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By Chen Lin

Tectonic stress is an important parameter for understanding the dynamics of underground engineering and for the exploitation of coalbed methane. Multiple-period structural features usually have complex spatial relationships in tectonic superposition areas, which provides evidence for identification of the sequence of the tectonic stress period. Conjugated joints and slickensides are used to reconstruct the tectonic stress of the No. 8 Mine in Pingdingshan. Based on the geological unit division and field measurements, data on hundreds of joints and slickensides are collected from 33 stations. The tectonic stress results indicated by the conjugated joints show that there are mainly four directions of tectonic stress: NEE-SWW, NW-SE, NE-SW, and NNESSW. The tectonic stress results of the slickensides indicate that there are mainly four directions of tectonic stress: NNE-SSW, NNW-SSE, NEE-SWW, and NW-SE. According to the systematic analysis of the joints and slickensides, this paper separates the superposed joint and slickenside sets and identifies the tectonic stress periods with their abutting relationships. Three tectonic stress periods are determined and the sequence of the tectonic stress periods is NE-SW, NW-SE, and NEE-SWW. The results are consistent with other tectonic stress measurements for both the region and the locality.

By Doris M. Hyde

In the past, mining has represented between 11% and 12% of the gross domestic product (GDP). In 1982, mining contributed over $150 million to the estimated $1.4 billion GDP.2 Overall economic growth for 1983 was projected at about 2%, primarily as a result of increased tourism. The inflation rate remained at or fell below the 1982 level of almost 4%. The Government continued its efforts to strengthen the industrial base by improving infrastructural systems and the establishment of a free trade zone. Laws against property ownership by foreigners or foreign-owned companies were strengthened, but the prohibition was softened to allow for close family inheritance. Otherwise, Government approval must be obtained to retain property acquired through inheritance, court order, mortgage, or other means. Special consideration was granted to foreign investors seeking to promote industries beneficial to the economy.

Jan 1, 1985

By M. K. Larson

The U.S. Bureau of Mines and Cyprus Shoshone Coal Corp. conducted a study of deformation mechanisms in strata around a longwall gate road system at two sites in an underground coal mine near Ham, WY. Of particular interest was timedependent (on the order of several months) roof deformation. Strata above and below the coal seam are very weak, carbonaceous mudstones that have cohesionless planes of weakness oriented along bedding, which dips approximately 8° to 16° at N 49° E. An extensive array of instrumented roof bolts, roof extensometers, and biaxial stressmeters were installed during development mining at these two sites under variable depth of cover [I83 to 335 m (600 to 1,100 ft)], seam dip (10° to 16°), and top coal thickness [estimated to be 0.30 to 0.61 m (1 to 2 ft) on the downdip side of the entry]. Bolt load and roof deformation histories during the entry development periods were compared. Bolt loads at site 2 were less than those at site 1, which is consistent with the amount of overburden. Deformation magnitudes at site 2 were similar to those at site 1, but deformation rates were approximately 44% greater and nearly constant over time, whereas the deformation rates at site 1 decreased exponentially over time. Also, most deformation occurred above the bolt horizon at site two, but extensometer measurements at site 1 showed that a significant amount of deformation occurred within the bolt horizon. The most significant factor that influenced bolt tension and timedependent strata deformation was strength and Young's modulus of the strata. Finite-difference models support this conclusion.

