Search Documents

By R Munoz, R González, J Vallejos, A Delonca

In panel caving in underground mines, it is essential to characterise and monitor the stress and stability state of production level pillars to ensure the extraction of the mineralised ore column and the safety of workers. Pilar Norte is a sector in the El Teniente mine that forms a pillar between the undercut fronts of the adjacent Esmeralda and Reservas Norte sectors. It exists in a high-stress environment, which may induce damage to the rock mass production pillars. Generally, numerical models are calibrated using observed damage in galleries. This procedure does not discriminate between the structural condition and/or the blasting damage effects. This paper proposes a technique that uses borehole cameras to measure stress-induced damage. This has the advantage of being at the intact rock scale, meaning that the effect of geological structures is negligible and the blasting damage factor is eliminated. Comprehensive geotechnical characterisation and tomography monitoring has been undertaken at Pilar Norte to describe and determine the rock mass behaviour of the production pillars. By combining analytical, empirical and numerical models, a correlation between the measured overbreak recorded by the borehole cameras and the stress level of the pillar was developed. The methodology can be routinely applied to estimate the stress state in the production pillars.CITATION:González, R, Munoz, R, Vallejos, J and Delonca, A, 2016. Characterisation and monitoring of the stress state of production pillars at El Teniente Mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 197–202 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Jorge Injoque Espinoza

El presente trabajo describe la mineralogía de la plata, cobalto, níquel y oro en los principales depósitos de cobre y hierro de la faja costera. Para la descripción de los depósitos se revisan los trabajos de Injoque, así como en diversos estudios de mineragrafía, microsonda y geoquímica.

Nov 1, 1985

By R. J. Gunderman

Cable reel systems for shuttle cars were investigated to determine whether an improved system could be identified. Interviews and mine visits were conducted to better define limitations and problems with present systems. Although simple and relatively inexpensive, present cable reel systems are not fully satisfactory. Several concepts for a different technical configuration were formulated and evaluated. An all ectric system using electronic control and external sensors was recommended for further development.

Jan 1, 1980

By S Winter, G Klenowski

During longwall mining in the Bowen Basin, open tension cracks formed by overburden subsidence occur to a height of about 175 m above the mining horizon. Within this zone, water in aquifers or inundated workings will flow into the mine.At the Oaky Creek mines Aquila seam, open cut pits containing pit water overlie German Creek seam longwall panels at a height of about 105 m. The highly saline water is classified as contaminated and cannot be discharged off-site. Because alternative water storage facilities were not available, innovative water management solutions were needed to allow longwall mining to proceed without underground flooding.Computer modelling and underground inflow measurements have been completed to accurately determine inflow rates into longwall mines from overlying water sources at increasing overburden heights. Research work has also included determining cost-effective blanket treatment of final voids and reshaping spoil piles to minimise downward seepage.Ponded water overlying the Aquila low, Grasstree south and A6 pits required remedial works prior to longwall undermining to prevent flooding. In the Aquila low pit it was necessary to partition the pit and remove water overlying longwall 32. Two in-pit bridges were constructed by dozing and track compacting low wall spoil. The final void above the longwall panel was kept dry during undermining. Maximum recorded underground inflow rate was 30.0 L/s.The Grasstree south pit final void, part of the ramp and much of the spoil piles were inundated prior to undermining of 308 panel. A bridge and blanket were required to prevent ponding above the longwall. Maximum recorded inflow during undermining was 23.2 L/s.The pit A6 south final void, which contained dumped, saturated rejects and inundated highwall mining entries was undermined by longwall 36 at the Oaky No 1 underground mine. Because mapping of highwall entries was not available, the maximum calculated inflow rate of 73.0 L/s was based on all design entries being fully inundated. The actual inflow rate during longwall mining ranged up to 20.0 L/s.Water management improvements that have been implemented include greater use of contaminated pit water to wash coal, use of evaporation fans, and installation of a 6 ML/day reverse osmosis plant for water purification.CITATION:Klenowski, G and Winter, S, 2017. Inflows into longwall mines from inundated overlying workings, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 183–190 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By T. P. Mucho

