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The AusIMM/AMIC code for reporting Reserves seeks to improve the calibre of professional reporting on this subject. But have they gone far enough? Should the code appreciate that the degree of reliability of estimates required will vary with the type of mining planned? How does one "confirm continuity" as required by the code? The aim of optimum development drilling is to achieve appropriate ore zone definition for acceptable estimates of reserves and their economic extraction. Can this procedure be in conflict with the code? How does it affect finance decisions?

Jan 1, 1989

By Ian Hooper, Alan Winter, Stefan Sadokierski, Craig Covil

The existing Tappan Zee Bridge was built in the late 1950s and has been working over its design traffic load for some time now. A new project, which is being jointly sponsored by the New York State Thruway Authority and Metro-North Rail Road, is looking at new alternatives to provide new road and rail crossings of the Hudson River. These include 2 to 5 mile and potentially longer tunnel crossing options that include hardrock TBM and EPBM opportunities. The paper describes the project needs and tunnel concept design work done on some of the alternatives. It also relates to the current EIS process for the project and talks about a possible double-stacked tunnel option. It also talks about the geology and environmental constraints relating to tunneling and provides and introduction to the tunnel ventilation work necessary for tunnel crossing of this magnitude. It does not report on the bridge engineering options being evaluated.

Jan 1, 2005

Detailed mineralogical investigation of a tailing sample from the Juno plant circuit at Tennant Creek was carried out to determine the nature of the unrecovered bismuth and whether any possibility existed for improving bismuth recovery. The investigation showed that the Ibismuth was present in a complex mixture of Bi-Pb-Ou-Se-S minerals (termed "bismuthinite"), of which about 74 per cent was locked (mainly with magnetite) and 26 per cent was liberated (18 per cent in the minus 7 µm slime). The results suggested that attention should be directed to both finer grinding and improved flotation of slime "bismuthinite", and testwork carried out by Peko Mines N.L. on the basis of these recommendations led to a significant improvement in bismuth recovery.Detailed mineralogical investigation of two Juno concentrates was carried out to determine the nature of the selenium present and whether any possibility existed for improving the selenium grade. The investigation indicated that virtqally all the bismuth, selenium, and lead was present in "bismuthinite", which showed a composition range of 32-82 per cent Bi, 0-42 per cent Pb, 0-24 per cent Se, and 5-18 per cent S. Differences in the Bi/Se ratios of the two concentrates could be attributed to different average Bi/Se ratios of the constituent "bismuthinite", and the relatively low selenium grade of the "bismuthinite" precluded the possibility of obtaining a high grade selenium concentrate with high selenium recovery.However, differential flotation and/or low intensity magnetic separation to remove chakopyrite, and magnetite, the main diluents of the concentrate, could be expected to upgrade the selenium content byup to 80 per cent (relative) and .festwork carried out by Peko Mines N.L. on the basis of the recommendations of the mineralogical investigation confirmed that depression of chalcopyrite in the flotation circuit could produce significantly improved selenium grades.These investigations illustrate the application of mineralogy to the practical problems of improving plant performance. Mineralogy has an important role to play in providing quantitative data on which the metallurgist can evaluate plant performance and base a programme of metallurgical testwork, and early mineralogical investigation of feeds, concentrates, middlings, and tailings can lead to the avoidance of much abortive and expensive metallurgical testwork.

Jan 1, 1974

By Hamid Maleki

Roof falls are one of the leading ground control problems that adversely influence productivity and worker safety in underground mines, construction sites, and nuclear waste repositories. To control roof stability problems, the operator needs to have practical methods for measuring changes in strata conditions and criteria for defining the timing of secondary support installation. The objective of this study was to develop measurement techniques and criteria for assessing roof conditions at the mining face. An integrated rock deformation and tomographic imaging method was developed and applied at two sites in a western U.S. trona mine. It was shown that rock damage occurred at a deformation of 30 to 60 mm (1.2 to 2.4 in) (2 to 4 pct strain) and was associated with a significant (16 pct) reduction in wave velocity. Thus, supplementary support may be installed when there is a measured change in wave velocity of at least 16 pct. Tomographic measurements can be obtained in rocks rapidly, thus providing a powerful tool for analyzing growth of failure and for installing supplementary support systems in a timely manner.

