an improvement of 8291%- over the D11 alternative. The energy comparison illustrates the importance of using more efficient electric power if possible, ahead of the internal combustion engine, and delivering power from a fixed ground position rather than through a moving track system. Another important energy observation is the comparative action of the dozer blade and the OS hoe. The former implement continuously digs and spills as it works the load forward. The OS hoe digs the load until full, the blade then lifts due to the contained load pressure and a shear plane forms under the mass, enabling it to slide forward in a force reduced - transporting mode. Economic comparison Table 2 operating cost per scheduled hour and unit cost comparison follows a format used in Tables 2 and 3 of Hrebar's paper and compares Case 1 Study with the OS alternative. Drill and blast costs are kept constant in both cases, although when larger OS units are considered, it is expected these costs will reduce because bigger hoe sizes will permit larger rocks to be transported efficiently.

Jan 1, 1995

The US economy grew at a rate of 4% in 1994 and the gross domestic product rose to $6.74 trillion. With 261 million people - 605,000 in mining, including petroleum -the United States has l 10 million dwelling units and 200 million licensed motor vehicles. New private housing units authorized in 1994 rose 14% to 1.4 million units. New car production rose 11 % to 6.6 million units, while truck and bus production rose 30% to 5.2 million units. The inflation rate was less than 3% and the prime rate of interest averaged 7.15%. The producer price index (1982 = 100) for fuels and related products and power was down 4% to 78, while metals and metal products rose 5% to 125. Chemicals and allied products rose 3% to 132, and non-metallic mineral products rose 3% to 124. The merchandise trade deficit rose 25% to $166 billion. Disorder in the former Soviet Union led to substantial dumping of mineral materials. With vast mineral resources, the former Soviet Union land area totaled 22.4 million km2 (8.6 million sq miles). In comparison, the North Ameri¬can Free Trade Agreement (NAFTA) area (United States, Canada and Mexico) totals 21.4 million km2 (8.3 million sq miles).

Jan 1, 1995

The choice between EPB - and Slurry Shields is influenced by the following factors: grain size distribution, cohesiveness, occurence of boulders, occurence of gas, feasibility of soil separation and muck disposal, and settlement properties of the soil. The simple equation cohesive soils = EPB Shields and non cohesive soils = Slurry Shield is very often superimposed by other facts. For example, the occurence of a large amount of boulders in weak cohesive soils, where the application of roller discs is not recommendable, may lead to the use of a Slurry Shield with a rock crusher, thus accepting the disadvantage of a sophisticated separation plant; whereas the occurence of contaminated groundwater or gas may exclude the use of a Slurry Shield. In the following examples the choice of a Slurry Shield or EPBS will be explained and justified with regard of the above factors.

Jan 1, 1995

By K. N. Han, J. J. Kellar, Y. Guan

The adsorption of zinc species onto silica in ammoniacal solutions was studied. The adsorption isotherms indicated that the adsorption of zinc increased with increasing pH. The adsorption density increased as the zinc equilibrium concentration increased up to =3.5x10-4 M. Above this concentration, the adsorption density was independent of the equilibrium concentration, and a maxima adsorption density was reached. Temperature had no significant effect on the adsorption density.

Jan 1, 1995

By D. Yeager

Researchers at the U.S. Bureau of Mines have successfully used a genetic algorithm to tune computer models of three column flotation units simulating a separation circuit. The computer models rely on empirical constants that are selected so that the models accurately predict the performance characteristics of individual column flotation units. Unfortunately, these empirical constants have traditionally been selected using a time consuming trial and error process. A new and more efficient approach to selecting empirical constants for computer models has been developed. A genetic algorithm has been used to select the empirical constants for column flotation models used to simulate a three column circuit. Genetic algorithms are search algorithms based on the mechanics of natural genetics. They rapidly locate near optimum solutions in difficult search spaces. Bureau researchers have used these innovative search algorithms to dramatically reduce the time needed to select empirical constants for column flotation models. The approach is applicable to the selection of empirical constants for numerous other computer models.