Strata behavior and support performance were evaluated in a longwall tailgate test area at the Eagle Nest Mine near Van, WV. The mine operates in the Eagle coalbed which ranges in height from 4 to 6 ft (1.2 to 1.8 m) on the mine property. Rugged topography results in rapid changes in overburden which ranges from 200 to 1200 ft (61 to 366 m). The immediate roof at this mine transitions from sandstone to shale. In some areas the sandstone appears to be massive while in many locations it is highly laminated, fossilized, and interspersed with coal streaks. Horizontal stress levels appear to be sufficient to create instabilities in the roof in some locations, especially where the roof is thinly laminated. Traditionally, hardwood cribs have been used at the mine to provide secondary support for longwall tailgates; Strata Products' Hercules cribs are installed on 8 ft (2.4 m) centers staggered left and right in the tailgate entry. In a 250 ft (75 m) tailgate test area, however, cable bolts were installed in lieu of cribs. The bolts were 12 ft (3.6 m) long tensionable cables anchored with 5 ft (1.5 m) of resin. Four cables were installed across the entry and rows were spaced on 6 ft (1.8 m) centers. Primary roof support was maintained in the vicinity of the test area using 42 in (1.1 m), grade 60, No. 6 (19 mm diameter) resin bolts installed on 4 ft (1.2 m) centers through T-2 channels. The cable test area was located under a stream valley in an area of relatively shallow overburden. Strata instabilities consistently had been associated with the stream valley in both the Eagle and the overlying Powellton coalbeds. In an effort to further expose the cables to the most difficult stress conditions available at the time of the test, the specific site chosen was directly beneath a barrier pillar remaining in the upper Powellton mine (approximately 150 ft (45 m) of interburden separates the two coalbeds).

Jan 1, 1996

By Robert E. Wilson

TO show the vital importance of our future oil supplies to our economy, I will merely point out that this country, with something like 15 per cent of the world's land area and something like 7 per cent of the world's population normally uses between 65 and 70 per cent of the motor vehicles of the world, between 65 and 70 per cent of the world's rubber, and produces and refines between 65 and 70 per cent of the world's petroleum. Despite all the arguments as to which is cause and which is effect, all will agree that all three of these important industries are mutually dependent. If we had not been able to produce 65 or 70 per cent of the world's oil in this country we would not have the degree of mechanization, or the efficiency of transportation, or the high industrialization that we enjoy. Furthermore, the fact that oil has been plentiful and cheap has had a tremendous effect on all the things in which we as engineers are interested. For that reason, if for no other, it is well to look ahead to see what the outlook is for the near and far-distant future.

Jan 1, 1945

"The characterisation of resources and description of variability across different ore domains is key to accurate prediction of probable metallurgical performance. Such characterisation testwork often has limited drill-core from which to work and this immediately confines the characterisation method to smallscale. For flotation feeds, the JKMSI (Mineral Separability Indicator) is being developed as a potential characterisation tool, building on earlier work by Chudacek, (1990), which used shaken test tubes, and was called the EMDEE device. In addition, the consistency of flotation recovery for specified size fractions has shown to be preserved, irrespective of the amount of material in that size fraction obtained by different milling conditions, so that the overall recovery can be estimated from knowing the particle size distribution (McIvor and Finch, 1991; Bazin et al, 1994, Runge, 2007 and Wightman et al, 2010) The JKMSI unit uses less than 10 g of material per test in narrowly sized classes and results to date have demonstrated the value of the test. This paper discusses the potential of the test by demonstrating the link between JKMSI performance and mineralogy of five different ores from Laguna Seca, Escondida Minera Limitada as well as the correlation to plant scale performance obtained in an earlier survey (Coleman et al, 2006). Further work to tie down the proof of representatively of the small sample has been identified and is discussed and included in the paper. INTRODUCTIONSince the uptake of the flotation process at the turn of the twentieth century, small scale, laboratory methods have been sought to characterise flotation response. Although laboratory batch flotation tests are the most widely used method to evaluate reagents, characterise ore variability and obtain suitable model parameters using various scale up factors Runge (2101) other methods using less ore would be useful where ore samples were limited.A method using test tubes for testing ores’s flotation response to reagents was first developed by Ian Walk (Wark & Wark, 1935; Wark; 1938; Sutherland and Wark 1955). In these tests a 50 cc stoppered measuring cylinder served as a means for a qualitative experiment, the aeration being effected through violent shaking by hand. In these experiments about 10 g of mineral was ground by pestle and mortar under water after which the ground material was deslimed and adequately conditioned with the appropriate reagents."

