Search Documents

By Wellington Pereira Inácio

This work investigated the toughness behavior of polyester matrix composites reinforced with up to 30% in volume of long, continuous and aligned sisal fibers by means of Charpy impact tests. It was found that the addition of sisal fibers results in a marked increase in the absorbed impact energy of the composites. Macroscopic observation of the post-impact specimens and SEM fracture analysis showed that longitudinal rupture through the sisal fiber interface with the polyester matrix is the main mechanism for the remarkable toughness of these composites.

Jan 1, 2010

The development of research activities at Risdon and the implementing of a policy of instrumentation in plant processes have, in recent years, entailed a considerable increase in research staff and created an urgent need for more space and modern laboratory facilities. The existing laboratories have been in use for 25 years and are now inadequate. New buildings have been authorized.The new buildings will comprise, firstly, a laboratory building of three floors giving a totai .floor space of approximately 11,000 sq.ft., and a pilot plant building as an annexe to the laboratory building, of approximately 4,900 sq.ft. The laboratory building will accommodate from 20 to 22 research workers, and additional plant operatives will be used for the control of processes in the pilot plant building. The new buildings are designed to provide facilities for three principal functions; the investigation and improvementof existing processes, the development of new processes up to the pilot plant stage, and the control and maintenance of instruments.LOCALITY AND ORIENTATION OF BUILDINGSThe site of the buildings is elevated ground on the eastern side of the main plant, near the main entrance and general office building. There will be no obstruction to sunshine at any time of the day, and the laboratory building will command views of wide radius from wooded hills across the River Derwentto the open sea on the south-eastern quarter.The buildings are located to provide space for future extensions. The main laboratory building faces approx...

Jan 1, 1949

By P C. Couper, P C. Keall, S J. Mathews, A Francis

An epithermal gold-silver deposit is presently being developed at the Golden Cross Mine in the Waitekauri Valley, 8 km northwest of Waihi, New Zealand. Highest grade mineralisation underground is mainly confined to an elongate zone of strongly banded quartz veining on the hangingwall. Footwall veining is irregular, flatter lying, and of lower grade. Hydrothermal breccias in the ore zone may have economic grades where clasts of vein quartz are present. Jigsaw breccias, shingle breccias, and layered breccias with sedimentary type structures such as layering, crossbedding, and graded bedding have been identified proximal to, and within, quartz veins. Mineralisation in the open pit occurs in and adjacent to stockwork quartz veining.   Three alteration zones are recognised: a central silicic zone enclosing Au-Ag bearing quartz veins, an argillic zone above the stockwork zone and in the footwall of the underground ore zone, and a propylitic zone which is gradational with argillic zone. Intense shearing is confined to the less competent argillic zone.   Precious metal mineralogy consists of electrum (65% Au; 35% Ag) and argentiferous tetrahedrite, polybasite, pyrargyrite, argentite, and native silver. Pyrite is the dominant sulphide mineral. Marcasite, arsenopyrite, and rare chalcopyrite and sphalerite also occur. Oxidation ranges from a few metres in the argillic western stockwork zone to 100 m in fractured rock in the footwall of the stockwork.   The open pit contains a proved and probable reserve of 2.1 million tonne grading 3.5 g/t Au and 17 g/t Ag. The underground mine will produce 2.7 million tonne grading 7.8g/t Au and 27g/t Ag.

Jan 1, 1991

By Clyde N. Baker

Foundations for the Sohio Corporate Headquarters in downtown Cleveland have column loads of 11,400 kips, which increase to 15,000 kips with wind loading. An extensive exploratory program was conducted and comprehensive studies made to select the economically dependable support for the 46-story structure. A test on bond or socket friction for the caissons has usable values.

Jan 1, 1984

The areas of concern lay in the processing of, and the subsequent hearing into, Waihi Gold's resource consent applications to extend Martha Mine. The proposed amendments to the Resource Management Act 1991 might see the introduction of contestability in the processing of applications - which would have assisted Waihi Gold; and the use of commissioners to hear the applications, with a right of appeal to the Environment Court on points of law only. It is also proposed to have major applications heard directly by the Environment Court. If Waihi Gold's applications had been heard at first instance by the Court, the delays in time and associated costs would have been reduced. However a hearing by commissioners only would not have been satisfactory, there being no right of appeal against the conditions of consent, which if implemented as granted by the Councils would have had a significant impact on the costs associated with the extended project.

