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By Th. Hassel

The application of magnesium as an absorbable biomaterial demanded the consideration of the alloy composition, the mechanical properties and the corrosion a special adapted material development in terms of the human biological system. Magnesium for technical applications mostly comprised alloying elements up to 10 wt%. Thereby often metals (e.g. rare earth and aluminum) with high toxic potentials are used to optimize the mechanical properties. To minimize toxic reactions during the degradation of a absorbable magnesium alloy, the Mg-Ca system is being selected and investigated because both elements belong to the mineral nutrients. Rods and small tubes are produced by extrusion of gravity die casting billets (Ca-content 0.4 to 4.0wt%). The positive grain fining influence of calcium and its improvement of the corrosion behavior are additional advantages. The microstructure, the mechanical properties and the corrosion attitude are investigated. The results show that an optimal composition of micro alloyed Mg-Ca and ideally processing parameters lead to 16% strain and a tensile strength up to 185MPa. Electrochemical investigations and measurements of the hydrogen production demonstrate the influence of the Ca-content to the corrosion behavior of the investigated alloys.

Jan 1, 2006

By Kaiwen Xia, Bibhu Mohanty, Per Svedensten, Sheng Huang

"The mechanics of crushing and grinding operations in mining and excavation processes has been investigated in a laboratory simulation study. It employs a multi-particle bedded rock target, which is subjected to multiple impacts. The impact set-up consists of a Hopkinson pressure bar and a Piston-holder system. The apparatus, employing a 38 mm diameter pressure bar, was used to apply varying but calibrated dynamic loading force on the rock particles. The energy consumed by the sample during fragmentation was determined by considering the energy carried by the incident wave and the reflected wave. The Pistonholder system is used to hold rock samples and to recycle fragments after each test for particle size analysis, for single as well as multiple impacts. The feed size selected was in the range of 9.5 to 12.7 mm for all rock samples, and the impact velocity was set at 14 m/s. Two strong granitic rocks and a relatively weak limestone were the target rocks. The resulting particle size distribution after each set of impacts, ranging from single to 10 consecutive impacts, were analyzed, and various size distribution functions (i.e. Rosin- Rammler, Swebrec, Grady and Gilvarry functions) were fitted to compare their suitability in predicting the fragment size distribution for each rock type. INTRODUCTIONCrushers are widely used in the mining industry all over the world. Understanding fragmentation behaviour of rock under crushing process is fundamental to improved productivity and efficiency in mining operations. This is particularly so as all subsequent size reduction processes such as crushing and grinding are far more energy intensive than the initial blasting process employed in breaking of in situ rock. A considerable body of experimental studies exists on the behaviour of rock crushers for specific rock types in order to aid in the design of various types of crushers. However, these studies are mainly site specific, that is, the results are largely empirical, and the fundamentals of fracture process that lead to size reduction have not been dealt with adequately. Most such studies have attempted to link the input parameters, such as feed size and crusher parameters, with output particle size, and global energy expended in the process. However the physical mechanism of crushing process is still not well understood. First of all, the energy consumed by the rock sample is hard to calculate during standard crushing or grinding tests; secondly, multi-particle test is hard to perform in the laboratory due to irregular shape of the subject rock sample. In This paper, describes a laboratory crushing apparatus for multi-particle rock samples, with sufficient control of the energy expended in the process, with a view to relate creation of new fracture surfaces in the size reduction process."

Jan 1, 2015

By László Guczi1

Nanosize model gold particles with varying size were fabricated by deposition of a 10 nm thick gold film onto SiO2/Si(100) substrate by electron beam evaporation followed by modification using low energy Ar+ ion bombardment. The change in particle size were monitored by the Au 5d valence band states determined by ultraviolet photoelectron spectroscopy (UPS). The gold/iron oxide interface was studied by iron oxide deposition on gold. It was found that the energy profile of Au 5d valence band states are strongly redistributed with decreasing the gold particle size mostly affecting at the lowest and at the highest binding energies. The size effect in the UPS spectra can be interpreted by the energy redistribution rather, than by narrowing the 5d states. The iron oxide deposition increases the catalytic activity in CO oxidation whether it is on gold nanoparticles or on a continuous 80 nm thick gold film. The activity enhancement is significantly larger in case of gold nanoparticles. The interface interaction is operative in enlargement of the catalytic activity even if gold particles are not exposed to the surface, but they are located below the iron oxide layer.

