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By N. Saracoglu, J. P. Golightly, R. H. Wallis, J. J. Brummer

"The McClean uranium deposits are located 11 km west northwest of the Rabbit Lake Mine. Their average grade is 1.8 % U3O8 , and they contain 6. 350 tonnes of uranium oxide in seven pods of variable grade and mineral assemblage. They are hosted by both basal Athabasca Group and the regolith developed on the underlying crystalline basement. The major mineral facies are: sulphide, arsenide, 'bleached', and hematite, with the important uranium minerals being coffinite, uraninite and pitchblende. Abundances of carbon and sulphur isotopes are consistent with their derivation from pyritic graphite in basement gneisses. Isotopes of oxygen and hydrogen suggest equilibration at temperatures of about 200°C. Ar39/ Ar40 age determination of illite associated with ore suggest mineralization began about 1300 m.y. ago and that significant alteration had ceased by about 1170 m.y. ago though Pb/ U data suggest the deposits continued to evolve into the Mesozoic.IntroductionThe McClean deposits lie on the eastern side of the Athabasca Basin of northern Saskatchewan where they are part of a cluster of uranium deposits lying west of Wollaston Lake (Fig. 1). The general stratigraphy is schematically portrayed in Figure 2 which emphasizes that mineralization is hosted by both the Athabasca Group and the underlying regolith and also that the deposits are preserved at depth and have not suffered from preand post-Pleistocene weathering and erosion. This circumstance, combined with their simple shape and the presence of seven separate zones of mineralization (pods) allows a description, based on over 450 fully cored drill holes, to be made of the wide variation in chemistry, grade, alteration patterns and position relative to the sub-Athabasca Group unconformity. Ar39 / Ar40 age determinations have been made of illites associated with regolith, Athabasca Group and mineralization and studies are in progress on C, S, 0 and H isotopes of mineralized material and host rocks. Only some of these data have been published; Brummer et al., (1981); Golightly et al., (1982); Bray et al., (1982); and Saracoglu et al., (1983). The only other published data on McClean geology are by Tremblay (1982, 1983)."

Jan 1, 1986

By Dave Rose, Jacques McMullen

"The Detour Lake mine is located 200 km northeast of Timmins, Ontario, Canada.The mill processes a free milling gold ore using both a gravity circuit and leaching with a state-of-the-art carbon-in-pulp circuit. The grinding circuit is a conventional SABC circuit with a tonnage of 55,000 tpd at 95 microns with the addition of pre-crushing upstream of the SAG mill.The Detour Lake mine has one of the largest gyratory crusher in the world (60"" x 113"") and over the years, many improvements have been made to this crusher with the result of improving plant throughput. This paper will present how choke feeding the gyratory crusher has been found to be one of the main influences on crusher product particle size and plant throughput. It will explain how the effect of choke feeding the gyratory was measured and from that, the various changes made to improve choke feeding of the gyratory crusher.IntroductionOre is hauled from the open pit mine and dumped directly into a single 60"" x 113"" primary gyratory crusher. The live capacity of both the feed and discharge hoppers of the gyratory crusher are designed for two (2) truck loads each, assuming a nominal payload of 300 tonnes per truck. The surge bin under the primary crusher feeds an apron feeder that controls the ore feed rate at approximately 4,200 tph onto a 227 metres long x 1.52 metres wide belt conveyor with a nominal capacity of 4,200 tph.The primary crusher is operated at an open side setting of 172 millimetres to produce a F80 feed to the secondary crushing circuit of 135 millimetres."

Jan 1, 2017

By E. G. Joe

The continuing increase in costs for power and fuel are affecting significantly the cost of milling Canadian ores. In order to ascertain the scope and source of energy consumption in Canadian mills for further energy conservation opportunities, CANMET, in cooperation with the Canadian Mineral Processors, carried out a detailed survey on the metallic mineral processing plants. Sixty-seven mills representing almost 300 million tons of annual capacity participated in the survey. The results indicated that, in general, copper and iron ore mills, representing the bulk of the tonnage, consumed relatively low levels of energy per ton. Nickel-copper, zinc-copper and lead-zinc .ore mills were moderate in energy consumption, and uranium and some copper-lead-zinc mills reported much higher energy consumptions due primarily to the increased heat requirements of the ore pulp. Although plant heating costs varied somewhat with location, it was apparent that the lowest heating costs were achieved by those plants built with proper insulation and energy conservation design. If the cost per million British thermal units is taken as $2.00, the mill energy costs generally ranged from 40ft to $1.20 per ton.

