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By Edmond Donovan, O&apos

With the increase in complexity of conveyor systems and the inexorable demand for more capacity and availability, the ability of designers to accurately predict performance is becoming increasingly important. Dynamic analysis techniques for modelling wave mechanics in conveyors are finding increased applications. Unfortunately, the reliability of these modelling techniques is dependent on a thorough understanding of the performance characteristics of the components that make up the system. These characteristics include such things as response rate, hysteresis and efficiency. Some parameters such as idler rolling resistance can be easily quantified by measurement. More complicated drive parameters are difficult or impossible to measure, particularly in large horse-power equipment. One method of quantifying or at least bracketing the performance envelope of complicated pieces of equipment is to construct a mathematical model. This can be done quickly and economically, and the influence of various parameters can be determined. This paper sets out to demonstrate by example the usefulness of this technique in gaining an understanding of complicated systems. The model is developed and the influence of a number of variables are examined.

Jan 1, 1996

By R. J. Essex

In support of the Conceptual Design of a Nuclear Waste Repository in Salt, a confined core pillar design method developed by others was reviewed. The method, which was developed for applications in coal, represents the confined strength of the pillar material in terms of a linear failure criterion. However, triaxial compression strength tests conducted on salt samples indicate that a non-linear strength criterion is more appropriate for salt. The rationale behind the confined core method is reviewed. A rederivation of the confined core method is then presented that incorporates a non-linear strength criterion. Benefits of the modified method are that the strength of the confined pillar core can be more accurately represented, and that two contributors of pillar strength, rather than one, can be addressed.

Jan 1, 1988

The current understanding of the mechanics of rock fracturing during smooth blasting is largely empirical and qualitative due to an inability to model the dynamic process at the fundamental level. In order to overcome this difficulty, a numerical simulation of smooth blasting is performed using the Dynamic Lattice Network Model. This model is capable of simulating material inhomogeneities and the dynamic evolution of fragmentation at the micromechanical level. In this study, smooth blasting techniques are numerically analyzed to characterize the development of the damage rock zone during explosive fracturing.

Jan 1, 1995

By D. Erik Spiller

A commercialized dry gravity concentrator is operating on an alluvial gold deposit in the Boludo Mining District, State of Sonora, Mexico. The technology base of the process is the Rotary Air Concentrator (a dry circular air jig) that recovers gold from the desert sand resource. An overview of the Mexican operation and the dry concentration technology is presented. Application of the dry technology to pretreat­ment of heap leach feeds and other heavy minerals is a pos­sibility.

Jan 1, 2000

By Wang Dianzuo, Luo Lin, Hu Yuehua, Qiu Guanzhou

This paper introduces a novel classification approach named the flotation classification approach which works by controlling interactions between particles. It differs considerably from the conventional classification processes operating on mechanical forces. In the present test, the micro-bubble flotation technology is grafted onto hydro-classification. Selective aggregation and dispersion of ultrafine particles are achieved through governing the interactions in the classification process. A series of laboratory classification tests for -44 pm kaolin have been conducted on a classification column. As a result, about 92 percent recovery for minus 2 pm size fraction Kaolin in the final product is obtained. In addition, two criteria for the classification are set up. Finally, a principle of classifying and controlling the interactions between particles is discussed in terms of surface thermodynamics and hydrodynamics.

Jan 1, 1995

By W. J. Mahoney

A good quality assurance program at a coal mine or power plant is accurate, timely, and consistent. The quality analysis is accurate due to a complete sampling of the coal stream loaded into the unit train. The sample analysis is accurate because standardized testing procedures are applied. Once the analysis is completed, the results must be communicated to the electric utility in a timely manner. The electric utility needs the results to better manage the coal inventory at the power plants. A quality assurance program can also help the mine deliver a consistent product to the electric utility's power plants. The importance of the three major tenants for a good quality assurance program: accuracy, timeliness and consistency, are based on major changes that are taking place in the electric utility industry.