Jan 1, 2013

By Xingjian Gao

The mechanical properties of a low carbon low alloy steel in the austenite and _-ferrite regions have been examined by thermal-tensile tests using a Gleeble-1500D system at temperatures in the range 600oC to 1300oC and at a strain rate of 10-3/s; these being the conditions that apply to the unbending operation during the continuous casting of steel. The yield strength and tensile strength of steel decreased with increasing test temperature and the embrittlement zone occurred in the temperature range 800oC to 970oC. In the embrittlement zone, the fracture surfaces and microstructures of the tensile specimens were examined by scanning electron microscope. The results showed that the cause of the embrittlement at 950oC in which the minimum %R of A was around 36% is the second phase particles precipitated along the _ grain boundary during deformation leading to inter-granular brittle fracture.

Jan 1, 2010

By W. Roy Dunbar

"The Porcupine area is in northern Ontario at the intersection of N. Lat. 48° 30' and 81° W. Long. It is 125 miles due north of the Sudbury nickel range. Practically all the mineral production of this area has come from the townships of Tisdale, Deloro, Whitney, and Ogden, in order of importance. The accompanying map of the Porcupine area and its extensions to the east and west (Fig. 4) has been included to show what I consider to be an essential objective of this paper, a perspective for exploration.The discovery of gold ore in the Porcupine area at such an early date resulted from the extension of the Temiskaming and Northern Ontario railway and exploratory survey lines north into unexplored territory, for the early history of Porcupine is inextricably tied to the exploration along Niven's survey lines and the extension of the railway north from Cobalt to Nellie Lake. The following are the more significant events leading to the discovery of gold in Porcupine.1896-E. M. Burwash, employed by the Ontario Bureau of Mines, examined the country along Niven's base line and noted quartz veins that carried traces of gold. He was attached to Niven's survey party.1899-The late W. A. Parks reported on the geology of the portage route from Mattagami river to Night Hawk lake, for the Ontario Bureau of Mines. He noted the occurrence of gold in quartz veins and reported “I regard the region south of the trail to Porcupine lake as giving promise to the prospector"". He also was attached to Niven's survey party.1901-Charles Camsell, while prospecting for the Algoma Central railway, did some work on a vein occurrence carrying low gold on ground now known to be part of the Hollinger mine (3).1907- Extension of the Temiskaming and Northern Ontario railway to Nellie Lake.1909- Bannerman followed up Indian story about occurrence of coal, and found iron formation. He remained to prospect and found the gold-bearing vein of the Scottish Ontario property."

