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By D. McFadgen

"THE Dominion Steel & Coal Corporation, through its subsidiaries, the Old Sydney Collieries and the Dominion Coal Company Limited, produces 4% million tons of coal annually from eight submarine collieries situated on the eastern coast of Cape Breton Island. The present workings have a frontage of 20 miles and extend 31/2 miles under the Atlantic ocean on gradients varying from 4 deg. to 24 deg. To date, some of the workings have reached .a depth of cover up to 2,800 feet.The pitching seams, the annual seaward advance, the resulting depth of cover and the rdatively soft roof and floor have necessitated the adoption of extensive longwall mining, with room-and-pillar mining con-fined to areas above the 1,000 foot cover line, where 60 per cent of the -coal is left standing in pillars to support the ocean floor. Longwall mining accounts for 87 per cent of the total production with the remaining outputs obtained from room-and-pillar work and the narrow work development. Seventy-four per cent of the longwall production and 41 per -cent of the room and development production is completely mechanized.Although 2 tons of water is pumped from the collieries for each ton of coal mined, the working sections are relatively dry as the heavy make of water is essentially surface drain-age from the land crop areas. The dry workings and the long haulage distances, which in many cases exceed 4 miles, have resulted in a continuing programme to combat the dust hazard, both at the working face and along the mine roadways."

Jan 1, 1960

By S. Yadav, T. G. Murthy, C. Saldana

"An experimental study has been carried out in order to study the deformation of porous brittle materials under plane strain indentation. Gypsum, which is well known model system for understanding the behaviour of soft rocks, is used in this study. The effect of wedge angle is investigated in this research through this series of experiments, using wedges of 3 different apical angles. High-speed, high-resolution images are captured using a CMOS camera during the experiment. The images obtained are analyzed using a Particle Image Velocimetry (PIV) algorithm in order to obtain the evolving velocity, strain-rate and strain fields.INTRODUCTIONThe problem of indentation, which is usually referred to in the context of hardness testing is ubiquitous as a material characterization technique for a large class of solids. Mechanical properties of materials such as yield stress, flow stress, fracture toughness, elastic moduli etc. can be related to the hardness of a given solid. The indentation problem involves a given material or solid (whose properties are to be determined) indented by a relatively harder material (indenter) allowing the solid to undergo plastic deformation, which is then related to the yield stress of the material. The problem of indentation and its variants see many applications ranging from mining and petroleum industry, infrastructure industry, manufacturing, and biomedical sectors. Indentation has been extensively studied in metals, with accurate measurement of deformation parameters, stresses and comparison with analytical solutions. On the other hand, understanding of indentation in other class of solids such as cellular solids, porous solids, rocks, and soft solids is still nascent. In case of rocks, a comprehensive understanding of the indentation problem is very crucial because of the obvious applications in mining, petroleum and infrastructure sectors. The inherent porosity, the brittle nature of the rocks, adds to the complexity of indentation in these porous brittle solids. Various theoretical models with degrees of simplifying assumptions have been proposed to study the indentation in rocks. The most common model used in the study of indentation in rocks is a cavity expansion model, wherein a blunt indenter indenting into a rock is approximated with the expansion of cylindrical or spherical cavity in an elastic-plastic material. Complementary studies in understanding fracture initiation and propagation due to indentation has been largely based on the studies of traditional brittle materials such as glass."

Jan 1, 2015

By William James Kempson

This paper discusses ore handling systems in shafts. These are considered from the loading facility at shaft bottom all the way through to the discharge mechanism in the headframe. These systems will be discussed from the following perspective: i. Intrinsic safety of the systems ii. The efficacy of the systems to perform consistently iii. The maintainability of the systems iv. Overall system cycle times Particular emphasis is placed on the following specific areas: 1. The Shaft Bottom Loading Facilities The various shaft loading systems currently in use are discussed, the selection parameters surrounding these are quantified and the specific selection criteria are outlined. 2. The Various Skip Configurations In this section the various skip configurations in use around the world will be described and the specific design details associated with these will be highlighted. The advantages and disadvantages of these systems will be compared and the overall efficacy of these will be discussed. 3. The effect of the loading and skip configurations on the Load Cycle Times. The overall cycle time which can be achieved by a shaft system is strongly dependant by the speed and efficiency with which the ore can be loaded and transported out of the mine. The potential of the various systems to be optimized will be discussed. The emphasis of this paper is to highlight the lessons which have been learned with respect to ore transport system design and provide a common basis against which these can be compared in future applications.