Jan 1, 1979

By J. W. G. Hannon

FOLLOWING the experimental work of Denny, Robson, and Irwin, and the clinical investigation by Crombie and Blaisdell, an investigation of aluminium therapy was begun at Washington, Pa., which is situated in a very large industrial section of the State. Some of the men to be studied were from plants manufacturing silica brick, refractories used in steel and glass manufacturing, and semi-porcelain table-ware; others were workers in foundries, sand blasters, and men engaged in the quarrying of ganister rock. This group of workmen gave an opportunity to study the effects of aluminium on various types of silicosis which differed somewhat from that found in hard-rock miners. EXPOSURE In their occupations, the men studied were exposed to silica dust concentrations ranging from 17 to 97 per cent free silica. In the silica brick industries, the unfired product averages 96 per cent silica in the form of quartz, whereas the fired brick contains 50 to 62 per cent cristobalite plus 17 to 30 per cent tridymite, forms of silica that, on account of their higher solubility, are more toxic than quartz. The operational dust counts in the plants varied from 15 to 9,500 particles per c.c., and the median particle size from the aerial samples was 1.0 micron for the green product and 2.0 microns for the fired product. The length of exposure varied with the occupation as well as with the individual plant, but disabling silicosis could be produced in less than four years in certain exposures. The average time needed to produce radiological silicosis in those susceptible to this disease was eight years. Some of the men in our series of cases have been treated as long as fifteen years after exposure had ceased, and have improved under treatment.

Jan 1, 1944

By François Robert

"The Eastern Abitibi Sub province (Quebec segment), contains two main types of gold deposits: the common quartz-vein type and the rare pyritic type. Both occur in areas dominated by volcanic rocks and are spatially associated with major fault zones.Quartz-vein gold deposits consist of simple to complex networks of quartz-carbonate-pyrite veins in reverse shear zones and extensional fractures. They occur in areas dominated by mafic volcanic rocks and are commonly associated with small syn- to late-tectonic porphyritic felsic intrusions. Associated alteration, which postdates peak metamorphism, is dominated by carbonatization, sericitization and pyritization of the wallrocks. These deposits formed late in the geologicalevolution of the Abitibi.Pyritic gold deposits range from deformed massive sulphide lenses to zones of syntectonic pyrite-rich veinlets and associated pyrite disseminations. These deposits occur in environments dominated by felsic volcanic rocks that are typically converted to sericite schists near the deposits. The associated pre-metamorphic aluminous alteration is now characterized by metamorphic sericite, andalusite, kyanite and chloritoid, overprinted by a late retrogression of alumino- silicates. These deposits probably represent deformed volcanogenic massive sulphide deposits, but the timing of gold introduction in these is not fully understood.The differences in geological attributes reflect significant differences in the genesis these deposits: the pyritic deposits probably have a multistage genesis, including a pre-tectonic stage, in contrast to a single stage late-tectonic genesis for the quartz-vein deposits.RESUMELa partie Est de la Sous-Province de l’Abitibi( segment québécois) renferme deux types de gites d' or: ceux de type ""veine de quartz"" et ceux, plus rares, de type ""pyriteux"". Ces deux types se trouvent dans des secteurs particulièrement riches en roches volcaniques et mantrent une association spatiale avec des zones de failles majeures.Les gites de type ""veine de quartz"" correspondent à des réseaux de complexité variable de veines de quartz-carbonate-pyrite se développant dans des zones de cisaillement inverse et des fractures de tension. Ils se concentrent dans les régions dominées par des roches volcaniques mafiques et s’associent fréquemment à de petites intrusions porphyriques felsiques syn- a tardi-tectoniques. L’altération associée ace type de glte est postérieure à la phase majeure du métamorphisme et consiste en une carbonatisation, une sericitisation et une pyritisation des épontes. La mise en place de ces gites est tardive par rapport à l'évolution géologique de l'Abitibi.Les gites d' or de type pyriteux consistent en des lentilles de sulfures massifs déformes, des zones d' abondantes veinules pyrite uses syntectoniques, et des zones de pyrite disséminée. Ces gites se retrouvent dans des empilements contenant surtout des roches volcaniques felsiques qui sont transformées en schiste à séricine pres des gisements. L’altération a l’umineuse pre-metamorphique associée a ce type de glte a donné naissance, lors du metamorphisme regional, a la sericite, a 'andal ousite, a Ia lcyanite et au chloritoi""de; par la suite, les alumino-silicates ont été affectes par une alteration retrograde tardive. Ces gites representent probablement des depOts de sulfures massifs volcan gènes déformes, mais la chronologie de la mise en place de l'or dans ceux-ci est encore mal comprise.Les caractéristiques géologiques propres à chacun de ces types de gites reflètent des conditions de formation différentes: le type ""pyriteux"" montre une histoire génétique polyphasée, incluant une étape pre-tectonique alors que le type ""veine de quartz"" s’est développe au cours d’une seule phase tardi-tectonique."