Jan 1, 1994

By Pierre Mousset-Jones

I wish to submit this discussion item on an article published in the August issue of MINING ENGINEERING by Wala and Altman on the use of canonical diagrams for mine ventilation networks. The advent of computer graphics and plotting has enabled complex underground mine layouts to be displayed and plotted in a variety of three-dimensional formats that very closely represent the actual mine layout. This enables the ventilation engineer, who is familiar with the mine, to display the network pressures, quantities, resistances, and fan locations in a way that can be understood by everyone working at the mine. This is important if the ventilation engineer needs to discuss changes in ventilation with production personnel, or escapeway procedures with union personnel. While I can see some of the potential advantages in the canonical ventilation network diagram described by Dr. Wala, it appears to me that the fact that the diagram has no visual equivalence with the actual mine layout means that most mine personnel will find such a diagram almost incomprehensible. The authors have alluded to certain advantages with the canonical diagram. However, I find it difficult to see that these outweigh the fact that almost everything listed can be duplicated in isometric diagrams, and in a manner that is easily understandable to everyone in the mine from the miner to the mine manager. Perhaps the authors could show a clear example comparing an isometric with a canonical portrayal of a mine network showing the information that is immediately available from the canonical network that is not obvious in the isometric diagram. There is in this country a severe problem with the need for ventilation engineering and expertise to be used and accepted by mine management as a necessary part of mine planning. It seems to me that to introduce the requirement for further explanation so that management can understand a canonical network display will hinder more than help the recognition that ventilation engineering needs at so many mines in this country. However, I can see that the canonical approach does have its place in assisting the practicing mine ventilation engineer, wherever he or she exists in the organization chart for a typical mine. In this case, could the authors please indicate the availability of the computer program to compute and plot the canonical diagram for a mine ventilation network.

Jan 1, 1990

By Pierre Mousset-Jones

I wish to submit this discussion item on an article published in the August issue of MINING ENGINEERING by Wala and Altman on the use of canonical diagrams for mine ventilation networks. The advent of computer graphics and plotting has enabled complex underground mine layouts to be displayed and plotted in a variety of three-dimensional formats that very closely represent the actual mine layout. This enables the ventilation engineer, who is familiar with the mine, to display the network pressures, quantities, resistances, and fan locations in a way that can be understood by everyone working at the mine. This is important if the ventilation engineer needs to discuss changes in ventilation with production personnel, or escapeway procedures with union personnel. While I can see some of the potential advantages in the canonical ventilation network diagram described by Dr. Wala, it appears to me that the fact that the diagram has no visual equivalence with the actual mine layout means that most mine personnel will find such a diagram almost incomprehensible. The authors have alluded to certain advantages with the canonical diagram. However, I find it difficult to see that these outweigh the fact that almost everything listed can be duplicated in isometric diagrams, and in a manner that is easily understandable to everyone in the mine from the miner to the mine manager. Perhaps the authors could show a clear example comparing an isometric with a canonical portrayal of a mine network showing the information that is immediately available from the canonical network that is not obvious in the isometric diagram. There is in this country a severe problem with the need for ventilation engineering and expertise to be used and accepted by mine management as a necessary part of mine planning. It seems to me that to introduce the requirement for further explanation so that management can understand a canonical network display will hinder more than help the recognition that ventilation engineering needs at so many mines in this country. However, I can see that the canonical approach does have its place in assisting the practicing mine ventilation engineer, wherever he or she exists in the organization chart for a typical mine. In this case, could the authors please indicate the availability of the computer program to compute and plot the canonical diagram for a mine ventilation network.

Jan 1, 1989

By J. M. Keane

The Solution Mining review arrived too late to appear in the May issue. Solution mining, in its broadest definition, includes all forms of leaching where a lixiviant solution is brought into contact with a metalliferous or non-metallic ore and the resulting pregnant solution is processed for recovery of the valuable soluble material. Technologies such as dump leaching, heap leaching, stope washing and in situ lixiviant solution injection and recovery fit into this definition of solution mining. A publication entitled the US Gold Industry (Dobra and Thomas) reflects the major impact that solution mining techniques have had on precious metal recovery. In 1989 (the last year for which statistics are available), the United States passed Australia to become the third largest gold producing country in the world after South Africa and the Soviet Union. It is estimated that when the final figures are in for 1990, the US will probably pass the Soviet Union in gold output. If the state of Nevada is ranked as a separate country, it will rank fourth in the world in gold production for 1990. A good proportion of this increase in gold production over the past few years can be attributed to the application of solution mining technology to low-grade, precious-metal-bearing material. Solution mining techniques have also made inroads in copper production. Many operations located at former underground mine sites employ in situ leaching as an adjunct to conventional dump and heap leaching practices.