Jan 1, 1996

By Hargraves A. J, Smith J. W

Experiments conducted at Tahmoor Colliery, Sydney Basin, have demonstrated the variability in chemical and isotopic composition of seam gases issuing from boreholes in the Bulli seam and desorbing from lump coal from the same source.From this work it appears that an immediate preferential release of methane accompanies the physical disturbance of the coal seam by penetration with development or drilling or by detachment. In addition, both early released methane and carbon dioxide are depleted in 13C relative to later desorbed gases, therefore the analyses of gas samples taken after such events may not reflect the true bulk composition of the undisturbed seam gas in situ. A method for overcoming this problem by taking gas samples at depth in the "steady state" is proposed.

Jan 1, 1987

By R. G. Bentsen, D. A. T. Donohue

The cyclic steam injection process has become the most widely applied and most successful thermal recovery technique in use today.1-4 Normally, steam stimulation is repeated several times during the life of a project. The problem is to select the optimum number and size of steam treatments so that the profits realized over the entire life of the project are maximum. Obviously, operating costs rise directly with the frequency and amount of steam injection. Operating efficiency, on the other hand, can be adversely affected if the amount and frequency of stimulation are insufficient. Thus arises a multistage decision problem; that is, a decision must be made at each sub-period (day, for example), as to whether steam should be injected, and, if so, how much. It is desirable that these decisions be made in such a way as to secure maximum net profit before taxes. This can be achieved by dynamic programming. To use dynamic programming, we must be able to predict not only the production rate-time curve resulting from a given stimulation, but also how changes in stimulation policy will affect this curve. In this study, the effect of steam injection on well performance is estimated on the basis of a simple model that takes into account both steady-state and transient flow. Oil production rate is calculated for both types of flow, and the larger of the two values is used. This allows the calculation to change to radial steady-state flow at such time as this mechanism becomes more effective than the transient mechanism. We propose to show how dynamic programming can be used to optimize the steam soak process with respect to net profit. For this, a mathematical representation of the steam soak technique is necessary. A further objective, therefore, is the formulation of a mathematical model capable of realistically simulating the physical process. Oil Production Response Model The advantage of using a mathematical model is its generality and ease of manipulation. However, the model must be an accurate representation of the physical process, for a solution derived from a model can be no better than the model itself. The question now arises as to how well the model should be expected to simulate reality. In general, the simplest model should be tried first, for additional accuracy is apt to require additional cost and time. Also, the search for a high degree of accuracy may yield only greater complexity and difficulty without yielding significantly better results. With this in mind, we kept our model as simple as possible, yet generally representative of the actual physical process. The number of state variables is limited to three, and stochastic variations in the parameters are ignored. As a consequence, use of this model should be restricted to cases in which the underlying assumptions are not severely violated. In

Jan 1, 1970

By J. Douglas, W. T. Ford, G. E. Henderson, I. F. Roebuck

An implicit numerical method is presented for simulating the differential and algebraic relations governing one-dimensional three-phase flow in porous media. The method is based upon compositional representation of the hydrocarbon system. Variable physical properties and water-oil capillary forces are included in the formulation; however, the effect of gravity is ignored. The effects of changing composition and mass transfer are considered through the use of known phase behavior concepts and correlations. The differential and algebraic equations and the numeric approximations to these equations are presented, and the computing algorithm is discussed in detail. This method is used to simulate a single-phase, two hydrocarbon-component gas displacement laboratory experiment. The method is also applied in simulating a solution gas drive and a gas injection problem using a reservoir oil represented as a nine-component mixture. For comparative purposes, the latter two problems also are examined with a one-dimensional volumetric model. The results of the simulation of the laboratory experiment demonstrate the relevance of this method to problems wherein the effects of mass transfer significantly enter the displacement process. The comparison of the results of the volumetric and compositional methods applied to a reservoir system illustrates not only the advantages and benefits derived from examining the hydrocarbon system composition, but also the necessity of this approach in application to a general reservoir problem. INTRODUCTION The advent of large memory, high-speed digital computers enabled reservoir engineers and mathematicians to pool their knowledge in the development of sophisticated techniques for the prediction of oil and gas reservoir performance. These techniques have progressed from volumetric and trend analysis calculations to the development of "mathematical models", or reservoir simulators. These latter models, in general, utilize finite difference approximations to the rather complex partial differential equations that mathematically describe the physics and thermodynamics of fluid flow in porous media. Many forms of this "model" type are available today, and much of the recent literature has been devoted to either improving known methods or developing new techniques for use in these prediction methods. The more advanced techniques in use at this time consist of the solution of differential and algebraic relations that describe a reservoir geometry in one, two or three dimensions and that incorporate reservoir hydrocarbon and water fluid systems that obey specified physical laws, having properties that might easily be measured in the laboratory. This type of model utilizes formation volume factors and other volumetric data, expressed directly as functions of pressure, to represent the reservoir fluid system. Experience gained with this type of simulator, commonly known as a "beta-factor model", has indicated that the approach has many outstanding defects, most of them due to the assumption that those properties measured in the laboratory completely describe the behavior of the fluid system throughout the life of the project under study. The effects of varying hydrocarbon composition and mass transfer between the phases of this hydrocarbon system must, by definition, be ignored. These defects, which may often be ignored in

