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By S. M. Shelton, W. A. Calhoun, M. M. Fine, T. L. Johnston

"INTRODUCTION An extensive test program is in progress by the Bureau of Mines to determine ways and means of recovering ferromanganese-grade ore 6/ from the wide-spread domestic manganese and manganiforous iron deposits. Samples for testing were received from the Interstate Manganese Co. in northeastern Tennessee, 11 miles west of Mountain City and 10 miles southwest of Damascus Va. The ore deposit occurs in the residual material of the Shady dolomite 7/ as an unconsolidated mixture of hard and soft manganese oxides and clay.Numerous tunnels and pits have developed a large reserve of ore in an area of about 15 acres. One pit 250 by 50 by 20 feet is being mined by rower shovels. The ore is hauled to a washing plant for log-washing, hand-sorting, and jigging. Coarse concentrates from the washing plant are marketed without further beneficiation.ACKNOWLEDGMENTSThe authors wish to acknowledge the assistance of R. F. Fisher, who made the roasting and magnetic tests."

Mar 1, 1942

GOLD has played a part in the development of Australia. The total yield exceeds SIX hundred million pounds sterling, while the glamour of gold-mining and the unfailing demand for the product have enhanced its influence. The production is still considerable, but the yield is less than one-quarter of that twenty years previously, while the number of men employed has dropped from 70,000 to 11,000. Not only has there been a marked decline in production, but it is anticipated that thisdecline will continue, and continue more markedly. It is therefore desirable to ascertain the causes of the decline and inquire into means for diminishing or preventing it.The problem under discussion is far from being only local. Finlay states: The grand feature of the history of the business has been the progress of an economic cycle unfavourable to gold milling. The USA yield fell from $101,000,000 to $44,000,000.South Afriea has for some time produced one-half of the world's gold; yet in the Mining and Scientific Press of 11th February, IH22, General Smuts is quoted as saying that if the premium disappeared entirely 24 out of 34 mines would shut down. The solution, however, might be either general eg, a great advance in the metallurgy of gold; or local eg, a bonus; but before discussing any of the proposed solutions it will be advantageous to review the situation.STATISTICS OF THE PAST AND PRESENT PRODUCTION OF THE WORLD AND OF AUSTRALIAThe inquirer soon finds that there is a good deal of uncertainty, and that much care is needed in collating figures. In some cases a considerable part of the output is not officially reported, and returns...

Jan 1, 1924

By S. M. Shelton, F. D. DeVaney, M. M. Fine

Ferrograde manganese ore or its equivalent is essential to the manufacture of every ton of steel produced ; although it is well -known that there are large deposits of low - grade ore in the United States , the production of substantial amounts of ferrograde material from domestic sources presents a problem that becomes more and more critical as the stockpiled ore is depleted through inability to obtain adequate supplies from foreign sources . Consequently, a program of laboratory and pilot - plant investigations designed to solve the problem of obtaining a domestic supply of manganese has been undertaken by the Metallurgical Division, Bureau of Mines . This paper is one of a new series that will include reports of results obtained in the various investigations conducted under the manganese program . The scope of the program and the organization that was set up to direct and supervise the work were discussed in the foreword of the first paper of this series , Report of Investigations 3606 , Manganese Investigations 1. Concentration of Manganese Ores from the Drum Mountain District, Utah, by S. R. Zimmerley, J. D. Vincent , and C. H. Schack . Other reports will be published as the work progresses .

Feb 1, 1942

By Larry Rayburn

In the spring of 1999, construction commenced on the new Steelers Football Stadium in downtown Pittsburgh, Pennsylvania. Richard Goettle, Inc. (RGI) was the successful bidder to install the specified augercast piles for the foundation package. Description - Pittsburgh Steelers Stadium The new stadium will house the Pittsburgh Steelers Professional Football Team. It is widely believed that if a team is provided with a modern playing facility, that a winning season will ensue (Not always the case). The new stadium location is on the north side of Pittsburgh on the Ohio River, and just downstream of the confluence of the Monongahela and Allegheny Rivers. The site is west of existing Three Rivers Stadium. The Three Rivers Stadium was built during the late sixties and housed both the Pirates Baseball and Steelers Football Teams. The Public Auditorium Authority elected to replace this outdated stadium with two new stadiums, one for each professional team. The landmark stadium was imploded in February of 2001.