Jan 1, 1998

By Oliver Bowles

"Underground operation.In its broader sense the term ""mining"" is applied to all processes whereby raw materials are taken from the earth to be used as sources of mineral products. In a more restricted sense ""mining"" is applied to underground operations as contrasted with open pit work designated as quarrying. The tern is used in the restricted tense in this paper; for it relates to the exploitation of limestone deposits by modern methods of underground operation rather than by open pit methods.Present tendency toward miningIt may seem to some readers that a paper on mining limestone will find little general interest among lime plant operators, for only a limited number of them have yet resorted to this means of procuring raw materials. It is noteworthy, however, that a growing tendency exists toward underground operation, for one by one quarry owners are faced with increasing difficulties in open pit operation. It seems desirable, therefore, for operators to keep closely in touch with this gradual change in process, to inquire into the underlying causes, to compare costs, and to study the effects of the change in method on subsequent steps in calcining the stone to produce lime."

Mar 1, 1924

By Eric Konigsmann

"Omai Gold Mines is a large scale open pit gold mining operation located in central Guyana, South America with a 12,000 tonne per day milling facility. Mill operations were initiated in December 1992 with commercial production beginning in January 1993. The entire operation employs approximately 120 expatriates and some 800 Guyanese nationals and is expected to produce in excess of 250,000 ounces of gold per year. The total mineable reserves contain 2.5 million ounces of gold with a projected mine life of twelve years.The milling circuits feature an SABC grinding circuit, gravity concentration and a conventional CIP gold recovery circuit. This paper will review the mill start up and ""run-in"" phase during the first year of operation. Emphasis will be placed on descriptions of start up problems and circuit modifications, mill performance trends in 1993, and personnel training and development. An outlook for 1994 is also given.IntroductionOmai Gold Mines is a large scale, open pit gold mining operation located in the Potaro district of Guyana, South America, some 160 kilometers south of the capital city Georgetown. Although there are numerous small scale gold mining ventures in Guyana, particularly with the dredging operations on the rivers, Omai is the first hard rock, open pit mine to be developed in the country. At present, this mining operation is one of the largest gold mines in South America.The Omai gold deposit has been exploited for over one hundred years. In the late 1800's, a German syndicate used hydraulicing with subsequent gravimetric separators such as sluice boxes and trommel screens to recover gold from saprolite, a soft, oxidized, claylike mineral which covers much of the claim area. Through the early 1900's and up until the 1950's, numerous mining companies including Anaconda Mining Co. Ltd. explored and drilled the Omai deposit but the technology and low gold price of the day made the reserve uneconomic to develop."

Jan 1, 1994

By WU Jian-hui

Keywords: metallic material; nickel powder; thermal decomposition; precursor; fibrillar powder; nanometer scale; passivation treatment The precursor thermal decomposition process of fibrillar nanometer scale nickel powder and passivation treatment of obtained powder are investigated, and the composition and morphology of the products are characterized by use of IR, TGA/DTA, XRD and SEM. The results show that the precursor morphology is a decisive factor to the product morphology of the nickel powder. The morphology of the product derived at low decomposing temperature is irregular. The nickel powders produced at the temperature higher than 480 coheres seriously. The product particles are reunited with the decomposition time prolong. The powder prepared under the optimal condition is fibrillar like woolen yarn; the grain diameter is less than 50nm.

Jan 1, 2005

By Stefan K. Schwank

The paper describes the two foundation techniques - mini piles and postgrouted bored piles. The mini pile system is presented with its design and installation parameters, especially the drilling technique. Two case histories demonstrate the application under extremely limited space and traffic conditions and the required modifications of the equipment. After the description of the postgrouted bored piles and its grouting technique, the paper gives a comparison of postgrouted piles and standard piles on a large basic test in Germany. The Brooklyn Queen's Expressway, N.Y., case history shows the application of this technique after redesign of the original proposal. 1. General Increasing requirements to improve existing foundations to carry additional loads and to increase the bearing capacity of bored piles leads to two new piling techniques: the mini-pile and the post grouted bored pile.