Jan 1, 1970

During the construction of storage caverns, and during their lifetime if the use to which they are put so requires, it is necessary to provide adequate ventilation to ensure the safety and comfort of the underground workforce. An analysis of likely contaminants during construction has indicated that where a large facility is situated in a rock mass of even moderate temperature climatic conditions are likely to be the limiting factor during most of the mining operation and atmospheric pollution when blasting is undertaken. Possible options for improvement are increased air flow, cooling of intake air and reduction of the heat source by altering the number and type of haulage units employed in the cavern. Local solutions are an alternative approach where heat problems are confined to a few specific locations

Aug 1, 1994

By D. W. Olson

Garnet has been used as a gemstone for centuries. However, garnet’s angular fractures, relatively high hardness and specific gravity, being chemically inert and non-toxic and free of crystalline silica, and its ability to be recycled make garnet ideal for many industrial applications. Garnet is the general name given to a group of

Jan 1, 2005

By Dennis Molvik, Roberto J. Guardia, Brad Cowles, Rick Andrews, Robert A. Robinson

A 220-meter (m) segment of the Henderson/ ML King Combined Sewer Overflow(CSO) consists of two 1.8-meter-inside diameter (I.D.) pipe-jacked tunnels that pass beneath Interstate-5 and the BNSF and UPRR railroads. A seismic tomography survey was conducted to develop a 3-dimensional profile of the tunnel zone and better define potential obstructions. The tomography was conducted through three 11 cm high-density polyethylene (HDPE) pipes installed in a triangular pattern around the future tunnel alignments using horizontal directional drilling methods. The pipe-jacked tunnels have been successfully completed, thus permitting a comparison between the predicted obstructions and those actually encountered. The top HDPE tomography pipe was also used to monitor settlements with an experimental horizontal profiler above the advancing tunnels during construction and located two areas of ground loss beneath I-5 that were subsequently grouted.

Jan 1, 2005

By A. T. Sweet, G. Douglas Gardner

"INTRODUCTION In the ammonium sulfate process for the production of alumina from clay,,3/ the clay is baked with amonium sulfate at about 400ºC. to form anhydrous ammonium alum and free ammonia or ammonium carbonate. The alum is leached from the baked product with water and circulating liquors and is purified by recrystallization. Aluminum hydroxide is precipitated by treating thus alum the alum the ammonia or ammonium carbonate from the baking step. Ammonium sulfate is recovered from the filtrate for reuse, and the aluminum hydroxide precipitate is calcined to produce high-purity alumina. In this process, as in other acid processes for the production of alumina, 4/ a large part of the iron in the clay is extracted. The iron tends to build up in the leach liquors and contaminate the crystals, so that its elimination is one of the most important problems in the process. A number of large clay deposits occur in the Western States. Those that have boon explored most extensively 5/contain an average of 24 to 30 percent available A12O3 and 2 to 8 percent available Fe2O3. 6/ The available Fe2O3 content of various other clays ranges from less than I percent to more than 20 percent. The available Al2O3 or Fe2O3 is usually 90 to 98 percent of the total but may be much less. In generals the iron content bears no fixed relation to the alumina content and may vary widely within a given deposit."