Jan 1, 1991

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 R. L. Grayson, S. Yuan

A goal-programming-based, worker-scheduling model has been incorporated in the Mine Management Support System (MMSS) for assigning workers to prioritized jobs on a shift basis. In the model, the accomplishment of each regular and non-regular job is a goal, and the objective is minimization of the deviations from the goals. A number of coefficients are employed as premultipliers of the decision variables to address practical considerations associated with the utilization of workers and the requirements of jobs. This model is applied to a 41-worker problem.

Jan 1, 1992

By R. E. Mclaughlin, R. J. McLaughlin, A. H. Danzberger

Acid mine drainage (AMD) can occur as a natural phenome­non through oxidation of sulfide minerals. Oxidation by air and water can be exacerbated by mining. Because AMD can exhib­it low pH, it is capable of extracting heavy metals from mineral deposits. The result is highly acidic drainage with elevated heavy metal concentrations - the combination of which can cause extensive environmental damage. Because of the importance of these factors, this paper is focused on sulfate based AMD. Due to widespread mining, the occurrence of AMD is ubiqui­tous. As a result, several approaches to treatment have been developed. Chemical treatment using alkali is most commonly employed to treat AMD. There are alternative methods of treat­ment, as well as alternative ways of handling treatment sludges or concentrates. Dewatering of sludge or concentrates is beyond the scope of this paper. Within the family of chemical treatment processes, there are three principal recognized methods, namely, "Conventional," "High Density Sludge" (HDS) and "Heavy Metals Removal Process" (HMRP). All three are now employed or specified for treating AMO at mining sites which are being reclaimed under Superfund. Only limited data are available for more specialized chemical treatment processes such as "ferrate", borohydride membrane and electrochemical methods. Therefore, these data are not included here. Performance data for these three processes are presented in this paper and comparison among them is made. Comparisons include consideration of water quality, sludge characteristics, and operational ease. Capital and operational cost comparisons of these processes were addressed in a previous paper by the authors (see bibliography). The results presented here are impo1tant not only to metals mining, but are also applicable to other industries experiencing metals-laden acidic wastes including: coal mining and prepara­tion, metal plating, and electronics circuit board manufacturing. The acceptance of any process should be based on bench scale demonstration before implementation is contemplated. The three processes included herein are discussed in relation to the particular sites at which they are in use, or their use is planned. The sites selected were representative of the various types of processes and the wastewater parameters.

Jan 1, 1998

By D. Lenartowicz, K. R. Alexander, M Collings

Cosmo Howley is a gold deposit in the Northern Territory of Australia. The geology is complex and the input of geological data is an important part of the grade control process. As the geology of the deposit has become better understood, grade control and mining techniques have evolved to meet the changing circumstances. Present grade control depends on the use of angled blast holes, 21/2 benches and selective mining. Data is processed on site using 2 386 PC's running Surpac software. An environmental protection programme is employed, including soil stripping and stockpiling, sulphide waste containment and water quality monitoring.

Jan 1, 1989

By Gregg A. Swayre, Roger N. Clark, Stephen J. Sutley, Kathleen S. Smith

Imaging spectroscopy is a relatively new remote sensing tool that provides a rapid method to screen entire mining districts for potential sources of surface acid drainage. An imaging spectrometer known as the Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) measures light reflected from the surface in 224 spectral channels from 0.4 - 2.5 µm. Spectral data from this instrument were used to evaluate mine waste at the California Gulch Superfluid Site near Leadville, Colorado. Here, the process of pyrite oxidation at the surface produces acidic water that is gradually neutralized as it drains away from mine waste, depositing a central jarosite zone surrounded by a jarosite + goethite zone, in turn surrounded by a goethite zone with a discontinuous hematite rim zone. Leaching tests show that pH is most acidic in the jarosite and jarosite + goethite zones and is near-neutral in the goethite zone. Measurements indicate that metals leach from minerals and amorphous materials in the jarosite + goethite and jarosite zones at concentrations 10 - 50 times higher than from goethite zone minerals. Goethite zones that fully encircle mine waste may indicate some attenuation of leachate metals and thus reduced metal loading to streams. The potential for impact by acidic drainage is highest where streams intersect the jarosite and jarosite + goethite zones. In these areas, metal-rich acidic dace runoff may flow directly into streams. The U.S. Environmental Protection Agency estimates (U.S. EPA, 1998) that mineral maps made from AVIRIS data at Leadville have accelerated remediation efforts by two years and saved over $2 million in cleanup costs.