Jan 1, 1990

By Delio J-J Tortosa, Fred F. Langford

"The Cenex orebody occurs at the intersection of northwest and northeast-trending fault zones that formed during post-Hudsonian uplift. The ore is localized in breccia zones, along faults, and in veins and adjacent wallrocks. The host rocks are Tazin quartzo-fe/dspathic mylonites and ultramylonites and chloritesericite- quartz-graphite-feldspar mylonite schist. The uraniumbearing minerals are finely disseminated pitchblende and uraniferous titanate.The earliest mineralization may have been associated with /ate-stage retrograde metamorphism in the mylonite schist. The main stages of mineralization were associated with brecciation, hematization, carbonatization, and chloritization of the mylonites and ultramylonites. Uranium mineralization was clearly much later than any igneous or metamorphic activity associated with the Hudsonian orogeny.Late post-orogenic uplift, erosion, and deposition of the Martin continental clastics in fault basins were coeval with uranium mineralization. The deposit is consistent with a meteoric-hydrologic system constituting a source for orebearing fluids, hence the close spatial relationship of the uranium deposits in the Beaverlodge area with the basal unconformity of the Martin Group."

Jan 1, 1986

By E. Douglas, V. M. Malhotra

"This report presents the results of a laboratory study undertaken to evaluate ground granulated blast-furnace slag from Algoma Steel Corporation, as a replacement for Portland cement in cemented mine backfill. The evaluation was based on the results of compressive strength tests performed on cylinders cast from mixtures made with a granulated blast-furnace slag and tailings from four different mines in the Sudbury basin. Various percent¬ages of slags and various binder to tailings ratios were used.Tests results show that, in terms of compressive strength, the slag performs as well or better than Portland cement as the binding agent in cemented mine backfill. Lime was found to be a poten¬tially good activator for ground granulated slag in mine backfill applications.A field test was conducted at one of the mines, consisting of placing a mixture of 95.5% ground granulated slag and 0.5% lime into a stope, and inspecting the floor slab as it hardened. The slag performed as expected, considering the backfill mixture proportions used and the preparation of the test site."

Jan 1, 1989

By W. E. Hale

An area of about 7,000 square miles within the eastern part of the Grenville Sub-province is underlain chiefly by granitic gneisses. There are, however, some exposures of mafic rocks which warrant further investigation, and some attractive structures, particularly basins, which deserve additional economic consideration. T HIS paper describes in a very general fashion the economic and geological features of an area of about 7,000 square miles on the north shore of the Gulf of St. Lawrence in the eastern part of the Grenville Sub-province (Figure 1). The scarcity of published geological data on this part of the Cana-dian Shield (DePuyjalon, 1899 and Longley, 1944) justifies the presentation of these tentative results. It should be appreciated, however, that the information which follows was acquired in a rapid reconnaissance designed specifically to out-line what might be interpreted as favourable geological environments for the occurrence of economic minerals, rather than to produce an authoritative analysis of the geological history of the region.