Jan 1, 1948

By J. B. Forrester

In the operation of the coal mines in Utah few adverse conditions confront us. Physical conditions for the economical extraction of the coal are as near perfect as it is possible for them to be. Still several obstacles are encountered to keep up our interest and prevent us from getting in a rut. Of these I shall speak only of Burning, Wants, and Sluffing of Ribs. Should one travel the outcrop from Ivy Creek in Emery county to the Utah-Colorado line, there would be one outstanding feature indelible impressed upon one's mind. That feature is the omnipresent indications of burning in place. Viewing the eastern escarpment of the Wasatch Plateau from a distance, many splotches of dark red are plainly seen always lying above the coal floor. This stratum is a felspathic sandstone, appearing as a white line running the full length of the above escarpment and about midway between the floor of the valley and the top of the plateau. The coal bearing complex consists of shales, sandstones and coal. This complex varies from two hundred to eleven hundred feet in thickness. The number of coal seams are exceedingly variable. As a rule the argilutites form the bulk of this complex. This material is baked by the burning of the coal and the iron present is oxidized to the ferric state, coloring the shale to a dark red. This baked material forms a shingle tales that in places cover the entire complex. It is natural to expect that the most extensive burning is in the canyons facing to the south and east and on the south slopes of the ridges running to the east or west. Such, indeed, is the case. Still in this arid region many crop fires have existed upon the north slopes, especially in those canyons that face to the east. In fact today, instances are not rare where grassy north slopes, heavily timbered with balsam and fir that have attained a diameter of 14 to 24 inches, are found growing upon the disintegrated baked shingle and later development proves that the coal has been burned at least 500 feet back from the outcrop. Still these conditions are not normal. In this arid climate the south and east exposures are steep and barren, except for the scrub pine, cedar, mahogany and kindred semixerophytes. Bunch grass is also a lover of such exposures. There is very little soil found in such places; it is either blown away as fast as formed or washed away by the rare torrential rains, or the rapidly melting snow. Thus we see that the physical conditions are favorable for the starting and maintainence of outcrop fires. This brings us to the probable origin of this phenomenon. There are four probable ways' that such fires, could be started, namely:

Jan 1, 1921

By A Croll

A panel cave using LHDs for ore extraction came into production at Premier in 1990 at a depth of 630 metres below surface on the western side of the mine in the BA5 mining block. A post-undercut mining sequence was used with all development on both the undercut and production levels completed prior to the undercut being advanced over the pre-developed drawbells. Support and rock mass damage on the production level was extensive as the undercut moved overhead. Undercutting and coarse fragmentation created problems. The mining sequence was changed to an advance undercut with the minimum of development and support undertaken on the production level prior to the undercut moving overhead. Only once the abutment stresses had stabilised were drawbells developed and final support installed. The height of the undercut drill design was decreased from 18 to 13 metres. The changes resulted in markedly less rock mass and support damage on the production level. Lessons learned in the BA5 mining block on the 630 level were incorporated into planning and scheduling the BB1E mining block which came into production on the 732 metre level on the eastern side of the mine in 1996. An advance undercut mining sequence was planned, undercut height was minimised and undercutting parameters were optimised in terms of the BA5 experience. Numerous problems still occurred. As the undercut area increased in size severe spalling from the cave back resulted in vertical propagation of the cave to a height of 30 metres instead of the planned 13 metres. The resultant coarse fragmentation created secondary blasting problems and an excess of undercut ore that had to be loaded and trammed, slowed the rate of undercut advance. The planned mining sequence was compromised and considerable support and rock mass damage resulted on the production level below. Once these problems had been overcome the undercut advanced at the planned rate and continuous caving initiated at the predicted hydraulic radius. At a later stage the unexpected ingress of water hampered undercut drilling and slowed the rate of undercut advance in a section of the cave. Leads and lags between adjacent tunnels and the overall face shape could not be developed as planned. The rate of natural horizontal cave propagation exceeded the rate of undercut advance and three undercut drilling tunnels were extensively damaged. More tunnel development on the production level prior to undercutting than was planned resulted. The slow advance of the undercut and high abutment stresses caused extensive damage to installed support and the rock mass on the production level, 15 metres below. Experience in the BB1E mining block on the 732 metre level has taught that an advance undercut mining sequence reduces damage on the production level markedly. Extremely tight control on the rate of undercut advance, leads and lags between adjacent tunnels and overall undercut face shape as well as extraction ratio, tunnel development and support sequence on the production level below is required. Premier Mine plans to implement a block cave at a depth in excess of 1000 metres within the next decade. All the experience gained on current mining levels together with data collection and numerical modeling is being used to plan the proposed mining operation. The geotechnical challenge of mining at this depth in weak rock has been identified as the greatest risk to the project. Challenges centre around adopting the correct mining sequence, limiting the extent of rock mass damage associated with undercutting and effective support. The hydraulic radius needed to initiate caving, fragmentation, drawpoint spacing, secondary blasting and the possibility of seismicity are geotechnical concerns that are being addressed. Results to-date suggest that a pre-undercut mining sequence with all development and support on the production level carried out only after the undercut abutment stresses have passed overhead will have to be implemented.