May 1, 2013

By John Starkey

This paper examines 5 years of SAGDesign testing data with particular emphasis on the grinding test results from two recent projects, the Fortune Minerals Limited NICO project, and the Aurora Energy Resources Inc., Michelin deposits, located in the Northwest Territories and in Labrador respectively. The context is to compare these results with the SAGDesign database. The required SAG mill pinion energy for these two ores showed vast differences, even though both ores had similar average Bond Ball Mill Work Index values - about 13 kWh/t each for the two deposits respectively. Bond Rod Mill Work Index values for NICO ranged up to 19.7 kWh/t for the hardest ore, confirming the harder nature of the coarse material. SAG mill pinion energy to grind the NICO cobalt-gold-bismuth-copper ore from F80 152 mm to T80 1.7mm varied from 16 to 35 kWh/t, while for Michelin uranium ore, it varied from 2 to 9 kWh/t. NICO ore is harder than any other material encountered to date using SAGDesign testing. SAG pinion energy is more than double the ball mill pinion energy using a transfer size T80 of 1.7mm and a final grind P80 of 74 microns. For NICO, the ore is ?off the charts? for simulation design techniques because there is no comparable operating SAG mill treating ore that is this macro-competent. For Aurora, the relationship between SAG and ball mill pinion energy is reversed in that the SAG mill requires less than half of the ball mill pinion energy using a transfer size T80 of 1.7mm and a final grind P80 of 90?. Because these discoveries are so important for grinding mill design, their impact will be dealt with in future papers, at the August METSOC Conference in Sudbury, and at the September SME Workshop in Tucson. It has now been concluded that the ratio of SAG pinion energy to Bond Ball Mill Work Index, is valuable data to use in designing a SAG/ball mill grinding circuit, to help choose the power split needed.

May 1, 2009

By F. Parada

During copper smelting and converting processes, slag generated is pyrometallurgically cleaned and then disposed, containing around 1 % of this metal. However, important amount of molybdenum initially contained in concentrates also goes to the slag phase. Research on molybdenum recovery from water granulated slags using acid leaching at low temperatures was conducted to find an efficient way for molybdenum extraction with lower magnetite in the slag. However because of the high fayalite content high acid consumption was found. Molybdenum can be recovered from solution using ionic exchange resins, but high silica content interferes with extraction. Some studies addressed to minimize silica extraction as well as alternatives of selective silica precipitation in order to develop a technically feasible process.

Jan 1, 2007

By BARRY BANNATYNE

About 90 per cent of Manitoba's industrial minerals production is for structural materials. Most of these come from the Paleozoic rocks west of the Precarnbrian Shield, or from glacial deposits that are extensive throughout Manitoba. The major raw materials are sand and gravel, and carbonate rocks for crushed stone (and also dolomite for high-magnesia lime, high-calcium limestone for lime and Portland cement, and dolomitic limestone for Tyndall stone). Glacial lake clays are used both in cement and in lightweight aggregate. The Jurassic and Cretaceous strata exposed along or near the Manitoba Escarpment include siliceous, carbonaceous, kaolinitic and illitic shales, all of which are quarried by Red River Brick and Tile in the Pembina Mountain and Ste. Rose areas for use in a brick plant at Lockport. Non-swelling bentonite near the base of the Pembina Member of the Upper Cretaceous Vermilion River Formation is of value as an absorbent clay, and is the only commercial source in production in Canada. It has been quarried by Pembina Mountain Clays Limited since 1940. Gypsum occurs in the Jurassic Amaranth Formation and supplies much of the market for wallboard and Portland cement additive in the Prairie Provinces. Quarries are operated at Gypsumville by Domtar Construction Materials Limited, and north of Amaranth by Westroc Industries Limited. Silica sand from the Ordovician Winnipeg Formation is of glass-grade quality, and about 100,000 tonnes are produced annually by Steel Brothers Canada Limited on Black Island . It is used as a glass sand, as foundry sand, for sand blasting, and as a filter-bed sand .