Jan 1, 1991

By H A. Myburgh

The beneficiation of heavy metal oxides, such as iron ore, is usually performed with heavy medium separation in cyclones, static baths and lately with Larcodems. Atomized ferrosilicon is most suitable as a heavy medium at densities above 3600 kg/m3 whereas a mixture of milled and atomized ferrosilicon is suitable at densities below 3600 kg/m3. When operating a beneficiation plant at densities higher than 3600 kg/m3 the quality of the ferrosilicon particles is an important factor that influences the control of the beneficiation process. Therefore, it is important to know how the rheology would be affected by the ferrosilicon quality as it also influences the control of the process at these elevated densities. Background The Kumba Resources Sishen Iron Ore Mine in South Africa produces 26.5 Mt iron ore per annum from its beneficiation plant. The ore body consists mainly of laminated and massive type hematite ore that is crushed down to ?90mm before being beneficiated by means of a combination of Wemco drums, Larcodem and dense medium cyclone separators. The need for higher densities When the percentage of high-density gangue2 is higher than normal in the run-of-mine (ROM), a higher separation density is necessary to produce a product to specification. Certain ore types of this quality in the Sishen reserves require a separating density higher than 4000 kg/m3, whereas densities would normally average 3600 kg/m3 when beneficiating ores of normal high-density gangue content. Sink and float tests conducted on the ROM material at Sishen revealed some interesting characteristics. In the waste fraction, (density < 3600 kg/m3) it was found that the %Fe was <21% (Fig. 1). Similarly, for the product fraction (density >3000 kg/m3), the percentage Fe varied between 35% and 67.2%. The bulk of the material (88%) actually had a density greater than 4000 kg/m3 and a Fe content that varied between 63% and 67.2%. At a density interval of 3600 to 4000 kg/m3, the Fe content varied from 37% to 60% with an average of 45%.

Jan 1, 2006

A method for the detection and analysis of tin in cassiterite ores is discussed. An empirical relationship was established between the tin content of an ore sample and the percentage absorption that this sample produced in a Mossbauer experiment. The time taken to complete an assay with this method is much less than with any of the methods currently in use. The equipment can be adapted readily for use in the field.

Jan 1, 1969

Ore from the &quot;Staimite&quot; lode in the Oonah mine, Zeehan, has a complex composition and contains an exceptional number of elements. Its chemical composition has been indicated by the following published figuresà

Jan 1, 1931

By Steve Kral

Despite low commodity prices and mining industry cutbacks throughout the world, Peru remains one of the industry’s bright spots. The country’s remarkable economic turnaround during the 1990s remains a model for other developing nations to follow. And the Peruvian government has not forgotten the industry that was instrumental in that turnaround. True, the country has not been spared the effects of the mining industry’s retrenchment that has occurred in other parts of the world. However, foreign mining companies remain committed to doing business in Peru. And the government remains committed to attracting foreign investment and maintaining a strong mining industry. This commitment was evident in September 1999during the 24th Convention of the Institutos de Ingenieros de Minas del Peru in Arequipa, Peru. More than 3,000 mining industry professionals from around the world attended the convention. And Extemin, the accompanying exhibit, featured more than 450 companies, many from the United States, Canada, Australia, South Africa and other countries.

Jan 1, 2000

By A. Frits van Tol, Rodriaan Spruit, Jan H. van Dalen

"Abstract In recent years, there have been major problems with deep excavations in urban areas supported by diaphragm walls. In some cases, like the fatal Nicoll Highway collapse in Singapore the quality of the D-walls was not the cause. However in other projects, like the problems with the major leak in the walls of the Boston Big Dig and with leakage in a few projects in Belgium and The Netherlands was related to poor D-wall quality. Leakage through the D-walls at the joints in deep excavations led in these cases to very serious settlement behind the walls, in the case of the North- South line in Amsterdam, there was severe damage to historical buildings. This paper describes ongoing research that focusses i on acquiring more knowledge on and improvement of D-wall installation, in particular the flow process prior and during casting ii on the detection of anomalies prior to excavation and iii on the composition of the concrete mixture in view of a better and more sustainable concrete quality of D-walls.INTRODUCTIONIn the case of deep excavations in urban areas close to neighbouring buildings, diaphragm walls are one of the best feasible solutions for the retaining structure. Although the costs of D-walls generally exceed the costs of alternative wall solutions, the advantages are decisive in many situations. The main advantages of D-walls are the limited impact of the installation on the built environment, the high stiffness and bearing capacity and the retention of water, even at considerable depths. This makes Dwalls often the preferred solution for deep excavations Sometimes the D-walls are the temporary support while for the final stage a complete concrete box is constructed in the excavation. In many other cases the D-wall has the permanent function of retaining soil as well as groundwater.In the last ten years, there have been major problems with deep excavations in urban areas supported by diaphragm walls. In some cases, like the fatal Nicoll Highway collapse, 2004 , the quality of the Dwalls was not the cause. In other important failures like the collapse of the Archives in Cologne, 2008 and Dubai Infinity Tower Flooding, 2007 a combination of design and quality issues played a role. However, the major leak in the walls of the Boston Big Dig was related to poor D-wall quality (McNichol, 2000). Van Tol et al, (2010) describe a number of case studies in Belgium and the Netherlands, with leakage through the D-walls at stop end joints. In several cases with deep excavations these leakage caused serious surface settlements behind the walls. In the case of the North-South line in Amsterdam, there was severe damage to historical buildings. All these cases have generated considerable additional costs and delays, and subsequently public and political concern. Van Tol et al. (2010) present several possibilities to improve the quality of D-walls.Other disputes related to D-walls deal with the quality of the concrete and the sustainability of D-walls applied as a permanent wall. In particular the porosity of the concrete cover is sometimes problematic."