Jan 1, 2001

By Robert H. Merrill, James V. Williamson, David M. Ropchan, George H. Kruse

In- situ rock stresses were determined by flatjack and borehole - deformation methods . Estimates of the stress distribution around a flatjack were obtained by a combination of flatjack and borehole - gage techniques . The investigations were part of a study , conducted jointly by the State of California and the Federal Bureau of Mines , to determine the stress in rock at the site of an underground powerplant for the Oroville Dam near Oroville , California . The stress distribution around each of three flatjacks was nonsymmetric ; however , stresses obtained from 9 flatjack and 157 borehole measurements are considered reasonably accurate for engineering purposes . The stress near the edge of the openings is between 800 and 1,600 psi ; the stress in the undisturbed rock is approximately 500 psi , nearly hydrostatic .

Jan 1, 1964

By Robert A. Clifton

This Bureau of Mines report discusses the mineralogy of zeolites, the properties that make them commercially valuable, the conditions of formation of both natural and synthetic zeolites, and present and potential markets.

Jan 1, 1987

By L. I. Gonzalez de Vallejo

SRC rockmass classification have been applied to 25 tunnels in Spain and Italy, for which it was found that much heavier supports than those estimated by the RMR index were required. SRC and RMR indices and other relevant geomechanical data were obtained during the site investigation and construction stages. Data corresponding to in situ stress measurements, analysis of tectonic structures, and instability problems arising during construction were used to asses the state of stress. The relationship between tunnel section convergence and the SRC and RMR indices was also analysed. Support measurements based on SRC and RMR classification were compared with those actually used during construction. These analyses indicate that for most of the tunnels examined, supports estimated using the SRC were much closer to those actually installed than those predicted by the RMR index. Bei der Verwendung des SRC-Systems zur Klassifizierung des Gesteins als Baugrund für 25 Tunnel in Spanien und Italien wurde festgestellt, dass viel schwerere Abstützungen benötigt wurden, als wenn die Beurteilung anhand des RMR-Systems angefertigt würde. Die Klassifizierung anhand des SRC- und des RMR-Systems, sowohl als auch andere wichtige geomechanische Daten wurden während des Ablaufs der Erkundungen und der Bauausführung gewonnen. Die Resultate der Messungen der Spannungen vor Ort, die Analyse der tektonischen Struktur und die Stabilitätsprobleme während der Bauausführung wurden dazu verwendet, um den im Felsgrund vorherrschenden Spannungszustand zu definieren. Das Verhältnis der Messungen der Tunnelkonvergenz zu dem SRC- und RMR-Index wurde auch analysiert. Die durch das SRC- und RMR-System vorhergesagte Grösse der Abstützung wurde mit der Grösse der Abstützungen verglichen, die am Bau letztlich verwandt wurden. Diese Vergleiche zeigen, dass für die meisten der studierten Tunnel die Vorhersage der Abstützungen, die anhand des SRC-Systems angefertigt wurden, viel näher der wirklich verwendeten waren als die Vorhersage anhand des RMR-Systems. SRC rockmass la classification ont été appliqué à 25 tunnels en Espagne et l'Italie, pour laquelle il a été trouvé que des appuis beaucoup plus lourds que ceux évalués par l'index RMR ont été exigés. SRC et des index RMR et d'autres données geomechanical appropriées ont été obtenu pendant l'enquête de site et les étapes(scènes) de construction. Les données correspondant aux mesures de stress(d'accent) in situ, l'analyse de structures tectoniques et des problèmes d'instabilité surgissant pendant la construction ont été utilisées aux ânes(culs) l'état de stress(d'accent). Le rapport entre la convergence de section de tunnel et le SRC et les index RMR a été aussi analysé. Les mesures d'appui basées sur SRC et la classification RMR ont été comparées avec ceux en réalité utilisés pendant la construction. Ces analyses indiquent que pour la plupart des tunnels examinés, les appuis évalués utilisant le SRC étaient beaucoup plus proches de ceux en réalité installés que ceux prévus par l'index RMR.

