Search Documents

By F. E. Heuze

This article deals with the effects of high-explosive and nuclear explosions in rock masses. We first highlight the strong influence of geological discontinuities, such as joints and faults, on ground motion characteristics. Then, we briefly introduce the Discrete Element Method, as a new technique for numerical simulations. II is shown to be far superior to continuum-based approaches, when dealing with the dynamics of discontinuous media such as jointed rocks. Finally, we simulate the ground effects from a generic contained nuclear explosion, which bears some similarity to the SHOAL event in granite. This calculation is intended to emphasize the influence of the near-source geology on the distribution of energy, and on the motion at various azimuths in the medium.

Jan 1, 1991

By G. Noce

The ever more present necessity for greater precision in foundation structures on vertical piles subject to horizontal forces applied to the heads, in the light of of the latest knowledge about the elastic-plastic behaviour of the soil has led to the use of numerical calculation for the formulation of a general resolution method for the problem. The calculation method that will be set out, applicable to piles with inertia moments variable discreetly along their axes is especially useful when studying steel structures for medium and large tonnage vessels for which the metal piles are often constructed for the assembly of section of equal external diameter but different thickness and therefore different inertia moments. Two examples are given of constructions whose foundations have been projected with these calculation tools, one in the railway sector (foundation pile for the river Nera viaduct - Italy) important for the limitation of horizontal relative deck displacement, the other maritime (Dolphins of the petroleum pier of the port of Bandar Abbas - Iran).

Jan 1, 1989

By Hidenori Hatta, Takero Watanabe, Hideo Yoshida

"The effect of the quenching rate on age hardening in an Al-6.0mass%Zn-0.75mass%Mg alloy sheet was investigated. The quenching rates and aging conditions were as follows: water quenching (WQ) or furnace cooling (FC) followed by pre-aging at 20°C,then artificial aging at 120, 160 or 200°Cwere performed. The peak strength of the FC and the WQ are very similarat120°C aging. It is important high strength was obtained even at the extremely slow quenching rate. On the other hand, the strength of the WQ significantly decreased compared to the FCat200°C aging. GP(I) zones were formed during the pre-aging at 20°C even if the cooling rate was very slow like the FC, and were transformed into the GP(II) ones at 70°C or higher and then into the ?’ phase. However, these zones were dissolved by reversion during heating to 200°C. Thus the strength of the WQ decreased. On the other hand, it is considered that an unknown cluster or GP zone with a thermal stability formed during the FC was not dissolved up to 200°C and was transformed into the ?’ phase. Therefore, a higher strength was obtained in the FC for the200°Caging.INTRODUCTIONAl-Zn-Mg alloys are widely available in commercial production because these alloy have lower quench sensitivity and can be produced by air cooling (AC). Heat treatable aluminum alloys are usually produced by water quenching (WQ) to increase their strength because a high cooling rate inhibits the precipitation of the stable phase during cooling and increases supersaturated solute atoms. However, Baba(1967)reported the strength of an Al-6%Zn-1.8%Mg(mass%) alloy without additional elements quenched by very slow cooling (15°C/min) was 96% of that quenched by WQ. Furthermore,the age hardening at room temperature (RT) occurs after annealing at 410°C followed by furnace cooling (FC, 0.5ºC/min or less)in these alloys. Therefore, the process of annealing at 410 to 430°C for 120 min followed by AC, and reheating at 230°C for 240 min, then cooling is recommended in the specifications (Japan Aluminum Association, 2011). Matsuda and Yoshida(1996)also recommended annealing at 300°C for Al-Zn-Mg alloy extruded products to inhibit age hardening at RT by precipitating the solute atoms and decreasing them in the matrix. It has been considered that the higher the content of excess quenched-in vacancy becomes by WQ, the higher aging rate at RT is obtained. Therefore,it is theoretically and commercially important to clarify the reason why the age hardening occurs relatively quickly in almost no excess quenched-in vacancies such as the FC, and why the same strength as the WQ can be obtained in the FC"

Jan 1, 2018

By H. Reimer

The rates of return on investment are examined for several major Canadian mining companies. Because we are dealing with a highly cyclical industry, subjected to widely fluctuating metal prices, rates of return are examined over a 20-year period. Conveniently, the first decade examined reflects the period when the industry enjoyed incentives to develop deposits; during the second decade, incentives were reduced and the industry became the most heavily taxed industry in Canada. The high rates of inflation since 1973 have distorted the real rates of return on investment if one considers replacement cost.