Jan 1, 2014

By Bruce Vandenberg

Two tests were set up as part of the course given by Blasting Analysis International. Both tests were performed using the prototype Velocity of Detonation Recorder (VODR). The prototype has several limitations, which have been rectified for the production units.

Jan 1, 1990

The Round Hill gold-scheelite deposit is located three kilometres from Macraes Flat and approximately 60 kilometres due north of Dunedin, New Zealand. A mining feasibility study is currently being undertaken on the deposit by BHP Minerals (New Zealand) Limited, who are the managers and operators of a Joint Venture with Home Reef Mining Limited. BHP has a 70 per cent equity in the project area.

Jan 1, 1987

By W. A. Wood, H. M. Bendler

Cylindrical fatigue specimens of OFHC* copper were subjected to alternating torsion while under axial tension. The superimposed tension strongly influenced the fatigue life of the specimens as well as causing characteristic changes in the structure of the fissures that form and develop throughout the life of the specimen. A further effect of the superimposed tension is a continuous extension of the specimen throughout its life in a manner formally similar to creep at elevated temperatures. RECENTLY, studies of the structural changes leading to fracture of metals by fatigue have been made by a technique which reveals, in section, the lattice distortion arising from slip movements inside the metal and the disturbances built up by these slip movements at the metal surface.1&apos;2 According to this approach, fatigue develops as follows: a) fine slip movements concentrate in bands, producing little strain-hardening and thus permitting abnormal totals of plastic strain before fracture and, therefore, abnormal amounts of lattice distortion along each slip band; b) both forward and backward slip movements occur in each band which, according to their distribution across the band, may build up surface disturbances that include sharp notches; c) these notches early in the life of a specimen penetrate the distorted slip zones and transform them into deep, fine fissures; d) the fissures on continued cycling locally saturate the metal and cause local collapse in the form of a microcrack. Thus, the significant consequence of fatigue or cyclic

Jan 1, 1962

By Shazad Hosein, William Birch, Douglas A. Anderson

This paper will present the results of tests of a new method for assessing explosive performance using wavelet transform analysis of standard blast seismograms. The theoretical background of the method was presented at an earlier ISEE conference.

Jan 1, 2015

By Barry Olson

The Peñasquito deposit in Mexico is one of the largest grassroots precious metal discoveries to be developed in recent years. Goldcorp Inc. acquired the gold-silver-lead-zinc property with the acquisition of Glamis in 2006. The company has since committed US$1.5 billion to construct the mine, mill and associated facilities. The first of two 50-kt/d (55,000-stpd) mill and flotation lines is currently being commissioned while engineering and construction continues on the second line. A high-pressure grinding roll (HPGR) will ultimately take total throughput to 130 kt/d (142,000 stpd). The Peñasquito property is located in the northeast corner of Zacatecas state, Mexico. The elevation of the property averages 1,900 m (6,200 ft) above sea level and it is situated in a wide east-west valley. Except for one small outcrop (Peñasquito), the area is covered by up to 30 m (98 ft) of alluvium.

Jan 1, 2009

By J. L. Howell, D. E. Pollock, A. B. Cecala, A. D. O’Brien

Dust from worker,s clothes has been shown to be a problematic source of personal dust exposure. A recently completed effort between NIOSH and the Unimin Corporation has resulted in a quick and effective way to clean worker clothing. The process involves a booth under negative pressure with an air spray manifold to supply compressed air to blow off the dust from the clothing. The overall system is designed to meet MSHA and OSHA requirements. Results of field testing indicated that the manifold cleaned the clothes 10 times faster and removed 50% more dust than cleaning methods used by workers today.