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In order to reduce waste and improve resource conservation, mine planning, and development, the U.S. Bureau of Mines is investigating the effects of multiple seam interactions associated with longwall coal mining. Field investigations were conducted at a mine located in Boone County, WV, where a longwall panel was operating subjacent to room-and-pillar workings in an overlying seam. To assess the effects of overlying workings on longwall headgate stability, the Bureau gathered various geotechnical information at this minesite. Headgate pillars and entries were instrumented and monitored to study their behavior during side-abutment loading as the longwall panel approached and passed beneath the overlying room-and-pillar developments. The two operations are separated by 800 ft of interburden, and although interactions between operations separated by this distance are uncommon, geomechanical measurements indicate the occurrence of an interaction. These measurements show that convergence on the headgate entries was most adverse subjacent to barrier pillars in the overlying mine. Pillar measurements indicate that side-abutment pressure increases were slightly greater than predicted values. Several factors related to both geology and mine design, believed responsible for this large interactive distance, are discussed.

Jan 1, 1990

By Leslie C. Richards

Sooner or later the potential miner of industrial minerals reaches the conclusion that of the various factors he must consider, the marketing of his product is. the most important. The sooner he realizes this the better, as successful industrial mineral producers .will confirm. Herein lies a difference between i.ndustria1 mineral mining and metal mining. Often in the latter, technical problems of mining or concentrating are equal to or even surpass those of marketing. This is not meant to imply that there are no problems in mining and beneficiation of industrial minerals, but these usually are outweighed by the problem of marketing. Recentlv. an official of a nationally known corporation :i the elecl.ro-metallurgical industry made an industrial mineral survey in the Pacific Northwest. In the course of his investigation he interviewed producers and potential producers of the various industrial minerals scheduled for use in the plant now being constructed in this area. He stated that he was interested in only three factors: namely, (1) Can your product meet our specifications? (2) Are you able to supply our tonnage requirements? and (3) What will be the delivered price? If there are several sources of supply of sufficient grade and tonnage, as is often the case in the Northwest, then the third factor becomes the important and deciding one. While industrial minerals are usually sold f.0.b. cars with the freight being paid by the buyer, it is the delivered and riot the f.0.b. price that determines the competitive position of the producer and his industrial mineral product. Unfortunately for both the consumers and producers of industrial minerals in the Northwest, the sources are generally a considerable distance from the markets. This necessitates long rail hauls, for which transportation charges make up the largest share of the delivered cost and the delivered price of the product. Is it any wonder then, that rail rates play such an important part in the marketing of industrial minerals? In order to sell his product, the producer must be able to deliver to the market at a competitive price. It must be remembered that his largest cost factor is rail transportation, and that he is limited to markets that he can reach competitively. Since the cost of rail transportation is so important, let us compare various freight rates in the Northwest and attempt to determine their influence on marketing. A study of all rates on all industrial minerals transported in this area, is beyond the scope of this paper. For the purposes of comparison, let us consider limestone (broken, crushed, or ground), and silica rock. These are widely used industrial minerals, and are carried by several different rail routes from.the sources of supply to the centers of consumption in the Pacific Northwest. Markets and Sources of Supply: Limestone has a number of uses in western Oregon and Washington. Among them are agricultural lime for the soils of the Willamette Valley and southwestern Washington; paper rock for the mills in such cities as West Linn, Oregon City, Newberg, St. Helens, and Salem, Oregon, and Camas and Everett, Wash.; chemical and metallurgical-grade limestone for the metallurgical plants centering around Portland, and the Tacoma-Seattle areas'; and sugar rock for the sugar refineries at Toppenish, Wash., and Nyssa, Oregon. Since limestone for cement manufacture is generally processed near the quarry, transportation

Jan 1, 1951

By Corry Goumans, Dwayne Wallace

"On July 1, 1997, a rockslide occurred on the I-40 in Hayward County, North Carolina that completelyblocked all lanes and disrupted traffic flow in the region. Remedial measures were undertakenimmediately in order to open traffic, however on-going geotechnical investigation revealed stabilityconcerns that necessitated closing the highway to ensure public safety. Access to the top of the slope was available only from the bottom of the slide on the Interstate I-40. Excavation and trim blasting started from the top and along the west slope of the failure, however, additional geotechnical evaluation indicated that slope stability remedial measures were required to support the western rock slope mass."

