• Title/Summary/Keyword: Bearing fault

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Analytical Study of Net Section Fracture in Special Concentrically Braced Frames (중심가새골조의 순단면 파단에 관한 해석적 연구)

  • Yoo, Jung Han
    • Journal of Korean Society of Steel Construction
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    • v.21 no.1
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    • pp.63-70
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    • 2009
  • Failure modes result in fracture or tearing, which may cause deterioration of resistance and reduction of inelastic deformation capacity. The potential failure modes for Special Concentrically Braced Frames (SCBFs) include fracture or tearing of the brace, net section fracture of the brace or gusset plate, fracture of the gusset plate welds, shear fracture of the bolts, block shear, excessive bolt bearing deformation, and buckling of the gusset plate. HSS tubular braces are commonly used in SCBFs, and net section fracture of the tubular brace may also occur through the brace net section at the end of the slot cut into the tube to slip over the gusset plate. This failure mode is categorized as a tension failure mode, and may cause dramatic loss of resistance and brittle behavior. Net section reinforcement is required according to AISC design specifications (AISC 2001). In this paper, the need to reinforce the net section area was discussed. Initially, the results of the net section fracture tests done by the University of California in Berkeley were presented with the modeling of these tests using FE models. To investigate the possibility of net section fracture in an actual frame, the slot end hole model was adapted to the frame FE model, and alternate near-fault histories were applied with tension-dominated cycles, since previous analyses showed that loading history was the most critical factor in net section fracture. The need for this reinforcement (cover plate) and the tension-dominated near-fault history were investigated.

Gold Mineralization of the Sepola District in Mali, Africa: Occurrence Characteristics of Gold and Fluid Inclusion Study (아프리카 말리 세폴라 지역의 금광화작용:금의 산출특성 및 유체포유물연구)

  • Heo, Chul-Ho
    • Economic and Environmental Geology
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    • v.42 no.3
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    • pp.167-175
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    • 2009
  • The geology of Sepola district in Mali is consisted of Birrimian group with metasedimentary rocks of lower Proterozoic and volcanoclastics, and later intrusive igneous rocks. Ore diposit in this district has the characteristics of vein- and disseminated-type gold deposit which was formed by infilling the secondary fracture zones related to the large-scale fault zone of NW direction within Birrimian group. It is confirmed as promising that Barani district has the gold grade of 0.53${\sim}$9.21 g/t with the extension of 1.3 km and width of 1 to 20.1 m. The ore mineralogy is simple with electrum, pyrite and galena. Fineness of gold grain ranges from 848 to 915(average 891) indicating mesothermal to hypothermal environment. Fluid inclusions are classified as liquid-rich type I. gas-rich type II and liquid-$CO_2$ bearing type III. Primary and pseudosecondary inclusions homogenize from 236 to 393$^{\circ}C$ with salinity of 0.0 to 8.6 wt% NaCl. Secondary inclusions homogenize from 103 to 184$^{\circ}C$ with salinity of 0.7 to 8.6 wt.%. From the relationship between homogeniztion temperature and salinity, it may be thought that auriferous fluid experienced dilution and cooling through inflow of meteoric water after fluid unmixing derived from pressure decrease in the temperature range of 400 to 250$^{\circ}C$. From the massive occurrence of quartz vein, simple mineralogy with paucity of sulfide, and presence of liquid-$CO_2$ bearing with high homogenization temperature, it is thought that gold mineralization in Sepola district correspods to the mesothermal to hypothermal ore deposit.