Oct 1, 2003

By Alex Matheson, Nick W. D. Massey, Peter T. Bobrowsky

Crowing pressures on aggregate resources include diminishing reserves, high transportation costs, sterilization and land use conflicts. In the absence of detailed resource knowledge for a particular region, aggregate resource potential maps provide the best "first approximation" regarding the surficial distribution of sand and gravel. The 1:50 000 scale Level Ill aggregate potential map integrates several important factors which influence the management of sand and gravel. Data used to generate this type of thematic map is readily available in most areas, fieldwork required is minimal, there is a logical quantitative evaluation of the data layers and integration is easily accomplished on a desktop PC-based platform. Also the aggregate potential map, with its focus on identifying areas of potential future aggregate exploitation as well as present inventory, provides a useful tool for the aggregate explorationist.

Jan 1, 2001

By J. C. Hampton, L. A. Matzar, C. R. Gamwell

In geomechanics, conducting uniaxial or triaxial compression tests require samples to be prepared to a certain length-to-diameter ratio. This ratio is typically defined as 2:1 (length to diameter) and is accepted as a common standard for all materials on which mechanical properties testing is performed. Variations in sample length can cause changes in measured strength properties across multiple material types, such as cement, rock, or soil. Within the oil and gas industry, it is not uncommon to receive samples for technical services work that are slightly under or exactly the length requirement before surface grinding and sample preparation. Many of these samples are discarded from uniaxial and triaxial compression tests and used in another manner; therefore, it is necessary to study the length-to-diameter ratio in efforts to understand the limits and validity of testing samples that are slightly out of the 2:1 ratio. This paper discusses uniaxial compression tests performed using Berea sandstone and a standard cement mixture of 2.54-cm diameter to study changes in rock strength and properties. Compressive strength for each lengthto- diameter ratio over a range of 0.5:1 to 2.2:1 was measured. The investigation was extended to study near-end effects, where the sample length is near, but not exactly twice the diameter. It was discovered that the cement samples conformed reasonably well to the suggested ASTM correction factors. The sandstone did not conform to the correction factors and further analysis is required to develop a correction factor unique to the material. Near end effects, in both the cement and Berea, were found to increase compressive strengths, especially when the L/D of the samples was increased slightly over a 2:1 L/D.

Jan 1, 2015

By André Desbiens, Frédéric Flament, Lionel Ryan

"In December 1991, the GRAHM (Groupe de Recherche sur Jes Applications de L'informatique a L'industrie Minerale), of Laval University started a KBAC (Knowledge Based Automatic Control) grinding project with Falconbridge Ltd. The project was shifted to the Kidd Creek concentrator in the summer of 1992, with the first phase involving the collection of data by GRAHM and Falconbridge personnel for the construction and tuning of a dynamic simulator. This grinding circuit dynamic simulator known as DYNAFRAG was used to assess various control strategies, with a PID-based strategy being selected for ease of installation on a Foxboro II A DCS.The ""B"" primary grinding circuit was chosen for the initial strategy development, which is one of three parallel divisions. The KBAC project was successfully completed in November 1994, with subsequent modifications being implemented by Kidd Creek staff.This paper summarizes, the current control strategy, the project costs, and the realized benefits. Some of the problems which were encountered with the initial installation, and the subsequent modifications are also dealt with in this paper.2.0 IntroductionIn the summer of 1992, the GRAHM of Laval University and Falconbridge Ltd. started a project to design a control strategy for the ""B"" grinding circuit at the Kidd Creek Division. Between 1992 and 1994 several papers have been written to describe the control objectives, the methodology followed, and some initial results (Flament, 1994A, 1994B). Since then, however, the control objectives changed, and several improvements were made to the circuit. In particular, maximizing tonnage was no longer a priority, a variable speed drive pump was installed on the cyclone feed, the ball mill power was lowered, and the geometry of the cyclones changed. As a consequence, the control strategy was revised. Table 1 summarizes the historical developments on the ""B"" division grinding control."