Jan 1, 1962

By P. C. Richards

"Future Integrated Gasification Combined Cycle (IGCC) power plants will have superior environmental performance and unmatched efficiency.The Shell Coal Gasification Process (SCGP) is a clean coal technology, which can convert a wide range of coals into clean syngas for high efficiency electricity generation in an IGCC plant. SCGP flexibility has been demonstrated for feeds ranging from bituminous coals to lignites and petroleum coke, and the process is ideally suited for combined cycle power generation, resulting in efficiencies of 42% to 46% (LHV).In the Netherlands, a 250 MWe coal gasification combined cycle plant based on Shell technology is being built by Demkolec, a development partnership of the Dutch Electricity Generating Board (N. V. Sep). The plant is scheduled to start up in 1993. IntroductionBasic ConceptShell's experience with gasification dates back to the 1950s, when the first Shell Gasification Process was commissioned with oil as feedstock. There are now over 140 SGP gasifiers licensed. The experience gained on oil gasification provided a firm theoretical and practical base for the start of coal gasification process development in 1972.At that time, there were serious concerns about the future availability and price of crude oil. Coal gasification (making carbon monoxide and hydrogen by the partial oxidation of coal) was considered to be an important option for refinery applications, because the synthesis gas (syngas) produced can be used as:• a chemical feedstock for making transportation fuels and chemicals;• a source of hydrogen (making use of the water gas shift reaction) for upgrading petroleum products; and• a fuel for heating process streams and/or generating electricity."

Jan 1, 1994

By J. Mirza, E. Nicol, J. Lipkowski

Gold passivation in thiosulfate leaching media is a major barrier to its implementation. Addition of Cu (II) into the leaching solution has shown to aid in gold dissolution, but the mechanism by which it acts, and its role in the passive layer, remains unknown. Surface Enhanced Raman Spectroscopy (SERS), in tandem with linear sweep voltammetry, were employed to determine the dependence of leaching currents on mass transport and for fingerprint identification of sulfur species on the surface of gold. SERS leaching experiments were performed using gold nanorod electrodes that showed increased stability compared to other SERS active surfaces.

Jan 1, 2011

By Louis J. Cabri, Donald Hoy

"Samples with contrasting gold mineralization were studied quantitatively prior to metallurgical tests. The AD samples are coarser-grained and characterized by abundant Sb minerals (jamesonite, berthierite, stibnite). The finer-grained MW sample has abundant pyrite and pyrrhotite, with arsenopyrite and galena next in abundance. A large number of gold mineral particles were determined by SEM investigation of hydroseparation concentrates, ranging from 150 to 597 per sample. The grain-size distribution of the gold minerals shows evidence of bimodal grain-size distributions (volume %), with the coarse fraction being most significant in sample MW-1 (maximum ECD=308µm). The coarsest gold minerals in the AD samples range from 139µm to 281µm ECD.The deportment of gold minerals is as electrum, aurostibite, native gold, and a possible new mineral (AuNiSb4). Gold also occurs in nisbite. The gold minerals are dominated by electrum in three samples and aurostibite is next in abundance. The major gold minerals are probably representative of three stages of gold mineralization. The first stage is represented by electrum, which is partly to completely replaced by Sb-rich mineralization forming aurostibite, and the last stage is native gold, often occurring as rims on one or the other earlier gold mineral. The gold minerals are strongly associated with sulphides in the AD samples (55 to 60 vol.%). At the grind used for the hydroseparation the liberated gold mineral quantity (volume %) is also significant, ranging from 65% for sample MW-1 to 30 to 37% for the AD samples.INTRODUCTIONThe Clarence Stream deposit is located 70 km south-southwest of Fredericton and 25 km northnorthwest of St. George, south-western New Brunswick, near the international boundary with Maine (Fig. 1)."