Jan 1, 1954

By R. A. Cattell

Progress of Bureau of Mines research related to oil and gas during the past fiscal year has been marked by the publication of more than 40 reports on the various phases of the work . These include papers dealing with the production of oil and gas , transportation of gas , chemistry and refining of petroleum , thermodynamic properties of hydrocarbons , and the processing and utiliza- tion of helium . As an additional service to Pennsylvania oil operators , a new suboffice was opened in Bradford , Pa . , during the year . With this addition , the work of the Petroleum and Natural Gas Branch of the Bureau of Mines is now conducted in two large stations , the Petroleum Experiment Station , Bartlesville , Okla . , and the Petroleum and Oil Shale Experiment Station , Laramie , Wyo . , and three field offices and laboratories at San Francisco , Calif . , Dallas , Tex . , and Franklin, Pa., and two suboffices, Wichita Falls, Tex., and the newly opened suboffice at Bradford, Pa. In addition, this Branch operates large-scale helium-production plants in Texas, Kansas, and New Mexico, and maintains ex- tensive helium-bearing gas reserves in Texas and New Mexico. All helium opera- tions are supervised from headquarters at Amarillo, Tex. A small headquarters staff is in Washington, D. C. A backward glance at the road traveled during the past several years by the Petroleum and Natural Gas Eranch of the Bureau of Mines brings out a general background for the events of the fiscal year 1949. Throughout the fiscal year 1945, the activities of the Branch were still mainly concerned with such war activities as making special field studies for the Petroleum Adminis- tration for War, finding ways of increasing rates of production, and supplying data pertaining to the manufacture of aviation and jet-propulsion fuels. A period of adjustment came in 1946, characterized by a turning from war to peace procedures and efforts to give wide distribution to technical facts ob tained in wartime research; also, there came a realization that the demands of war had broadened the horizons of research. This was emphasized in 1947, when a peacetime program was restored, based upon the long view of the Bureau's place as a research agency in oil and gas. Close attention was given to tech- nical detail in 1948, and emphasis was placed on maintaining a balance between the industrial need for technical knowledge and Governmental-research possi- bilities in the fields of (1) withdrawal of petroleum from natural deposits, (2) utilization of petroleum and its products, and (3) commercial utilization of helium. Studies of petroleum production and utilization and helium production and utilization are the normal functions of the Branch. These functions (sometimes expressed in different words) have been the mainstay of this organization since initiation of the work. The details of approach vary with changing conditions, but, fundamentally, the functions have been the same in both peace and war. The work of the past fiscal year has emphasized the advantages that accrue when Government and industry join in a wise use of technical and scientific knowledge gained through research. Outstanding evidence of the beneficial results of cooperative effort by the Bureau of Mines and various organizations is found in the following typical examples, the details of which are discussed in the body of this report. Working in close cooperation with operators along the Gulf Coast, the Natural Gasoline Association of America, and the National Association of Cor- rosion Engineers, the Bureau found, through field testing, that corrosion protection by means of chromates in high-pressure gas-condensate wells costs less than $1 per million cubic feet of gas produced. Laboratory experiments to measure the corrosion effects of carbonic and propionic acids on various steels and alloy steels gave data that will serve as guides in the selection of new. materials for the construction of well equipment to be tested by industry under actual service conditions.

Feb 1, 1950

By M. Mahan, D. D. Blue, O. C. Garst, F. Fraas, L. Fink

"Early in World War II it became apparent that the known bauxite re- serves might not be adequate to supply the demands of the American aluminum-producing industry, as the transportation of bauxite from abroad to this country might easily be interfered with by hostile action. Consequently, the Bureau of Mines set up an intensive, well-integrated program for the production of cell-grade alumina from low-grade domestic ores. This pro-gram of investigation covered the production of alumina from clay, alumite, red mud, and other low- and marginal-grade ores. In line with the Bureau's usual policy of conservation of natural resources, it was decided that the investigation should be extended to cover the production of alumina and other valuable byproducts from aluminum dross.Statistical information showed that during the year 1943-44, an average of 2,900 tons of aluminum dross was generated monthly. This dross, after partial removal of free metal, had an average metallic aluminum content of approximately 9 percent. Some of this dross was produced by the melting of alloyed aluminum; but a large proportion 1,700 out of 2,900 tons - was generated by two producers of primary aluminum, and the dross did not contain an great proportion of alloying metals. Compared with dross from other sources, this 60 percent of the country's capacity can be assumed to have relatively uniform composition. Moreovcr, the problem of collection and distribution can be minimized because of the relatively small number of plants included in the organization of these two producers of virgin metal.Except for large pieces of metallic aluminum that easily can be mechanically separated for remelting, this dross has been discarded and scrapped. Inasmuch as chemical analyses show that the alumina content of dross is far higher-than ordinary ores - 111 percent alumina equivalent in dross compared to 57 percent alumina in bauxite - aluminum dross is a far richer source of aluminum than any known naturally occurring ores. The discard, of this waste material during the war and reconversion periods would be unsound economically. The work reported herein describes tests at the College Park Station of the Bureau of Mines on the recovery of metal, alumina, ammonia, methane, and abrasive-grade corundum from dross."