Stable Isotope and Fluid Inclusion Studies of Gold-Silver-Bearing Hyarothermal-Vein Deposits, Cheonan-Cheongyang-Nonsan Mining District, Republic of Korea: Cheongyang Area (한반도 천안-청양-논산지역 광화대내 금-은 열수광상의 안정동위원소 및 유체포유물 연구 : 청양지역)

  • So, Chil-Sup;Shelton, K.L.;Chi, Se-Jung;Choi, Sang-Hoon
    • Economic and Environmental Geology
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    • v.21 no.2
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    • pp.149-164
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    • 1988
  • Electrum-sulfide mineralization of the Samgwang and Sobo mines of the Cheongyang Au-Ag area was deposited in two stages of quartz and calcite veins that fill fault zones in granite gneiss. Radiometric dating indicates that mineralization is Early Cretaceous age (127 Ma). Fluid inclusion and sulfur isotope data show that ore mineralization was deposited at temperatures between $340^{\circ}$ and $180^{\circ}C$ from fluids with salinities of 1 to 8 wt. % equiv. NaCl and a ${\delta}^{34}S_{{\sum}S}$ value of 2 to 5 per mil. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a range of pressures from < 200 to $\approx$ 700 bars, corresponding to depths of ${\approx}1.5{\pm}0.3\;km$ in a hydrothermal system which alternated from lithostatic toward hydrostatic conditions. Au-Ag deposition was likely a result of boiling coupled with cooling. Meaured and calculated hydrogen and oxygen isotope values of ore-forming fluids indicate a significant meteoric water component, approaching unexchanged paleometeoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship among depth, Au/Ag ratio and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved meteoric waters, but only deeper systems (${\geq}1.5\;km$) are exclusively gold-rich.

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Lead-Zinc-Tin-Silver Mineralization of Tangguanpu Mine, Hunan Province, China: Fluid Inclusion and Sulfur Isotope Studies (중국 호남성 당관포 광산의 연-아연-주석-은 광화작용: 유체포유물 및 황동위원소 연구)

  • 허철호;윤성택;소칠섭
    • Economic and Environmental Geology
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    • v.34 no.2
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    • pp.157-166
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    • 2001
  • Numerous base-metal bearing hydrothermal quartz vein deposits occur in the Hunan province of southern China. The Tangguanpu lead-zinc-tin-silver mine is the major producer among these deposits. Lead-zinc-tin-silver mineralization occurs in a single stage of massive quartz veins which filled fractures in fault zones within Paleozoic metasedimentary rocks. Sphalerite, chalcopyrite, galena, pyrite, arsenopyrite and pyrrhotite are the principal sulphide minerals in the Tangguanpu lead-zinc ores with minor amounts of tin- and antimony-bearing sulphides (stannite, teallite, boulangerite and tetrahedrite). Based on the iron and zinc partitioning between coexisting stannite and sphalerite, the formation temperature for this mineral assemblage range from 300$^{\circ}$ to 330$^{\circ}$C, which relatively agree with the upper part of homogenization temperature of fluid inclusion in quartz (20T-358$^{\circ}$C). Fluid inclusion data show that main lead-zine-tin-silver mineralization occurred from $H_{2}O$-NaCl fluids with relatively low salinities (11.2-7.3 wl.% eg. NaCI) at temperatures between 207$^{\circ}$ and 358$^{\circ}$C. The relationship between homogenization temperature and salinity suggests a history of cooling and dilution followed by initial boiling. Evidence of initial fluid boiling may indicate the fluid trapping pressures of 180 bars. The ${\delta}^{34}S{{\Sigma}S}$ values of -5.0 to 1.1 %, indicate an igneous source of sulfur in the Tangguanpu lead-zinc-tin-silver hydrothermal fluids.

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The Deformation Properties and their Formative Processes in Ogcheon Terrain around Ogcheon Town, North Chungcheong Province, Korea (옥천대(沃天帶)의 변형특성(變形特性)과 그 형성(形成) 과정(過程) -충북(忠北) 남서단(南西端)을 예(例)로 하여-)