Jan 1, 2007

By D. McConchie

The use of Bauxsol? (physically and chemically modified alumina refinery residues) to treat acid rock drainage (ARD), and sulphidic waste rock and tailings, provides new options for managing some intractable environmental problems at both derelict and active mine sites. Treatment of ARD waters using the Bauxsol technology shows that the effectiveness of raw Bauxsol material can be enhanced by including modest amounts of selected industrial minerals or common chemical additives. The type and amount of additive required and the amount of the blend needed to treat the water depends on the initial composition of the water and the target water quality; for some ARD waters, optimum treatment may require one or more changes in the type or amount of additive used. Maximum treatment efficiency can be achieved only when a balance is maintained between the rate of trace metal binding and the rate of change in water pH; adding treatment reagents faster than can be accommodated by the reaction kinetics will not result in more rapid water treatment. This paper presents the results for treating several ARD waters to illustrate the importance of blend selection and treatment procedure. Although treating ARD water is often necessary, this strategy treats the symptoms rather than the cause. The best permanent solution is to treat the sulphidic waste rock or tailings such that they do not continue to oxidise and produce acidic metal-rich leachates; sulphide oxidation needs to be stopped or slowed to a rate that can be accommodated by normal environmental processes. Capping lined impoundments is not a solution because all caps and linings will inevitably fail some time in the future creating a nasty surprise for some future generation. Adding lime is also less than ideal because the lime leaches from the treated material; treatment often appears to be effective for a few years and then fails. Bauxsol technology offers effective alternatives to conventional liming and capping procedures and Bauxsol blend application rates and procedures can be planned to ensure that no acidic or metal-rich water can ever escape from the site. Bauxsol can be physically mixed with the sulphidic mine wastes or it can used to form subsurface permeable reactive barriers, or both. Bauxsol treated waste rock and tailings can be immediately and effectively revegetated. In this paper we present leachate quality and plant growth rate data for several sulphidic waste rock and tailings deposits treated using the new technology.

May 1, 2003

"In mineral exploration and mining applications, it is sometimes necessary to reduce sampling error in order to improve representivity of individual sample assays. Historic efforts to reduce sampling error have relied on the belief that larger samples exhibit less sampling error. Justifications for this belief traditionally have coupled the binomial theorem with an ideal geological material consisting of ore and gangue particles of equal size and shape (an equant grain model) and empirical tests of geological materials, to illustrate an inverse relationship between sample size and sampling variance. To date, no proof exists of this sample size-sampling variance relationship in real geological materials exhibiting variations in grain size, shape, composition, and degree of liberation.Using first principles calculus and the formula for the mean, sample mass and sampling variance are proven to be inversely proportional in all geological materials. Distribution assumptions and physically ideal geological models are not used in this proof. Furthermore, algebraic manipulations of expressions describing the variances of equant grain models consistent with binomial, hypergeometric, and Poisson distributions reveal that these models also exhibit an inverse sample size-sampling variance relationship. Thus, the sampling behaviors of these models are numerically consistent with the sampling behaviors of real geological materials, and these models can be used to estimate sampling errors in real geological materials using simple sampling parameters."

Jan 1, 2007

By C. -M. Katsari, G. N. Anastassakis

"Copper is considered one of the most important industrial metals because of its properties (conductivity, malleability) and variety of uses. Approximately 70% of the global copper is used for various electrical applications, with a significant part of copper originating from recycling, since copper can be recycled and re-used countless times, without any loss of performance and difference in the quality of recycled copper in comparison to that from ore. Copper recycling significantly contributes to natural resources conservation, waste minimization, energy saving, and overall cost reduction. Approximately, 35% of the globally produced copper originates from recycled copper.The objective of the current work is to investigate the recovery of copper from electric wire scraps using wet shaking table as an alternative to air separation methods that prevail over the wet ones in recycling processes. The tests were carried out using feed of correspondingly high- and low-grade in copper. In the first case, the wire scraps had been subjected to shredding only, prior to tabling separation; in the later, the low-content tailing of prior air separation was used as feed ?n table separation.In regard to testing, the following factors were examined: table tilt, water flow-rate, and reciprocating speed. The results of the tests clearly denote that copper wire separation from plastic polymer is feasible, as in most cases, table separation resulted in heavy products of high purity in copper and high recovery, and tailings of very low copper grade. The results of the current work clearly denote that wet tabling can be applied efficiently for the separation of recycled copper wire from plastic, as an alternative to air separation methods, as well as for the recovery of copper from the low-grade tailings derived from air separation methods."