Jan 1, 1999

By B. Hosseini

Considering the subtractive trend of the sulfide and high-grade zinc ores in worldwide and also in Iran, Nowadays special attentions have been drawn to the extraction of zinc from its other resources such as low-grade oxide ores and secondary resources. Oxide ore of the eastern part of Mehdi-abad lead and zinc mine is silicate and has an average grade of 7% (with cut off grade of 4%). Main mineral of the Mehdi-abad ore is Hemimorphite and this mineral is associated with Goethite, Hematite, Ferrous Dolomite, and Manganese oxide mineral so that oxides of Iron, manganese and silica include almost 50% of the total ore. In this paper, the results obtained from the leaching kinetic study of the low-grade zinc oxide ore using Sulfuric acid are presented. The effects of particle size, reaction temperature, acid concentration, and solid percent on the dissolution rate have been investigated. The results obtained from the Taghochi approach showed that the zinc recovery is about 78% under the following optimized conditions: particle size: 106µm, leaching time: one hour, temperature: 45°C, acid concentration: 15% and solid percent: 15%. Kinetics study was revealed that zinc minerals leaching controlled by diffusion rate through the product layer during leaching time with the activation energy of 5 KJ/mol and compliance with the 1- (2/3. x) ? (1- x) 2/3 = k. t model. Keywords: leaching kinetics, kinetics models, sulfuric acid leaching, taguchi methods, low grade zinc ore, mehdi-abad mine

Sep 1, 2012

By Leslie C. Richards

The competitive position of producers of industrial minerals depends upon the delivered price of their product. Freight charges are a major factor in the sales to consumers. A comparison of freight rates on movements of limestone and silica rock in the Pacific Northwest shows a wide variance in mills per ton mile for like hauls, thereby favoring some localities over others. Introduction: Sooner or later the potential miner of industrial minerals reaches the conclusion that of the various factors he must consider, the marketing of his product is. the most important. The sooner he realizes this the better, as successful industrial mineral producers .will confirm. Herein lies a difference between i.ndustria1 mineral mining and metal mining. Often in the latter, technical problems of mining or concentrating are equal to or even surpass those of marketing. This is not meant to imply that there are no problems in mining and beneficiation of industrial minerals, but these usually are outweighed by the problem of marketing. Recentlv. an official of a nationally known corporation :i the elecl.ro-metallurgical industry made an industrial mineral survey in the Pacific Northwest. In the course of his investigation he interviewed producers and potential producers of the various industrial minerals scheduled for use in the plant now being constructed in this area. He stated that he was interested in only three factors: namely, (1) Can your product meet our specifications? (2) Are you able to supply our tonnage requirements? and (3) What will be the delivered price? If there are several sources of supply of sufficient grade and tonnage, as is often the case in the Northwest, then the third factor becomes the important and deciding one. While industrial minerals are usually sold f.0.b. cars with the freight being paid by the buyer, it is the delivered and riot the f.0.b. price that determines the competitive position of the producer and his industrial mineral product. Unfortunately for both the consumers and producers of industrial minerals in the Northwest, the sources are generally a considerable distance from the markets. This necessitates long rail hauls, for which transportation charges make up the largest share of the delivered cost and the delivered price of the product. Is it any wonder then, that rail rates play such an important part in the marketing of industrial minerals? In order to sell his product, the producer must be able to deliver to the market at a competitive price. It must be remembered that his largest cost factor is rail transportation, and that he is limited to markets that he can reach competitively. Since the cost of rail transportation is so important, let us compare various freight rates in the Northwest and attempt to determine their influence on marketing. A study of all rates on all industrial minerals transported in this area, is beyond the scope of this paper. For the purposes of comparison, let us consider limestone (broken, crushed, or ground), and silica rock. These are widely used industrial minerals, and are carried by several different rail routes from.the sources of supply to the centers of consumption in the Pacific Northwest. Markets and Sources of Supply: Limestone has a number of uses in western Oregon and Washington. Among them are agricultural lime for the soils of the Willamette Valley and southwestern Washington; paper rock for the mills in such cities as West Linn, Oregon City, Newberg, St. Helens, and Salem, Oregon, and Camas and Everett, Wash.; chemical and metallurgical-grade limestone for the metallurgical plants centering around Portland, and the Tacoma-Seattle areas'; and sugar rock for the sugar refineries at Toppenish, Wash., and Nyssa, Oregon. Since limestone for cement manufacture is generally processed near the quarry, transportation

