Search Documents

By Steven J. Schatzel

Gas drainage through surface bore-holes has been the conventional means of methane control for U.S. longwall gobs. However, these vertical boreholes are becoming so costly, and the surface rights so difficult to obtain, that the Bureau of Mines is developing underground gob gas drainage as an alternate means of methane control for U.S. longwalls. Holes are drilled into the roof over the panel and on retreating longwalls, towards the working face from a location inby the face. As the longwall retreats, an increasing portion of the hole intercepts the fracture system over the caved gob. A surface exhauster maintains a vacuum on a pipeline parelleling the panel and draws the methane mixture out of the mine. Auxiliary systems of gob gas drain-age during longwall mining will be essential for an increasing number of coal mines. Deep and gassy mines often find ventilation insufficient for adequate dilution of methane in bleeder entries. Although this cross-measure method of degasification has been used successfully in Europe, some of the European techniques cannot be directly applied to U.S. mines. This is the first study of its kind in this country.

Jan 1, 1982

By Walter W. Lilly, Issa S. Oweis

Application of rock engineering in geotechnial consulting practice considered herein is in areas of: (a) bedrock verification for foundation support, (b) bearing capacity and settlements, and (c) excavations. A routine geotechnical investigation usually provides data on depth to rock, rock classification, and rock quality. In cases of rock outcrop, such outcrops are mapped for geologic structures and rock mass description. In addition, the regional geology and the general aspects of the groundwater regime are usually known from either published literature or previous experience. The predominant technique for ground and site investigation are usually drilling and geologic reconnaissance. Other techniques involving seismic and geophysical soundings, borehole camera, and oriented cores are used by by no means routine. Performing laboratory strength and compressibility tests is often made to be considered as routine. The use of the point load test is gaining increasing use in the United States and would, perhaps, become a routine field or laboratory test due to its simplicity and, more importantly, its relatively low cost. The purpose of this paper is to describe cases where mostly routine investigation and testing were used to arrive at engineering decisions. Bearing Capacity and Settlements The allowable bearing values for foundation support on rock is usually dictated by local building codes which presumably should reflect local experience. The interpretation of the code, however, can present a problem, especially if the interpretation is made by a designer under the delusion of knowledge in rock engineering. For

Jan 1, 1982

By G. T. Adel

This paper presents the highlights of a general-purpose simulator for mineral processing plants that is being developed at the University of California, Berkeley. The state-of-the-art structured design methodogy based on a top-down design approach is being used to construct a modular and completely structured simulator such that it is independent of the unit operation models and routines. The simulator provides for two levels of operation allowing prebuilt or user-built simulation flowsheets depending upon the degree of computer knowledge expected of the user. The philosophy used in designing this simulator appears to be unique in the field of flowsheet simulation. The paper also includes a mini-example demonstrating the usage of the simulator.

Jan 1, 1982

By A. Koursaris, H. M. Friede, A. A. Hejja

The features of smelting slags from South African prehistoric sites and of related cinder material are described. Chemical analyses of twelve slag samples found in the Transvaal, Swaziland, and Botswana are reported and discussed. An attempt is made to establish a relationship between these slags and the ores collected at the Early Iron Age site of Broederstroom, which date between AD 350 and AD 600. The liquidus temperatures of29 slags were determined by the use oh hot-stage microscope. The major mineral phases of 16 slags were identified by X-ray diffraction and microscopic examination. It appears that the slags investigated were formed at temperatures below 1250°C or - in some cases - at temperatures only marginally in excess of 1250°C.

Jan 1, 1982

By Constance F. Acton

This paper presents an overview of -- the carbon-in-pulp process for gold and silver recovery as seen in the early 1980's. Traced back to its origins in the mid-nineteenth century the process development through the present state-of-the art is described. The process technology and equipment design are described in detail for the carbon-in-pulp process. A typical process flowsheet is given with a description of appropriate design criteria. Technical advantages and disadvantages as compared to the traditional countercurrent decantation process are discussed including some illustrative comparisons of capital and operating costs. A summary of currently operating carbon-in- pulp plants throughout the world is given with an insight into future developments in this industry.