Jan 1, 1996

In the course of work being carried out in the Lubricants and Bearings Section of the Council lor Scientific and Industrial Research on the production of copper4ead 'bearings for 'use in aircraft, it has been found necessary to develop special metallographic methods. For proper control of the production of steel-backed copper-lead bearings it is necessary to adhere to rigidly controlled conditions, and it is essential that a method of examination be adopted which will readily detect actual defects or any variations in quality. Some defects can be observed with the naked eye, whilst others are detected by radiographic examination. This latter method is invaluable as a rapid, reliable test in the production of aircraft bearings, but it is necessary to observe the structure of the alloys under the microscope, both to be able to interpret the radiograph correctly and to determine what has occurred to the metal during and after solidification. The use of a sound metallographic technique is'particularly important in developmental work and research connected with these bearings.Polishing TechniqueCopper and lead are practically immiscible in the solid state, but whilst they are miscible only in certain limited proportions in the liquid state; consequently "alloys" of copper and lead consist of a mixture of the constituent metals. The metallographic difficulties are obvious. Copper is a relatively tough metal, although it readily scratches, whilst lead is extremely soft and easily deformed. It wouId be expected if any normal polishing technique were applied that the lead would be readily torn out of the surface being prepared, and, in addition, that the lead would tarnish very easily.Grange(2) has described a method by which these difficulties can be overcome. The method involves an etch-polish procedure using "chrome regia" as an etchant for the copper. The chrome regia was a solution of chromium trioxide and hydrochloric acid in water. This type of etchant has been adopted, but it was found necessary to make certain changes.The method now adopted in this laboratory is as follows: The specimen (which is usually mounted in bakelite) is wet ground in a series of successively finer Hydro-Durexsil emery papers down to 60.0· grit paper.The specimen is then etched in the chrome regis, etchant (the composition of this etchant will pe discussed later) for approximately five seconds.Most efficient etching is obtained by swabbing the surface of the specimen...

Jan 1, 1944

By A. W. Khair

Laboratory studies indicate that the specimen size influences the compressive strength of coal significantly. In the past, the diameter/height ratio of coal and rock specimens with different geometry and its influence on failure characteristics was discussed (Khair, 1993; Khair, 1994; Khair and Xu, 1994). In the current attempt, tests are designed and carried out under uniaxial condition in the laboratory to investigate the influence of specimen size. Cubical specimens of coal with edge dimension ranging from 5 cm (2 in.) through 20 cm (8 in.) were prepared according to the standards and tested uniaxially. Results show that compressive strength of coal is dependent on specimen size until certain level and later the change in specimen size would not yield significant change in compressive strength. Cubical specimens were chosen for testing because they are not only in close resemblance to underground pillars, but they are also the most stable shape under loading. The failure characteristics of these specimens were analyzed and their applicability to pillar design aspects in coal mines is studied. A detailed analysis of the physical and mechanical properties of the tested coal seam is also presented.

Jan 1, 1996

By Jochen Belz, Allan Henneker, Nod Clarke-Hackston

For the construction of tunnels and other underground structures, extraction of the exact amount of material is of paramount importance both economically and for engineering purposes. In the Sequential Support Method (NATM) immediate (sequential)and smooth support by means of shotcrete, steel arches, lattice girders and rockbolts, either singly or in combination are used; cutting of the precise (albeit sometimes of complex geometry) profile is an integral part of the method. In order to save unnecessary excavation and provide better information to the machine operator, VMT GmbH has developed a system to support precise excavation of the tunnel profile when using road headers or other partial face cutting machines. This paper outlines the principles of this system with examples from Australia, Ger-many, Sweden and Spain and will cite examples of typical savings achieved.

Jan 1, 2007

By Charlie Brumbaugh

Antarctica with its diverse conditions such as severe cold, high winds, rock and ice structure and limited explosives available posed many obstacles. This paper will give an overall view of the methods used to overcome these obstacles on a daily basis on the highest, driest, coldest continent on earth.

Jan 1, 2000

By William R. Barton

Anthracite has been mined from the Narragansett Basin of Rode Island and Massachusetts sporadically, and with limited success, for more than 170 years. Beginning in 1974, interest in the coal of the Basin was renewed because of increasing prices and supply uncertainties involving petroleum products. During 1974-77 the Bureau of Mines analyzed 28 samples of Basin coals and conducted washing tests on 20 of them. Results, reported herein, indicate that the coals are low-sulfur, moderate- to high-ash anthracites and semianthracites, suitable for physical preparation to a product generally containing less than 10 percent ash. Additional exploration, sampling and testing will be required to permit appraisal of the potential value of the Narragansett Basin coal resources.