Jan 1, 2003

By S. F. Diehl

Weathered mine waste consists of oxidized primary minerals and chemically unstable secondary phases that can be sources of readily soluble metals and acid rock drainage. Elevated concentrations of metals such as Cd, Cu, Fe, Mn, Ni, Pb, and Zn are observed in deionized water-based leachate solutions derived from complex sedex and Cu-Pb-Zn mine wastes. Leachate (USGS FLT) from the Elizabeth mine, a massive sulfide deposit, has a pH of 3.4 and high concentrations of Al (16700 ug/L), Cu (440 ug/L), and Zn (8620 ug/L). Leachate from the sedex Faro mine has a pH of 3.5 and high concentrations of Al (2040 ug/L), Cu (1930 ug/L), Pb (2080 ug/L), and Zn (52900 ug/L). In contrast, higher-pH leachates produced from tailings of polymetallic vein deposits have order of magnitude lower metal concentrations. These data indicate that highly soluble secondary mineral phases exist at the surface of waste material where the samples were collected. Sulfide minerals from all sites exhibit differential degrees of weathering, from dissolution etched grain rims, to rinds of secondary minerals, to skeletal remnants. These microscale mineral-dissolution textures enhance weathering and metal leachability of waste material. Besides the formation of secondary minerals, sulfide grains from dried tailings samples may be coated by amorphous Fe-Al-Si minerals that also adsorb metals such as Cu, Ni, and Zn.

Jan 1, 2011

By L. Salnais

"Aluminum alloy structural components f or aircraft designed prior to the early 1970s, were machined from 2024, 7075 and 7079 plate, bar and forgings in either the T3xxx of the T6xxx tempers. Protective treatments for these parts consisted of chromic acid anodizing and alkyd zinc chromate primer, plus a nitrocellulose lacquer for exterior parts.The major service problem with these parts was the frequent occurrence of exfoliation corrosion and stress corrosion cracking (S. C. C.). Therefore, 2024 and 7079 alloys, with min or exceptions, were not used in aircraft designed after the early 1970s. Replacement materials were 7075 and 7050 alloys in the overaged, exfoliation corrosion and S. C. C. resistant, T73xxx tempers.The use of improved materials together with the upgrading to chromated epoxy primers, polyurethane enamels and the introduction of water displacing corrosion inhibiting compounds have significantly reduced corrosion in aircraft. IntroductionThe prevention of corrosion in aircraft has been a challenge to aircraft designers for many decades. With the design of the first all-metal aircraft, the designer and builder were thrust into the relatively new field of protective treatments as corrosion started to become more prevalent. This resulted from the continually increasing importance and wider utilization of aircraft, and their exposure to a wider variety of ho stile environments such as urban industrial pollution, high humidity tropical areas and salt ladened marine environments.Corrosion advanced another significant step when, after World War II, designs of new and larger aircraft utilized larger and thicker metal sections in the manufacture of structural components. With thicker mill products came higher residual heat treat, fabrication and assembly stresses resulting in an increased number of stress corrosion and exfoliation corrosion problems.Apart from the exterior environment, aircraft interior s can be exposed to a number of fluids which are either directly or indirectly responsible for corrosion. The most common of the fluids is water which is usually introduced as a result of condensation, especially in pressurized fuselages, and spillage from lavatories, galley s and electrolytes from batteries. These fluid s have a degrading effect on protective treatments and are also corrosive to the substrate metal. Fluids such as phosphate ester hydraulic fluids and ester based turbine engine lubricating oil s are not corrosive to the substrate metal, albeit they do contribute to corrosion by the degrading effect on protective treatments."