Jan 1, 1995

By S. S. Peng

To prevent mine floor heave, the mechanisms of floor heave must be fully understood. Based on the field study, the mechanisms of two types of floor heaves are analyzed in this paper. The mechanical models for the two types of floor heaves are developed. The floor heave can be predicted by the developed mechanical models and the control measures are recommended.

Jan 1, 1995

By M. Mohammed, S. J. Jung

The prime criteria in the design of underground openings with complicated geological structures is ground control. Stability of underground openings for deep mines is critical because incorrect orientation or geometry of the shaft, stopes and accessways often results in the failure of openings due to high stress conditions. Current design procedures for complicated orientation and geometry of mines are rapidly becoming inadequate. In this study, the finite element method (ANSYS) has been used with optimization criteria to design safer, more stable underground openings.

Jan 1, 1995

By Mustafa Yalçin, Ali Ihsan Arol

Coconut shells are the most widely used raw material for the production of activated carbon used in the gold production by cynanide leaching. There have been efforts to find alternatives to coconut shells. Shells and stones of certain fruits, have been tested. Although promising results to some extent were obtained, coconut shells remain the main source of activated carbon. Türkiye has become a country of interest in terms of gold deposits of epithermal origin. Four deposits have already been discovered and, mining and milling operations are expected to start in the near future. Explorations are underway in many other areas of high expectations. Türkiye is also rich in fruits which can be a valuable source of raw material for activated carbon production. In this study, hazelnut shells, peach and apricot stones, abundantly available locally, have been tested to determine whether they are suitable for the gold metalurgy. Parameters of carbonization and activation have been optimized. Gold loading capacity and adsorption kinetics have been studied.

Jan 1, 1995

By John A. L. Dr. Campbell, James W. Haskew, F. Hoy Lee, Elliott P. Dr. Doane

Emissions of particulates, unburned hydrocarbons, nitrogen oxides (NO[ ]) and carbon monoxide (CO) from diesel engines are of concern in mines, particularly underground mines. All these undesirable products except NOx are the result of incomplete combustion in the cylinders. Various approaches to achieving more complete combustion in diesel engines have included different fuel compositions, use of catalysts, fuel additives, engine modifications, and oxygen-enriched intake air. The present study shows that injecting minute quantities of primarily platinum group metal catalysts into the intake air of a Deutz/MWM D916-6 mine diesel engine substantially reduces emissions in the exhaust. The catalyst injection system, which was developed by National Fuelsaver Corporation (Robin. 1981), transfers catalyst compounds in solution to a stream of air bubbles by a process called Bubble Fractionation (Lemlich et al.. 1966, 1968. 1970). The amounts are so minute that concentrations in the engine exhaust should be well below OSHA/NIOSH Time Weighted Average (TWA) exposure limits at steady state, a fact that was confirmed by analysis of collected particulates in the exhaust. When the catalyst injection was used along with a pleated paper filter to remove exhaust particulates, the filter operating life was shortened greatly. Therefore, this system is not recommended for use on diesel engines equipped with a water scrubber and a filter. It does offer a practical and relatively economical way of reducing exhaust emissions from other diesel engines, such as those in outby mine service

Jan 1, 1995

By M. Ghiani, R. Peretti, A. Zucca

The paper deals with the experimental application of a pilot flotation column to baryte and fluorspar ores. The column has been installed in parallel with the cleaning stages of two different industrial flotation plants where the above ores are processed using conventional cells with mechanical impellers. The effect of several parameters, including froth height, wash water additions, pulp feedrate and air supply rate, has been investigated. It has been shown that by finely tuning the above parameters good flotation performances can be achieved. The experimental results demonstrate the greater versatility of the column flotation and its superior separation efficiency, especially for the fine particle size fractions, over conventional cells.