Jan 1, 2000

By A. Bruce Waugh, W. W. Wen, Kevin N. Clark, Neville C. Lockhart, Bruce A. Firth

Australia is the world's largest coal exporter, and technological advancement is a key element of the coal industry strategy. The issues include: increased recovery of saleable coal; enhanced quality, i.e. lower ash, moisture, fines, phosphorus (sulphur is a relatively minor problem for Australian coals); better quality control; higher throughputs/lower costs; improved handling and transport; and reduced environmental impacts. In process terms, many coal preparation operations, particularly fine coal circuits, are relatively inefficient, and all circuits must also be matched and integrated for optimum overall operation. A holistic approach to technological improvement is desirable. This paper summarises research and development efforts, within CSIRO and its collaborators, across the unit operations as outlined in the title.

Jan 1, 1995

By Gerrit V. R. Goodman, Charles D. Taylor

A technique was developed to determine the fraction of air recirculated from the scrubber exhaust toward the face and the fraction of gas captured by the scrubber. To determine these two values, a series of tests was required. In the first test, gas was released at the face area and concentrations measured at the scrubber exhaust. In the second test, gas was released directly into the scrubber with concentrations again measured in the scrubber exhaust. The simultaneous solution of two independent flow expressions gave values of recirculation and scrubber capture. A series of tests was conducted with various combinations of scrubber flow, curtain flow, setback distance, and machine location. Statistical analyses then were conducted to determine those factors which influenced the levels of scrubber recirculation and scrubber capture in a deep cut. INTRODUCTION As cutting depths increase, the trend is toward the use of blowing face ventilation systems. With these ventilation systems, the potential exists for recirculation between the scrubber exhaust and the intake air stream. One concern is that methane gas, having been removed from the face area, is subsequently recirculated back into the intake airflow. Under these conditions, methane-laden air could be substituted for fresh intake air, leading to increased methane concentrations at the face. There is currently no standard for recirculation between the scrubber and intake airflows. The implied understanding of the Mine Safety and Health Administration (MSHA) is, and has always been, that any recirculation of ventilation air is unacceptable. To minimize recirculation potential, MSHA suggests that operators maintain scrubber and curtain flows within 0.47 m3/sec (1000 cfm) of each other. Given that recirculation may occur in some circumstances, the question arises as to how much recirculation constitutes a hazard for the face workers. Unfortunately, there is currently insufficient information to answer this. Emphasis must instead be placed on means to quantify the amount of recirculation between the scrubber and face area. Methods must also be examined to control this phenomenon. This paper presents a technique for quantifying recirculation and scrubber capture levels in a blowing face ventilation system. Several ventilation parameters are investigated to determine their effects on these levels. DEVELOPMENT OF RECIRCULATION EXPRESSIONS One way to measure airflow quantities at a point near the face would be to measure the gas flow rate Qgas, and gas concentration c at that location. The airflow Qair, would be simply the ratio of these two values, Qair, = Qgas/c. Although gas concentration values, c, can be obtained easily with existing gas monitoring equipment, it is more difficult to obtain gas flow readings, Qgas, at specific locations. To obtain these values of Qgas, another method was needed. Previous work in this area was conducted by Kissell and Bielicki (1975). However, the calculations in their model assumed a constant gas concentration in the region around the continuous miner. In a deep cut, it is questionable that gas concentrations would remain constant or uniform around the mining machine. The technique presented here does not rely on this assumption. It instead assumes that the gas concentration in the scrubber exhaust remains constant. A quantity of gas released at the cutting face either flows into the scrubber inlets or bypasses the inlets and flows around the off-curtain side (in this example, the right side) of the continuous miner (Figure 1). The fraction of the face gas that flows

Jan 1, 1993

By Jacek Paraszczak

Numerous problems encountered in the mining of narrow vein deposits challenge the productivity, competitiveness and profitability of many mines. Mechanization of mining operations is one of the most important means to ensure the healthy survival of this mining sector. Vein deposits account for nearly all the world's primary silver production, as well as a significant portion of gold, tin, copper lead and zinc. In North America, narrow vein mining constitutes an important sector of the industry. Operators exploiting such deposits are concerned with the most appropriate mining method and equipment to mine in such a way as to minimize waste rock dilution. Unfortunately, most of the equipment available does not meet the additional geological and economical restrictions typical of narrow vein mining. Thus, mining these deposits is labor intensive and can result in low productivity. Consequently, the profitability of many such mines is reduced. Increased mechanization is one of the solutions to ensure their healthy survival. This paper reviews the state-of-the art in mining equipment with reference to narrow vein mining limitations. Problems encountered Geological conditions and economical factors have a decisive impact on the choice of mining method and equipment. Many ore bodies are relatively small, usually erratically distributed, often less than 2 m (6.5 ft) wide, with dips ranging from 0° to 90°. To make things worse, ore body limits are sometimes difficult to determine and the ground is hard and abrasive.