Jan 1, 1951

By Horacio Destaillat

Desde hace aproximadamente 15 años se encontró por experiencia empírica que se puede “neutralizar” el efecto del plomo sobre la maleabilidad en caliente de cobre proveniente de la refinación térmica de chatarras mediante control de la composición química. Este hallazgo ha resultado de aplicación industrial. Si bien el contenido porcentual de plomo se reduce por refinación convencional y con cierta facilidad hasta 0,02 – 0,03 %, este valor es elevado [1] para laminar en caliente. Bajar el nivel de plomo hasta los valores exigibles por normas, requiere procedimientos especiales y costosos. La técnica cuyo mecanismo aquí se investiga, consiste en ajustar el contenido de plomo y estaño dentro de ciertas proporciones, ya que el balance de estos elementos, permite proceder sin problemas de fisuraciones a la colada y laminación en línea del cobre. Con el control de la composición química del sistema se logra que el plomo y el estaño se adhieran [2] sobre las partículas de eutéctico Cu-Cu2O. Esta disposición micro estructural en borde de grano explica la acción favorable del estaño en la maleabilidad. El procedimiento que aquí se describe no es aplicable a cualquier caso pues no funciona en materiales con contenido elevado de oxígeno (“Tough pitch”) ni en cobres desoxidados. Solamente lo hace en formas de baja sección que hayan sufrido enfriamiento rápido.

Aug 7, 2018

By R. W. Smith. Discussion by D. Watson, R. M. Manser

D. Wotson, R. M. Monser (Watten Spring Laboratory, Stevenage, Herts., U. K.) - This is a valuable and interesting paper and will make an important contribution to the development of a general theory of silicate flotation. In particular the dominance of surface reactions which produce fluosilicic acid and its ions has been convincingly demonstrated. In a paper to be published shortly, however, we offer some evidence which is not consistent with the feldspar activation theory proposed by Prof. Smith. This theory, given in Eqs. 17-20, suggests that activation takes place through the exchange of SiF6 ions for OH- at aluminum sites. This results in a negatively charged site facilitating adsorption of RNH3 Firstly, we have determined the flotation response (using the vacuum flotation technique) and the adsorption of dodecylamine on a natural feldspar (albite) and on the same feldspar after washing with perchloric acid at pH3. This pre-treatment was shown to remove surface adjacent aluminum atoms. It was found that although the acid washed feldspar floated much less easily than the untreated sample, the function of fluoride ion - giving activation over the pH range 4-6.5-was preserved. Moreover, the amount of dodecylamine adsorbed either with or without fluoride present is little affected by acid-washing, despite the depression caused by this treatment. This suggests that surface aluminum atoms can be of little importance in the fluoride activation mechanism. Secondly, we have determined the changes in solution concentration of F- and H+ (or OH-) accompanying reaction of the surface with fluoride ion. The ratio of H+ lost from solution to F- lost is high, ranging from 6.9 at pH4 to 1.0 at pH 7.5. This is consistent with reaction of HF (6 molecules for every Si removed) at the surface, producing SiFi-ions, but not with the re-adsorption of these ions.

