• Title/Summary/Keyword: rock specimens

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Application of Modelling Stress-Strain Relations (Part II) -A Trend of Parameters- (응력-변형률 관계 정식화의 적용성(II) -파라메타의 경향성-)

  • Park, Choon-Sik
    • Journal of the Korean Geotechnical Society
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    • v.29 no.10
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    • pp.19-27
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    • 2013
  • Tatsuoka and Shibuya (1991) suggest a new single formulation applicable not only to a wide range of geo-materials from soft clay to soft rock, but also to a wide range of strain levels from $10^{-6}$ to $10^{-2}$. We have carried out the plain strain compression test employing 7 kinds of research standard sand specimens and 2 kinds of glass beads, which have been used at world-renowned research institutes. With the result applied to Tatsuoka and Shibuya's newly suggested formulation, we studied a trend of parameters. In conclusion, as the value of confining pressure increases, the value of $C_1(X={\infty})$ becomes greater but there are hardly any changes in the value of $C_2(X={\infty})$. The value of $C_1(X={\infty})$ also becomes greater as the ${\delta}$ value increases, regardless of sand types. However, the values of $C_2(X={\infty})$ and $C_2$(X=Xe) do not show any significant changes when there are changes in the value of ${\delta}$, while the values of ${\alpha}$ and ${\beta}$ tend to decrease as the ${\delta}$ value decreases.

An experimental study on bonding and bearing capacities of thin spray-on liner to evaluate its applicability as a tunnel support member (터널 지보재로서의 적용성 검토를 위한 박층 뿜칠 라이너의 부착성능과 지보성능의 평가)

  • Han, Jin-Tae;Lee, Gyu-Phil;Park, Young-Taek;Choi, Soon-Wook;Hwang, Gwi-Sung;Choi, Myung-Sik;Chang, Soo-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.6
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    • pp.571-583
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    • 2013
  • The use of Thin Spray-on Liner (TSL) as an alternative to shotcrete has drastically increased since 1990s when it was first developed and introduced to mines. In this study, tensile strength test, bond strength test, compression test with specimens coated by TSL, and two kinds of bending tests proposed by EFNARC (2008) were performed with two kinds of TSLs with different material compositions in order to evaluate their support capacities. As a result, both TSLs were shown to be satisfactory for the minimum performance requirements for a structural rock support suggested by EFNARC (2008) and tensile strength of a TSL was shown to increase as its content of polymer was higher. In contrast, its bond strength was shown to increase proportional to the content of a cementitious component especially at the early age.

Applied Mineralogy for the Conservation of Dinosaur Tracks in the Goseong Interchange Area (35번 고속도로 고성 교차로 지역 공룡발자국의 보존을 위한 응용광물학적 연구)

  • Jeong Gi Young;Kim Soo Jin
    • Journal of the Mineralogical Society of Korea
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    • v.17 no.3
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    • pp.189-199
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    • 2004
  • Cretaceous sedimentary rocks bearing dinosaur tracks in the Goseong interchange area were studied for their conservation and public display in the aspect of applied mineralogy. Black clay layers alternate with silt layers in the sedimentary rocks. The verical and horizontal fissures are commonly filled with calcite veinlets, supergenetic iron and manganese oxides. The rocks are composed of quartz, albite, K-feldspar, calcite, chlorite, illite, muscovite, and biotite, with minor apatite and rutile. Silt layers are relatively rich in calcite and albite, whereas clay layers are abundant in quartz, illite, and chlorite. Al, Fe, Mg, K, Ti, and P are enriched in the clay layers, while Ca, Na, and Mn in silt. Most of trace elements including V, Cr, Co, Ni, Cs, Zr, REE, Th, and U are enriched in clay layers. Inorganic carbon are present in silt layers as calcite, while organic carbon in black clay layers. The black clay layers were partly altered to yellow clay layers along the fissures, simultaneously with the decrease of organic carbon. Selective exfoliation of clay-rich black and yellow clay layers, calcite matrix of silt layers and calcite infillings of fissures are estimated as the major weakness potentially promoting chemical and physical degradation of the track-bearing rock specimens.