Jan 1, 1988

The paper point out the testwork has been carried out with real process solutions from the Chambishi cobalt plant in Zambia, showing that the ISEP® continuous ion exchange system can effectively remove nickel from cobalt sulphate electrolyte. Laboratory testing confirmed published data, and was subsequently verified on site at Chambishi in a pilot test program. Based on the testwork data, a commercial unit is being installed at Chambishi.

Sep 13, 2001

By Clarence Hall, S. P. Howell, W. O. SNELLING

The explosives used in coal mines not only occasion accidents such as occur in the use of explosives elsewhere, but they frequently cause widespread disasters by igniting explosive mixtures of mine gas and air and of coal dust and air, or both. In addition, the firing of ex- plosives so shakes the walls and roofs of the mines as to cause falls, with their attendant casualities. Considering the large number of explosives and their wide range in composition and properties, it is obvious that certain of them should prove more suitable for use in coal mines than others. The problem is to determine which explosives are the most suitable for this purpose and the precise conditions under which they may be used with the greatest safety. Of course this problem could be worked out in actual mining, but experimental investigations when accompanying commercial opera- tions are hazardous and slow. To obtain the information sought, in the speediest and most economical manner, laboratory methods must be resorted to. The adoption of such methods began about 30 years ago with experiments in an iron gallery mounted on wheels, at Zwickau, Germany. This laboratory method of attacking the prob- lem has so commended itself that it has not only been repeated else- where in Germany but has at intervals been officially adopted, with many modifications and additions, by the Governments of Belgium, Austria, France, and Great Britain. Such was the status of coal-mine investigations in Europe when in 1904, an organization in the Geological Survey, which in 1907 be- came the technologic branch, was created to investigate the mineral- fuel resources of this country. At that time no division of the Na- tional Government had official cognizance of conditions existing in our mines, but through its system of collecting fuels for tests the technologic branch was forced to recognize that coal-mine accidents are a factor that must be reckoned with in determining the extent and availability of our mineral-fuel resources. This became so apparent, and it was so obviously a function of this branch to make a systematic research as to the cause and prevention of such acci- dents, that in July, 1907, experts were appointed especially to deal with this problem. As a result, not only was Bulletin 333, on Coal- Mine Accidents: Their Causes and Prevention, prepared and pub- lished, but through personal inspection of foreign testing stations, and a study of their reports and the critiques of their methods and operations, definite plans for the establishment of such a testing station in this country were formulated. In the latter part of 1907, four grave disasters occurred in close succession consequent on explosions in the Monongah mines in West Virginia, where 368 men were killed, the Darr mine in Pennsyl- vania, where 160 were killed, the Naomi mine in Pennsylvania, where 34 were killed, and the Yolande mine in Alabama, where 61 were killed. These frightful disasters so quickened the public con- science, and so plainly demonstrated that both humanitarian and economic needs demanded that steps be taken to prevent the re- currence of such accidents, that in 1908 Congress made a special appropriation for an investigation as to the "causes of mine ex- plosions." A similar appropriation was made in the following year. By act of May 16, 1910, the Bureau of Mines was created "to make diligent investigation of the methods of mining, especially in relation to the safety of miners, the use of explosives, the prevention of accidents," and other matters relating to mining. Therefore, these investigations are at present conducted in obedience to an organic act instead of being dependent solely upon special appropriations. The first appropriation became available July 1, 1908. Through the courtesy of the War Department a portion of the grounds and buildings of the arsenal at Pittsburgh was granted for the use of the technologic branch of the United States Geological Survey. Work was immediately begun in procuring and erecting the necessary instru- ments and appliances for carrying out the desired tests and inves- tigations and in adapting the existing buildings or in erecting new structures to contain the apparatus. The Pittsburgh testing station was officially opened and regular work was commenced on December 3, 1908, the apparatus and appliances having been tested, the force drilled in their use, and the equipment and methods inspected and passed upon by foreign experts.