Jan 1, 1996

By Courtney E. Cleveland

THE gold deposits of the Pioneer and Bralorne mines, in the Bridge River district of British Columbia, are closely associated with a long, narrow intrusive body of extremely variable composition, outcropping on the northeast side of Cadwallader creek and lying almost entirely within the property boundaries of the two companies. Other masses of the same type of intrusive rock are found in the district, more or less along the line of the main axis of the Pioneer-Bralorne in trusive, and have associated with them variable amounts of gold-quartz mineralization (Figure 1). The ore deposits of the district have been the subject of investigation by officers of the Geological Survey of Canada at various times during the past 25 years, and articles on the geology and mines of the district have been published by various individuals in technical journals. A list of the more important re-ports follows: SELECTED BIBLIOGRAPHY

Jan 1, 1938

By C. G. Anderson

Industrially proven and applied nitrogen species catalyzed (i.e. NSC) acidic pressure leaching has been utilized to treat a number of ores, concentrates and recycled materials. This versatile technology offers many advantages including low temperatures, low pressures, low capital costs, low operating costs, faster throughput and less costly materials of construction than conventional pressure oxidation. This paper will elucidate the application of this technology for production of gold, silver, palladium, rhodium, zinc, germanium, gallium, cobalt, copper and nickel. Recycled material applications will also be elucidated. In addition, details of an application for treatment of a refractory chalcopyrite copper and gold bearing ore will be presented and pertinent economics discussed.

Jan 1, 2004

By Xuanxue Mo, Zengqian Hou

"Abstract -Yidun Island Arc in Sanjiang Region is one of the important Kuroko-type volcano­ genic massive sulfide deposits (VMS) districts in southwestern China. Tectonically, the region is situated in the eastern portion of the Tethys orogenic belt, and is a late Triassic extensional island-arc. The island-arc underwent earlier arc construction, intra-arc rifting, later arc construction and back­ arc spreading during its evolution and formed a complete trench-arc-basin system, i.e., the Ganzi­ Litang suture zone, forearc basin, outer arc, intra-arc rifting zone, inner arc and back-arc basin from east to west across the island-arc.Kuroko-type VMS deposits and occurrences discovered so far are limited to within the intra-arc rifting zone of the Yidun Island Arc and tend to occur in groups or clusters distributed in separate fault­ bound basins; e.g., Zengke, Gacun and Xiangcheng basins, in which submarine volcanic rocks, especially bimodal volcanic suites, were extensively developed. The VMS deposits formed in the waning stages of volcanic eruption in the late Triassic and are hosted in the uppermost section of acidic volcanic rocks (rhyolitic-dacitic) within a bimodal suite. The orebodies are associated with these host rocks: rhyolitic-dacitic pyroclastic rocks and exhalites and chemical sedimentary rocks.Ali VMS deposits in Sanjiang are of the Zn-Pb-Cu type. The architecture of the deposits is two­fold, consisting of concordant lenses and layers of massive sulfides and an underlying discordant stockwork. Ali deposits show metal zoning. The hydrothermal alteration related to mineralization is strong and asyrnmetrical, and is found dominantly within the stockwork zone and host rocks surrounding the ores. There are two alteration patterns: (1) chloritization - sericitization - silicification from outer sides to core of the alteration pipe; and (2) silicification + sericitization - silicification + carbonate from the lower to upper part of the alteration pipe_The mineralization temperatures of ore-forming fluids vary in the range 200°C to 335°C. Thermal evolution of the fluids displays temperature profiles that first increase and then decrease with progression of mineralization processes. The majority of black-ore minerais (Groups I and II) formed during intensifying stages of hydrothermal activity, and the majority of serni-yellow-ore minerals (Group III) formed during a thermal maximum . There followed the formation of fine-grained black-ore minerals (Group IV), which interacted with barite layers during decreasing temperature phases.Oxygen and hydrogen isotope studies show that the sources of ore-forming fluids for the Kuroko­ type VMS deposits are two-fold: seawater and magmatic hydrothermal solutions, represented by the Kuroko deposits in Japan and Kuroko-type VMS deposits in Sanjiang, respectively. In the latter case the hydrothermal solutions reacted with host rocks and mixed with cold seawater percolating downward, and circulated through volcanic rocks resulting in development of alteration zones and formation of ore minerals in Kuroko-type VMS deposits."

