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By Heinrich Ries

Jan 1, 1907

By P. R. Sheorey

I read this interesting paper on pillar strength in some detail because this is also my area of interest. It has long been the desire of mining rock mechanicians to predict pillar strength from laboratory compression tests. Considerable literature is available on compression strength of rocks and coal but many of these experiments were conducted not for pillar design but for rock behavior. I have a few comments on the author's approach to pillar design, especially equation (33). Two important factors, which the author seems to have excluded, can be added to the right side of equation (2): time-dependence of strength and the influence of mine environment on strength (moisture and weathering.) The author has taken considerable pains to analyze a large amount of testing data in [Table 1], yielding the various exponents ci of equation (2) (or the subsequent equations derived from it.) He has, however, not shown by means of a worked out example how these values of [Table 1] could be applied to a practical pillar design situation. It would have been interesting to compare predicted pillar size using equation (33) with an actual case. Alternatively, equation (33) could have been used to explain the failure of a pillar, if such a case history were available. Consider we have a large number of case histories of stable and collapsed pillars in a seam and we conduct a large number of tests in a laboratory press. The exponents [ci] can then be determined for actual pillars as well as for test specimens. Thus, equation (2) will read [ ] Since laboratory testing conditions (e.g., between steel platens) are different from the conditions on pillars, the exponents [ci] in

Jan 1, 1983

By T. B. Massalski, Horace Pops

Martensitic transformations were observed by optical metallography and electrical-resistivity measurements during cooling at cryogenic temperatures of the bcc pr-phase Au-Zn alloys. The com-position dependence of the MS, MF, AS , and AF temperatures have been determined. It is concluded that the martensitic platelets which grow mainly in the lengthwise direction and which are associated with a very small temperature hysteresis are "thermoelastic" martensite. In some cases the observed structure seems to have no definite crys-tallographic habit or consists of a mixture of- plates and broad transformed areas. THE majority of the bcc /3-phase alloys in systems of copper, silver, and gold with zinc and cadmium are unstable at low temperatures and undergo a transformation upon further cooling into another structure. A large number of such transformations are martensitic. The composition dependence of the Ms temperatures has been determined and reported for CU-~n,' Ag-Cd,' and AU-C~~ alloys. The 50 at. pct ordered Au-Zn p' alloy has been reported by Jan and pearson4 to transform martensitically at 58°K in connection with their study of the de Haas-van Alphen effect The p' phase in the Au-Zn system has the ordered CsC1-type structure. The phase field is shown in Fig. 1: it has the typical V shape which is characteristic of all copper-, silver-, and gold-based binary /3-phase alloys. There appears to be no a priori reason why the transformation should be limited to the equiatomic composition and the availability of a cryogenic stage for optical metallography5 has permitted studies down to the liquid-helium temperature of a series of alloys in this system. EXPERIMENTAL PROCEDURE Predetermined weights of 99.999 pct pure gold and zinc were melted and cast under a partial atmosphere of helium in sealed quartz capsules. Thorough mixing of the molten metals was achieved by vigorous shaking, followed by a rapid quench into a brine solution. All ingots were homogenized at 640°C for 4 days. The loss in weight was usually less than 0.04 wt pct and was assumed to be due to

Jan 1, 1965

By Frank C. Frischknecht

Most early development and application of electromagnetic prospecting methods took place in Scandinavia, where geological conditions favor their use. In other parts of the world these methods have aroused cycles of interest, but in Scandinavia they have been used continuously and successfully since the 1920's. Electromagnetic methods may be classified into two general groups. One group includes methods in which the source of the electromagnetic field remains stationary while the receivers are moved about to explore the area. The other includes procedures in which the energizing and receiving systems are moved together. Other classifications could be based on the size of the energizing source, the particular components of the electromagnetic field which are measured, or the mode of trans- porting the equipment. The difference between fixed-source and moving-source methods, however, is of such great fundamental importance that it will be emphasized in this discussion.