Jan 1, 1995

By Gábor Antal, József Bõhm, Barnabás Csõke

From the waste material of the production of aluminium foil aluminium pigment is produced for the paint industry by grinding it in white spirit. During grinding 1-2 % iron impurity gets into the product, weakening its quality, from the wear of the mill armour and the grinding bodies and from the contamination of the raw material. For deironing the product, a stage-operated electrically induced magnetic filter separator was developed and put into operation. The separator was sited in an explosive environment and therefore required a special design and safety system. The paper describes the results of the development work. the device that was developed, the safety system as well as the results of and experiences with the operation of the separator.

Jan 1, 1995

By Y. M. Jiang

Many underground instabilities, such as excessive shield loading and roof falls, occur at longwall faces causing safety problems and production losses. Such instability problems are directly related to roof conditions which can be categorized using geological information. . However, most geologic information describing anomalies and variations of immediate and main roofs are not available before mining resulting in unexpected problems in a longwall face. It is apparent that the evaluation of these geologic anomalies provides a great benefit for longwall stability. The purpose of this study is to evaluate roof categories associated with geological anomalies employing fuzzy set theory. The evaluation is based on real-time monitoring information, such as shield leg pressure, developing load on shields, intervals of periodic weighting, and the ratio of developing loads during periodic to normal times. This paper introduces the application of fuzzy set theory for characterizing roof conditions and evaluating of roof similarities.

Jan 1, 1995

By Ping K. Di

A naturally aged and synthesized manganese oxide-coated granular media was found in our laboratory to have the capability of the removal of soluble Mn(H) from mine drainage by adsorption and oxidation. Mine drainage commonly also includes other heavy metal ions. Extending this principle, this paper presents the removal of heavy metals including lead, copper, cobalt, zinc and nickel in the aqueous solution by using the synthesized manganese oxide-coated granular media. It was found that the adsorption of lead, copper, cobalt, zinc and nickel on the manganese oxide-coated media follows both Langmuir and Dubinin-Radushkevich adsorption isotherms except in the concentration range less than 0.1 mmole/L. The adsorption mechanism involves the ion exchange between the heavy metal ions and synthesized manganese oxide coated on the media. The synthetic manganese oxide surface has a strong metal binding ability to the heavy metals in the order of Pb2+ > Cu2+ > Ni2+ > Zn2+ > C02+ based on the adsorption results using batch and continuous column operations. The breakthrough curves of these heavy metals showed that the synthesized media could be used effectively in the removal of these heavy metal ions in a cell or packed column. The process can simultaneously facilitate the immobilization of the heavy metals on the synthesized manganese oxide coated media. A subsequent pH adjustment dislodges the heavy metals and regenerates the synthetic media. Thus, the process accomplishes the adsorption, immobilization and concentration of the heavy metal from waste stream in one monolithic procedure.

Jan 1, 1995

By K. L. Kayler

The Bardon Trimount, Inc. stone quarry in Ashland, Massachusetts was the recent subject of a quarry closure review report. The quarry produces aggregate using standard drilling and blasting techniques. Stone is processed at an on-site plant. Noise monitoring data collected during the closure review indicate that the quarry generally operates within the quiet range. There is a decrease in noise while the quarry is not operating. Levels of dust associated with the quarry are low. Unpaved roadways are the greatest contributors of fugitive dust associated with the mining operation. The quarry cannot be seen from any homes within the town of Ashland, except during the winter months. The visual impact of the quarry on surrounding properties is minimal. Further quarry development is likely to reduce visibility of the quarry from some areas.