May 1, 1946

By F. R. Jones, B. W. Taylor, A. R. MacPherson, L. J. Lamb

"The Lake St. Joseph Iron Deposit is in Northwestern Ontario. Exploration to date by Steep Rock Iron Mines Limited has indicated an ore reserve of 683 million long tons. Metallurgical investigations have proved that suitable oxide pellets and/or superconcentrates can be economically produced from this ore. Studies of the Lake St. Joseph iron ore deposits have covered the period 1956-71, and have embodied applications of the improvement in mining and processing technology over this period. Market demand in the early 1960's for high-grade oxide pellets as a replacement for natural iron ores for the blast furnace first drew attention to the potential of the Lake St. Joseph deposit. The current market trend toward utilization of sponge iron to replace steel scrap as feed to electric furnaces and cupolas now suggests that the deposit can better be exploited as a prime source of superconcentrates."

Jan 1, 1972

By C. G. Maier

Relatively infrequent use by metallurgists of the term "sponge chromium" as contrasted to more than occasional reference to "sponge iron" may be ascribed to the fact that the former material is not a commercial product, while the latter has been known and used, at least in one form (Swedish sponge iron), for several decades. It is doubtful whether a true sponge chromium ever has been prepared heretofore in the laboratory by more than one or two investigators. Nature presents a much. more difficult problem to the investigator endeavoring to make sponge chromium than pertains to the production of more easily reducible elements such as iron or nickel. Recent widespread interest among metallurgists in the possibilities of powder metallurgy is ample incentive to explore the feasibility of producing pure chromium metal in finely divided form. The shift in terminology of this statement from "sponge" to the "finely divided form" is deliberate in emphasis of distinction between terms that occasionally have been used loosely. It would seem desirable that a uniform usage descriptive of finely divided metals be adopted. While to some it might seem preferable that the terra "powdered" metal be reserved for a finely divided form produced by mechanical means, as, for example, chromium produced by the mechanical comminution of electrolytic sheets or flakes, current usage of the term "powder metallurgy' involves no distinction as to source type of material. It is usually accepted, however, that a sponge metal is one reduced from oxide or other combined form at temperatures below the melting point of metal or oxide so that the particles of metal are pseudomorphic, at least macroscopically, with the source material, and, in consequence of the loss of material without change of external shape of the particles necessarily have an open, porous, or "spongy" structure.

Jan 1, 1942

By John J. Mulligan

The Bureau of Mines investigated the tin deposits of the Cape Mountain area during July and August 1962 to test the effectiveness of detrital-cover sampling in permafrost areas as a relatively cheap and simple means of guiding mine development and exploration. Results indicate that systematic detrita1-cover sampling can be used effectively to delineate obscure deposits with sufficient accuracy to permit sampling with a minimum of trenching or drilling. Extensions of known outcroppings were traced in sufficient detail to guide lode sampling and several previously unknown tin-bearing lodes were found and sampled. Lode sampling was limited to the minimum needed to establish the reliability of detrital-cover sampling results. The results of previous lode and placer investigations are summarized and detrital-cover sampling methods and results are described in detail.

