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By M. K. Larson

The U.S. Bureau of Mines conducted a study to evaluate support interaction between conventional bolts and the rib at two Western coal mines. The principal goal was to develop guidelines for designing rib support under various conditions. At mine A, seven rib bolts were installed with load cells and monitored over a 4-month period. Fifty-seven pull tests were conducted with two types of anchors at various depths. At mine B, 163 pull tests were conducted. Results showed that during the 4 months of monitoring bolt load, tension in the bolts decreased over time in some situations and that anchorage capacity was reduced in a yielded zone. Load-versus-deformation plots from pull tests in the rib showed fundamental differences in anchorage behavior at the two mines, particularly when comparing results of tests in old pillars at mine A and tests in new ribs at mine B. Numerical modeling experiments indicate that coal bonding strength was the most significant factor in determining postyield anchorage capacity. Correlation of anchor yield point with anchor depth were more pronounced at mine A than at mine B; measuring torque may be a reasonable method of monitoring deteriorating anchorage capacity in a rib undergoing fracturing and yield.

Jan 1, 1996

Two of the problems long associated with the complete extraction of level pillars in the wide ore bodies of Broken Hill have been: (1) The high cost of maintaining level gangways through areas of slow subsidence to provide adequate trucking roads for the transport of sand filling; and (2) The difficulty and high cost of completely filling depleted areas. This paper deals with the experiments conducted to devise an apparatus for transporting, with the aid of compressed air, sandfill from the underground sand passes to the stopes and describes the sand blower which has been developed. This apparatus has to a large degree overcome the difficulties and removed much of the hazard associated with the rapid extraction of level pillars.Special attention is drawn to the sizing analysis of the sand and to the fact that it is not dry material. It was early found that these factors were determinants in the design and development of the apparatus described.Acknowledgment is made to the General Manager of Broken Hill South Limited for permission to present this paper, to the engineering department for assisting in the design of the apparatus, and to the underground staff for their co-operation in training the operators and in bringing to success this method of stope filling.PREVIOUS FILLING METHODSThe South Mine, with a monthly production of approximately 32,000 tons of lead-sHver-zinc sulphide ore by cut-and-fill mining methods, requires about 11,000 cubic yards of filling per month. With the exception of a small and variable quantity of developmental mullock, all this filling is...

Jan 1, 1941

By A. M. R. Neiva

The WNW-ESE-trending hydrothermal veins cut alternating mica schists and quartzites of mainly Ordovician age and, to the west, a Hercynian muscovite-biotite granite. They have been prospected and developed to a depth of 300 m and reserves of 20 t Au estimated. The paragenetic sequence and chemical compositions of the ore minerals are generally similar to those at Jales to the south. Gold, electrum and aurian silver form inclusions in arsenopyrite, pyrite, galena, sphalerite, pyrrhotite and quartz and also occur in veinlets that cut these minerals. Silver has been found in gold, electrum, aurian silver, tetrahedrite, freibergite and the Ag-Pb-Sb sulphide owyheeite. Early arsenopyrite crystallised at an estimated 480 degrees C and the more common, later arsenopyrite in which Au and Ag are generally included at 430-300 degrees C. Sphalerite crystallised at 307-100 degrees C. Monoclinic pyrrhotite may have been formed by the inversion of hexagonal pyrrhotite at 248 degrees C

Jun 16, 1905

Used in conjunction with geology and geophysics, geochemistry provides powerful exploration tools of special relevance to Australian environments. New methods are needed that will confront the forthcoming emphasis on locating concealed orebodies. Deep weathering is conducive to techniques using groundwaters or gaseous emanations as sample media. Increasing use is anticipated for isotope measurements and for recognition of country rock characteristics that denote proximity to mineralization. Improvements in the sensitivity, reliability and portability of analytical instruments will underpin the contributions of geochemical methods to future mineral exploration.

Jan 1, 1982

High Pressure Grinding Rolls Scale-Up and Experiences

Sep 13, 2010

By Andre Vervoort

Falls of ground, such as falls of roof and sidewall collapses, are a major cause of fatalities and injuries in South African collieries. Based on information obtained from the accident reports of the various Chief Inspectors of nines, a statistical analysis was conducted covering the period 1970 to 1988. This study shows that the volume of rock in a fatal fall of ground is often quite small. In intersections, fatal falls are on average larger than in roadways and at the face. It was also found that in 36 % of all fatal falls of ground no temporary or permanent support was installed at the site of the accident.