Jan 1, 2000

By Pekka Taskinen

Advanced optimizing control of the fluidised bed zinc roaster has been in use for an extended period at Boliden Kokkola and the implications are seen as extended bed stability, increased throughput and far better on-line availability. The roaster furnace control system developed is based on a dynamic and predictive furnace model, with parameters determined experimentally at the site. The controller maximises the concentrate feed and keeps the furnace operational parameters inside limits given by raw material mix and equipment constraints. The products of a zinc roaster, calcine, sulphur dioxide and the side products, such as mercury, meet gradually more stringent requirements, in particular as to their assays and total recoveries in the process chain. The end users of sulphuric acid in northern Europe, among others in the pulp and paper industry, require mercury levels much less than the conventional 0.2-0.4 ppm Hg. Therefore, secondary de-mercurising circuits have been used over the last five years for further cleaning the SO2 stream allowing production acid grades with less than 0.08 ppm Hg.

Jan 1, 2008

By G. H. Lind

Research into the safe and economic extraction of underground coal pillars in the Witbank and Highveld coalfields of South Africa highlighted that future practices will have to consider pertinent risks associated with this least safe of all underground coal mining methods conducted in South Africa. To this end, a computer-based program called A-PEP (Analysis for Pillar Extraction Potential) was developed to assess three aspects of this mining practice, viz. risks associated with the physical attributes, operational risk attributes and economic attributes. This intelligent tool can thus be used when planning to conduct underground pillar extraction to ensure that all pertinent risk elements and legislative requirements are considered to conduct this mining method safely before a submission is made to the Department of Minerals and Energy. Keywords: operational risk management, mine planning, underground coal mining, pillar extraction.

Jan 1, 2003

For the first time in its history, the George A. Fox Conference let its focus venture away from the friendly confines of the East Coast of the United States to spend part of the one-day conference looking at projects from around the globe. With a record-setting attendance of 377 people, the conference, titled ?Tunneling: An international perspective,? opened with a keynote speech from special guest In-Mo Lee, professor, Korea University in Seoul, South Korea. He is also the president of the ITA-AITES. In a sweeping presentation, Lee walked the packed audience through some of the most fascinating and challenging projects in his home country. Among the projects he spoke about were Korea?s longest railway tunnel, the Solahn Tunnel and the Inje Tunnel, a freeway tunnel that is 11.94 km (7.4 miles) long.