Jan 1, 1993

By P. Tukkaraja, K. Katzenstein

"Block caving is one of the most economical and efficient underground mining methods and has gained popularity around the world especially for extracting low grade and massive ore bodies. However, during the extraction of ore from the draw bells, gases trapped inside the cave could emit into the working areas; hence, ventilation plays a key role in operating block cave mines successfully where gas emission is a concern. To design an effective ventilation system for a block caving mine, given the dynamic nature of the caving process, it is necessary to develop airflow characteristic curves (P-Q) for a given cave. This study uses a 1:100 scale physical model with an exhaust fan system, and a Computational Fluid Dynamics model of a block cave to investigate the airflow behavior through the cave filled with broken rock material. From this study, it was observed that the cave airflow resistance increases with the decrease in cave porosity and the particle size.INTRODUCTIONThe block cave mining method is gaining popularity owing to its low cost and high productivity. This study considered a case where this bulk mining method is used for the extraction of an orebody that contains uranium mineralization. During the extraction of broken ore from the draw bells, radioactive gases trapped in the cave zone could be released into the production drifts and could create unsafe working conditions in the mine. Mine ventilation systems play an important role in regulating the migration of radon in working areas. One of the strategies to control radon migration in a block cave mine is to exert negative pressure on the cave zone by using an exhaust fan above the cave zone. In order to select an appropriate exhaust fan system, it is necessary to study the airflow resistance of the cave zone (Loring & Nelson, 2006).Extraction of broken ore via drawpoints creates a void volume inside the cave called the air gap. Air gaps with larger heights can lead to air blasts in a block cave mine should the cave collapse. Besides that, the air gap can also lead to decrease in ventilation system efficiency due to recirculation of air flow and associated shock losses. Air gap height can also have a profound effect on the variation of cave airflow resistance (Erogul et al., 2015, 2017). The knowledge of cave airflow resistance is also important for predicting the intensity of an air blast. Cave airflow resistance is a function of cave properties such as broken rock size, air gap, and porosity inside the cave zone (Baysal et al., 2017). Initially, a scaled experimental model with a forcing system was developed to investigate the airflow behavior through the cave, however, this model couldn’t provide an observable change in the airflow resistance when the cave properties were changed (cave porosity, and airgap) This was attributed to the difficulties associated with forcing system in terms of achieving lower porosity values with the available material (lightweight shipping boxes) for simulating broken rock inside the cave zones, and controlling air leakage from the model (Ajitha et al., 2018)."

Jan 1, 2019

By A. Gronningsater

Introduction As is well known, the fight between the blast furnace and the reverberatory furnace in copper smelting during the second decade of the century ended with a victory for the latter, a result which must largely be attributed to the introduction of flotation methods. To my knowledge, no new blast furnace has been blown-in at any American copper smelter since the War. As the metallurgy of nickel, up to and including matte smelting, is generally considered a close parallel to that of copper, the introduction of reverberatory smelting in the big new smelter of the International Nickel Company at Copper Cliff, built in 1928-30, seemed a logical adherence to a well established trend. In view of these facts, considerable comment was made when Falconbridge Nickel Mines decided to retain the blast furnace in their smelter built about the same time, in 1929. A presentation of the reasons governing this choice should therefore be of interest. The basic principles underlying the Falconbridge practice, and the considerations guiding the successive steps in the operations, will be discussed in the following. To understand the problems involved, the character and mode of occurrence of Sudbury ore must be kept in mind. Large amounts of disseminated ore are generally present. Although the gangue usually runs only about 50 per cent Si02, the ore hoisted as a rule contains more silica than needed in the smelting operation; until recently this excess was removed entirely by hand picking (in later years supplemented by magnetic sorting methods), a difficult and not very satisfactory method, in which 'the border line between ore and waste is entirely arbitrary, and therefore too much depends on the judgment of the picker.