Jan 1, 1977

By C. Lorimer Colburn

"The diverting of men from industry to combat in the world's war focused the attention of the operators in this country upon mechanical means of doing things. The demand for man-power -was so insistent that every available agency for multiplying it had to be employed. It was during the 1period of the war and immediately thereafter that development of the use of underground loading devices made most rapi4 progress. In all parts of the United States, mining engineers and mine managers were diligent in their efforts to develop mechanical loaders. The mining engineers of the U. S. Bureau of Mines in every section of the country have secured, with the cooperation of the mine operators, data on the actual performance of the mechanical shovels in their districts, and have made them available to the author of this paper.No effort has been made to discuss exhaustively the subject of underground loading devices. It has been the object to collect together in one paper, records of the performance of all machines now in actual use. Improvements in the design of machines are constantly being made the performance records given in this paper relate to operation prior to March 1 1 1921. The records prior to 1920 cay not fully represent the work that could be accomplished with the present models of the same machine.The data secured are given exactly as reported by the mine operators. Since this data were collected there have been two underground loaders, of a different design, put into operation in the iron mines of the Lake Superior District. One is the John Mayne Sub-level loader, being tried by the Cleveland-Cliffs Iron Co., Ishpeming, Mich., and the other is the Cole-Goudie shovel, being tried by the Oliver Mining Company, at Ironwood, Mich. No information has been secured regarding the performance of either of these machines."

Oct 1, 1921

By G. M. Molinda

Ground Penetrating Radar (GPR) is being investigated for the potential to determine roof hazards in underground mines. GPR surveys were conducted at four field sites with accompanying ground truth in order to determine the value of GPR for roof hazard detection. The resolution of the current system allows detection of gross roof fractures (>63 cm (s1/4 in) zone) or rider beds in coal measure roof. Data quality is not yet sufficient to detect small bed separations or subtle lithologic changes in the roof. Differences in data quality are discussed, as well as suggestions for collecting improved data.

Jan 1, 1996

The pressure of low commodity prices forced the design process for the second lift of Northparkes E26 Mine to adopt a continuous improvement philosophy. The emphasis was to minimise capital expenditure while still maintaining the excellent low operating costs achieved on Lift 1. Although the first block cave lift at Northparkes is the most productive underground mine in the world and is held up as a benchmark for the use of technology in mining, areas for improvement were identified. Every area was critically assessed and investigated for the possible application of new techniques and technologies. Key learnings from the construction and production phases of Lift 1 were captured, documented and used as the starting point for the Lift 2 design. This paper shows how and why the design parameters initially used onLift 1 were changed to become the current E26 Lift 2 developmentproposal. The main differences between the two block caves arehighlighted. The alternative techniques and equipment that wereconsidered are also discussed. * Originally published in the Proceedings of MassMin 2000,published by The AusIMM.

Jan 1, 2001

In today?s high tech world, systems are getting bigger, faster, better. To remain at the leading edge, in any business, depends on accurate but flexible design thereby allowing operational managers to provide alternatives to improve their operations. The ultimate goal is to deliver to plan, with optimum economics. Mining is no different, with falling prices and escalating costs, improved margins become the focal objective. There are many ways to achieve this, ranging from operational efficiency improvements through production scenarios to planning initiatives. Of all, planning usually receives the least attention, yet it is the area of most influence on the NPV of the reserve. With computer technology, numerous concepts and iterations are possible thereby closing the gap between optimal and actual design. This paper discusses the application of the split shell design at the De Beers Venetia open pit in South Africa.

Jan 1, 2001

By Eder Salazar

El presente texto describe la optimización de la productividad en la empresa minera a través de la mejora contínua en la cadena de valor en SMEBSAA, los siete pasos de la calidad, proceso de mina, planta, soporte y la cuantiificación de dicha mejora en la cadena de valor en SMEBSAA. Asimismo, la implementación de los diversos sistemas de gestión refuerzan los resultados, siendo el Sistema de costeo basado en actividades el gran agrupador de toda la información de los módulos: Logístico, Control Patrimonial, Orden de Servicio, Planillas y Contabilidad.

Sep 12, 2005

By E. J. (Kirk) Conway

The objectives of this project were to: (1) determine the extent to which maintainability design concepts and principles have been applied to the design of underground coal mining equipment, (2) try to assess its impact on productivity and personnel safety, and (3) develop maintainability guidelines to enhance the design of new or rebuilt equipment. An equipment design review was completed at ten operational coal mines. The purpose was to identify design approaches and features that enhanced and degraded the maintenance process. Mine management, safety, and maintenance personnel were also interviewed to identify machine specific design problems. Six original equipment manufacturers were visited and the procedures used to enhance the maintainability of Their equipment discussed. Volume I of the Final Technical Report presents an overview of procedures and protocol used and a summary of the findings. Volume II includes the maintainability design guide for mobile underground mining equipment.

