• Title/Summary/Keyword: 중형 공진주시험

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Evaluation of Dynamic Properties of Crushed Stones Used as Reinforced Trackbed Foundation Materials Using Midsize Resonant Column Test apparatus (중형 공진주 시험기를 이용한 국내 쇄석 강화노반재료의 동적특성 평가)

  • Lim, Yujin;Lee, SeongHyeok;Lee, Jinwoog;Cho, Hojin
    • Journal of the Korean Society for Railway
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    • v.15 no.5
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    • pp.476-484
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    • 2012
  • In this study, a mid-size RC test apparatus equipped with analyzing program is developed that can test samples up to D=10cm diameter and H=20cm height which is larger than usual samples of D=5cm and H=10cm used mostly in practice. Thus, crushed stones with larger grains up to 38mm in diameter used mostly in Korea as reinforced trackbed materials in track construction could be considered effectively than conventionally used RC apparatus for evaluation of the dynamic properties of the materials by using the newly developed RC apparatus. The RC test apparatus was designed and assembled based on the concept of fixed-free fixity conditions and driving mechanism proposed by Stokoe. Using the developed RC test apparatus, three types of representative crushed reinforced trackbed materials were tested in order to get the dynamic properties of the materials such as $G/G_{max}$ reduction curves and damping ratio D. For comparison purpose, a small RC test apparatus has been used to test the same materials.

Analysis of Shear Modulus(G)-Shear Strain(γ)-Degree of Saturation(S) Characteristics of Compacted Subgrade Soil used as Railway Trackbed (다짐된 궤도 흙노반 재료의 전단탄성계수(G)-전단변형률(γ)-포화도(S) 관계특성 분석)

  • Choi, Chan Yong;Lee, Seong Hyeok;Lim, Yu Jin;Kim, Dae Sung;Park, Jae Beom
    • Journal of the Korean Society for Railway
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    • v.18 no.2
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    • pp.127-138
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    • 2015
  • It is important to evaluate the stiffness characteristics of compacted subgrade soil under track that is loaded dynamically. Using a mid-size Resonant Column test apparatus, normalized shear modulus and shear modulus variation with changing of confining pressure were investigated with change of degree of saturation (DOS). From an analysis of the test results, it was verified that the maximum shear modulus decreased with increases of DOS. However, normalized shear modulus increased with increases of DOS. Using the test results, a relation of G~${\gamma}$~DOS can be constructed and characterized. In the future, by performing tests with soils used as trackbed broadly in the field, a prediction model for DOS~G~${\gamma}$ can be proposed.

A Possible Test Method Proposed for Resilient Modulus (MR) and Analysis of Correlation between Resilient Modulus and Shear Modulus of Track Subgrade Soil (흙노반재료의 회복탄성계수(MR) 결정을 위한 반복삼축압축시험법 제시 및 변형계수 상관성 분석)

  • Park, Jae Beom;Choi, Chan Yong;Lim, Sang Jin;Lim, Yu Jin
    • Journal of the Korean Society for Railway
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    • v.20 no.1
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    • pp.85-98
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    • 2017
  • In general, under the repetitive dynamic load generated by rail cars running on the track, subgrade soil experiences changes of stress conditions such as deviatoric stress (${\sigma}_d$) and bulk stress (${\theta}$). Due to the repetitive change of deviatoric stress (${\sigma}_d$) with number of loadings, the resilient modulus ($M_R$) can be obtained by using the measured resilient strain (${\varepsilon}_r$) after a sufficient number of loadings. At present, no plausible and unified test method has been proposed to obtain the resilient modulus of railway track subgrade soil. In this study, a possible test method for obtaining the resilient modulus ($M_R$) of railway track subgrade soil is proposed; this test, by utilizing repetitive triaxial compression testing, can consider all the important parameters, such as the confining stress, deviatoric stress, and number of loadings. By adapting and using the proposed test method to obtain $M_R$, $M_R$ values for compacted track subgrade soil can be successfully determined using soil obtained in three field sites of railway track construction with changing water content range from OMC. In addition, shear modulus (G) ~ shear strain (${\gamma}$) relation data were also obtained using a mid-size RC test. A correlation analysis was performed using the obtained G and $M_R$ values while considering the strain levels and modes of strain direction.

Evaluation of Dynamic Properties of Subballast Materials Used in Korea Using Midsize Resonant Column Test Apparatus (중형 공진주 시험기를 이용한 보조도상 재료의 동적특성 정량화)

  • Lim, Yu-Jin;Sin, Joong-Hoon;Park, Kyung-Su;Park, Jae-Hak;Hwang, Jung-Kyu
    • Proceedings of the KSR Conference
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    • 2011.05a
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    • pp.1214-1221
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    • 2011
  • It is an well-known fact that dynamic properties should be considered in design and maintenance of civil structures undergoing dynamic force such as rail track. For designing of the rail tack structures, dynamic properties of track bed soil such as shear modulus (G) and damping coefficients(D) obtained in small to medium range of shear strain must be known. In general, small size sample of D=5 cm and H=10cm has been used mostly for test convenience. However, ratio of largest particle diameter of the soil to sample diameter is very important and affects to the values of dynamic soil properties in track bed. In this study, an RC/TS test apparatus was built and was run for testing a medium size soil sample that can handle with compacted soil sample up to 10 cm diameter and 20 cm height.

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