Jan 9, 1959

By Brian White, Hamid Maleki

Sudden, violent failures of rock around mine openings influence access, ventilation, and safety in both hard-rock and coal mines. To develop predictive tools for assessing the potential for violent failure, the authors initiated a comprehensive study using (1) multiple linear regression and numerical modeling analyses of geological and mining conditions at 25 sites to identify the most significant factors contributing to stress bumps in coal mines and (2) investigations of the geological and mining factors contributing to rock bursts in the Coeur d'Alene Mining District of northern Idaho, particularly the influence of preexisting structures on rock bursts. Twenty-five factors were initially considered in the study of coal bumps. The most important variables were identified as (1) mechanical properties of strata, (2) gate road geometry and/or gate pillar factors of safety, (3) roof beam thickness, joint spacing, and stiffness characteristics, and (4) stress gradients associated with previous mining and anomalous geologic conditions. In the Coeur d'Alene district, burst damage related to preexisting structures results primarily from (1) sudden buckling and crushing of rock layers where surfaces of development and production openings lie at low angles to bedding, faults, or other planar structures and (2) disturbance of loose ground caused by seismic fault-slip on preexisting faults or previously sheared bedding planes that intersect veins near pillar-stope margins.

By J. K. Whyatt

Assuring ground control safety in many mining and tunneling projects depends, at least in part, on an understanding of in situ stress conditions that will be encountered. Yet it is rarely practical to conduct more than a very limited number of stress measurements. Stresses along the route of a proposed excavation are typically interpolated from available measurements, often assuming a linear variation of stress with depth (or elevation). However, projects where multiple stress measurements are conducted often report more complex variations of in situ stress, usually in apparent relationship to geologic structures. These structures often include lithologies of contrasting elastic properties. A method is proposed for estimating stresses in these cases by first back-calculating regional loads from available stress measurements and then modeling the distribution of stress throughout the rock mass. The method has been successfully applied to a set of in situ stress measurements from the Coeur d’Alene Mining District of northern Idaho, USA. Results provided new insights into district stress conditions and the distribution of rockburst hazards along mine drifts and between various mines. This success should transfer readily to suitable deep tunneling projects.

The increasing transportation of solids by pipeline, in South Africa and internationally, replacing the conventional transportation methods of rail, road, and conveyors, has resulted in much research into this area of solids transportation. Pipeline wear continues to be an area of specific concern, since it constitutes a major cost during the life of a pipeline installation. Wear data from an accelerated wear test and actual pipeline tests are presented. Trends in the performance of the pipeline materials tested are discussed, and possible solutions to the problem of pipeline wear are presented.

Jan 1, 1992

By Ibrahim AR

The experimental phosphate mine of abu Tartur has been recently placed into production. Some problems'have been encountered in maintai- ning grade control due to the differences between early block estimates and actual produ- ction grade. An area of 100 km2 is evaluated by using four methods of evaluation , namely polygonal, inverse distance , inverse distance squared and geostatistical methods. The results of calculations are compared statistically with the control values of grade and thickness. The comparison showed that the. kriging technique gave better estimations for the relative ore reserved, while for grades or thickness any of these techniques except the polygonal can be Used.

Jan 1, 1986

By Fred P. Giese

Southeastern reserves of titanium ores are large, widespread, and ample for anticipated demand. The leading titanium industries are mining and beneficiating sand deposits, principally in Florida, and manufacturing titanium pigments. Most of the mineral output is consumed by the producers themselves. In 1962, 20 percent of the national pigment capacity was in the Southeast.

Jan 1, 1964

By M. G. Corson

UNTIL recently, the characteristics of cast copper have seldom been studied and such study as has been made has been inadequate. The prevailing idea seems to be that since pure copper is infrequently used in the cast state, there is no reason for trying to establish precise data regarding the properties of the metal in that condition. On the other hand, wrought copper either in the shape of sheets or wire rarely fails in service, except as a result of the action of reducing gases at the annealing temperatures, so there is little incentive to study the properties of the cast shapes -cakes, bars, ingots and billets-for the sake of tracing the causes of failures of the wrought metal to the cast stock. However, about a decade ago, wirebars of American origin often cracked badly while being hot-rolled in mills in Germany. This led to four investigations: by E. Seidl and E. Schiebold,1 by P. Siebe,2 by 0. Bauer and G. Sachs,3 and by G. Welter.4 These authors came to the conclusion that failures in hot-rolling were due essentially to the presence of a' wide zone of columnar crystals between the thin layer of fine crystals near the surfaces of the bars and the large but more nearly: equiaxed grains of the central core. This macrostructural defect was explained in turn by the probable upward deviation in the temperature of the metal while it was being poured into the molds of the casting machine. More recently, cast shapes of copper were investigated by N. P. Allen5 and by C. Blazey.6 Allen examined vertically cast wirebars and horizontally cast wedge cakes of electrolytic tough-pitch copper, but only for the distribution of densities; i.e., porosity. Blazey was interested mainly in the mechanism of the variations in electrical conductivity due to cold-work and anneal, but gave introductively an account of the composition and average densities of the tough-pitch horizontally cast wirebars used. As far as the present writer can tell, no investigation was undertaken for the sake of presenting a picture of the distribution of mechanical characteristics in the wirebars of copper, tough-pitch or otherwise.