Jan 1, 1912

By Jim Sadowski, Steve Stewart, Bob McMurdy, Martin Nevens

"Mohawk Garnet has been operating a small pilot plant near Sudbury, Ontario for several years attempting to produce commercially viable garnet. The challenges of operating a pilot scale mining, processing, and product handling operation as a full time plant have led Mohawk Garnet to seek a better way. In co-operation with Mohawk Garnet, Outotec (USA) Inc. has taken on the technical and design challenges of increasing garnet product from twenty tonnes per day to two hundred tonnes per day.Outotec performed a comprehensive test and flowsheet development program applying Outotec’s density separators, spirals, flotation, and other technologies to design a successful process for the separation and recovery of the valuable garnet for Mohawk.This paper explores the test program, the process flowsheet development work, plant design and preliminary engineering of a new garnet processing. The various technical challenges, process technologies involved, and design concepts will be discussed.INTRODUCTIONMohawk garnet has been operating a small-scale garnet mine and process plant in Wahnapitae, Ontario near Sudbury.The current operation was intended to be a pilot plant and so only produces 20-25 tonnes of garnet concentrate per day. The garnet is bagged and sold for use as abrasive. The process is inefficient with low yields, poor material handling and very high cost per tonne. Mohawk garnet approached Outotec to help them improve their garnet process and transform themselves into a larger scale and more efficient operation."

Jan 1, 2010

By Smith N. S, Rholl S. A, Otterness R. E

The Bureau of Mines is conducting research to develop blast designs for the control of fragmentation and rock displacement and the reduction of overall mining costs. This Bureau experiment, a program of 25 reduced-scale blasts conducted at the University of Missouri-Rolla's experimental quarry, determined the effects on fragmentation of changes in burden, spacing, explosive diameter, and stemming-explosive length. Combined with previous work at this experimental quarry examining air gap, delay, and decoupling effects, this experiment provided a data base of over 50 shots. The fragmented rock, 1000 to 3000 kg from each 3- to 4-hole blast in the 1 m bench of massive dolomite, was completely screened to assess fragmentation. The explosive used for all the tests was extra dynamite initiated by seismic caps fired from a sequential blasting machine with delays of 5.2- to 13-ms/m of burden. Empirical equations were developed which predicted the effect of shot design parameters on the fragmentation. These formulas predicted the average fragment size of each of the 25-shots to within 13 percent. For spacing to burden ratios of 1, 1.4 and 2, there were optimum burden to explosive diameter ratios (B/de) of 30, 26 and 20, respectively. Decreasing the B/d. ratio beyond these levels resulted in little or no reduction in the average size. For B/de ratios above these levels the average size increased but, at least a 15 percent reduction in the average size results when the shot design parameters are optimized.

Jan 1, 1990

By Patrick J. Hannigan, Alex Ryberg, Rozbeh B. Moghaddam

Driven piles are widely used for foundation support. In the vast majority of cases, an increase in pile capacity occurs with time which is referred to as “set-up.” However, in a very limited number of cases, a decrease in capacity with time can occur. This phenomenon is referred to as “relaxation.” This paper will provide a brief review of the relaxation phenomenon, as well as pile driving information and dynamic test data on cases where relaxation has occurred. The pile types in the presented relaxation cases include H-piles, open-end and closed-end pipe piles, prestressed concrete piles, and prestressed concrete piles with H-pile stingers. The soil conditions where relaxation occurred includes dense to very dense fine sands, heavily over consolidated clays, and weak laminated rocks. Relaxation information from 36 piles at 26 sites is assessed. The collected data will assist foundation designers by identifying the subsurface conditions where relaxation has occurred, as well as by documenting the corresponding relaxation magnitude. One method of addressing relaxation when it is encountered is to drive the foundation piles to a greater end of initial driving capacity than required long-term. Hence, the identification and quantification of the relaxation magnitude will be beneficial to foundation designers installing similar pile types in similar subsurface conditions. The paper will also present pertinent observations and recommendations on mitigating relaxation when encountered. INTRODUCTION One of the earliest observations of a decrease in redriving resistance following initial driving was reported by Miller (1937). He reported that piles driven into a saturated, coarse grained soil could lose 40 to 50% of their resistance when redriven 24 hours after initial driving. Yang (1956) similarly reported that after a break in driving, a decrease in driving resistance could be encountered for piles driven in dense fine sand, inorganic silt, or stiff fissured clay. Parsons (1966) in his paper that described piling difficulties in the New York City metropolitan area termed this phenomenon “relaxation”. In this time period, pile capacity was most often evaluated from a pile driving formula frequently checked by a static load test. Hence, the true magnitude of the capacity decrease on a given pile was often poorly quantified. Furthermore, dynamic measurements that could determine what influence driving system performance variation had on the observed redriving resistance were not yet readily available.