  • Lee, Byung-Joo;Park, Bong-Soon
    • Economic and Environmental Geology
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    • v.16 no.2
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    • pp.111-123
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    • 1983
  • The studied area is situated in tho southern part of the Ogcheon fold belt, where the "Ogcheon Group" is widespread with Jurassic and Cretaceous intrusions. The regional stratigraphy may be divided into three formations, the lower pebble bearing phyllitic, the middle dark grey phyllitic, and the upper black phyllitic formations. For the purposes of the present study, the area has been partitioned to three structural subareas based on major fold axes and fault line. The main subjects of the research have been discussed from two different points, multiple deformation and minor-micro fold styles. The former is analyzed by pebble elongation, folding and lineation in a pebbly formation as well as schistosity, crenulation cleavage and crenulated lineation in the phyllitic formation. The later describes the characteristic features of fold style in each formation and structural subarea. Although minor fold axes within broad pelitic rocks usually tend to trend northeast and to plunge northward, most of these were probably formed by two stages, first a similar fold phase and second a kink fold phase. Measured structural elements indicate that crenulation cleavage in phyllite formed parallel to fold axes of folded pebble followed a NE phase of first deformation and a fold axes of pebbles diagonal to bedding of phyllite are represented by a NW phase of a second deformation. Microscopically, quartz and mica grains form a micro fold enabling one to establish tectonic levels which occur in different deformation modes in each stratigraphic sequence. Microtextures such as crenulation cleavage, kink band, aggregate band of mica and pressure shadows of porphyroblast of quartz related to qarnet and staurolite may suggest the time relation of crystallization and tectonism. The result of this study may conform that three deformation phase, NE first phase-NE second phase-NW phase, occurred in the area.

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Development of the Multichannel Vibration Monitoring System (다채널 진동 모니터링 장치 개발)

  • Hong, Tae-Yong;Park, Soo-Hong
    • The Journal of the Korea institute of electronic communication sciences
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    • v.11 no.7
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    • pp.671-676
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    • 2016
  • This study is about design for the Rotational Instrument of the Industry factory which is used management safety and maintenance. We developed the multichannel vibration monitering system of the self-diagnosis for middle level CMS(Condition Monitoring System) market, and that system are new features to the expandability and flexibility. Normally one channel is used for treating one signal, but developed instrument can treat four channel with one signal processing card. One rack have redundant power supply and displace and it can check vibration measurement value in field without computer. Bearing fault detection is fundamental of vibration surveillance, but sometimes can not check with vibration velocity and acceleration. So it need the filtering and the amplitude modulation on the acceleration enveloping technology when irregular vibration is happened. We developed the vibration analysis instrument which is applied such technology. And the development prototype shows activated within the vibration error limit.

Geology and Ore Deposits in the Haman-Kunbuk Copper District (함안군북지구(咸安郡北地區)의 지질(地質)과 동광상(銅鑛床))