Jan 1, 1984

By A. A. Bakke

"The Fort Knox gold deposit is hosted within the Fort Knox Pluton, a Cretaceous multiphase granitic body that intrudes the Fairbanks schist. Gold occurs along the margins of stockwork veins and veinlets, quartz-filled shear zones, and along fractures within the granite. The mineralization is generally sulphide-poor and closely associated with trace amounts of bismuth, tellurium and to a lesser extent with molybdenum and tungsten. At present, proven/probable reserve estimates, based on a cutoff grade of 0.39 g/t Au, are 158.3 million tonnes grading 0.83 g/t Au.The Fairbanks schist comprises the bulk of the country rock. The dominant lithologies present include muscovite-quartz schist and micaceous quartzite. Immediately north and south of the main orebody, mixed metamorphic lithologies of the Cleary sequence, a subunit of the Fairbanks schist, have been mapped. Development of local zones of weakness, most likely due to a broad regional warping event, resulted in brittle-ductile deformation and activation of a northwest-southeast shear couple between contrasting lithologies.The Fort Knox Pluton consists of at least three phases based primarily on textural differences. Intrusion of a fine-grained granite was followed by a medium-grained porphyritic granite. The youngest intrusive phase is a coarse-grained, seriate porphyritic granite, the Vogt Stock. The Vogt Stock forms an elongate dome with the axis in the east-west direction. Structures displayed in the overlying units, believed to be the result of doming, include tension fiSSUres and longitudinal fractures.Premineralization fractures, the result of the magmatic doming, provided conduits for initial stockwork quartz vein development and quartz enrichment in shear zones. Weak development of vein-controlled phyl/ic, potassic, albitic, and argillic alteration styles are present. Evidence of a late thermal event resulting in a low-temperature alteration assemblage of calcite + zeolite (stilbite) + chalcedony + clay occupies breccia zones, joint surfaces, and fractures within the granite."

Jan 1, 1995

By David W. Smith

"This paper is devoted mainly to a discussion of the hydrocarbon potential of the offshore, with a few brief remarks concerning the inorganic mineral potential.OFFSHORE OIL AND GAS POTENTIALIN ORDER TO HAVE HYDROCARBON ACCUMULATIONS, we must satisfy three basic requirements. First, we re-quire a sufficient thickness of sedimentary rocks which contain some porous and permeable formations to act as reservoirs. Second, we require some type of trapping mechanism, such as faulting, folding or stratigraphie trapping. Finally, we require that large quantities of hydrocarbons have been generated within the sedimentary rocks and have migrated to the traps."

Jan 1, 1969

By P. Au, P. Patnaik, H. Saari, D. Y. Seo, S. Bulmer

Ti-48Al-2Cr-2Nb-xW (where x = 0, 0.5, and 1 at. %) powders were consolidated by hot isostatic pressing (HIP). The consolidated samples were solution heat treated above the a-transus followed by stepped cooling to room temperature. Selected samples were subsequently aged at 950 °C for up to 72 hours. The post-heat treatment microstructure was examined by optical and electron microscopy. It was found that increasing holding time above the a-transus generated a more homogenous microstructure. Utilizing the stepped cooling sequence, especially with a transition temperature of 1270 °C, massively transformed gamma (Ym) was diminished. Aging caused coarsening of the fully lamellar microstructure in the 0%W and 0.5%W samples while almost no coarsening occurred in the 1 % W sample. Precipitates began to form during aging in samples containing W. The precipitates at the lamellar interfaces are fine and have a needle like shape, while precipitates at the lamellar grain boundaries are coarse and circular in shape. The size and number of the precipitates depend on aging time and the level ofW content.