Pattern on Ascaris lumbricoides Infection in a Rural Area of Keread (한국농촌(韓國農村)에 있어서의 회충감염상(蛔虫感染相))

  • Lee, Joon-Sang;Kim, Kwang-Rock;Ko, Dae-Kyoung;Sung, Dae-Rim;Lee, Ja-Young;Rim, Han-Jong
    • Journal of agricultural medicine and community health
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    • v.5 no.1
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    • pp.28-33
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    • 1980
  • This study was undertaken to evaluate the present status of A. lumbricoides infection in a rural area of Korea. The 307 residents of all age group in Gumsa Myun, Yeo Ju Gun were examined by Kato's cellophane thick smear technique. Pyrantel pamoste was administered to the Ascaris infection cases by a single dose of 5mg/kg of body weight. The whole amount of 24 hour stool during two or three consecutive days were collected sepatately. The expelled A. lumbricoides worms from the unfiltered stool remnants were collected. They were measured by the length and weight, and the sex of the worms were differentiated. The results are as follows: 1) The incidence of A. lumbricoids infection of the 307 specimens examined was 40.1%(male: 40.9%, female:39.0%). The difference according to guman sex distribution was not statistically significant. 2) Seventy two Ascaris infected cases expelled 163 worms of various size. The mean number of worms per infected case were calculated as 2.3. The sex ratio of examined female and male Ascaris was 1.5:1 3) Among the expelled 97 female worms, the genital girdle were found in 60 female worms(61.9%). Genital girdle of gemale worm was located from the head in the position of $38{\pm}4$ of total length 100. 4) The average body length of male Ascaris was $16.3{\pm}3.1cm$ and female Ascaris was $21.7{\pm}3.5cm$ 5) The relationship between the weight(Y) and the length(X) of individual Ascaris worm was plotted. Y(gm).0.32$\fallingdotseq$(cm)-3.1 in female and Y(gm)$\fallingdotseq$0.1X(cm)-0.1 in male.

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Variation of Engineering Geological Characteristics of Jurassic Granite in Wonju Due to Freeze-Thaw Weathering (동결-융해 풍화에 의한 원주지역 쥬라기 화강암의 지질공학적 특성변화)

  • Um, Jeong-Gi;Woo, Ik;Park, Hyuck-Jin
    • Economic and Environmental Geology
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    • v.42 no.3
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    • pp.261-272
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    • 2009
  • An experimental study of the accelerated weathering was performed to investigate the variations of physicomechanical properties of deteriorated rocks due to freeze-thaw weathering for the Jurassic granite specimens from Wonju, Gangwon-do. Each complete cycle of freeze and thaw was lasted 24 hours, comprising 2 hours saturating in vacuum chamber, 8 hours freezing at -20$\pm1^{\circ}C$ and 14 hours thawing at room temperature. Freeze-thaw cycles were implemented with measuring the index physical properties as well as geometries of microfractures. The seismic velocity was found to decrease with increasing freeze-thaw cycles. On the other hand, absorption tends to increase with freeze-thaw cycles. In the end, it was concluded that variations of the index properties of deteriorated specimen depend on its initial properties and flaws in rock. The size and density of the traces of the microfracture on slab specimen were changed continuously with increasing freeze-thaw weathering. The results obtained in this study show that the box fractal dimension($D_B$) has the strong capability of quantifying the combined effect of size and density of the microfractures.

Structure and physical properties of Earth Crust material in the Middle of Korean Peninsula(2) : Comparison between elastic Velocity and point-load of core specimen of sedimentary rocks. (한반도 중부권 지각물질의 구조와 물성연구(2) : 퇴적암류 코아시료의 탄성파 속도와 점재하 강도 비교)