Jan 1, 1934

By Paul Clayton

Case Study ? Site: BMA Saragi Coal Mine Queensland Australia ? Model: Marion 8050 ? YOM: Mid 1970s ? Boom: 97M ? Bucket: Original capacity of 100 Tonnes upgraded to 125 tonnes at time of filtration upgrade. ? Apps: Swing, Hoist & Drag Gearboxes ? Oil: Oil Castrol Alpha TT1200 Viscosity of 1208 cSt @ 40° C (104° F) 720ltr Oil Volume Trial and Installation Justifications ? To reduce gearbox overhauls. Typical schedule being 5 years. ? Bucket upgrade from 100 tonnes to 125 tonnes. Increased gearbox demand and stress. ? Increase of overhauls out to 10 years + ? Saving per Dragline estimated to be US$8-10M in downtime and maintenance if successful. ? In compliance with BHPBilliton Global Maintenance FLAC program ? Fuels, Lubricants, Air and Coolants ? Cost Justification ? Downtime: 4 days ? Lost production: $420,000 ? Cost of parts: $162,000 ? Labour and misc: $41,000 Gearbox failure cost $623,000

May 1, 2008

By Gordon L. Kidd

The object of this paper is to show the relations of the East Coulee coal area to the near-by Willow Creek, Wayne, Rosedale, and Drumheller areas, all being parts of the Drumheller field. The word ?area? is here used in a more local sense than that employed by Dr. J. A. Allan, whose. 'area' is rather comparable with the 'mining division' in British Columbia. I have drawn freely from the published information, particularly from Dr. Allan's report on the "Geology of Drumheller Coat Field, Alberta", and from Dr. E. Stansfield's paper on " A Chemical Survey of Alberta Coals", to whom thanks are due. The Drumheller field is served by branch lines of the two principal Canadian railways. The C.N.R. traverses the district by its Goose Lake line from Calgary to Saskatoon; and the C.P.R. by a line from Calgary to Acme and then southeasterly to Drumheller, where it effects a junction with the C.N.R., over which the C.P.R. has running rights as far as Rosedale. From Rosedale, a joint line built during the summer of 1928 extends about forty miles down the Red Deer river to the mouth of Bull Pond creek. From that point the C.P .R. turns more southerly to connect with the Bassano-Empress line. The C.N.R., it is expected, will eventually proceed eastward to connect with a transcontinental line. The joint line from Rosedale down the Red Deer river opened up the Willow Creek and East Coulee areas.

Jan 1, 1929

By M. E. Hurst

SINCE 1934 there has been a marked revival of interest in the Porcupine district, especially in the eastern portion of the area, where exploration on the property of Pamour Gold Mines has indicated the presence of extensive gold-bearing deposits. Owing to the prevalence of overburden and the limited amount of exploratory work that has been done, little information is available as yet concerning the distribution and structural relationships of the rocks in the area to the east of Porcupine lake. In order to throw some light on the structural conditions in this section, a brief discussion of the sequence and character of the formations in the better known, producing section of the camp has been included. It should be emphasized that this paper is a preliminary study and that, consequently, the conclusions expressed should not be regarded as final. The writer wishes to acknowledge his indebtedness to P. C. Benedict, whose study of the geological relationships on the Foley-O'Brien property has made possible a fuller understanding of the structure in the central portion of the area. The writer also wishes to express his appreciation of the information and facilities placed at his disposal by R. M. Macaulay and C. D. Stevenson, of Pamour Gold Mines, and by A. Bell, of Noranda Mines, Limited.