Jan 1, 2012

By Joe Roby

Rolling disc cutters are the business end of hard-rock and mixed-face tunnel boring machines (TBMs). Since their first successful employment on a TBM more than 50 years ago, disc cutter technology has constantly evolved, allowing modern TBMs to excavate very hard and abrasive rock efficiently. Disc cutters have also been employed successfully on earth pressure balance (EPB) and slurry machines, cutting rock under water and ground pressure. The range of materials excavated by machines today is broader, excavation rates are higher and cutter costs are lower than ever before, proving the value of investment in cutter development. Disc cutters are used on a range of tunneling equipment, from pipe jacked slurry micro-TBMs less than 1 m (3.3 ft) in diameter to 15 m (49 ft) in diameter, hard-rock boring TBMs. The geological conditions under which they are employed range from sands and gravels, with several bar of water pressure, to extremely hard, massive rock with UCS up to 420 MPa. Regardless of the type of machine or geology, one thing remains constant: changing worn out cutters is costly. When cutters must be changed in the middle of a tunnel, the contractor incurs the cost of downtime as well as the cost of refurbishing or replacing the cutters. In the case of catastrophic cutter failures, the project can be stopped completely for long periods, and the costs mount up rapidly while tunnel production is at a stand still. Catastrophic cutter failures include the occasion when hard-rock disc cutters are failed in groups (called a ?wipeout? phenomenon) and the operator fails to stop the machine, which results in severe damage to the cutterhead. The cause of this can be either an undetected failed cutter propagating damage to surrounding cutters or operator error in steering. Regardless of the cause, the resulting damage can take days or even weeks to repair. When cutters fail prematurely on EPB or slurry machines in certain geological conditions, it is impossible to evacuate the chamber and, therefore, impossible to get [ ] into the chamber to change the cutters. The solution is frequently an unplanned intervention shaft that must be sunk at great cost. The importance of being able to predict cutter life accurately, and in all geological conditions, cannot be overemphasized. For these reasons, cutters have been developed for specific machine types and sizes, as well as for specific geological operating conditions. Different size cutters are required for different size machines. For example, while 483- and 508-mm (19- and 20-in.) cutters are used on large diameter TBMs, it is impossible to employ cutters so large on a small micro-TBM. Also, the cutter must be designed for the specific geological conditions under which it will be operating. The disc cutter rings required to bore extremely hard rock are the most expensive of cutter rings. However, they provide little advantage in weaker rock formations where less expensive rings will do the job as well. It is important to choose the correct cutter for the machine and the geological conditions in order to get the best balance of cost and risk.

Jan 1, 2009

Reliable and discriminating small, laboratory scale methods of study have been developed and used successfully in the critical evaluation and interpretation of the carbonization characteristics of a wide range of raw and prepared materials, the variable factors in the coking process, and' the mechanical properties of the carbonized products. The simple and highly economic technologies have been successfully and effectively integrated with detailed surface and subsurface geological exploration programmes (particularly in the coalfields of the .Central Bowen Basin of Queensland) as well as with quality and utilization studies of a nUII!ber of representative Australian and Japanese coals. Previously, only the results of comparatively large, laboratory scale studies have provided information reasonably indicative of those to be anticipated hi industrial practice, but these suffer serious disadvantages in terms of economy of material, time and resources; they have been difficult or even impossible to use as an essential part of any normal or comprehensive exploration programme. On the other hand, although previously developed smaller scale laboratory methods derive considerable advantage from their flexibility, amenity to critical control and inherent potential for speed and economy, they have hitherto permitted no effective or direct comparison with the results of industrial practice or full scale assessment. Comprehensive study results achieved through technologies developed recently at the University 'of Sydney demonstrate that carefully controlled small laboratory scale methods of evaluation quite suitable for use in exploration and, other programmes may be used to predict with considerable accuracy and reliability (in some cases exceedingthat of pilot scale study) the principal strength index of one of the established and internationally recognized full sc:ale tests-the Japanese Industrial-Standard Drum Test. It is probable that further study may establish satisfactory correlations with the results of other standard industrial procedures.

Jan 1, 1969

Following a short review of selected literature, a back analysis of stress measurements of stress regeneration in a closed mini-longwall is shown. The agreement is good, lending confidence to the parameters used in the proposed numerical model. Foundation yielding was modelled in the absence of total stope closure. A ?Prandtl? wedge was formed, coinciding with the yield point of the pillar/foundation system. Some theoretical work is used as a starting point for the formulation of a new design methodology for strike or dip stabilizing pillar/foundation systems in deep level goldmines. The existing guideline for the stability of foundations (APS< 2.5UCS) is critically examined. Finally, the advantages of the new approach, and the work required to substantiate the proposed new design methodology, are outlined.

Jan 1, 1998

By Oliver Bowles

Sandstone, a widely distributed siliceous sedimentary rock, is the third most popular building stone in the United States. It is formed by the breaking down of preexisting rocks by weathering, subsequent segregation of the detrital quartz grains into discrete deposits by the sorting action of water or wind, and finally cementation of the quartz sand into a coherent rock. The homogeneity and resistance to weathering of the resultant sandstone make it suitable for exterior construction. Its excellent wearing properties explain its popularity for flagging and stair treads. However, quarrying and dressing methods and costs are adversely affected by the abrasiveness and hardness of sandstone especially as compared to limestone.

Jan 1, 1963