Jan 1, 2006

By Xuanxue Mo, Kaihui Yang

"The Laochang mine, located in the Sanjiang area of southwestern Yunnan Province of China, is a volcanogenic massive Pb-Zn-Cu sulfide deposit. It is hosted by a pyroclastic sequence of Early Carboniferous age, namely the lower member of the Yiliu Group, which was intruded by syenite and rhyolite porphyry. The volcanic suite is basaltic or basaltic-andesitic in composition, has alkaline affInities, and is associated with the initial rifting along the margin of the Baoshan-Shanstate continental microplate (Yang, 1989). The ores are typically Pb>Zn>Cu in composition, averaging 3.820/0 Pb, 3.51% Zn, from 0.01% to 1.85% Cu (0.107% av.), a high average content of Ag (113 glt) and recoverable amounts of Au, n, Gd, Ga, Ge, In. A massive sulfide zone, in which lenticular and stratiform orebodies are localized in a sulfide-<:arbonate-silica shale unit or sulfidic tuffIte horizon that usually overlies coarse-grained pyroclastic rocks, is underlain by a stringer sulfide zone developed in a subvolcanic intrusion or volcanic sequence. The sulfIde mineral assemblages, from the top to the bottom of the deposit, are: realgar + orpiment - galena + sphalerite + pyrite - chalcopyrite + pyrite + pyrrhotite + arsenopyrite. Oxide and sulfate minerals occur rarely in the massive ores. The massive ores are generally fme-grained and banded, but coarse-grained ore, colloform and framboidal texture, and growth-zoned pyrite and sphalerite are common. Sedimentary features such as graded bedding, brecciated and deformed ore clasts, and chaotically emplaced blocks, are well preserved, indicating that the massive orebodies have undergone slumping and displacement. Alteration is weak in the hanging-wall rocks, but strong in the stringer zone. Two distinctive alteration zones have been identifIed: the upper zone, characterized by an assemblage of quartz, carbonates, chlorite, albite, zeolite and sericite, and the lower zone containing diopside, tremolite, actinolite, gamet, clinozoisite, and epidote.The general features of the Laochang deposit are in accord with the descriptive model of VMS deposits (Lydon, 1984). However, it falls into neither the Zn-Cu group nor the Zn-Pb-Cu group chemically (Franklin et al., 1981). The depositional setting of the Laochang deposit is quite different from Cyprus or Besshi-type massive sulfide deposits. Laochang is hosted by alkaline lavas that were erupted in a submarine continental rift. Although some features of the Laochang deposit are similar to those of Kuroko-type deposits, there are remarkable differences in the alteration mineral assemblage, the proportion of ore-forming elements (lead enriched) and the amounts of oxides and sulfates. These suggest corresponding differences in ore fluid composition and the associated ore-forming environment. Thus, the authors suggest that the Laochang deposit may be a distinct type of VMS deposit."

Jan 1, 1993

By W. R. Bacon

"MAGNETITE HAS BEEN found in many .parts of the coastal area of British Columbia, but the more important deposits are on Vancouver Island and Texada Island. The locations of these deposits are shown on Figure 1.Interest in the magnetite deposits dates back to the 1870s, when land was acquired on the southwest coast of Texada Island by the Puget Sound Iron Company. This ground included the Prescott, Paxton, and Lake deposits. During the years 1885 to 1903, and 1908, 28,898 tons of magnetite ore was shipped to the company's blast-furnace plant at Irondale, Washington, U.S.A. This production was almost entirely from the Prescott open-pits.In the years following the Texada Island discoveries, other magnetite deposits were found in the coastal area, and various plans were proposed to utilize the local ores in the establishment of a steel industry in the Pacific Northwest. None was carried to fruition but, in 1951, open-pit mining was begun at Iron Hill, Vancouver Island, to furnish iron concentrates for steel mills in Japan. In 1952 mining of the Texada deposits was resumed to supply the same market. Production figures for these recent operations are as follows:"