Jan 1, 1936

By K. Sinding, R. Poulin

"Recent land-use decisions in British Colwnbia, and the publication of a report on compensation for expropriations of resource interests, have highlighted the nature of land use policies. Landuse decisions, such as the creation of large new parks, raise three principal issues which have implications for how land-use policy is conducted and how it impacts on the mining industry. The first is the identity of the parties advocating different land-use policies and their motives for doing so, the second is the changing nature of benefits derived from land, and the third is the change of property-rights regime which is devised to accommodate the (changing) benefits from using land and natural resources, as well as the interests of the different parties involved.Involved Parties and BenefitsThe process of establishing or modifying property rights depends on the interest groups involved. Three distinct categories, each with distinct incentives which can influence the process, must be distinguished: private claimants, politicians and bureaucrats (Libecap, 1989).The first groups claim rents and management powers through asset ownership. They may be incumbent owners seeking enforcement of the status quo, new claimants seeking redistribution of assets, or third parties who depend on the distribution of assets (e.g. lenders, labour suppliers and contractors). Some infonnal property arrangements can be negotiated within the group whereas others requires action in the political arena through lobbying politicians for (re)allocation of property rights and influencing bureaucrats for favourable administrative decisions. The second category is politicians, who direct the powers of the state to change or enforce property rights. Both incwnbents and office-seekers fall in this category and their actions and opinions are shaped by their constituencies and financial backers. However, not all causes can be championed and trade-offs have to be made, resulting in decisions that maximize political benefits. The third category of parties in the process is the bureaucrats. The power to manage has been delegated by politicians but bureaucrats also have opportunities and incentives to further their own interests. These can include maintaining or expanding jurisdictional turf or increasing operating budgets (Libecap, 1989)"

Jan 1, 1994

By Abhiram Shankar

Construction projects are becoming more demanding both in terms of time and complexity. This necessitates intricate planning and sequencing of activities at the macro and micro level and continuous flow of resources across the project in order to achieve planned targets. Work and Resource planning need to be done in such a way that limited resources give optimal output. Currently dominant activity-based scheduling techniques like Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT) do not model work-flow or resource-flow through a project life cycle. An extension to the conventional activity based planning is Location Based Management System (LBMS). LBMS has been explored and utilised in the case of repetitive and cyclic projects such as high rise buildings. This study focusses on the application of LBMS to repetitive and non-repetitive components of Power Transmission and Distribution (PT&D) projects involving construction of substation and cable laying. This paper presents the findings on comparing the current planning practice for cable laying with an LBMS based approach. A key finding of the study was that the conventional practice resulted in a schedule with several coordination issues that could not be identified in the planning reports. Using the LBMS based approach these issues could be identified and decisions required for resolving these could be made.

Aug 1, 2013

By G. S. Hume

Introduction O WING to the mineral discoveries which have recently been made in the Great Bear Lake region and the possibility of the need for fuel for transportation and development, it seems.timely ro review available information regarding the oil prospects in the vicinity of Great Slave lake and Mackenzie river, where a vast area is underlain by Palreozoic and younger sediments that undoubtedly are petroliferous. Exploratory surveys were carried out in this area by the Geological Survey and others in the latter part of the 19th century, but it was not until 1920, when drilling for oil actually began, that any serious attention was paid to the oil prospects. This is readily accounted for by the remoteness of the region, the lack of quick transportation facilities, and the shore summer season. Numerous and copious oil seepages had been reported, however, from widely separated localities, and interest was stimulated by the knowledge that these occurred in Devonian strata which had given a remarkable record of sustained production of high-grade oil in the oil-fields of southwestern Ontario. . Accordingly, during the four years 1920 to 1923, inclusive, several parties sent out by the Geological Survey made as thorough an investigation of various parts of the area as seemed warranted at that time, and from these surveys most of our information regarding the details of the stratigraphy is derived. In such a large area, it is inevitable that the lithology and thickness of rocks of the same age would show wide variations, and hence it should be recognized that conditions as regards oil prospects in the vicinity of the west end of Great Slave lake are quite distinct from those that occur near Fort Norman, 400 miles farther to the northwest, and these again are in all probability quite different from those in the less well known Arctic Red River area, 250 to 300 miles still farther north.