Jan 1, 1977

By A. C. Fieldner

This is the tenth annual report of research and technologic work conducted by the Bureau of Mines on the occurrence, properties, mining, preparation, and uses of coal and coal products. These annual reviews are guide's to the current work-and publications of the Bureau but do not replace the more complete reports published under the authorship of the individual investigators on specific problems in Bureau of Mines bulletins, technical papers, reports of investigations, and information circulars and in the technical press. The Annual Report of the Director of the Bureau of Mines to the Secretary of the Interior for the Fiscal Year ended June 30, 1945, summarizes the year's work on coal as follows: Coal and Coal Products The United States maintained its No. 1 industrial position in supplying fuel for war and in preparing for peace through more complete mining, improved preparation and up-grading of coal for special uses, and better utilization of coal in industrial establishments and homes.

Jan 1, 1946

By Helen D. Robinson

Traditional practice to resist large lateral loads on foundations is the use of large diameter caissons, battered driven piles, or battered micropiles. Dense urban construction environments, however, limit the usefulness of these systems due to the close proximity of below- and above-grade obstructions. This paper presents two micropile construction projects in the United States where a complex scheme of battered micropiles and grade beams was developed to counteract large lateral loads at the foundation level. The paper also presents a procedure used to design vertical micropiles for large lateral loads, which can greatly simplify the design of foundations subject to significant lateral loads in urban environments. A design example shows a case where vertical micropiles were used to support allowable design lateral loads greater than 80 kip per micropile.

Jan 1, 2010

By Frederic P. Dewey

The Bureau of the Mint of the United States Treasury maintains 13 ofEces for the purchase of gold-bullion, and this paper describes an investigation to establish the reasonable differences in the assay-results at the various institutions which may be commercially allowable in the settlements between them. Beginning with the comparative assay of proof-gold at the Philadelphia mint and the Utrecht mint, which shows 0.00002 as the closest agreement now possible, nine tables of comparative results, taken from the regular work of the service, are given..These tables begin with very fine gold, produced in an electrolytic refinery, showing close agreement in the assay-results, and follow through decreasing gold fineness and increasing amounts and complexity of base metals to very impure and complex bars produced at cyanide-mills, some of which give widely-varying results. Next is given a series of results on samples, prepared and sent out to various laboratories in the service, to test the influence of different metals and various combinations upon the agreement of the assay-results ; 11 samples were sent out and each one was assayed from 44 to 71 times, making a total of 623 assays. To these ire added 107 assays of identical samples of coin-gold. On a previous occasion,' I have endeavored to show the degree of accuracy that may be expected in the ordinary everyday analysis of various materials, and on another occasion,2