Jan 1, 1995

By Landy A. Stinnett

Coal mines in the United States are the most productive in the world in terms of efficient labor employment. This is because of an abundance of workable coal beds, large infusions of capital, improved management practices and continuing competitive pressures. The standard unit of measurement for labor productivity is expressed as tons/manshift, although for underground mines, operators often refer to tons per machineshift. Articles written concerning labor productivity generally focus on measurement techniques, safety considerations, application of technology and training. This article will illustrate by example the impact of labor efficiency (or inefficiency) on the ultimate selling price of coal, f.o.b. mine site. During the past several years, the coal industry has seen significant improvement in labor use. Figure 1 shows the trends in productivity for all active mines in the United States from 1985 through 1994. Productivity in 1985 was 20.1 t/manshift (22.1 st/ manshift). This factor has increased almost linearly throughout that period to 37.5 t/manshift (41.2 st/manshift). This is a 7.2% annual compound growth rate.

Jan 1, 1995

By H. Suharyono

A laboratory investigation of flocculation following polymer addition during slurry flow through pipes and in-line (static) mixers is described. Results are presented showing the effects of flow velocity, pipe length, in-line mixer elements and the use of multiple addition points on flocculation performance as measured by settling rate and supernatant turbidity. The effects of agitation and mixing time are shown to be generally consistent with the results of equivalent tests, both batch and continuous, conducted in stirred tanks.

Jan 1, 1995

By K. N. Han, Y. Guan

The dissolution behavior of silver and copper from silver/copper alloys in ammoniacal solutions was investigated using a rotating disc. Oxygen was used as an oxidant. The effects of the alloy composition, concentration of lixiviants, stirring speed and temperature on the overall dissolution kinetics were studied. Three silver/copper alloys (containing 76.7, 46.9 and 24.1% silver) were used in this study. The rates of dissolution for these alloys were compared to that of pure silver and copper under the same testing conditions. Emphasis was given to the galvanic effect on the overall dissolution rates.

Jan 1, 1995

By Liang Ruilu, Guo Lihua

In light of the properties on process mineralogy of the old tailings in a certain copper mine in the People's Republic of China, a new process of combined reagent and stepwise flotation is applied in which the flotation of copper sulfides is followed by the flotation of copper oxides. Recoveries of copper and associated gold and silver have been greatly increased. The tailings obtained were subjected to the gravitational separation-magnetic separation process to recover iron minerals. Tailings from iron separation are taken as fillers and sent to the pit underground. Thus, the secondary resources are comprehensively utilized.

Jan 1, 1995

By Alan L. Mierke

West Virginia's economy has been closely linked with coal. West Virginia is consistently one of the top three coal-producing states. Its 149 Mt (164 mil¬lion st) produced in 1992 represented 16.5% of total US coal production. In recent years, the state's economy has experienced a diversification away from its traditional employment base of min¬ing and heavy manufacturing. However, the coal industry remains an integral part of the lives of West Virginians. Coal is mined in 33 of the state's 55 counties. In many of these counties, the coal industry is the largest private employer and contributor to the economy. West Virginia has three major coal-producing regions. The northern region produces coal high in gas and sulfur content (steam coal). It is consumed primarily by utility and industrial markets. The southeast region produces high-grade coal low in sulfur content but high in carbons and Btu (metallurgical coal). The southwest region produces metallurgical and steam coal. The high-grade metallurgical coal is used in the production of coke for steel manufacturing. Metallurgical coal also comprises the majority of coal exported from the United States. During 1993, West Virginia was the country's largest exporter of coal, accounting for 44.5% of total US coal exports.

Jan 1, 1995

By R. K. Singhal

Canada is a world class producer and exporter of minerals and mineral products. Today's highly mechanized Canadian open pits use state-of-the-art equipment and support technology. They are taking advantage of larger equipment, including in pit crushing and conveying, truck dispatch systems and electronic management tools. Mine planning is computerized. Environmental issues are dealt with in all phases of planning, and equipment modifications are pursued to keep them functioning in the hostile Canadian north. In 1991, Canada's mineral production (excluding fuels but including coal) totaled $C 16.9 billion, a decline of 13.8% from the 1990 total of $C19.6 billion. It is a major producer of nickel, zinc, asbestos, potash, molybdenum and uranium. Canada is also an important source of copper and iron ore (Fig. 1).

Jan 1, 1995