Jan 1, 2019

By F. A. Rutledge, H. Marstraander, J. H. Hulbert, G. A. Apell

"INTRODUCTION The inability of Alaska coal mines to supply the quantity of coal required by public and private consumers and by the armed forces in Alaska caused the Coal Procurement Section of the Alaska Department, U. S. Army, to be established. It proposed to investigate the coal deposits and to expedite production of coal. The Bureau of Mines has closely cooperated in this program and was in direct charge of exploration. As to develop and equip an underground coal mine would have taken time and the need for coal was acute, a deposit that could be prepared for mining quickly was desirable. Several such deposits of stripping coal were known to occur in the Nenana field and were examined by the Bureau. One of these, the Diamond strip mine 4 miles west of Healy, was brought into production late in the fall of 1943. This mine was operated for the Army Coal Procurement Section by the C. F. Lytle Co. and the Green Construction Co.The Roth property, or Leasing Block No. 28, in the Healy Creek Valley offered the largest available tonnage of both stripping coal and total reserves. A program of exploration by the Bureau of Mines was inaugurated in 1943 and completed in 1944. Field parties of the Federal Geological Survey mapped the area had correlated the coal beds during the 1944 and 1945 summer seasons."

Nov 1, 1946

By Job Goostray

IN THIS paper, as in so many other discussions of historical nature, there is little chance for original material and much has had to be rewritten from older papers, documents, accounts, reports, and the like, some of which are of doubtful authorship or contain conflicting statistics. Fully aware of these little historical pitfalls, the authors have tried to quote the origin where possible, and also to seek further confirmation when the statement warranted it, but cannot assume responsibility for certain facts and dates. The Encyclopedia Britannica was frequently consulted. The authors wish to acknowledge assistance from MacKintosh-Hemphill Co.-formerly the Fort Pitt Works-and also from officials of the Watertown Arsenal who loaned valuable books and gave much necessary information. They are particularly indebted to Colonel Dixon of that institution. The data on modern guns were furnished by Mr. F. Brauer of the Watertown Arsenal; Mr. H. S. Chaffee assisted by obtaining records and data of work carried on by the Builders' Iron Foundry of Providence, R. I.