Jan 1, 1910

By D. J. Steynfaard

Sishen Iron Ore Mine is situated 280 km north-west of Kimberley in the Northern Cape Province of South Africa. The mine produces and sells high quality iron ore of various specifications to various national and international clients. The saleable product is derived from the blending and beneficiation of different types and qualities of hematite iron ore. This paper documents the new developments which were implemented (or are in the process of being implemented) on the mine in the long-term planning, medium-term planning, grade control and material tracking in the beneficiation plant with special attention being paid to the quality of the final, saleable product. The process starts with the long-term planning where the pit shell and pit optimization is determined by Whittle 4X. New developments include the introduction of a linear programming based scheduling system to enhance the long-term schedule generated by Whittle 4X. The LP route was decided on in order to take into account all the constraining factors of the final product that could not be configured in Whittle. To complement this the XPAC Auto Scheduler scheduling package was introduced to do the medium-term mine scheduling. This 18-month rolling plan includes cost parameters to enable the planner to extract a detailed operational budget from the scheduling while ensuring that production standards are maintained and grade constraints are met. The existing grade control system was enhanced with GPS capabilities and a computer system to do material tracking. The high precision GPS system introduced on the shovels allows for the accurate control of the loading procedures at the mining face. Because of the complicated geology and grade composition of blasting blocks it is imperative to accurately differentiate between different materials in the same blasting block and being able to excavate that with the loading equipment. The GPS system on the trucks allows for accurate location monitoring of dumping in order to keep track of specific material types. The state-of-the-art material tracking system developed for Sishen will enable the grade control officer to keep track and record various parameters of the material from its in situ position in the blasting blocks, through the crusher and onto different stockpiles, in various stages of the beneficiation process and onto the blending beds, into the dispatching trains and eventually into the ships for international distribution. These developments elevate the Sishen planning and grade control systems to a new level of service excellence from which management can obtain accurate and timely information on product status. It also enables Sishen to maximize resource utilization while still complying with the tough market constraints.

Jan 1, 2003

By J. Kunze, R. Degal

During the last 100 years, the submerged arc furnace has been one of the most amazing diversified melting units. These furnaces have found their application in more than 20 different main industrial areas such as iron, ferro alloy, chemical industry, lead, zinc, copper, refractory, titanium oxide, recycling, phosphorus etc. Such an evolution was only possible because of tremendous efforts in research and development and due to the large range of design solutions. The worldwide strong competition also forced the industry and plant suppliers to develop highly efficient, economically balanced units in optimized sizes and with long lifetimes, to adapt to the market conditions. Regarding the environment, the plants improved significantly in terms of water treatment plants and off-gas treatments as well as on site recycling units. This paper will give a short overview regarding the history of the furnace and the latest developments in today?s main application fields: ferro alloys, non-ferrous, special application and recycling. In addition new activities in research and developments are briefly discussed.

Jan 1, 2004

By Met M. E, Worner H. K

During the past two years, a large number of creep tests has been carried out on electrolytic lead, special assay lead and ordinary refined (Port Pirie) lead. Some of these tests have already been reported.1§ In addition, an attempt has been made to estimate the influence of the individual elements present in small traces in Port Pirie lead. The present paper gives the results obtained when small additions are made to "U" lead of the composition shown in Table 1.(which has been used throughout these investigations during the past few years). The additions were silver, antimony, bismuth and zinc. The results of the addition of tellurium have already been communicated. This investigation was intended to run parallel with a similar one using electrolytic lead as a basis and adding one element at a time.Actually, the experiments using "U" lead have got rather ahead of the others. The important point has emerged, however, that the effect of a .given addition may be appreciably influenced by the presence of traces of other elements.In most of these tests, an initial stress of 500lb. per sq. in. has been used. Whilst it is fully appreciated that this stress is higher than those used in practice, it has to be borne in mind that an improvement in creep resistance was *Manuscript received December 11th, 1936.

Jan 1, 1936

By D. A. Ainsworth

"The first known use of activated carbon dates back to the Ancient Egyptians who utilized its adsorbent properties for purifying oils and medicinal purposes. Centuries later, the early ocean going vessels stored drinking water in wooden barrels, the inside of which had been charred. (However, by modern definition the carbon used in these applications could not truly be described as activated.) By the early 19th century, both wood and bone charcoal was in large scale use for the decolorization and purification of cane sugar.However, it was not until the beginning of the First World War that the potential of activated carbon was really capitalized upon. The advent of gas warfare necessitated the development of suitable respiratory devices for personnel protection. Granular activated carbon was used to this end as, indeed, it still is today.By the late 1930's there was considerable industrial scale use of carbon for both gaseous and liquid phase application and new manufacturing processes had been developed to satisfy the needs of industry. During the 1939-1945 war, a further significant development took place - the production of more sophisticated chemically impregnated carbon for the removal of both war and nerve gases."