Jan 1, 1967

By P. Ruz

A melt transfer ladle was 3D modeled by means of a mathematical fluid dynamics and heat transfer program. Internal temperature profiles were calculated as a time function for a normal ladle and for a pre-heated refractory lined ladle. It was shown that in a normal ladle the molten metal cools down quickly forming accretions. By using an inner lining there are practically no accretions build up within a typical time of operation. Therefore, by applying a refractory lining to a melt transfer ladle and keeping it at a moderate to high temperature it is possible to reduce cold dope circulation in the smelter.

Jan 1, 1999

By Lawrie D. C

Finely ground beryl was decomposed by mixing with ground limestone and soda ash and heating at 900°C for 4-6 hr. The sintered mater:al was then crushed and leached by boiling under reflux with 5N sulphuric acid for up to 4 hr. The liquor containing Be, AI, Fe and other elements as sulphates, was separated from the residue which consisted mainly of silica and gypsum, either by filtration or bydecantation washing.The clarified leach liquor was first treated to remove Fe+++ by contacting with a primary amine-kerosene solution in 2 countercurrent stages. The iron free liquor was then passed to a 4-stage counter-current extraction unit where it was contacted with O·5M di- (2 ethyl hexyl) phosphoric acid (EHPA) in kerosene. Under the operating conditions, 99 per cent of the Be and 7 per cent of the Al was extracted.The Be and Al were stripped from the organic phase by sodium hydroxide solution of suitable concentration to form soluble "beryllate" and "aluminate" respectively. Most of the Be was subsequently precipitatedas Be(OH)2 by heating the alkaline solution to 90°C, the Al remaining in solution. After filtration and washing, the Be(OH)2 could be ignited directly to BeO at about 1000°C or used as a feed to further purification stages if required.A small counter-current extraction unit was operated continuously using liquor derived from the sintering and leaching stages. Dataobtained in batch laboratory tests were confirmed. A product obtained by ignition of the washed "beryllate" precipitate contained more than 99 per cent BeO.INTRODUCTIONIn 1958 an investigation was commenced into the recovery of beryllium oxide from beryl, as part of a programme to utilize mineral resources of South Australia. A survey of the literature indicated that little work had been done on direct solvent extraction of beryllium from aqueous liquors, so it was decided to apply the experience gained in this field in uranium processing to the current problem.Preliminary extraction tests on solutions of beryllium...

Jan 1, 1965

By H. H. Campbell

In the extending employment of open-hearth steel for structural purposes, it is a matter of prime importance that the test-piece shall represent with practical accuracy the characteristics of every portion of the heat from which it comes. In ordinary practice this homogeneity is assumed; but inasmuch as leading exponents of the revolving-hearth system have claimed that a reasonable uniformity could be obtained by their method alone, it may be pertinent to offer a few facts on the subject. The following heats made by the Pennsylvania Steel Company, for bridge-work, were tested by casting two four-inch ingots, one being taken during the first third and the other during the last third of the cast. Test-pieces obtained from these small ingots usually give results inferior to those obtained from larger sizes; but for purposes of cornparison they are equally conclusive. Many of the tests were made for experimental purposes within a few hours of the time of rolling, and before sufficient time had elapsed for the usual molecular redistribution necessary for the best results. All the tests were made on 3/4-inch rounds just as they left the rolls and without annealing; the results, therefore, are subject to the errors caused by variations in the diameter, and in the temperature at which the bar was finished. The tests from any one heat, however, were always nude as nearly as possible under the same conditions; and inasmuch as these data include the results of every heat so tested, and inasmuch as the errors could not by any chance always support any single theory, we may be certain that the unanimons testimony of the experiments indicates a valid conclusion.