Jan 1, 1988

By K. J. Liles

Research was undertaken by the Bureau of Mines to determine the technical feasibility of producing lightweight aggregate from the waste glass fraction of municipal incinerator residues. Tests were conducted to determine the amount and optimum size of glass, the amount of sodium silicate, and the method used to form the material to be expanded. The most suitable mixture, 78 percent glass, 20 percent clay, and 2 percent sodium silicate, was pelletized and then expanded by exposure to a temperature of 1,550° F for 15 minutes The resulting lightweight material had a bulk density of 38 lb/cu ft and exhibited excellent pore structure. Concrete test cylinders made from the light weight aggregate had a unit weight of 104 lb/cu ft and a compressive strength of 2,550 lb/sq in after a 28-day steam cure.

Jan 1, 1976

Jan 1, 1967

By K. H. Coats, M. H. Terhune

Analysis and example applications have been performed to compare the accuracy and computing speed of alternating-direction explicit and implicit procedures (ADEP and ADIP) in numerical solution of reservoir fluid flow problems. ADIP yields significantly greater accuracy and requires about 60 per cent more computing time than ADEP, not 300 or 500 per cent more as reported elsewhere. l,2 INTRODUCTION Several recent papers 1-3 discuss an alternating-direction explicit difference approximation (ADEP) to the diffusion equation. Example applications of ADEP and ADIP4 were reported to support conclusions that ADEP is comparable in accuracy to ADIP and requires one-fifth to one-third the computing time of ADIP. Applications of ADEP in calculation of two-phase flow in reservoirs was also proposed. 3 This study was performed to compare further the relative merits of ADEP and ADIP in simulation of two-dimensional flow of one and two fluid phases in reservoirs. Since two-phase flow equations are often essentially elliptic rather than parabolic, the efficiency of ADEP in solving the elliptic equation was also examined.

Jan 1, 1967

By Y. Q. Zhang, S. S. Peng

Numerical modeling was used to design the pillars and bolting plan for a mine with weak roof and multi-seam stress condition. Previous mining experience, pillar/roof yielding and in-situ horizontal stress were considered in the models. By modeling the upper seam yielding and vertical stress transfer, a multi-seam influence zone was obtained. Appropriate pillar sizes were designed for conditions with and without upper seam stress influences. Roof support for the track and belt entries, using fully-grouted resin bolts and cable bolts, was proposed and implemented in the model. The bolting plan was evaluated under the weak roof condition.

Jan 1, 2004

By P. Foster, A. Burton

Over the past decade there has been a great deal of research into the use of virtual reality (VR) and computer graphics in the mining industry. Much of this has led to developed applications including training simulators and accident re-construction. One other area where there is considerable potential for virtual reality is that of mining ergonomics. This paper identifies those common ergonomic limitations associated with mining equipment that can be effectively modelled using VR techniques. From this, two simple models have been developed namely (i)remote control continuous miner operation and (ii) free steered vehicle sightlines, which demonstrate the practical use of VR in this area.

Jan 1, 2003

By Paul Weir

FOR the first time in 1938, bituminous coal production for the week ending Nov. 19 surpassed that of the corresponding week in 1937, and indexes of industrial activity indicated the possibility that the remaining weeks of 1938 would run ahead of the corresponding weeks of the preceding year. But regardless of this year-end pickup, total production in 1938 was approximately 25 per cent less than in 1937. The estimate of 340 million tons for 1938 places the bituminous industry slightly above the production level of 1933 and approximately 10 per cent above the modem low of 1932. Anthracite production is not subject to the same extent as is bituminous coal to fluctuations arising out of the rate of industrial activity, hence the decline from 1937 has not been so great being approximately 14 per cent under 1937. The estimate for 1938 production is approximately 45 million tons, but this represents the lowest level reached in the last fifty years with the possible exception of several strike years.

Jan 1, 1939