Jan 1, 1982

By Michael Hood

Subsidence profiles above two adjacent panels in Illinois are compared with pro- files predicting subsidence behavior obtained using the (i) National Coal Board (NCB, 1975) method, (ii) the profile function method and (iii) the influence function method. The NCB method predicts the maximum subsidence values at the center of the troughs accurately, but, the overall shapes of these predicted profiles do not match the profiles from the measured data well. Consistent values for the angles of draw were measured but these angles were different in the transverse (average value 43 degrees) and in the longitudinal (average value 17.5 degrees) directions. Time dependent subsidence effects are shown to be small but measurable. These displacements continue at a linear rate for at least a 12 month period. A comparison of measured horizontal distances, interpreted as horizontal strain, and the NCB predictions for strain shows that the peak measured strains are greater by a factor f about four than the predicted strains. The relationship between surface curvature and strain is investigated. Problems associated with calculation of surface curvatures from vertical displacement data are highlighted and a recommendation is made for future studies to consider direct measurement of this parameter. Surface curvatures above a moving face are found to be about three times less than the curvatures at the stationary end of the panel. On the other hand, a hyperbolic tangent profile function is shown to serve as an accurate predictive tool for subsidence behavior in two adjacent longwall panels at Old Ben Number 24 mine in Illinois. This function predicts not only the vertical displacements but also the surface curvatures above both panels. Influence functions are shown to be more problematic, although potentially more flexible, in their application than the profile functions.

Jan 1, 1982

By J. Absil, H. Dreissen

Upgrading low-concentration ores is of increasing importance today. The heavy medium cyclone process, due to strong centrifugal forces, effectively separates particles varying only slightly in specific gravity but widely in size. The paper discusses separation efficiency, assessment of that efficiency, and the influence of such factors as medium solids. The operating results of nine heavy medium cyclone plants, each handling a different mineral, are reported.

Jan 1, 1982

By Ronald R. Bauer

Wollastonite is a little known industrial mineral of the silicate group. The largest and purest known deposit in the free world is being mined and beneficiated in Millsboro, New York by NYCO, A Division of Processed Minerals Incorporated. The associated garnet and diopside are separated from the wollastonite using dry high intensity magnetic separators. Beneficiated wollastonite is used extensively as an additive and filler in the ceramic, paint, refractory, and wallboard industries. Wollastonite acts as a functional filler due to its unique chemistry and physical acicularity.

Jan 1, 1982

By Reichman J, Chapman G

The features of seam gas drainage from the point of view of mathematical modelling are outlined and discussed: 1. The use of conventional single phase gas reservoir simulator for very simplified modelling. 2 Alteration of a conventional petroleum reservoir simulator into a specialised simulator for seam gas drainage. 3. Application. of a conventional petroleum reservoir simulator for modelling of seam gas drainage by the way of pseudo-functions and sacrifying one dimension.

Jan 1, 1982

Significantly reduce respirable dust exposures of longwall shearer operators when cutting out at the headgate. Approach As a result of Bureau research, a ventilation curtain is recommended to be mounted between the stage loader and the coal rib to more effectively prevent the ventilation air from blowing across the shearer drum as it cuts out at the headgate. Some mine operators already employ this method of reducing dust, but a vast majority do not. How It Works One source of extreme concentrations of respirable dust for longwall shearer operators is the shearer headgate drum as it cuts through into the headgate entry. As the drum cuts into the entry, it is exposed to the primary ventilation airstream. The high velocity air passes through and over the rotating drum, picking up large quantities of dust.

Jan 1, 1982

By Bruce H. Baker

Studies of used or unused refractory materials are excellent examples of applied mineralogy in industry. Refractory materials are mineral substances containing ceramic or chemical bonding systems. Knowledge of the mineral composition, bonding, and textural relationships often explains the resulting physical property values of a refractory and contributes to the interpretation of refractory wear mechanisms occurring in steel plant service.

Jan 1, 1982

By Robert L. Sundeen, Richard V. Wenberg

INTRODUCTION Shotcrete can be defined as spray-applied concrete with a maximum size aggregate in excess of 9.5 mm (0.375 in.). The concept evolved from guniting, which uses smaller aggregate and generally produces concrete with poorer physical properties. The larger aggregate used in shotcrete requires less water in the mix, while offering larger bonding surfaces, thus imparting greater tensile and compressive strengths. TYPES OF MACHINES Two basic designs of shotcrete machines in general use are the wet or prehydrated zero slump and low slump type, and the dry or nozzle hydrated machines. Fig. 1 shows a typical zero-slump machine in a con¬figuration commonly used for small-volume require¬ments. The prehydrated zero-slump machine mixes exactly proportioned batches in a sealed pressurized chamber. "Slugs" of hydrated shotcrete mix and com¬pressed air are sent through a distribution hose to the nozzle where the wet mix emerges as a spray. The spray is directed onto the rock surface by the nozzle operator. The low-slump machine is similar, except that a thick slurry mix of aggregate is delivered throughout the distribution hose to the nozzle. Fig. 2 shows a typical low-slump shotcrete machine used in moderate-volume applications. The nozzle-hydrated shotcrete machine accepts a premixed "dry" (4 to 6% moisture) batch of aggregate and cement. A constant feed of this mix is directed by compressed air through the distribution hose to the nozzle. At the nozzle, water for hydration is introduced into the emerging spray. The hydrated mixture is di¬rected onto the rock surface by the nozzle operator. Fig. 3 shows a typical dry-mix machine. The major difference between the two basic machine designs is the consistency of the shotcrete quality. Pre¬hydrated machines have high degrees of consistency and produce high-strength concrete, resulting from their ability to produce exact mixtures of zero or low-slump concrete within the machine. Nozzle-hydrated machines tend to produce poorer quality concrete because of the difficulty in controlling the water content at the nozzle. Water input essentially is an art. As such it is not precise, and the shotcrete produced is of variable quality. MATERIALS HANDLING Materials handling presents a problem to either type of shotcrete machine. At times considerable quantities