Jan 1, 1949

By Mark W. Masson, David B. Stevenson, David W. Broughton, Douglas R. Cruji, Steven E. Parry

"Abstract-The Amalgamated Kirkland gold deposit is located at Kirkland Lake, Ontario, within the Archean Abitibi Greenstone belt of the Canadian Shield. It lies on a fault or "break", termed the Cyprus Break, which is a splay off a regional structure termed the Cyprus-Battle Mountain Break. The Cyprus Break merges with the Cyprus - Battle Mountain Break above the -250 m level, as it was not encountered in shallow drilling or surface exploration. These structures lie 1.5 km south of the 727 000 kg (23 million ounce) Kirkland Lake Main Break and 0.5 km north of the 872 000 kg (30 million ounce) Larder Lake Break.The deposit is hosted by alkalic Timiskaming Group volcanic and sedimentary rocks which are overthrust by older Larder Lake Group tholeiitic and komatiitic flows along the Larder Lake Break. Timiskaming syenitic intrusives, similar to the host rocks for the Kirkland Lake Main Break gold deposit, intrude both suites.The Amalgamated Kirkland deposit consists of lode-style gold mineralization which is mainly hosted by altered and pyritized Timiskaming trachytic volcanics which wedge out or thin at depth, between two sedimentary units. The intersection of the Cyprus - Battle Mountain and Cyprus Breaks, in conjunction with the westward plunge of the volcanic wedge, appears to control the westerly plunge of the Amalgamated Kirkland deposit at approximately 50º.Mineralization is characterized by blue-gray brecciated and "wormy" quartz-ankerite veins which contain up to 10% fine-grained pyrite and, in decreasing order of abundance, minor galena, chalcopyrite, sphalerite, molybdenite and visible gold. The sulfides and gold commonly occur along fractures and wallrock inclusions within the veins. Native gold occurs as fine pinpoints distributed in 1-mm to 5-mm size clusters of up to ten or more grains.The auriferous veins occur within a quartz-ankerite-sericite-pyrite alteration assemblage which is enveloped by a broader zone of ankerite-sericite±hematite±quartz-pyrite alteration up to 60 m wide. This latter assemblage overprints the regional greenschist-facies chlorite-calcite assemblage.The Amalgamated Kirkland property has had a long history of exploration activity beginning with the first discovery of mineralization in 1911 on the Hunton Shaft claim located in the northeast corner of the property. Since that time various prospecting, mapping, trenching, geophysical surveys and diamond drilling programs have concentrated on either carbonate zones along the Larder Lake Break or quartz veins along the northern side of the property in association with complex trachyte flows and syenite dikes.Battle Mountain Canada Inc. located the Cyprus - Battle Mountain Break through a prospecting, trenching and geophysical program in 1989. Drilling by Battle Mountain and Cyprus Canada under the surface showing, coupled with several revisions to the structural interpretation of the Cyprus - Battle Mountain and Cyprus Breaks, resulted in delineation of the Amalgamated Kirkland deposit. Location of an auriferous structure through basic surface exploration within 1 km of a world-class orebody demonstrates both the subtle nature of Archean gold deposits and the potential for finding new mineralization in heavily prospected camps."