Jan 1, 2016

By Shuji Owada

Scrap electrical and electronic appliances, so called "E-waste", are not a present target to be collected and recycled under Japanese regulations. This material, however, contains considerable amounts of base, precious, and rare metals and it is necessary to recover these elements for maintaining stable supply and establishing "the society of environmentally-sound material-cycle". This paper describes recent trends of rare metals recycling in Japan and technological approaches to achieve the above objective. Also a research work to concentrate rare metals from the printed wiring boards by combining brand new comminution and physical separation methods is discussed.

Jan 1, 2011

By H. F. Maulson

For the benefit of those who are not familiar with the history of the western Provinces-Manitoba, Saskatchewan, and Alberta-as regards our natural resources, a few words of explanation may be in order before taking up the consideration of the Mines Act of 1930. In 1867, The British North America Act was passed by the Imperial Parliament. That Act, which is our constitution, created a union between the provinces of Nova Scotia, New Brunswick, and Upper and Lower Canada (now known as Ontario and Quebec respectively) under the name of the Dominion of Canada. Provision was made therein for embracing other parts of Canada from time to time. That portion of Canada which today comprises the Provinces of Manitoba, Saskatchewan, and Alberta and the lands to the north of them, was then known as Ruperts Land and the North West Territory. In the year 1670, King Charles II had granted by Letters Patent to Prince Rupert and his associates, known as ?The Governor & Company of Gentlemen Adventurers of England, Trading into Hudson's Bay?, commonly known as the Hudson's Bay Company, the lands and territories therein described, being roughly all the lands adjacent to and west of Hudson's bay; also the gold and silver to be found or discovered therein and other rights as more fully described in said Letters Patent. The land so granted was called 'Ruperts Land'.

Jan 1, 1930

By Thorndycraftm R. B.

"PURPOSEThe purpose of this presentation to the Canadian Mineral Processors is to review gold heap leaching systems currently in use and discuss their applicability to Canadian ores. The author's experience with the development and operation of heap leaching spans the past four years at. Pinson, and visits to many ether heap leaches in the western United States.INTRODUCTIONBy way of introduction to the heap leaching system, I will describe in slight detail the method used at Pinson Mining in northern Nevada. This will be followed by a discussion of optional methods in use at other operations visited.The Pinson orebody is a finely disseminated, well-oxidized hydrothermal deposit. Gold particles are finer than 20- microns. The orezone hostrocks are metamorphosed and silici¬fied limestone and shale. Sulfides and carbonaceous materials are negligible.The Pinson open-pit mine has operated since June 1980. It produces 1500 tpd of C.I.P. mill feed averaging .10 oz gold per ton, and 1500 tpd of heap leach material averaging .025 oz gold per ton. Cutoff grades are 0.04 for mill feed, and 0.01 for heap leaching. Stripping ratio is 9 tons of waste and leach grade to 1 ton of mill feed.The project is located in northern Nevada at 4900 feet above sea level.,Winters are fairly severe, with freezing conditions affecting operations from early December through April. Although officially designated as ""high-mountain desert"" country, snow and/or freezing rain occur almost every week of the winter.To date, all Pinson production-scale heap leaching has treated run-90,000 tons of ore are stacked on 300 foot square clay leach pads. Cyanide leach solution is applied through ""wobbler"" sprinklers at .0025 gpm/sq ft for 60 to 90 days. The pregnant solution flows from the heap by gravity to plastic-lined ditches, into a collection sump and then through buried piping to the 2.2 million gallon pregnant solution pond."