Jan 1, 1984

Four taconite plants were studied to establish the extent of hazard to plant personnel which exists based on long-term exposure to noise. The criteria for evaluation include the 90 dBA and 85 dBA summations of partial exposures. Data from extensive interviews were used to determine all work stations or locations which employees occupied and how much time they spent in ach location in a typical working day. Noise level measurements at every designated location were then made. By means of a computer program, these time and noise level data were us d to find the optimum noise reductions which would be required throughout each plant to meet both noise criteria. Subsequently, each plant was examined in detail so that the apparent sources of noise for each of the locations requiring noise reduction could be delineated. In tabular form, this report presents the hazardous locations for each plant, the existing noise level, the optimum noise reduction which would be required to meet the current and proposed laws, and the sources of noise which produce the existing noise level.

Jan 1, 1977

At the Prospectors and Developers Annual Convention (PDAC) in Toronto, Canada mining and exploration companies of all sizes were on hand to discuss the year that was and those that will be. The following is a look at some of the companies with Canadian operations that were on hand for PDAC 2009. Iamgold Corporation is a leading mid-tier gold mining company producing approximately 31 t (1 million oz) of gold from seven mines on three continents. With record revenues of $870 million ? up 28 percent when compared to 2007 ? the company is focused on growth with a target to reach 56 t (1.8 million oz) gold production by 2012. During 2008, the company acquired the Essakane project in West Africa. The project is fully permitted, under construction and will contribute more than 9.3 t (300,000 oz) of lower cost production by late 2008. Iamgold increased its reserves by 55 percent, to 385 t (12.4 million oz) and its resources in-creased by 16 percent to 821 t (26.4 million oz) in 2008. Going forward, Iamgold has three areas of focus ? West Africa, Guyana Shield and Quebec ? with seven gold operations, five advanced projects and the Niobec niobium mine included. The Rosebel Mine in Suriname is Iamgold?s fl agship property. With measured and indicated resources of 300 t (9.6 million oz), it accounts for 30 percent of Iamgold?s production. Production there was up 20 percent compared with 2007 and further production increases are expected in 2009 and 2010. Mill expansion and optimization increased throughput from 8.9 Mt/a (9.8 million st) to 10 Mt/a (11 million stpy). In West Africa, Iamgold has joint ventures at Sadiola in Mali; Tarkwa in Ghana; Yatela in Mali and Daman in Ghana. Iamgold also has 100 percent ownership of the Mupane gold mine in Botswana and the Doyon gold mine in Quebec, Canada. Also in Quebec, Iamgold has 100 per-cent ownership of the Niobec niobium mine in Quebec. Niobium is used in high strength specialty steels.

Jan 1, 2009

By J. Shawn Peterson, David S. Yantek, Adam K. Smith

Occupational noise-induced hearing loss continues to be one of the most pervasive health problems in the mining industry, despite over 25 years of regulation. One of the loudest pieces of equipment used in underground mining is the continuous mining machine. Noise sample data collected by the Mine Safety and Health Administration indicate that 42% of noise overexposures between 2000 and 2005 involved continuous mining machine operators. Previously conducted field and laboratory tests have determined that the continuous mining machine conveyor system is a dominant noise source. Loud impacts occur as the conveyor chain flight bars, used to move the mined aggregate, traverse their path from the top to the underside of the conveyor deck. Various noise control treatments have been applied to abate noise caused by the conveyor system. A durable polyurethane coating has been developed for the conveyor flight bars, resulting in a time-weighted average reduction of 3 dB(A) for an eight-hour work shift. In an attempt to further reduce continuous mining machine operator overexposures, a similar urethane coating has been applied to the tail roller component of the conveyor system. Laboratory results showed a 2 dB(A) reduction in sound power levels, but the component failed during underground durability testing. An outer steel sleeve has been added to the urethane coating of the tail roller to enhance wear resistance during mining. The urethane jacketed tail roller is the latest effort, combined with previous noise treatments, to bring the continuous mining machine into compliance with federal noise regulations.