Jan 1, 1995

By Mark W. Masson, David B. Stevenson, David W. Broughton, Douglas R. Cruji, Steven E. Parry

"The Amalgamated Kirkland gold deposit is located at Kirkland Lake, Ontario, within the Archean Abitibi Greenstone belt of the Canadian Shield. It lies on a fault or “break”, termed the Cyprus Break, which is a splay off a regional structure termed the Cyprus-Battle Mountain Break. The Cyprus Break merges with the Cyprus – Battle Mountain Break above the -250 m level, as it was not encountered in shallow drilling or surface exploration. These structures lie 1.5 km south of the 727 000 kg (23 million ounce) Kirkland Lake Main Break and 0.5 km north of the 872 000 kg(30 million ounce) Larder Lake Break.The deposit is hosted by alkalic Timiskaming Group volcanic and sedimentary rocks which are overthrust by older Larder Lake Group tholeiitic and komatiitic fows along the Larder Lake Break. Timiskaming syenitic intrusives, similar to the host rocks for the Kirkland Lake Main Break gold deposit, intrude both suites.The Amalgamated Kirkland deposit consists of lode-style gold mineralization which is mainly hosted by altered and pyritized Timiskaming trachytic volcanics which wedge out or thin at depth, between two sedimentary units. The intersection of the Cyprus – Battle Mountain and Cyprus Breaks, in conjunction with the westward plunge of the volcanic wedge, appears to control the westerly plunge of the Amalgamated Kirkland deposit at approximately 50º.Mineralization is characterized by blue-gray brecciated and “wormy” quartz-ankerite veinswhich contain up to 10% fne-grained pyrite and, in decreasing order of abundance, minor galena,chalcopyrite, sphalerite, molybdenite and visible gold. The sulfdes and gold commonly occur alongfractures and wallrock inclusions within the veins. Native gold occurs as fne pinpoints distributed in 1-mm to 5-mm size clusters of up to ten or more grains.The auriferous veins occur within a quartz-ankerite-sericite-pyrite alteration assemblage which is enveloped by a broader zone of ankerite-sericite±hematite±quartz-pyrite alteration up to 60 m wide. This latter assemblage overprints the regional greenschist-facies chlorite-calcite assemblage.The Amalgamated Kirkland property has had a long history of exploration activity beginning with the first discovery of mineralization in 1911 on the Hunton Shaft claim located in the northeast corner of the property. Since that time various prospecting, mapping, trenching, geophysical surveys and diamond drilling programs have concentrated on either carbonate zones along the Larder Lake Break or quartz veins along the northern side of the property in association with complex trachyte flows and syenite dikes.Battle Mountain Canada Inc. located the Cyprus – Battle Mountain Break through a prospecting, trenching and geophysical program in 1989. Drilling by Battle Mountain and Cyprus Canada under the surface showing, coupled with several revisions to the structural interpretation of the Cyprus –Battle Mountain and Cyprus Breaks, resulted in delineation of the Amalgamated Kirkland deposit. Location of an auriferous structure through basic surface exploration within 1 km of a world-class orebody demonstrates both the subtle nature of Archean gold deposits and the potential for finding new mineralization in heavily prospected camps."

Jan 1, 1995

By G. Couture

In the introduction to this presentation, we will cover the market of motorized recreational products. We will introduce the public to what is produced and sold worldwide, what is the nature and general behaviour of the customers for such products. We will cover the evolution of this market and put in evidence how drastic must be the changes in the manufacturers organizations in order to, in one hand, constantly adjust to the customer demand, and in the other hand, react to the competitors&apos; offensives on the market.

Jan 1, 2006

By J. Ellis Thomson

For many years the value of qualitative microscopic investigation has been recognized in both of the fields of pure and applied science. In particular, its aid has been invoked in the determination of rock specimens in thin section, and some at least of the interrelations of minerals present in any one section have been observed and, to a limited extent, applied for the solution of different problems. During the past decade this form of research has also been diverted to the determination of ore minerals in polished section, with some observation of their structural relations. Microscopic research of a quantitative character, on the other hand, while started nearly one hundred years ago, has found but a limited application in petrography and has scarcely been used at all in the more modern science of mineragraphy. This is very largely due to the methods employed, since most of them consumed too much time and were, in addition, too laborious to encourage many workers in their use. The details of procedure for these earlier methods will be found in another paper by the writer, and will be omitted from this discussion as being of small interest to practical mining men.