Jan 1, 1932

By The Staff

THE gold mining industry in Canada is today the most important stabilizing influence in the country. This factor was brought out particularly during the 'depression' years, when steady employment was given to men in that industry and the monies spent in supplies and power in turn benefited the country to a great extent. At the same time, a commodity was produced which was saleable in any market of the world, thus maintaining Canada's credit in foreign markets and keeping her trade balances equalized. We have a vast area known as the Precambrian Shield. The agricultural possibilities of this area are practically negligible and it will depend entirely upon the mineral and forest resources to make this district an economic factor in the life of Canada. To date, from the mineral point of view, we have been highly successful. There are, however, still vast areas to be explored. It is tedious and laborious work, entailing great individual hard-ships and the expenditure of much energy and money. During my thirty years' experience in the search for, and operating of, gold mines, I have come to the conclusion that although individuals may give all their time, energy, and money, Governmental assistance is absolutely necessary in the development of hydro-electric power sites and roads. The Governments, to date, have given splendid co-operation along these lines, but in order that this great industry may go ahead they should continue their good work and, if possible, give greater relief from taxation to mines situated at a considerable distance from the railway.

Jan 1, 1938

By Qin-yong Ma, Jing-shuang Zhang, Bo Han, Pu Yuan

In order to improve the utilization rate of blasthole and blasting effect in vertical shafts, 5 kinds of millisecond blasting model tests with three circle vertical blastholes have been conducted in various delay times with concrete as model material. The blasting effects of millisecond blasting model tests are investigated from cutting volume, cutting depth, and blasting fragmentation, then a reasonable delay time is obtained. In the middle of concrete model, there are 4 blastholes uniformly distributed in the first circle, 6 blastholes uniformly distributed in the second circle, and 10 blastholes uniformly distributed in the third circle. Each blasthole is charged with one millisecond delay electric detonator, and the rest is blocked with stemming. The depth of blastholes in the first and second circle is 180mm, which is 20mm deeper than those in the third circle. After initiation, the blasting cavity is cleaned up, then the cutting volume and cutting depth are measured. Meanwhile, the blasting fragments are gathered and have analysed by function Rosin-Rammler. The test results show that when the inner two circle blastholes initiated simultaneously and the third circle blastholes initiated with millisecond delay, the reasonable delay time is 50 ms. At this time, the cutting volume and cutting depth of blasting model are 3920 cm3 and 68 mm respectively. The fragmentation indexes of blasting fragments, X50 and X80, are 53.2 mm and 74.6 mm respectively. While when all three circle blastholes initiated with millisecond delay, the reasonable delay time is also 50 ms. At this time, the cutting volume and cutting depth of blasting model are 10705 cm3 and 118 mm respectively. The fragmentation indexes of blasting fragments, X50 and X80, are 51.0 mm and 81.7 mm respectively. The researches indicate that for millisecond blasting with multiturn blastholes, the reasonable blasting scheme is multiturn blastholes initiated in millisecond delay and the reasonable delay time is 50 ms.

Jan 1, 2015

By W. J. Wolfe

"THE DETECTION OF BURIED MINERAL DEPOSITS by chemical analysis of vegetation (biogeochemistry) or visual observation of plant cover type (geobotany) is based on fundamentally simple principles. The root systems of vegetation collect aqueous solutions from a large volume of moist ground below surface and act as efficient sampling mechanisms by providing a composite sample of a reasonably large area. These aqueous solutions constitute a source of ore-associated metals that may ultimately be concentrated in the upper parts of the plant. Although certain plant species have a limited ability to break down primary minerals and extract elements, biogeochemistry normally detects only metals capable of moving in solution. Metal concentrations in the underlying soil must therefore exist in a form that is immediately available for uptake by the root systems - generally in the ionic state in aqueous solution or in readily exchangeable form on the surfaces of soil clay minerals. As a result, biogeochemical responses are closely related to variables such as soil pH, Eh, exchange capacity and complexing agents that control metal mobility in the surface environment. In terms of cost, reliability and anomaly contrast, soil geochemistry will normally be more useful than biogeochemistry in locating buried mineralization in regions of residual overburden or thin transported cover. However, in areas where the root systems penetrate thick deposits of transported post-mineralization overburden, plants can provide an effective mechanism of sampling below the transported material. Biogeochemical research in Canada, Scandinavia and the U.S.S.R. has therefore focused on the potential use of plant prospecting methods (1) in areas where the upper horizons of podzolic soils do not provide an adequate response to anomalous conditions under thick deposits of glacially transported till and (2) in widespread regions of peat and muskeg terrain where near-surface mineral soils are absent."

Jan 1, 1971