Jan 1, 1990

By F. A. Jones

Increased mechanization .of coal mines has emphasized the need for study of actual power requirements of the various machines employed in the production of coal and losses in the distribution of power to these machines. These studies are being made in order that hazards, excessive use of power, and high maintenance cost of equipment resulting from these losses may be analyzed and eliminated where possible. Research on the use of electric power in-coal mines was suggested by the Advisory Committee of the Bureau of Mines in 1937, and it was decided to begin with a study of individual machines of various types under operating conditions in modern coal mines. The transmission of power, particularly line losses and inadequate return circuits, should be a part of the investigation. This report presents some of the data of an initial study in commercial mines. ACKNOWLEDGMENTS The superintendents, engineers, and other officials of the two mines studied cooperated fully and aided in setting up and transporting the test equipment, giving such information as was requested.

Jan 1, 1942

By F. A. Jones

Increased mechanization .of coal mines has emphasized the need for study of actual power requirements of the various machines employed in the production of coal and losses in the distribution of power to these machines. These studies are being made in order that hazards, excessive use of power, and high maintenance cost of equipment resulting from these losses may be analyzed and eliminated where possible. Research on the use of electric power in-coal mines was suggested by the Advisory Committee of the Bureau of Mines in 1937, and it was decided to begin with a study of individual machines of various types under operating conditions in modern coal mines. The transmission of power, particularly line losses and inadequate return circuits, should be a part of the investigation. This report presents some of the data of an initial study in commercial mines. ACKNOWLEDGMENTS The superintendents, engineers, and other officials of the two mines studied cooperated fully and aided in setting up and transporting the test equipment, giving such information as was requested.

Jan 1, 1942

By Christopher Mark

Pillar recovery continues to be one of the more hazardous activities in underground coal mining. Safety requires that the roof above the intersection remain stable until after the pillar has been extracted. Artificial supports (timbers and Mobile Roof Supports) arc essential to roof stability, but so is the final remnant stump or pushout. Traditional mining practices usually called for the complete extraction of the final stump, but the recent trend (both in the U.S. and internationally) seems to be towards mining plans that leave a remnant stump. For this study, a sample of roof control plans from the Mine Health and Safety Administration (MSHA) Coal Districts were analyzed to determine current pillar recovery practices. Both full- and partial- extraction plans were included. Special attention was paid to whether plans require that a final stump be left, and whether requirements regarding the dimensions of the remnant stump are included. Foreign experience with final stumps is also summarized. It seems that the risk of major pillar falls can often be reduced by leaving final stumps that are large enough to protect the intersection, but small enough that they do not inhibit the caving of the gob. Because final stumps are often irregular in shape, a new approach for estimating their strength is described. Analyses were conducted to assess the effect of seam height and depth of cover on the potential variation in the size of remnant stumps.

Jan 1, 2001

By M. L. Free, L. Anthian

Electrochemical, chemical, and image analysis techniques were utilized together with statistical analysis methods to determine the effect of various anode impurities on copper electrorefining performance. Results indicate that arsenic is a beneficial anode impurity. Anode lead and sulfur are shown to decrease electrorefining performance. Specific emphasis is given to the influence of individual elements on current efficiency, slime particle generation, and cell voltage parameters.

Jan 1, 2000

By K. O. Bennington

Enthalpies of formation of three sodium titanates were determined by hydrofluoric acid solution calorimetry, The values obtained for formation from the elements at 298.15° K are -370.9±0.5 kcal/mole for Na2TiO3, -832.1±0.9 kcal/mole for Na2Ti307, and -1,510.9±1.7 kcal/mole for Na2Ti6013. Tables of enthalpies of formation and Gibbs energies of formation are given as a function of temperature both from the elements and from the component oxides for Na2Ti03 and Na2Ti307.

Jan 1, 1973

By D. H. Horswill

The Red Dog Mine is the world’s largest zinc mine. It is located 145 km (90 miles) north of the Arctic Circle in northwest Alaska on lands owned by the Inupiat Eskimo organization called the Northwest Alaskan Native Association (NANA) Development Corp. NANA acquired surface and subsurface title to this resource as part of its settlement lands under the Alaska Native Claims Settlement Act. In 1982, NANA entered into a lease agreement with Cominco. Cominco is an international mining company focused on zinc. It built and operates the Red Dog Mine. NANA’s principle objective in the development of the mine was to have it contribute to the development of sustainable communities within their traditional region. This meant creating job opportunities in a modern economy while preserving the traditional subsistence lifestyles. Preservation of their culture, language and traditions are as important to the NANA people today as they were in the past.