Jan 1, 1982

By Sterling J. Anderson

To define the technical competence and capabilities of a nonexplosive excavation concept, the Bureau of Mines conducted reduced-scale laboratory tests of a mechanical excavation tool called a rock splitter. Hydraulically actuated splitters, capable of generating both radial and axial loads on a predrilled hole, were designed and fabricated. Through paired variable testing and drifting simulation, reduced-scale splitter performance was evaluated in concrete. Testing proved that the rock splitter is capable of excavating within the highly confined drift set-ting and that it offers a distinct advantage over splitters that can generate radial loads only.

Jan 1, 1982

By P. W. Udo Graefe

"An interactive computer model of a dragline, windrow and spoil pile has been developed for modelling oil sands mining operations. The model is to be used in conj unction with models of other oil sands mining equipment, such as bucket-wheel excavators and reclaimers, conveyors, hoppers, bins, trucks and shovels, to study mining operations on a minute-by-minute basis. From the orebody description and mining selectivity, layers of ore and reject are determined and mined by the dragline. Reject is dumped on the pit floor; ore is either dumped on a windrow for later removal by a bucket-wheel reclaimer or directly dumped into a hopper feeding a conveyor. The model allows for the presence of pads as a dragline base, key cuts and a number of interruptions to the mining operation such as shift changes, boom checks, engineering services, repairs, delays, preventative maintenance, etc. A CRT display keeps the model operator informed about equipment status and performance. The model operator can direct the course of the simulation by issuing commands to the model at any time during the simulation.IntroductionThis paper describes an interactive computer model of a dragline, windrow and spoil pile. The model was designed by the author based on information and specifications provided by Canstar Oil Sands Ltd. The model design was implemented and tested on Petro-Canda's IBM computer system by DMR and Associates Ltd. of Calgary, Alberta.The model was designed to form three components of an oil sands mining operations model, described in reference I. Figure 1 shows the interaction of those components with the remainder of the oil sands mining model.An ""Ore/Waste Body"" data base provides information to the dragline model about the location and composition of or e and waste in the mine. The dragline model is used to simulate mining this ore/waste body, to build up spoil piles for center reject (waste) and to dump ore onto windrows or hoppers (situated over conveyors) to deliver the ore to the extraction plant. The windrow model component provides a data base which will be used by a model of a bucket-wheel reclaimer which simulates the loading of ore from the windrow on to a conveyor via a bridge."

Jan 1, 1982

Various aspects concerning gold are mentioned below. These have no common theme but suggest points of interest any one of which, if warranted, could lead to development later and elsewhere. 'High level' auriferous gravels The gold deposits of Victoria are commonly classified as being either primary or secondary. Most primary occurrences comprise gold present in quartz reefs, together with other lode-like occurrences in which gold is associated with various sulphides, with or without quartz. Secondary occurrences are derived by physical release of primary gold and subsequent concen- tration of it as a constituent of sediments. Secondary gold deposits may be themselves eroded so leading to third or even fourth generation gold.

Jan 1, 1982

By Robert B. Hill

A history of gravity classification shows the development of many types of equipment with several prominent types continuing in use today. Part of the development and evolution is the spiral classifier. Data will be presented showing characteristic size separations in a closed circuit grinding operation. Comparisons with hydro- cyclone operation will be shown including operating cost comparisons. Effects of variables will be shown in spiral classifier operation. Finally, other uses for spiral classifiers will be described.