Jan 3, 1925

By M. Hakala, P. Tolppanen

A method to predict stress-induced failures around excavations based on the mapped geological and rock mechanical information is studied. Totally of 7 km of newly excavated tunnels are mapped in the Inmet’s Pyhäsalmi mine in Finland at depth between 1000 - 1440 m from which the results and conclusions from the firstly mapped 1.7 km of tunnels are reported. The main rock type at the site is very hard volcanite having uniaxial compressive strength of 230 MPa in median and GSI-value 72 - 80. The maximum in situ stress around the tunnels is 65 - 85 MPa. The prediction of observed stress failures was preceded by comparing elastic 3-D simulation results of tunnels with three statistical yield criteria. Read’s or Hoek & Brown’s yielding criteria are found the most relevant, though, the effect of anisotropy was found to be significant. The most important parameters having a correlation with stress failures are the tunnel orientation and the foliation of rock. Also, the rock type and its strength, tunnel shape and the geological anomalies have their effects. Further, a delay time on mapping was found to clearly diminishing of the most violent failures. Une méthode de prédiction des contraintes à la rupture autour d'excavation, établie sur la base de cartographie géologique et d'information sur la mécanique des roches, à été étudiée. Au total, 7 km d'un tunnel nouvellement percé à une profondeur de 1000 à 1400 m ont été cartographiés dans la mine de Inmet’s Pyhäsalmi en Finlande. La roche principale du site est une vulcanite dur ayant une résistance à la compression uniaxiale de 230 MPa (valeur moyenne) et une valeur GSI de 72 - 80. La contrainte in situ maximale autour du tunnel se situe entre 65 et 85 MPa. La prédiction des contraintes à la rupture observées a été évaluée en comparant les résultats d'une simulation 3D d'un tunnel avec trois critères de limite d'élasticité statistiques. Le critère de limite d'élasticité de Read ou de Hoek & Brown’s se trouvent être les plus important, même si les effets de l'anisotropie sont significatifs. Les paramètres les plus importants ayant une corrélation avec la rupture sont l'orientation du tunnel et la foliation de la roche. De plus, le type de roche et sa résistance à la compression, la forme du tunnel et les anomalies géologiques ont aussi leur importance. Finalement, un délai dans la cartographie résulte en une diminution nette des ruptures violentes. Basierend auf kartierten geologischen und felsmechanischen Informationen, wird eine Methode untersucht, um spannngsbedingtes Versagen um Ausbrüche herum vorherzusagen. Insgesamt werden 7 km neu ausgebrochenen Tunnels in einer Tiefe zwischen 1000 und 1400 m in der Inmet Pyhäsalmin Mine in Finnland kartiert. Das hauptsächlich vorkommende Gestein ist sehr hart und vulkanischen Ursprungs mit einer mittleren einachsialen Druckfestigkeit von 230 MPa (Medianwert) und einem GSI-Wert von 72-80. Die maximale In-situ-Spannung im Tunnel beträgt 65-85 MPa. Die Vorhersage von beobachteten Spannungsversagen werden weitergeführt indem man elastische 3-D-Simulationsergebnisse von Tunneln mit drei statistischen Fliesskriterien vergleicht. Read's oder Hoek's Fliesskriteria werden dabei als die relevantesten Kriterien angesehen, obwohl auch der Effekt der Anisotropie als wesentlich erachtet wird. Die wichtigsten Parameter für eine Korrelation von Spannungsversagen sind die Orientierung des Tunnels und die Schieferung der Gesteinsschichten. Desweiteren haben Gesteinsart, Tunnelprofil und geologische Anomalien ihren Einfluss. Ausserdem zeigt sich, dass eine Verzögerung bei der Kartierung die ausgeprägtesten Versagen deutlich verringern.

Jan 1, 2003

By K. D. Dill, S. D. Rosenthal

"This project analyzed the efficiency of incorporating the use of directional drilling technology into coal overburden blasting. Directional drilling is currently in use in the petroleum industry and it is believed that it will be a valuable asset in the mining industry. This project has shown that directional drilling can be a viable technology for use in the coal overburden removal process resulting in increased drill utilization and potential for cost savings. Future work regarding blasting and geotechnical evaluation should be performed to solidify the concept. INTRODUCTION Determine the Potential Drill Utilization Improvements and Rock Fragmentation Requirements Using Directional Drilling in a Coal Mining Overburden Highwall Application was a project funded by Atlas Copco Drilling Solutions (Atlas Copco) based in Garland, Texas. The project was developed and researched by Montana Tech of the University of Montana. This project was intended to show how the use of directional drilling can increase drill utilization, while decreasing costs, without sacrificing overburden blasting results. This paper discusses a review of the literature, the methods performed, conclusions and future work Background Atlas Copco theorized that an alternative approach to drilling a cast blast pattern would be beneficial to coal mining operations by increasing drill utilization and therefore, decreasing overall costs. Increasing drill utilization results in an increase in the amount of time the drill is being productive, more drill bit time in ground. Atlas Copco’s theory is that by incorporating directional drilling in the design of a cast blast pattern, a drill rig could drill multiple directional holes, which are the length of the cast blast, from a single drill set up. A drill goes through a series of steps to complete a blast pattern, these steps include: tramming to the hole location, leveling the drill, drilling the hole, cleaning the hole, and retracting the drill steel. This process is repeated hundreds of times until the whole pattern is completed. The most time intensive part of this process is drilling out the blast pattern. Integrating directional drilling into this process could decrease the overall time it takes to drill out a blast pattern by minimizing the amount of time spent tramming and setting up for each subsequent hole. Tramming and drill set up are two aspects of the drilling process where the drill tool is not engaged with the ground and, therefore, not being utilized. A cast blast pattern designed to utilize directional drilling will allow the drill tool to be “in the hole” longer and will improve drill utilization. This change in drill utilization was analyzed. Drilling and blasting is an integral part of the mining process, without it mining would be a slower process and less material could be mined. Drilling provides holes for explosives to be loaded and then blasted. Blasting has been found to be the most cost effective method of fracturing rock in mining for material removal. Blasting is also used as a low-cost method to move the rock in open cast mines, commonly referred to as cast blasting. A cast blast is a large blast designed to allow for the maximum amount of overburden to be removed using explosives in a single blast thereby uncovering more coal at a lower cost. Not all the material is blasted to cast-to-final, which requires that material to be moved with large mining machinery. Material that is considered cast-to-final is material that has been thrown far enough to never be moved again in the coal extraction process, therefore it is in its final resting place. A typical cast profile and cast-to-final area is shown in Figure 1."