Jan 1, 2000

By G. Hames, A. Drake, B. Sampson

The Timbarra opencut gold mine is located about 30 km(19 miles) southeast of Tenterfield in northern NSW some 4 hours by car from Brisbane, the capital city of Queensland in Australia. It was a small operation designed to produce about 40000 ounces of gold per annum utilising contract mining and company owned crushing plant feeding heap leach pads. This is a standard setup except that the mine owner was in charge of all aspects of drill & blast design even though a contract drilling & blasting (shotfiring) service was being provided. The major problem was that the blasting operations were yielding massive amounts of oversize due to the jointed partially weathered nature of the granite. This was adversely affecting all downstream aspects of the operation as well reducing gold output as ore boulders were being dozed over the side of the mine as they were impinging on mining productivity. The oversize problem had to be solved as the mine was struggling to achieve design gold output. Significant design & trialing effort using minesite resources were utilised to reduce the oversize but this failed even when powder factors up to 1kg/bcm(1.68lb/yd) were used. Dyno Consult from Dyno Nobel were therefore called to investigate, review & trial options to reduce oversize from the top flitch.

Jan 1, 2003

By F. G. Horino

This report presents the theory and design of a stiff loading machine used by the Bureau of Mines. The machine incorporates three high-strength steel columns as the restraining member in parallel with the specimen. The theory presented gives the basis of design and the dimensions of component parts of the machine. Laboratory verification of the theoretical stiffness is described using three different setups involving a hydraulic jack and spacers and confirms the stiffness calculations to within 1 percent. Experimental techniques, testing procedures, and special equipment designed for determining the complete stress-strain behavior of NX cores of both hard and soft rock are described. Typical test data are presented as force-displacement curves for two rock types, a marble and a granite.

Jan 1, 1972

By Tsunenobu Nozaki

"AbstractThe PRESS-IN METHOD is widely recognised as “an environmentally friendly piling method”. However, this characteristic is only one of the fundamental advantages of the method and this paper presents the most up-to-date capabilities of the method. Due to the evolution in recent years, the Press-in Method is now applicable to 2.5m thick retaining walls, over 50m deep foundations, overcoming rock conditions and confined construction conditions.The Press-in PrinciplesThe basis of the Press-in Method is simple. The Silent Piler presses a pre-formed displacement pile into the ground by static jacking force. The reaction for the Press-in Force is generated by gripping previously installed piles. As a pile is pressed into the ground, “A Pressure Bulb” is formed around the pile toe. Accordingly, higher bearing capacity can be generated compared to driven piles without disturbing the ground and producing any vibration. (A comparison of jacked, driven and bored piles in sand (2005), Deeks et al.)Applicable Pile ProfileThe Press-in Method is applicable to most of the steel piles available on global market i.e. U sheet pile in single form and pair, Z sheet pile, also in single and pair and Tubular Pile as described in Figure 2. Wall thickness of those piles can be 0.3m to 2.5m and moment of inertia of the wall ranges up to about nine million biquadratic cm per meter, which can deliver similar elastic modulus EI (kNm2/m) to 2.0m thick diaphragm walls and can be utilised for extremely deep excavations required in today’s construction industry"

Jan 1, 2014

Hoisting ropes are constructed of wires and strands positioned helically around the axis. This helical positioning causes that, in the rope loaded at the end with the weight Q, the longitudinal displacement u, axial force P, torsional displacement v and constant torsional moment M are generated. More over, the proper weight of the rope q gives the force acting along the axis of the rope. This force changes its value from 0 at the bottom to qL at the top. This force gives, along its length, a variable torsional moment making the rope rotate. During the movement of the conveyance downwards the falling part of the rope rotates, which makes it untwist on the section up to the half-depth of the shaft and twist on the other half-depth. As the result, the twisting lay of the rope changes increasing in the upward direction and decreasing downwards. The angle of twist of the strands changes in an apposite way. When moving upwards, the uplifted rope does not twist and retains its state of deformation up to the moment when it passes over the pulley. Next, the cycle of untwisting and twisting repeats during the movement of the other conveyance downwards. This phenomenon is known from mining practice. It was also analysed, in the works of Glushko (1966) and Popowicz (1963).