By Mike Watts

Since the first longwall panel development started in the new mining, (Southern) area, a number of roof falls have occurred in L1 and L2 gate-entries. The longwall was delayed for a total of two months due to roof falls in the gate-entries. To prevent roof falls in future gate-entries, an extensive ground control analysis has been conducted which incorporated regional horizontal stress and panel orientation, tectonic stress, roof strata, surface stream valleys, etc. Results of the analysis indicate that a combination of these factors caused the roof falls. Therefore, a Roof Instability Rating (RIR) system was constructed to predict the roof condition and identify areas where supplemental support should be implemented. The L3 gate-entries, supported by the prediction using the RIR system, have not experienced any roof problems.

Jan 1, 2000

By B. P. Watson

The Bushveld platinum group metal deposits are two distinct, shallow-dipping stratiform tabular orebodies which strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 300 m. The mining method is a variation of planar open stoping. Pillars are widely employed to support the open stopes. In the deeper levels, in-stope pillars are required to fail in a stable manner soon after being cut, and the residual pillar strength is used to stabilize the hanging wall. These pillars are commonly known as crush pillars. Little work has been done in the past to determine pillar peak and residual strengths, and pillars have been designed using experience and formulae developed for other hard-rock mines. This has led to over and undersize pillars with consequential loss of ore, pillar bursts and potential collapses. This paper describes a crush pillar design methodology, and provides design charts. Three mining environments were incorporated in the investigations, which included underground and laboratory measurements, analytical solutions, numerical model sand back analyses. The results of the study are suitable for the areas where the research was carried out, and may also be applied with caution in other similar environments.

Jan 1, 2010

By C. Richard Tinsley

INTRODUCTION The economic analysis (Chapter 3), the engineering studies (Chapter 10), the credit structure (and the consequential funding sources) - Chapter 11, and the overall feasibility structure for any venture are all directed to determining one major decision element: How much and how certain is the reward for taking these risks? Risk assessment is a surprisingly weak area of analysis and is usually addressed in a checklist fashion. It is much preferable to deal within a risk system so that the inevitable tradeoffs among risks are correctly made. DEFINITION The first step toward risk definition must be to ascertain all of the risks to which a project or a company is exposed; otherwise one will remain ignorant of the possibility of a financially crippling loss until it occurs. (Carter and Crockford, 1974). However, simply stating what "risk" is can lead to debate. For example, risk could be (adapted from Vaughan, 1982): -the chance of a loss - uncertainty of loss -possibility of loss - uncertainty -dispersion of actual from expected results - probability of an outcome different from the one expected - possibility of an occurrence of an undesirable contingency -a condition in which a possibility of a loss exists. For the minerals industry financier, the last definition is probably the most appropriate. However, from a mineral company's point of view the definition might well include the possibility of not achieving the expected financial return. RISK CLASSIFICATION Risk identification will be readily agreed as the all-important first step. There are five major "branches" of risk classification. These are: -Statistical -Modellers -Checklist -Project Financing -Insurance The Statistical set discovered probability theory and any risk discussion soon deteriorates into a mathematical jungle (Megill, 1977; Hartman, 1976; Reutlinger, 1970; and Pouliquen, 1970).Their use of terminology tells its own story: coin toss (binomial distribution), gamblers' ruin, delphi (oracle) techniques, monte-carlo simulations, random walks, etcetera. These techniques inadequately represent the judgements necessary in an increasingly complicated and interrelated world. The risk Modellers have turned to the computer to handle these inter-relationships but soon find barriers because of "simultaneity". Certainly the computer has its uses to conduct various analyses (marketed as "sensitivity" analyses) but very often one finds that this involves changing one or two variables at a time, all other things being equal. Unfortunately, in a modern and complex world all other things do not remain equal. The statisticians will, no doubt, jump to their own defence by citing this