Jan 1, 2017

By Joseph A. Hrabik

The Bureau of Mines compared the feasibility of mining deep phosphate deposits by a borehole mining system with mining by proven conventional techniques. An economic comparison of the borehole mining system with conventional dragline and bucket wheel excavator mining systems was completed at various mining depths and production rates. Hypothetical phosphate deposits, with various overburden thicknesses and reserve tonnages, were defined. Geologic conditions necessary for the application of the borehole system were identified. Discounted cash flow analyses based on derived capital and operating costs were used to generate rates of return and product prices. Borehole mining was found to be more economical where overburden thickness was 150 ft or greater; however, at 50- and 100-ft thicknesses, conventional surface mining was more economical. Overburden thickness has a great effect on the economic feasiblity of the conventional mining systems but less effect on the economics of borehole mining. Economies of scale are only realized in conventional mining, since larger equipment is employed to achieve greater production, whereas increased production from borehole mining is achieved using additional equipment units. A comparison of the environmental effects of borehole and conventional surface mining systems showed that borehole mining is environmentally more desirable.

Jan 1, 1983

By D C. McPhail, S L. Rogers, J Brugger

Using iron- and sulfur-oxidising bacteria to catalyse the breakdown of sulfides that host the gold is an important biological method for the pretreatment of refractory gold ores. Following this biological treatment a combination of chemical and physical methods are used for leaching (such as the cyanide process) and concentration (such as carbon-in-pulp or electrowinning) of gold. Although these methods are well accepted by industry, they harbour limitations in the processing of low-grade refractory ores, and regulatory agency/public acceptance of cyanide use. Thus, it is beneficial to industry to develop environmentally friendly, cost-efficient leaching and concentration techniques that are based on micro-organisms. This may soon be possible by adapting the results of recent regolith geoscience research, which has shown that micro- organisms are capable of driving a biogeochemical cycle of gold dispersion, transport and reconcentration in the supergene environment. The indigenous microbiota in biologically active soil microcosms from a number of Australian sites are capable of solubilising up to 80 wt per cent of the gold contained in these materials during 50 days of incubation. Studies using molecular microbial techniques have shown that a metallophilic bacterium, Ralstonia metallidurans, is present in biofilms on gold grains from a number of Australian sites. R metallidurans is capable of actively accumulating gold from solution, suggesting that the bacterium may contribute to the formation of secondary gold grains and nuggets. Identifying the biochemical and physiological pathways that lead to the dispersion and accumulation of gold in regolith, and quantifying the reaction kinetics of these processes may thus lead to the development of industrial bio-processing capacities for gold-containing ores.

Jan 1, 2007