Jan 1, 1995

By H. H. Einstein

This paper reviews how uncertainty has been dealt with over the past 40 years using the decision making cycle as a frame of reference. The review of the phases of this cycle, as applied to rockmechanics and rock engineering, namely characterization, performance analysis, updating and decision making shows that in each, progress has been made over the past 40 years, although most of the basic concepts existed already in the 1960’s. Characterization is the area in which the greatest scientific steps were taken, this phase and performance analysis also gained from the tremendously expanded computational capabilities which allow one to use both more complex and more practically oriented models. The greatest practical advance is without using any doubt in risk based decision making although its acceptance shows interesting differences between different professions. Dans l’article suivant on utilise le cycle de décision pour illustrer le développement du traitement des incertitudes en mécanique des roches et en construction en roche dans les quarante années passées. La revue des phases du cycle de décision montre qu’on a fait du progrès dans chaque phase du cycle de décision, c’est à dire dans la caractérisation, dans l’analyse et la prédiction du comportement, dans l’actualisation et dans l’acte de décision, même si les concepts fondamentaux existaient déjà dans les années 1960. Les plus grands avancements scientifiques se trouvent dans le domaine de la caractérisation tandis que l’analyse prédictive profitait du développement de l’informatique qui a mené à des modèles plus complexes mais aussi plus pratiques. Le plus grand progrès est sans doute dans le domaine de l’acte de décision sur la base des risques. Ce procédé est devenu assez commun même s’il y a encore des différences d’acceptation entre différentes professions. Im vorliegenden Artikel wird der Entscheidungszyklus gebraucht, um darzustellen wie sich derUmgang mit Unsicherheiten im Felsbau während der letzen 40 Jahre entwickelt hat. DerÜberblick über die Phasen des Entscheidungsprozesses zeigt, dass bei der Anwendung in derFelsmechanik und im Felsbau, in allen Phasen d.h. bei der Charakterisierung, bei der analytischenVorhersage, beim Aktualisieren und bei der Entscheidungsfindung Fortschritte gemacht wurden,obwohl die grundlegenden Konzepte bereits in den 1960er Jahren existierten. Im Gebiet derCharakterisierung gab es wohl die grössten wissenschaftlichen Entwicklungen, während dieanalytische Vorhersage vor allem von den Fortschritten der Informatik profitierte, welchekomplexere wie auch praktischere Modelle möglich machte. Der grösste Fortschritt ist ganz sicherin der Entscheidungsfindung zu beobachten, wo Risikobetrachtungen gang und gäbe sind, obwohlhier noch einige Unterschiede zwischen verschiedenen Berufsgattungen zu finden sind.

Jan 1, 2003

By Gary A. Kingston

Low-cost hydroelectric energy in the Pacific Nortnwest has been an important factor in the development of a ferroalloy industry. Eleven companies, employing approximately 1,000 persons, produce about 116,000 tons (1954-58 average) annually of ferrosilicon, ferrochromium, ferromanganese, ferrophosphorus, silicomanganese, and ferronickel. About 7,500 tons (1954-58 average) of these ferroalloys is consumed in the Pacific Northwest States of Washington and Oregon; the rest is used principally in other western and mid-western markets. In 1959, the Bureau of Mines began a study to determine the current status and to evaluate the potential of the ferroalloy industry in the Pacific Northwest. The Bureau gathered information from operating alloy plants in Oregon, Washington, Idaho, and Montana; from published materials; and from consumers of ferroalloys.

Jan 1, 1962

By Timothy M. Bruner, William J. Maloney

Faced with rapid growth that strained their current water supply capabilities, the Somerset Water Service in Somerset, KY decided to construct a new intake structure on the shore of Lake Cumberland. With an existing intake structure within 200', very hard limestone geology with calcite geodes, and lake level fluctuations as high as 50 ' ,this project posed many challenges. The following paper discusses how mechanical excavation techniques were used to overcome these obstacles.

Jan 1, 2001

By Stephen C. Tadolini, Dennis R. Dolinar

The risk of injury caused by minor roof falls continues to increase in underground mining. Most ground control injuries result from small rock falls that occur in a supported area, but do not involve the failure of the support system. In the roof, these are the "skin failures" that occur between previously installed primary or secondary bolting systems. To minimize skin failures and the associated accidents, several devices were designed and tested in the laboratory to maximize stiffness, minimize material thickness and weight, and ease material storage and handling on roof bolting machines. The goal of this project was to design and evaluate devices that can be installed with traditional primary or secondary roof supports, and that are easy to handle/install under temporary or previously supported roof.