Jan 1, 1938

By J Sibbel, K Goh

A key issue facing mine managers in remote locations in Australia and overseas is that of managing a fly-in, fly-out (FIFO) workforce. Current Australian research (Sibbel, in prep) indicates that FIFO employees and their families do not differ from the general population in terms of their overall mental health and the well-being of their family relationships. However, they do face unique issues/pressures associated with the lifestyle, the impacts of which are dependent on the policies and practices of the company as well as individual coping and support mechanisms. Successful management of a FIFO site and its employees therefore requires specialist knowledge and skills beyond those of a solely residential operation. The well-being of the FIFO workforce depends on both site and individual employee characteristics, and has implications for productivity and turnover, as well as safety and health. In addition, although FIFO separates individuals and their families in time and space, the interaction between work and home must be acknowledged and taken into account. Drawing on findings from recent Australian and international FIFO research (eg Annear, Poot and Kingston, 2006; Beach, Brereton and Cliff, 2003; Brereton et al, 2006; Gallegos, 2006; Keown, 2005; Parkes, Carnell and Farmer, 2005; Sibbel, 2001, 2004, in prep; Shrimpton and Storey, 1996; Storey, 2001; Watts, 2004) this paper discusses key understandings of both the positive and negative impacts of FIFO employment on employees and their families, and provides practical management strategies as an aid to the development of best practice. Individual impacts including fatigue and loneliness, as well as family issues such as communication, continually changing roles and responsibilities and the impacts of regular parent absence are key areas which can be ameliorated by appropriate management understanding and action. A flexible framework approach is presented that is suitable for a diversity of operations, including principal and contractor workforces of different sized operations.

Jan 1, 2006

By Lawrence W. Scott

This report presents several systems for continuously monitoring the quality of air in underground mines that are being developed by the Bureau of Mines. Underground stations measure methane, carbon monoxide and nitrogen dioxide concentrations, air velocity, and air temperature. This information is transmitted over a single telephone pair to central stations located on the surface. The central stations display alarms and the data is selectably displayed on digital panel meters.

Jan 1, 1977

Base metal sulphide mineralisation on the northern end of Great Barrier Island is spatially associated with hypabyssal intermediate to acidic intrusives, in transgressive structures in indurated, complexly deformed greywackes and argillites. Copper predominates in the mineralisation, with minor accompanying lead and zinc and also some gold and silver. However, in some cases lead or zinc may be the dominant constituent. The mineralisation is generally characterised by only narrow envelopes of weak alteration (propyliticassemblages dominated by chlorite and epidote) and with only minor amounts of quartz accompanying the sulphides, which form a cement in zones of hydraulic fracturing. There are two distinct structural settings to the mineralisation: at MinerÆs Head, in a structurally complex situation in a shell-like zone of crackling in hornfelsed greywacke, in association with both north- and east-striking fractures and rubble breccias associated with the apical part of a large intrusive; and in very narrow, but very strike-persistent, 1inear steeply-dipping fracture zones, exposed on the north coast and inland areas near Tataweka.

Jan 1, 1984

By Ronald J. Roman

All mining and milling complexes can, within limits, operate at a variety of production rates. Factors of economic importance that are affected by production rates are costs per unit production, recovery and product grade. Once the relationship between the production rate and cost is established, dynamic programming techniques can be used to define the optimum production schedule (that is, the production schedule that maximizes the present worth of the operation) for the life of the deposit. In general, assuming that the capacity and efficiency of the physical plant remain unchanged throughout the life of the deposit, the optimum production rate is not constant for the life of the deposit, but declines gradually as the deposit is being exhausted.