Jan 1, 1982

By David A. Campbell

There has been a long history of ironmaking on the North East coast of England centered around the River Tees. The industry developed here because of the availability of good coking coals to the North in Co. Durham, and the discovery in 1851 of ironstone in the nearby Cleveland Hills, South of the .River. Cleveland ironstone is relatively poor in quality, with an iron content not exceeding h% and high proportion of sulphur and phosphorous. The iron exists in chemical association with alumina and silica, and physical beneficiation processes involve a serious loss in iron unless the upgrading is limited, when the economics of the process become doubtful. Over the years, richer foreign ores have replaced the local ironstone, and the last operating mine was closed in 1964.

Jan 1, 1982

By R. W. Pugh, D. G. Bellow

"This paper will describe how cultivator shanks are made in one company and how the manufacturing was studied with a view to increasing product consistency and reducing manufacturing cost. The product: which is used extensively in the agriculture industry, was analyzed to determine which geometric parameters optimized its design and whether there was justification for the great variety of styles and shapes that are available in the market. Finally, an extensive series of field trials were undertaken which showed that it is advantageous to the manufacturer to be better aware of the loads and forces that his product is subjected to by another industry.IntroductionStelco maintains a Research Group for its Western Region operations headquartered in Edmonton, Alberta. Because of the small staff, a location that is isolated with respect to its Burlington, Ontario centre and a diverse set of processes and products, a university relationship has developed which may be different from that which would be developed at a larger integrated Steel Works. This paper outlines the type of cooperative studies carried out by Stelco Inc. in Edmonton and the University of Alberta. .To meet the research needs covering a wide variety of steelmaking processes and steel products produced in Edmonton would require more staff and equipment than the sales volume in the West justifies. The gap is filled by cooperation with university personnel. This cooperation has provided these benefits to Stelco Inc.:• access to specialized test equipment and a trained staff to operate it; and• assistance from experts in the areas of product testing and problem solving.Moreover, the close proximity of the university to the plant allows frequent meetings and ensures that practical solutions are developed and implemented. A good example of the ongoing university I industry relationship developed is the joint work on improving cultivator shanks."

Jan 1, 1982

The additional information that Clarke and Taylor (1982) provide about the important but poorly documented Ardlethan deposit is, of course, very welcome. However their contention that structural considerations, in conjunction with petrology, alter the interpretation of the mineralogical and geochemical data presented previously (Scott, 1981) is not accompanied by adequate supporting evidence. Indeed characteristics of the orebodies studied invalidate their arguments.Heterogeneity between matrix and fragments is not a problem in the South Cherry and Ardwest orebodies because most samples are comprised entirely of interlocking hydrothermal assemblages with a fabric and mineralogy that is uniform through both former breccia fragments and matrix. In hand specimen, the rock superficially resembles altered granite and, as indicated by Clarke and Taylor (1982), a brecciated texture is difficult to discern. In thin section, relict brecciated textures can be observed as localized changes in the grainsize or in the distribution of minerals that outline former breccia fragments (P. J. Eadington, 1982, personal communication).Because of the intense brecciation and comminution of rocks (fragments < 10 mm are usual) in the South Cherry and Ardwest breccia bodies, hydrothermal recrystallization was complete, resulting in homogenization of fragments and matrix. Furthermore, the amount of sample analysed (-100 g for drill core and 2-3 kg for hand specimens) is sufficiently large to be representative of both former breccia fragments and matrix. The Carpathia and Stackpool orebodies, with their abundance of sedimentary fragments, have alteration superimposed on a heterogeneous fabric, and were not studied. Thus the problems of differentiating between fragments and matrix (Clarke and Taylor, 1982) are irrelevant to the particular orebodies described in my paper.Within the alteration halo, which is several hundred metres wide (Paterson, 1976), the very uniformity of the alteration assemblages implies that subsequent, postmineralization brecciation is of only minor significance.Indeed tourmaline pipes in the Ardwest pit are less than several metres across (Clarke, 1979) and produce minimal alteration in the surrounding rocks. Therefore the interpretation of the mineralogical zonation is not compromised by the recognition of several periods of brecciation.

Jan 1, 1982

By Ray W. Amstutz

The shaft was drilled on US government land m the Piceance Creek basin and was funded by the US Bureau of Mines (USBM). It was drilled to 723 m to provide access to rich deposits of oil shale, nahcolite, and dawsonite for geotechnical test work and environmental mining research. Rotary drilling and dual-string, reverse-air, jet-assist circulation methods were used. Drilling required eight months. Site preparation, running, and cementing the casing required another four months. A 2.44-m ID steel welded casing, 508 mm thick was installed and 2.7 kt of cement were slurried and pumped into the annulus.

Jan 1, 1982