Jan 1, 1984

By Jos. Kalbhenn

MR. G. G. BOWSER: Mr. Kalbhenn's paper is an excellent one and is a concise description of a very interesting piece of work. It is well known that a great deal of preliminary study was given to this job before the final plans were made. It is due to this thorough preparation .chat the work progressed so satisfactorily, smoothly, and safely. The ideas carried out in the construction of the hardwood pack, timbered compartment, inclined raise, loading chute, and steel-boomed room, all contributed to a successful conclusion of the work. The extra care in being certain that the compartment shafts were well timbered was especially necessary on account of the difficult blasting conditions. In other words, the foundations .of this job were well and truly laid. The blasting in this work was very difficult due to the nature of the Strata. Working under an ever precarious roof condition and completing .this job with only two lost-time accidents is a record of which to be proud. The shaft men engaged on this work are also due for praise. I regret I did not visit this work while it was in progress. It was not in lack of interest. This, however, more or less proves that the blasting end .of this job went along with practically no trouble. I have seen the nature of the rock, as I made several visits to the tunnels while they were being put through from the Phalen to the Harbour seam. According to figures in Mr. Kalbhenn's paper, the explosives consumption works out to 1.61 pounds per cubic yard of rock in the solid, or 0.8 pounds per ton. The explosives consumption in the tunnels ran from 2.86 to 3.46 pounds per cubic yard or an average of 1.58 pounds per ton of rock. Of course, the rock in the shaft was blasted in the most economical way possible, as far as powder costs are concerned, as the face advanced at close -wright angles to the strata and gravity was acting with the explosive. The tunnels were driven nearly 'end on' the strata and bottom holes had to be lifted, and I believe there was some re-drilling of ribs left in the floor. I would like to congratulate Mr. Kalbhenn on his very fine paper.

Jan 1, 1944

By Xing-Liang Sun, Xian-Min Han, Zheng-Guo Zhu

The study on the material properties of frozen soils in China was being developed quickly in the past decades of years, because of the increase of the engineering constructed in frozen soil regions on the Qinghai–Tibet Plateau, and numerous research results were achieved mainly about strength and deformation behaviour and constitutive models of frozen soils. Studies have shown that the deformation procedure of frozen soils is irreversible; therefore, it is more appropriate to research mechanical properties of frozen soils by means of damage mechanics theory. In this paper, an elasto-viscoplastic anisotropic damage model is presented by introduction of Perzyna viscoplastic equation into analyzing the deformation of frozen soil. In addition, an anisotropic damage evolution equation is obtained by means of extending non-viscous damage to viscous damage. Triaxial tests at different strain rates are chosen to illustrate the application of this model, and good agreement between experimental data and numerically simulated results is obtained. The calculated results indicate that, under the same conditions, the damage at higher strain rate is less than that at low one. So the phenomena are explained from damage mechanics that the frozen soil has larger elastic modulus and shear strength at higher strain rates, and explained from mechanism that the emergence and development of micro-cracks in the body of frozen soil can be to some extent retarded at higher strain rates.

Jan 1, 2015

By J. E. Dutrizac, J. M. Zinck

Ferrihydrite is often the initial precipitate resulting from the rapid neutralization of Fe(III) sulphate solutions, and it seems to be a major constituent of zinc plant neutral leach residues. The most important parameters affecting ferrihydrite precipitaton are temperature, solution pH and the neutralization rate. Low temperatures and rapid neutralization rates yield poorly filterable ferrihydrite, whereas higher temperatures and slower neutralization rates produce readily filterable precipitates; in all instances, however, the precipitates are two-line ferrihydrite. Significant amounts of Zn are incorporated in the ferrihydrite precipitates, and the Zn contents increase with increasing Zn concentration, pH or temperature. Generally, the sulphate contents of the precipitates decrease as the Zn contents increase, and this may indicate that the Zn is adsorbed on the ferrihydrite. Discrete Zn phases were not detected. Neither Cd nor Tl is precipitated with ferrihydrite, although thallium jarosite co-precipitates with ferrihydrite at high Tl concentrations and elevated temperatures. Virtually all of the Sn added to the solution precipitates with the ferrihydrite, but the tin is believed to be present as intimately admixed amorphous SnO2.nH2O. Although selenite extensively precipitates with the ferrihydrite, selenate remains mostly in solution, likely because of the close similarity of the SeO4 2- ion to the SO4 2- ion which is present in high concentrations and saturates the available sites for anion adsorption.

Jan 1, 1998