Jan 1, 1966

By Charles D. Haynes

Outside air for ventilating coal mines in Alabama varies considerably in both temperature and moisture content during the year. Alternate condensation and evaporation of the moisture on mine roofs may result in stresses detrimental to the strength of mine roof. It is well known that the clays in shales absorb moisture, and many investigations have noted the weakening of shales by absorption of moisture. Parker (1970) concluded that there is an annual cycle of rock deterioration in mine roof rock caused by the annual temperature-humidity cycle at the surface. He further noted that moisture reduces the strength of dry rock by one-half, that moisture added to dry rock can cause failure in compression, and that drying of wet rock causes tensile stress buildups by shrinkage. His recommendations for alleviating the moisture-temperature problem was to seal the rock in critical areas and to control ventilation so that air temperature will be lower than rock temperature. The latter recommendation will avoid condensation on the rock surfaces. Hartmann and Greenwald (1941) published the results of a very comprehensive experimental project to determine the effect of temperature and humidity changes on the behavior of mine roof. Their general conclusions included statements that roof rocks were very sensitive to moisture changes, but had low coefficients of thermal expansion. The coefficients were twice in the direction normal to the bedding plane as compared to the parallel

Jan 1, 1975

By José Rogério de Oliveira Júnior, Carlos Eduardo dos Santos, Geraldo Lúcio de Faria, Sidney Nicodemos da Silva, Rogério Felício dos Santos, Darlan Vale Bayão, Emiliana Cristina Marques Arthuso, Ivete Peixoto Pinheiro

A fase sigma () é conhecida por afetar negativamente as propriedades mecânicas e a resistência à corrosão dos aços inoxidáveis duplex (AIDs). Dessa forma, a exposição da liga a temperaturas elevadas durante os processos de produção, soldagem ou tratamentos térmicos devem ser realizadas de maneira cautelosa a fim de se evitar a precipitação da mesma. Assim sendo, modelos adequados para predizer a precipitação da fase são ferramentas muito úteis. Entre os numerosos modelos, a relação de Johnson-Mehl-Avrami-Kolmogorov (JMAK) é um dos modelos mais comumente utilizadas para descrever a cinética das transformações isotérmicas de fases em muitos sistemas regidos pelos mecanismos de nucleação e crescimento. Diante disso, o presente trabalho teve como objetivo realizar um estudo cinético baseado na aplicação do modelo JMAK, da precipitação da fase em um AID UNS S31803 envelhecido isotermicamente nas temperaturas de 750ºC, 800ºC e 850ºC. Concluiu-se que a cinética de precipitação da fase na liga obedeceu ao modelo JMAK, pois foi obtida uma boa correlação entre dados experimentais e os simulados. Observou-se que o aumento da temperatura de envelhecimento de 750ºC para 850°C acelerou a cinética de precipitação de A energia de ativação determinada (182,4 kJ/mol) para precipitação da fase neste sistema, sugere que a difusão do Cr na ferrita seja o principal mecanismo envolvido na formação dessa fase.