Jan 1, 1886

MARCEL R. DALY (written discussion+).-I have read with great interest Mr. W . Van Der Gracht's discussion of my paper and I fail to see where his theory contradicts mine on any fundamental point. My contention is that petroliferous accumulations are generally coincident with diastrophic deformations, synchronous with them and essentially a result of them. This implies that the causes which have led to the distortion of the strata, whatever these causes may be (thrusts, torsion, etc.), have also led to the concentration and accumulation of the hydrocarbons existing in the strata at that time. It is in this respect that both set of phenomena may be said to be related in space and in time and that we may speak of an identity of causes. It is evident that no concentration of the hydrocarbons could take place where these hydrocarbons would not exist. But whenever they do so exist, deformation will tend to concentrate them; and whenever they are found to be concentrated (or accumulated) the cause of their accumulation will have to be traced directly to distortion. I have tried to show, in some previous papers,' the probable sequence of such a mechanical process in the simple case of a series of parallel, superposed, horizontal and homogeneous layers, individually uniform in thickness, but variable in composition and resistance; and I have pointed out that the general results so obtained would harmonize with some striking features recognized in the field. But I have also stated that conditions being much more complicated in nature than in the theoretical instance considered above, a complex superposition of effects would. have to be expected as a general rule, though the leading principle would remain the same. Mr. Van der Gracht admits that the motion of the primary oil, when it has been formed, and its accumulation in adequately porous containers, if any, that would be mostly found on the front edge of the original geosynclines, would be due to the action of the mountain-building forces. Our agreement on this point seems to be complete. But Mr. Van der Gracht wants also the formation of the bituminous matter in its primary form to be coincident only with the earliest phase of the uplift, viz., after the slow geanticlinal upheaval has been completed, and the accumulation

Jan 3, 1918

By Frederick K. Allgaier

This report presents the final data from a 5-yr Bureau of Mines study designed to determine the surface subsidence characteristics resulting from longwall coal mining in a geologic environment common to the Western United States, It includes a description of the geologic setting of the study site, the mine plan, measurement techniques, and results of the monitoring program. Measured subsidence values were obtained over four adjacent longwall panels- Major subsidence characteristics such as longitudinal and transverse profiles, angles of draw, time-related subsidence development, and critical width are discussed. The maxima subsidence value of 5.8 ft was 68 pct of the mining thickness. The average angle of draw was 30°, Subsidence at the center of the first panel continued for 46 months following undermining. The lengths of the longwall panels precluded a definitive determination of the critical width and maximum possible subsidence.

Jan 1, 1988

By Graham Farquharson, Jame Marshall

"Mining towns have always been an important part of Canadian geography. Many Canadians grew up in them. The frontiers of northern Canada would be a lot closer to the United States border but for the pioneering of new mines, new towns, and new transportation routes. Names such as Labrador City, Chibougamau, Val d’Or, Rouyn-Noranda, Kirkland Lake, Timmins, Sudbury, Red Lake, Thompson, Flin Flon, Yellowknife, Whitehorse,Trail and Kimberley are some of the better known larger communities that have grown to become major commercial and government centres, but which started as the base for a mining development.Many other smaller towns never grew beyond being small communities, dependent upon the local mine and many of these are still alive, but perhaps not quite what they used to be. In this list would be Buchans, Schefferville, Chapais, Cadillac, Virginia town, Lynn Lake, Uranium City, Pine Point, and Keno Hill.Nevertheless, all these towns and dozens more like them were residential communities where people lived and raised families and were quite accustomed to being days from the major centres of Montreal, Toronto, Edmonton and Vancouver, and not just hours away as wet end to measure travelling time today."