  • Moon, Chung Uk;Kim, Myung Whan;Lee, Ji Hern;Choi, Chung Jung
    • Economic and Environmental Geology
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    • v.3 no.2
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    • pp.55-73
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    • 1970
  • The district investigated covers the central and southern portions of the Uiryong Quadrangle amounting to $40km^2$ in area and is bounded approximately by geographical coordinates of $128^{\circ}$ 28' $40^{{\prime}{\prime}}{\sim}128^{\circ}$ 24' 25"E in longitude and $35^{\circ}10{\prime}{\sim}35^{\circ}14^{\prime}06^{{\prime}{\prime}}N$ in latitude. The purpose of this investigation was to provide basic information in drawing up a comprehensive development plan of the copper ore deposits known to exist in the HamanKumbuk district with special emphasis given to the ascertainment of geological and paragenetic characteristics. The area consists chiefly of shale, sandy shale and chert, all belong to Kyongsang System of Cretaceous age. Intruded into these rocks are andesite, granodiorite, basic dikes, and acidic dikes. The mineralization which took place in the area, consists of mostly fissure-filling vein deposits, numbering several tens, with varying magnitudes. The fissures and shear zones created in rocks, such as chert and granodiorite, hosted the deposition of mineralizing vapors and/or hydrothermal solutions along their openings. The strike lengths of these veins vary from 50 to 600 meters in extension and 0.1 to 3 meters in width. Although the degree of fluctuation in width is great, it averages 0.3m. The stuctural patterns, which apparently affected the deposition of veins, are fissure patterns, trend NS to $N30^{\circ}W$, and steep-pitching tension fractures as well as normal fault pattern. Ore minerals associated with vein matters are primarily chalcopyrite and small amounts of scheelite, cobaltiferous arsenopyrite, and gold and silver intimately associated with sulphide minerals. Associated with these ore mineral are pyrite, pyrrhotite, magnetite, specularite and arsenopyrite. Gangue minerals noted are quartz, calcite, chlorite, tourmaline and hornblende. In terms of the compositions of associated minerals, the vein deposits in the district could be grouped under the following four categories: 1. Pyrrhoitite, Arsenopyrite, Gold and Silver Bearing Copper Vein (Type I) 2. Calcite-Scheelite-Copper Vein (Type II) 3. Magnetite-Pyrite-Copper Vein (Type III) 4. Tourmaline Copper Vein (Type IV) Of the four types, the first and the fourth are presently yielding relatively higher grades: of copper ores and concentrates. The estimated ore reserves total some 222,000 metric tons with the following breakdown in terms of metal contents: Name of Mines Au(g/t) Ag(g/t) Cu(%) Reserves(M/T) Kunbuk 15.92 78.69 6,074 60.498 Cheil Kunbuk - - 1.040 60,847 Haman - - 2.688 101,204 222,549 As rehabilitation of old workings and/or exploration of veins at depth proceed, additional estimation of ore reserves may become apparent and necessary. With regard to the problem of beneficiation and upgrading of low-grade ores in the district, it would be advisable to make decisions on location, treating capacity and mill flowsheet after sufficient amount of exploration is completed as suggested in the report.

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Hydrothermal Gold mineralization of the trabong district, vietnam : Mineralogical and geochemical study (베트남 짜봉(Trabong) 지역의 열수 금 광화작용 : 광물 및 지화학적 연구)

  • 한진경
    • Economic and Environmental Geology
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    • v.32 no.2
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    • pp.129-139
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    • 1999
  • Hydrothermal gold deposits of the Trabong district in Vietnam occur as single-stage quartz $\pm$ calcite veins (0.3-1.2 m thick) which fill fault fractures in graphite-bearing gneiss and schist of the Chulai Complex and Kham Duc Formation of the Proterozoic age. Ore grades are 1.3 to 92.4 g/ton Au. Ore mineralogy is very simple, consisting mainly of pyrite with minor amounts of base-metal sulfides and electrum. Gold grains occur in two assemblages as follows: (1) early, Fe-rich (7.2-10.4 mole % FeS) sphalerite + electrum (50.4-64.3 atom % Au) assemblage occurring as inclusions in pyrite; (2) late, Fe-poor «4.7 mole % FeS) sphalerite + galena + electrum (47.6-81.7 atom % Au) assemblage occurring along fractures of pyrites. Based on fluid inclusion data and thermochemical considerations of ore mineral assemblages, ore minerals were formed at high temperatures (about $230^{\circ}C$ to $420^{\circ}C$) from $H_{2}O-CO_{2}(-CH_{4})$-NaCI fluids with the sulfur fugacity of about $10^{-6}$ to $10^{-10}$ atm. Fluid inclusion data also indicate that ore mineralization occurred mainly as a result of fluid unmixing accompanying $CO_2$ effervescence. Calculated oxygen and measured hydrogen isotope compositions of mineralizing waters (${\delta}^{18}O_{V-SMOW}$ values = 5.3 to 8.6$\textperthousand$, ${\delta}D_{V-SMOW}$ values = - 60 to - 52$\textperthousand$), along with the sulfur isotope compositions of vein sulfides (${\delta}^{34}S_{CDR}$ values = - 1.2 to 2.8$\textperthousand$) and carbon isotope compositions of inclusion $CO_2$ (${\delta}^{13}C_{PDB}$ values = - 4.7 to - 2.0$\textperthousand$) indicate that the high temperature (mesohypothermal) gold mineralization formed from a magmatic fluid.