  • 송무영;황인선
    • The Journal of Engineering Geology
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    • v.3 no.1
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    • pp.21-37
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    • 1993
  • In order to investigate the correlation of sedimentary rock properties. specific gravity, porosity, water content, sonic wave velodty, and point4oad strength index of core samples of limestones, sandstones and shales were measured. The relationships between density and velocity show $V_p=16300d-38719.3,{\;}V_s1896.4d-29225.1$ of regression equation for sandstones and $Vp=4085d-10264.8,{\;}V_s=3519d-7841.3$ for shales and <$Vp=4085d^2-20747d+303,{\;}V_s=3899d^2-21442d+318$ for limestones. Seismic wave velocity of shales which have high density is lower than that of sandstones, and this seems to be an effect of bedding in shale. P-wave velocity and S-wave velocity of limestones, sandstones and shales show the linear relationships as a whole. The regression equations are respectively calculated V_s=0.26V_p+1041.6m/sec,{\;}V_s=0.43V_p+424.2m/sec,{\;}and{\;}Vs=0.51V_p+261.9m/sec$ and the correlation coefficients of the velocity show r= 0.86 in sandstones, r= 0.75 in limestones and r=0.86 in shales. According to the point4oad strength test for limestones, point4ord strength anisotropy was not so dear even though the specimens show generally the banded structure. Variations of dip angle of bedding whihin the range $30^{\circ}-60^{\circ}$ does not have much influence upon the diametral strength index and axial strength index. From the result of point load test, P-wave velocity increases with point4ord strength index but the regression equations are $V_p=98.5lI{s_d}+4082.1m/sec,{\;}V_p=106.41{s_a}+3954m/sec$ and their correlation coefficient is low.

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A preliminary study of watertightness and salt water resistance of spray-applied membrane (뿜어붙임멤브레인의 방수성능 및 염수저항성의 기초평가)

  • Choi, Soon-Wook;Kang, Tae-Ho;Chang, Soo-Ho;Lee, Cheol-Ho;Kim, Jintae;Choi, Myung-Sik
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.2
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    • pp.283-299
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    • 2017
  • The leakage of tunnel causes the long-term durability of the structures such as concrete lining to deteriorate. The cause of durability degradation can be various substances contained in groundwater such as chloride, sulphate, water, and gas. In this study, a series of test were carried out to determine the watertightness performance and the resistance to salt water of the spray-applied membrane used as non-structural rock support or as a waterproof material for tunnels. As a result, it was found that the penetration of water could occur in a specimen, and the reason was that the internal pores generated by the mixing of the liquid polymer and the powder material and the internal pores were connected by the water pressure. The tensile strength of the test specimens immersed in distilled water and saline water was found to be reduced to less than half of the tensile strength in normal condition. In addition, The elongation was measured to be higher in distilled water than in salt water. However, this result will require further investigation.

The homogenization analysis for permeability coefficients by fracture aperture variations (균질화 해석법을 이용한 단열 간극변화에 따른 투수계수 해석)

  • 채병곤
    • The Journal of Engineering Geology
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    • v.14 no.1
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    • pp.47-60
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    • 2004
  • The permeability coefficients were calculated by the homogenization analysis method with sufficient consideration of fracture geometry dependent on aperture change. According to the results of aperture measurements using a confocal laser scanning microscope, apertures on each measuring point display different magnitudes, indicating that fracture walls can not be assumed as parallel feature. After construction of fracture model based on the aperture values measured on each pressure level, the homogenization analysis was conducted to compute permeability coefficients. The calculated permeability coefficients distribute in the ranges of $10^{-1}~10^{-3}cm/sec$. Most of the specimens show decreasing permeability coefficients with the increase of the applied pressure. However, the decreasing rates of permeability coefficients do not show a constant trend on each pressure level. This phenomenon is well matched to the observation results of Chae et al. (2003). It proves that aperture change strongly influences on permeability characteristics. Three sections of each specimen have all different values of permeability coefficient. It suggests that the variation of permeability coefficient depends sensitively on aperture magnitudes and characteristics of fracture geometry. It is very important to consider accurate fracture geometries for analysis of permeability characteristics in rock fractures bearing different aperture distribution. Therefore, it needs to consider sufficiently the fracture geometries for calculating the permeability coefficients of fractures.