Jan 1, 1996

By Rong Lu, Hao Wu, Bing Dai, Guoyan Zhao, Li Cheng, Weizhang Liang

Affected by the disturbance of blasting activities, deformation instability and rock dynamic disasters are prone to occur in deep hard rock roadways. Thus, it is particularly necessary to understand the failure behavior of rocks and roadways under dynamic loads. In this study, a series of impact loading tests were carried out on sandstone samples with and without a circular cavity by a modified split Hopkinson pressure bar (SHPB) test system. The mechanical properties and energy evolution of the samples were systematically investigated, and the effect of cavity size was analyzed. The results showed that the presence of the cavity in the samples weakens the dynamic compressive strength by more than 10%, and the peak strain and brittleness are also reduced to varying degrees. Under dynamic loading, spalling cracks occur first on the roof and floor of the cavity, and then different numbers of shear cracks are formed on the sample diagonals. The eventual shear failure mode is the result of the connection of the shear cracks and the cavity. As the cavity radius increases, the dissipated energy density and fractal dimension both grow accordingly, leading to smaller and smaller rock fragments. The dynamic failure behavior of the circular cavity can be well explained based on the dynamic stress distribution law. Overall, this study can provide a reference for the study of the mechanism of rock burst in deep roadways.

Feb 18, 2021

By Manqiu Xu, Glen Robertson, Steve Wilson, Pete Quinn

"The middlings circuit, once called the pyrrhotite rejection circuit, at Inco’s Clarabelle mill was a single flotation stage. It used to process a combined feed consisting of the main flotation scavenger concentrate and the non-magnetic portion of the magnetics flotation circuit tails. The typical circuit metallurgy was 55% nickel recovery at 6.5% Cu+Ni concentrate grade. In the past few years, a research project with the objective of improving the circuit metallurgy was initiated between Inco’s research laboratory and the Mill’s Process Technology group. This project has gone through three steps: a) initial laboratory studies, b) on-site pilot plant investigation, and finally c) full plant implementation.The present paper describes the initial laboratory test work. The development of a two-stage circuit consisting of separate rock and pyrrhotite rejection stages to replace the simultaneous rejection of both rock and pyrrhotite in a single stage is discussed. A two-stage circuit simulation based on batch laboratory flotation data is also presented. Further development work, including the on-site pilot plant test work and the plant implementation of the new circuit design, will be described in a later publication.INTRODUCTIONThe milling operation at Inco’s Clarabelle mill, Copper Cliff, Ontario processes a rich complex sulfide ore from several large production mines around the Sudbury basin (Agar, 199 1). The sulfide mineralization is simple, consisting of chalcopyrite (Cp), pentlandite (Pn) and pyrrhotite (Po). The main gangue minerals are pyroxene, feldspar and quartz with minor amphibole and talc. Estimates of mineral composition are routinely calculated from Cu, Ni and S assays. In the mineralogical calculations, all gangue minerals are conveniently grouped and treated as rock (Rk)."

Jan 1, 2000

Analysis of Procedures and Drivers for Industrial Waste Management

Sep 13, 2010

By N. Giguère

Until recently, the heat treatment of pressure die cast parts has always been considered unpractical because the solution heat treatment resulted in unacceptable blistered parts. This was due to the presence of massive porosity associated with the die casting process where the inflow of metal inside the mold cavity is extremely turbulent. With the steady improvement of foundry practices and the generalization of vacuum die casting, porosity defects have been reduced to the point that a partial solutionizing heat treatment can be applied without any damage to the casting. However the solutionizing temperature must be lower than that applied to macroporosity free castings and for much shorter time. The object of the present study was to determine the optimum solutionizing temperature that can be applied to aluminum 383 die cast brackets along with the optimal temperature and time of aging resulting in the highest improvement in mechanical properties (both strength and ductility). This was done by testing strength and deformation on the casting itself using a specially designed jig; the crushing force to deformation curve was analyzed so as to quantify the improvement in both strength and ductility gained with the partial precipitation hardening heat treatment.