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Mode of Occurrence and Chemical Composition of Electrums from the Gubong Gold-Silver Deposits, Republic of Korea (구봉 금-은광상에서 산출되는 에렉트럼의 산출상태와 화학조성)

  • 유봉철;최선규;이현구
    • Economic and Environmental Geology
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    • v.35 no.3
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    • pp.191-201
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    • 2002
  • The Gubong gold-silver deposits if gold-silver-bearing hydrothermal massive quartz veins which were filled the fractures along fault shear (NE, NW) zones within Precambrian banded or granitic gneiss of Gyeonggi massif. Ore mineralization of this deposits is contained within a single stage of quartz vein which was formed by multiple episodes of fracturing and healing. Ore minerals are comported mainly of arsenopyrite, pyrite, sphalerite, chalcopyrite, galena with minor amounts of pyrrhotite, marcasite and electrum. The frequency and volume percentages of electrum associated with ore minerals from this deposits are recognized as follows; 44.5% and 54.3% with arsenopyrite, 24.3% and 33.8% with quartz, 12.6% and 0.1% with pyrite, 11.0% and 4.8% with galena, 5.0% and 7.0% with sphalerite and 2.5% and 0.02% with chalcopyrite, respectively. They show irregular (41.6%), subround (34.7%), elongate (17.0%) and granular (6.6%) shapes, respectively. Their grain size ranges from 2 to 150 um, but 90.9 percent of the grains are below 30 um. The chemical composition of electrums ranges from 26.39 to 72.51 Au atomic %. These composition (Au atomic %) on the basis of associated minerals are from 44.97 to 71.75 with arsenopyrite, pyrite, sphalerite and quartz, from 44.37 to 72.51 with quartz, from 35.40 to 41.01 with sphalerite and chalcopyrite, from 26.39 to 54.84 with pyrite, chalcopyrite, quartz and galena, from 28.49 to 53.28 with galena, respectively. We suggest that optimum recovery of gold would be obtained with reference to these results.

Geochemical Studies of Hydrothermal Gold Deposits, Republic of Korea : Yangpyeong-Weonju Area (한반도 열수 금광상의 지화학적 연구 : 양평-원주지역 광화대)

  • So, Chil-Sup;Choi, Sang-Hoon;Lee, Kyeong-Yong;Shelton, Kevin L.
    • Economic and Environmental Geology
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    • v.22 no.1
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    • pp.1-16
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    • 1989
  • Electrum-galena-sphalerite mineralization of the Yangpyeong-Weonju Au-Ag area was deposited in three stages of quartz and calcite veins which fill fault breccia zones. Fluid inclusion and stable isotope data show that ore mineralization was deposited at temperatures between $260^{\circ}C$ and $180^{\circ}C$ from fluids with salinities between 8.9 and 2.9 equivalent weight percent NaCl. Evidence of boiling indicates pressures of <50 bars, corresponding to depths of 220 to 550 m, respectively, assuming lithostatic and hydrostatic loads. Au-Ag deposition was likely a result of bolling coupled with cooling. Within stages I and II there is an apparent increase in ${\delta}^{34}S$ values of $H_2S$ with paragenetic time ; early -1.4~2.7‰ to later 6.6-9.2‰. The progressively heavier $H_2S$ values can be generated through isotopic re-equilibration in the ore fluid following removal of $H_2S$ by boiling or precipitation of sulfides. Measured and calculated hydrogen and oxygen isotope values of ore-forming fluids suggest meteoric water dominance, approaching unexchanged meteoric water values. Comparison of these values with those of other Korean Au-Ag deposits reveals a relationship between depth and degree of water-rock interaction. All investigated Korean Jurassic and Cretaceous gold-silver-bearing deposits have fluids which are dominantly evolved, meteoric water, but on1y deeper systems (${\geq}1.25km$) are exclusively gold-rich.

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