Jan 1, 1992

By Ben L. Seegmiller

INTRODUCTION Site characterization using oriented borehole core is the subject of this paper. Borehole core is a standard source of data for rock mechanics investigations. Oriented borehole core provides data whereby the geometric orientation of various geologic discontinuities (faults, joints, bedding, etc.) may be determined. The orientation and strength characteristics of discontinuities are important in many engineering investigations and in particular, in slope stability analyses. In heavily vegetated or soil covered situations, oriented borehole core may provide the only means of assessing the subsurface planes of weakness which characterize the site. The purpose of this paper is to briefly describe various methods or orienting core, core characteristics which may be logged and the methods of processing and using the data for site characterization.

Jan 1, 1977

By M. M. Champion

INTRODUCTION Since the first introduction of explosives into mining operations, safety considerations have prohibited the use of machinery in association with the explosives. Only within the last 25 years has this situation changed appre¬ciably; the closest thing to "machinery" used by a powderman in the "old days" was his wooden tamping stick. With the blackpowder and dynamite used during the first 150 or so years of mining blasts, substituting a drill steel or a metal "spoon" invited serious disaster. With the advent of ammonium nitrate-fuel oil (ANFO) explosives (1950s) and water-gel explosives (1970s) for underground blasting, machinery started to play a large part in blasting procedures. The lower sensitivity of ANFO and water gels allows these prod¬ucts to be loaded in a variety of safe ways. Not only has this meant cost savings in labor and blasting materials, but it has also resulted in whole new mining concepts where the limitations of dynamite previously made those concepts uneconomical, impossible, or excessively risky. Increasingly (totally for some mines), the traditional tamping stick has given way to a variety of pneumatic machines for loading explosives and blasting agents. The resulting blasting operations have become safer, more efficient, less uncomfortable for personnel, and a major step forward in mining technology. ANFO LOADING EQUIPMENT Three basic types of loaders are used for ANFO explosives, these being the pressure-vessel loaders, Venturi loaders, and combination loaders. Pressure-Vessel ANFO Loaders ANFO consists of prilled ammonium nitrate (porous pellets I to 2 mm in diam) and fuel oil in the appro¬priate 94 to 6% blend. The material is fairly dry, pourable, and easily conveyed by an air stream. One device or system for handling (hole loading) ANFO is the pressure-vessel loader. ANFO is dumped into the vessel or "pot," and the vessel then is pres¬surized. The ANFO is conveyed out of the bottom of the vessel into a semiconductive hose that has been inserted into the blasthole. Fig. 1 illustrates a typical pressure-vessel loader in use. Applications: The use of pressure-vessel loaders is widespread in room-and-pillar mines, including salt, potash, trona, lead, and other rubber-tired mines where the heavy pressure vessels can be mounted on a vehicle for transport from face to face. The vessel often is large enough to hold eight or more 23-kg (50-1b) bags of ANFO, so several faces can be loaded before refilling. Pressure-vessel loaders also are suitable for effec¬tively loading long holes such as those that are 6 m (20

Jan 1, 1982

By Warwick Hoffmann, Robin Batterham, David Conochie

CRA has been actively involved in developing a bacterial oxidation process for the treatment of low grade, refractory gold resources. Success in this application is dependant on the design of large, energy efficient reactors. It was identified at an early stage, that the conventional, bottom sparged bioreactor is inherently inefficient because air must be compressed to a pressure above that at the bottom of the tank. This inefficiency increases as the size of the reactor increases. CRA has developed a novel approach to the aeration problem. In this, venturi aeration is used to aspirate air into a liquor stream. The stream is then reintroduced at the top of a draft tube bioreactor. The advantages found with this technique include · low energy requirements and high oxygen utilisations. From results at the 30 m3 scale, we predict an energy usage of -500 kWh/t sulphur oxidised at a scale of 1000 m3.

Jan 1, 1993