Nov 2, 2019

By R. J. O'Dea

"The United States hat large reserves of titaniferous iron ores that are a potential future source of both iron and titanium. Although it is not now economically feasible to recover iron and titanium metals from these ores, they may become important in times of stress and, in some instances, already have served as a source of pigment-quality titania.The iron- and titanium-bearing constituents of the ores considered in this report are not completely separable from each other by ore-dressing methods, and chemical (or smelting) procedures must be employed. It is im¬portant, therefore, that information be available concerting their reactivities. The most important titanium-bearing constituent is ilmenite (FeTiO3), the thermodynamic properties of which were discussed in a previous publication.3/ The results of thermodynamic studies showed that both hydrogen and carbon monoxide are relatively ineffective reducing agents for the iron in limonite. On the other hand, carbon theoretically is effective at tempera¬tures above 8510C., at which. point the combined equilibrium pressures of CO and CO2 from the reactionsFeTiO3 + C = Fe+ TiO + COand200 = C+ CO2reach 1 atmosphere.This report gives results of small-scale tests of selective reduction by carbon of the iron in titaniferous iron ores, both with and without addition of sodium carbonate. It is shown that the bulk of the iron may be reduced and separated without serious reduction or loss of titanium. Three Wyoming ores, Iron Mountain, Shanton, and Taylor, wore studied. The principal factors investigated were temperature, time, carbon:ore ratio, particle size, and sodium carbon ore ratio.Two methods of investigation were employed. In the first, intimate mixtures of ore and carbon were roasted and the reduced iron and titanium evaluated by leaching with dilute sulfuric acid and analyzing the leach solution (and, in some instances, the dried residues).Twenty grams of ore were mixed thoroughly with carbon and tamped into an alundum thimble having a loosely fitting cover. The thimble and contents were placed in a test-tube end porcelain tube and heated to the desired temperature in a Globar tube furnace. The open end of the porcelain tube was connected to a bubbler containing sulfuric acid, in a manner that permitted complete shut-off of the tube when desired. This allowed removal of the tube from the furnace at the end of the roast period without exposure of the contents to the atmosphere."

Jun 1, 1946

By R. S. Handy

This paper describing the milling practices at tae concentrators of the Bunker Hill and Sullivan Mining and Concentrating Co. is one of a series being prepared by the United States Bureau of Mines on milling methods and costs in the United States. The possibility of useful comparisons has prompted the description of all five of the mills operated by the Bunker Hill and Sullivan Company in northern Idaho. The general features of these mills are tabulated below: [ ]

Jan 1, 1930

By D. T. Bergado

The uppermost subsoil profiles of the Bangkok plain can be divided into four layers, namely: weathered clay, soft clay, stiff clay, and dense sand layers. The soft Bangkok clay is a normally consolidated marine clay with built-up preconsolidation effects and overlain by a weathered crust. Up to the present, a large number of full-scale tests on excavations and pile foundations has been made by numerous investigators. Based on these results, the available data are reviewed and evaluated. The results show that for test excavations, the excess pore pressures were overpredicted by the existing theories. The vertical and lateral movements in the excavations can be predicted by the bilinear and non-linear finite elements using appropriate modulus values. Relationships among probability of failure, safety factor, and safety margin of the excavation were also obtained. In the case of pile foundations, good agreement between the measured and predicted ultimate pile capacities were obtained for long piles. The adhesion factors ranged from 0.4 to 1.0 while the average skin friction factor was found to be 0.33. The ultimate capacity of the pile was also predicted successfully by using the Dutch cone data. For lateral deflection of piles, Davisson and Gill's theory predicted well in the low deflection zone while Poulos' theory agreed well in the high deflection zone. From the probabilistic analysis of ultimate pile capacity, the probability of failure was related to the central factor of safety. The piles usually used in Bangkok area are mainly precast concrete piles

Jan 1, 2010

By Steve Kral

The Prospectors and Developers Association of Canada (PDAC) was established in 1932 in response to proposed regulations that would have threatened prospectors in Ontario. From there, the association grew to represent the interests of Canada?s mineral exploration and development industry. The PDAC?s mission statement reads: ?The PDAC exists to protect and promote the interests of the Canadian mineral exploration sector and to ensure a robust mining industry in Canada. The PDAC will encourage the highest standards of technical, environment, safety and social practices in Canada and internationally. ?Today, the PDAC?s 6,000 individual members include prospectors, developers, geoscientists, consultants, mining executives and students. In addition, the association?s membership includes 950 corporate members, representing senior, mid-sized and junior mining companies in addition to organizations that provide services and equipment to the mining industry. In 2010, the PDAC adopted its e3 Plus principles, a framework to guide its membership in responsible exploration.

Jan 1, 2011