Scaling up of single fracture using a spectral analysis and computation of its permeability coefficient (스펙트럼 분석을 응용한 단일 균열 규모확장과 투수계수 산정)

  • 채병곤
    • The Journal of Engineering Geology
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    • v.14 no.1
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    • pp.29-46
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    • 2004
  • It is important to identify geometries of fracture that act as a conduit of fluid flow for characterization of ground water flow in fractured rock. Fracture geometries control hydraulic conductivity and stream lines in a rock mass. However, we have difficulties to acquire whole geometric data of fractures in a field scale because of discontinuous distribution of outcrops and impossibility of continuous collecting of subsurface data. Therefore, it is needed to develop a method to describe whole feature of a target fracture geometry. This study suggests a new approach to develop a method to characterize on the whole feature of a target fracture geometry based on the Fourier transform. After sampling of specimens along a target fracture from borehole cores, effective frequencies among roughness components were selected by the Fourier transform on each specimen. Then, the selected effective frequencies were averaged on each frequency. Because the averaged spectrum includes all the frequency profiles of each specimen, it shows the representative components of the fracture roughness of the target fracture. The inverse Fourier transform is conducted to reconstruct an averaged whole roughness feature after low pass filtering. The reconstructed roughness feature also shows the representative roughness of the target subsurface fracture including the geometrical characteristics of each specimen. It also means that overall roughness feature by scaling up of a fracture. In order to identify the characteristics of permeability coefficients along the target fracture, fracture models were constructed based on the reconstructed roughness feature. The computation of permeability coefficient was performed by the homogenization analysis that can calculate accurate permeability coefficients with full consideration of fracture geometry. The results show a range between $10^{-4}{\;}and{\;}10^{-3}{\;}cm/sec$, indicating reasonable values of permeability coefficient along a large fracture. This approach will be effectively applied to the analysis of permeability characteristics along a large fracture as well as identification of the whole feature of a fracture in a field scale.

Spectrophotometric analysis of the influence to shade of zirconia core on the color of ceramic (지르코니아 코아의 색조부여가 전부도재관의 색조에 미치는 영향에 대한 분광측색분석)

  • Baek, Ki-Hyun;Woo, Yi-Hyung;Kwon, Kung-Rock;Kim, Hyeong-Seob
    • The Journal of Korean Academy of Prosthodontics
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    • v.46 no.4
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    • pp.409-419
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    • 2008
  • Statement of problem: At all times people have tried to fabricate tooth restorations using tooth colored materials. Recently, demands for esthetics, even in restorations requiring strength, has brought a revolution to dentistry and increased use of zirconia. The basic color of zirconia is white to ivory. The color can be partially adapted by veneering it with ceramic materials. However, it would be better if the substructure could already be adapted to the basic color shade of neighboring teeth. By adaptation to the basic shade, it can help to reduce the necessary layer thickness of the veneer ceramic to achieve the desired color. Purpose: The purpose of this study was to spectrophotometrically evaluate the influence of shading of zirconia core on the final shade of all-ceramic restorations using the CIE $L^{*}a^{*}b^{*}$ system. Material and methods: Core specimens (n = 20 per group) of Lava Frame Zirconia, KaVo Everest Zirconia, Digident CAD/CAM Zirconia were fabricated at 20 mm in diameter and 0.5 mm in thickness. Halves of each groups were shaded in A3 color. These core specimens were veneered with A3 porcelain of the recommended manufacturer at thickness of 0.5 mm. CIE $L^{*}a^{*}b^{*}$ coordinates were recorded for each specimen with a spectrophotometer (Model CM-2600d, Minolta, Japan) at 0.5 mm, 0.4 mm, 0.3 mm in thickness. Color differences were calculated using the equation ${\Delta}E^{*}=[({\Delta}L^{*})2+({\Delta}a^{*})2+({\Delta}b^{*})2]1/2$. Results: 1. In the case where porcelain layer has a thickness of 0.5 mm, Lava Frame Zirconia and KaVo Everest group did not show clinically perceived color difference, however Digident CAD/CAM Zirconia group showed clinically perceived color difference according to shade allowed on core. 2. When the thickness of porcelain layer decreased from 0.5 mm to 0.4 mm, Lava Frame Zirconia and KaVo Everest group did not show clinically perceived color difference, on the other hand Digident CAD/CAM Zirconia group showed clinically perceived color difference according to shade allowed on core. 3. When the thickness of porcelain layer decreased from 0.5 mm to 0.3 mm, clinically perceived color differences were observed from all three groups. Conclusions: Ziroconia system, which is possible to allow shade on core, are thought to be much more favorable to reproduce natural shade compared to systems that is impossible to give shade. Therefore, clinicians ought to choose adequate system for certain clinical situation by considering above specific character.