Jan 1, 1985

By Jacob W. Young

A casual reading of the geological literature extant to-day would give one the impression that carbon is an element which by some chance or another always existed at or near the surface of the earth, and was never of a magmatic origin. The carbonaceous matter in shales is said to be of vegetal derivation; petroleum is stated to have been derived from vegetable matter or from marine animal bodies; if carbon or bituminous matter is found in igneous rocks or associated with metallic ores, the statement is made that deeply buried carbonaceous sedimentaries were undoubtedly the source from which such carbon or bituminous matter was derived. This, I do not consider a reasonable or common sense view of the matter. Carbon is one of the elements of which the earth is composed. In the table giving the periodicity of the elements it comes sixth in the order of increasing atomic weights. It is an element formed like all the rest were formed, and must be as common to the interior of the earth as the rest of the eighty-odd elements so far discovered. The spectroscopic analysis of light from the sun, and the stars, shows the presence of carbon in the sun and in the colder stars. Thus with carbon, an element, found throughout the universe as well as on the earth, it is entirely reasonable to consider it as present in the interior of the earth with the other elements. Such being the case, the magmatic origin for the various forms of carbon in rocks and ores is a rational and logical conclusion. If but a small fraction of thought and effort was made along these lines, which is made in fostering the idea of the organic origin of the carbon found in the earth's crust, untold advances in this phase of geological science would result.

Jan 1, 1925

By H. P. LeVan

The aced for reliable reserves of the essential element, manganese, has been a continuing concern of the Federal Government for more than three decades. Because of the increasing vulnerability of outside sources of supply efforts have been intensified to find a means for beneficiating United States domestic deposits. The deposits of most interest would of necessity be near, or have access to, suitable transportation to processing plants. The Georgia manganiferous iron deposits represent some 10 million tons4 of ore readily available to southern iron and steel industries, if a manganese recovery process capable of functioning in the presence of large quantities of iron can be developed. In addition, a successful method for beneficiating the Georgia ore could produce a significant quantity of high-grade iron concentrate. The Differential sulfatization process developed 47 the Bureau of Mines5 seemed to be well suited for this application, particularly because it results in low concentrations of iron in the leach liquors with relatively complete extractions of manganese. In this process, manganese in the presence of iron is preferentially reacted with sulfur dioxide at elevated temperatures and subsequently extracted with water.

Jan 1, 1962

By P González, J Videla, E Córdova, I Gottreux

Currently, underground mining of deeper massive deposits with lower grades, harder rock conditions in high strength environments, entails difficulties in caving, fragmentation and seismicity of the orebody.So far, the use of preconditioning (PC) with hydraulic fracturing (HF) has shown positive results in terms of seismic response and caving performance, while PC combined with explosives aims to weaken the rock mass, causing an additional effect on fragmentation.In particular, mines commonly referred to as ‘supercaves’, operated by caving methods, have the need to integrate mine to plant processes, where rock fragmentation appears as a key tool. In fact, it implies making mining and comminution processes more efficient to the plant and for mines, it justifies the search of innovative solutions in drilling and blasting techniques to precondition the rock mass. The following paper aims to show the feasibility of numerical blast modelling to weaken the rock mass using explosives, mainly through sensitivity analysis applied to designs to minimise bias and uncertainty in the results. It is shown how the presence of structures, their geometry and in situ stresses influence or interfere with the PC method being used.From the work, it is concluded that better knowledge on the application of explosives weakening allows specialists to strengthen numerical models associated with every design and therefore previously validate their applicability, helping to understand complex phenomena such as the propagation of mechanical waves in non-elastic heterogeneous media. In this sense, it is understood that while there are studies (Sanchidrián, Segarra and López, 2006) showing that the transfer of energy in the rock mass could be even greater in a confined environment, the more competent rock mass and higher in situ stresses interfere mostly on the effectiveness of a technique using explosives.CITATION:Gottreux, I, Córdova, E, González, P and Videla, J, 2016. Preconditioning modelling and explosives effectiveness in block caving, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 683–688 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016