Jan 1, 2014

By Zay Jeffries

This paper will include a brief discussion of Prof. Howe's paper on The Supposed Reversal of Inheritance of Ferrite Grain Size from that of Austenite.l The general subject of grain refining in steel and iron will also be treated. The conclusions reached are stated in the following hypotheses which are discussed more in detail below. 1. The ferrite grain size in pure iron, the ferrite and pearlite grain size in hypoeutectoid steel, the pearlite grain size in eutectoid steel and the cementite and pearlite grain size of hypereutectoid steel are not inherited from the grain size of the mother austenite. 2. The only structural feature that is generally inherited from the austenite of hypo- and hypereutectoid steels on cooling through their transformation ranges is the position of the excess ferrite or cementite at the austenite grain boundaries, sometimes causing complete and sometimes incomplete networks which outline the old austenite grain boundaries. Rapid cooling through the transformation range will cause the non-inheritance of this structural (network) feature. 3. The austenite grain boundaries themselves are nearly always effaced in all steels and also in pure iron during the At transformations. 4. The grain-size refining of steel and iron is brought about by the combined effect of non-inheritance of the transformation products on either heating or cooling, i.e., the austenite transformation products do cst inherit their grain size from the austenite on cooling through the transformation range nor does austenite inherit its grain size from the products which form austenite on heating. 5. In general, in both iron and carbon steel the larger the austenite grain size, the larger will be the grain size of the transformation products on cooling. This, of course, assumes all other conditions constant except the austenite grain size. An exception is found to this general rule in very pure iron such as electrolytic iron. In this instance small austenite grains may form very large ferrite grains on cooling through Arg.

Jan 1, 1918

By A. K. Bakshi

An on-line rheometer, suitable for use with slurries, has been developed at Michigan Technological University. This rheometer can be used with both Newtonian and non-Newtonian slurries, and produces complete shear-rate/shear stress curves which characterize the time-independent rheology of the slurry. The sensor utilizes the Hagen-Poiseuille equation and Boyle's Law to calculate the shear rate, slurry flowrate, and shear stress from a series of pressure measurements. The design of the unit allows the measurement sample to be continuously collected from operating process streams in the often-hostile on-line environment. The shear rate/shear stress curves can be used to conveniently calculate the apparent viscosity at any given shear rate, and also to measure any yield stress or other deviations from Newtonian behavior.

Jan 1, 1999

By Richard Deakin

This case study describes aspects of the design of bridge foundations using 320mm diameter steel tube piles in the vicinity of Montréal, Canada. In this area, these piles are a very commonly used and cost effective solution for deep foundations. Typically they are driven through thick Champlain Sea Clay to bear onto stiff, strong rock. However, in some locations there is a layer of glacial till between the base of the clay and the rock which cannot always be fully penetrated by the piles. There is currently little published information, about the bearing capacity of these piles in the local till, and this paper presents and discusses some pile-test data from a recent project. The nature of the glacial deposits in the study area is presented using information gained from published geological data, the project ground investigations and site observations. The design approach and assumptions are discussed, together with the aims and outcomes of preliminary field driving trials and pile tests. The paper then discusses the results of dynamic tests undertaken on production piles. Bearing capacity factors are back analysed from the dynamic test results and compared against values assumed within the design. Observations are made that designers of future foundations in similar conditions may find informative.

Jan 1, 2011

The latest in mining technology and equipment will be show-cased this month at MINExpo International 2004. The event, billed as the world’s largest mining equipment exhibition, is set for Sept. 27-30at the Las Vegas Convention Center. MINExpo, sponsored by the National Mining Association (NMA), is held every four years in Las Vegas, NV. This year’s event is expected to attract more than 40,000 mining industry professionals and executives from around the world. And several key members of the U.S. Congress and other senior government officials are expected to attend. In addition, senior industry and government officials from Asia, Europe, Australia, Africa and South America will be on hand.

Jan 1, 2004

By J. P. F. Charpin

The transport of large boulders in a furrow from a mining area to a nearby pond was considered. The furrow is filled with a mixture of water and soil particles flowing down to the pond at high velocity. Due to operating constraints, the slope of the furrow is reduced progressively. A relationship is derived, relating the slope of the furrow and the composition of the fluid to the maximum size and shape of the transported boulders. The characteristics of the boulders carried all the way down to the pond may then be determined.

Jan 1, 2007

By Mike Zimmermann

With the steady decline in the production of dynamites throughout the world, a gap appeared in the market which could only be adequately filled by rigid paper packaged explosives. To fill this need, the Dri-Gel technology, which is the subject of this report, was developed.

Jan 1, 1998