Jan 1, 2011

By Howard J. Brown

The Lucerne Valley limestone mining district is in the San Bernardino Mountains, one of the major ranges in the Transverse Range Province of southern California. Several large limestone mining operations are present along the north range front in Lucerne Valley, and the area is one of the premier limestone mining districts in the country. Resources are contained in Paleozoic carbonate rocks that are part of a thick late Precambrian and Paleozoic sequence that uncomformably overlies crystalline basement. The district has been affected by multiple episodes of metamorphism and deformation, as well as by a complex sequence of late Cenozoic structural events. Detailed studies, however, have demonstrated that these rocks can be divided into formations correlatable with late Precambrian to Permian strata of the Cordilleran miogeocline. The district is the leading producer of white, high-purity calcium-carbonate products in western North America. Pluess-Staufer (California) Inc. mines and processes high-purity white limestone from extensive deposits, and is one of the largest producers of high-quality limestone fillers and extenders in the western United States. Major factors influencing the genesis of economic carbonate deposits in the district include depositional environment, post-depositional processes such as diagenesis, dolomitization and/or silicification, regional and/or contact metamorphism and associated intrusive activity, faulting, folding, uplift and erosion, and preservation from erosion. Regional geologic studies, detailed geologic mapping, intimate knowledge of stratigraphy, and recognition of complex structural relationships have proven to be invaluable tools in the discovery of high quality calcium carbonate deposits in the district.

Jan 1, 1987

By Carlos Benavente

La actividad sísmica del Perú se origina en el proceso de convergencia de la Placa de Nazca bajo la Sudamericana, donde la geometría de la placa oceánica presenta dos tipos de segmentos, una que subduce con un ángulo de 30º hacia el este y la otra, de bajo ángulo o subducción plana. En esta perspectiva, el presente texto describe la estructura y cinemática de la Falla Purgatorio Mirave (FPM) ubicada en la vertiente pacífica de la Cordillera Occidental del sur del Perú, entre la ciudad de Tacna y Moquegua. Dicha falla tiene una longitud aproximada de 40 km al nivel, donde la placa oceánica subduce con un ángulo de 30º al este y el vector de convergencia es oblicuo en relación a la zona de contacto de las placas. Asimismo, la geometría de la costa afecta también la distribución de la deformación y la morfología resultante. La geometría, morfoestructura y cinemática de la estructura se puede dividir en tres segmentos: el segmento Este presenta una traza de falla rectilínea, morfoestructura bien conservada y el último movimiento de tipo inverso, el segmento central de traza rectilínea y escarpe de falla bien conservado, donde se observa el mayor desnivel de la FPM (3.5 m) y que afecta los depósitos cuaternarios, según las medidas de estrías en el plano de falla nos indica que el ultimo movimiento fue de tipo dextral. Finalmente, el segmento oeste presenta su parte más oriental una traza rectilínea para luego hacerse curvilínea y formar una geometría de tipo cola de caballo o echelón hacia su parte occidental, este segmento muestra evidencias deque su último movimiento es de tipo inverso, formando pliegues de propagación de falla que afectan depósitos cuaternarios.

Sep 14, 2009

By J. D. Dixon

This Bureau of Mines report describes the results of an investigation for developing and applying procedures for stabilizing excavations openings in highly yielding ground. The approach developed in this report involves nonlinear modeling of the progressive relaxation of the zones of rock mass around the excavations opening where Coulomb criterion of failure is exceeded. Stresses are calculated by using a computer code; Coulomb-failure condition is examined for both intact rock and joints (using strength parameters [~] and c). The rock mass in the failed zones is relaxed by reducing the Young's modulus of the rock based on an empirical formulation that is a function of the shape of the opening and the extent of the failed zone. In addition, the material in the failed zone is assigned reduced strength paramters 0' and c'. The limiting (or convergent) relaxed zone is obtained through an iterative process by manually changing the rock modulus and the strength parameters between iterations. Support pressures are computed by applying forces normal to the excavation surface. The approach is applied to the analysis of stability and support requirements for an entry in a longwall coal mine.

Jan 1, 1985