Jan 1, 1930

By Finch. J. A., C. Perez, J. M. Ortiz, G. Cortes, A. B. Yañiez, F. Coddou, P. Morales, H. Elgueta

A campaign to perform characterization tests in a TankCell®-300 flotation cell installed at Chuquicamata Codelco&apos;s concentrator was conducted. The campaign included integrated gas dispersion measurements (gas velocity radial mapping and single point gas holdup and bubble size) and determination of frother concentration. Cell streams were sampled to assess metallurgical performance at the same time. The experimental program was designed to establish the bubble surface area flux operating range and its effect on performance, and the effect of using longer residence times and of a device designed to enhance mixing in the collection zone (FlowBooster(TM)). The gas dispersion results and their relationship to metallurgical performance are discussed.

Jan 1, 2009

By A. Singh

Deformation structures after tensile and compression tests on Mg926Zn64Y alloy extruded at 250°C and 400°C are studied, in as-extruded and heat treated conditions. The icosahedral phase particles stimulate recrystallization during extrusion, resulting in fine grain size. Tensile and compression tests at room temperature show comparable yield strength, with a yield asymmetry ratio up to 0.98. c-type dislocations are observed in the grains near the submicron size icosahedral phase particles. The source of these dislocations is believed to be dissociation of <c+a> type non-basal dislocations. No dislocation pile-ups on icosahedral phase particles are found. {10 1 2} type twinning occurs in compression.

Jan 1, 2006

By Bong Sun You

AZ31 magnesium plate of 300mm in width and 40mm in thickness was produced by horizontal continuous casting machine, and its microstructures were analyzed on the surface and in the plate interior. The defect formation on the surface and subsurface, such as side cracks, buckling, pores and segregation, was very sensitive to the casting condition and processing parameters. Especially, casting speed and secondary cooling were the most dominant parameters to control the solidification behavior of magnesium melt, for example the position and shape of the solid/liquid interface in the mould. The cyclic marks on the surface were obvious because the plate were drawn by 4-step cycle and can not be removed. The average grain size of as cast plate measured as 50-65µm at the near surface and 300-400µm in the center of the plate was relatively small because secondary cooling water was applied to control the surface quality resulting in rapid solidification of the melt in the mould.

Jan 1, 2006

By D. Y. Li, C. D. Ma, T. Zhou, T. J. Cheng

In this paper, a number of experimental tests are carried out to study the strength difference on rectangular prismatic marble specimens with different height-to-width (H/W) rations. The specimens have a nominal size of 45×15 mm in the compressive cross-section (W×T) and different heights (H = 22.5 mm, 45 mm, 60 mm and 90 mm). It is to say that the height-to-width ratios are equal to 0.5, 1.0, 1.33 and 2.0, respectively. The quasi-static uniaxial compressive tests are finished by a servo-controlled INSTRON machine (the strain rate at about 10-5/s), and the dynamic compressive tests are finished by a diameter of 50 mm cylindrical SHPB apparatus (the strain rate reaching about 101/s). The rock failure process of marble specimens is captured by a high speed camera in order to distinguish the fracture propagation behaviour. It is found that the compressive strengths increase when the H/W ratio of marble specimen changes from 2.0 to 1.0 due to the end clamping effect both for quasi-static and dynamic loads. However, when the H/W ratio changes from 1.0 to 0.5, the apparent compressive strengths decrease both for the two loading conditions. The strength decrease of short marble specimens may be attributed to the change of failure mode from shear to slabbing, which can be identified by the fracture patterns of the specimens. Based on the uniaxial compressive tests, the slabbing strength of the marble was found to be about 40% of its UCS for the specimens with a nominal height-to-width ratio of 2.0. In addition, it is found that the dynamic increase factors (DIF) are affected by the specimen’s aspect ratios. It implies that the same aspect ratios should be used to compare the dynamic and static compressive strength of rocks. Meanwhile, both the static and dynamic tensile strengths of the marble are obtained by the Brazilian disc tests. The ratio of the dynamic tensile strength to the static tensile strength of the marble is about 2.68.

Jan 1, 2015

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