• Title/Summary/Keyword: 인장강도

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Influence of Rock Inhomogeneity on the Dynamic Tensile Strength of Rock (암석의 동적 인장강도에 미치는 불균질성의 영향)

  • Cho, Sang-Ho;Yang, Hyung-Sik;Katsuhiko Kaneko
    • Tunnel and Underground Space
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    • v.13 no.3
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    • pp.180-186
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    • 2003
  • The fracture processes under dynamic loading in tension were simulated using a proposed numerical approach and analyzed to determine dynamic tensile strength. The dynamic tensile strength and the scatter of the strength data decreased with increasing uniformity coefficients. The differences of static and dynamic tensile strength were due to the stress concentrations and redistribution mechanisms in the rock specimen. Although there were different mechanisms for the static and dynamic fracture processes, the static and dynamic tensile strengths were close to the mean microscopic tensile strength at high values of the uniformity coefficient. This paper shows that the rock inhomogeneity has an effect on dynamic tensile strength and is a factor that contributes to the different specimen strengths under dynamic and static loading conditions.

Experimental Investigations on Tensile Strength of Sand at Low Moisture Contents (저함수비 모래의 인장강도에 대한 실험적 연구)

  • Kim, Tae-Hyung
    • Journal of the Korean Geotechnical Society
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    • v.18 no.3
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    • pp.23-31
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    • 2002
  • This study shows that tensile strength in moist sand clearly exists due to moisture and it is possible to simply and accurately measure the tensile strength of sands at low moisture contents. These measurements were made through the use of a newly developed direct tension apparatus and technique which are able to produce highly accurate results. The magnitudes of the tensile strengths of these moist and relatively clean sands are not equal to zero, as is widely assumed. Tensile strength increases with increasing moisture content and this trend is more noticeable at increasing relative densities. The influence of tensile strength in geotechnical problems was also examined by considering a simple rigid circular footing in sandy soil. It clearly shows that a small amount of tensile strength can significantly enhance the stability of a geotechnical system.

A Comparative Study on the Tensile Strength of Frozen Soil according to Test Methods (시험 방법에 따른 동결토의 인장강도)

  • Seo, Young-Kyo;Kang, Hyo-Sub
    • Journal of the Korean Geotechnical Society
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    • v.24 no.4
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    • pp.57-66
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    • 2008
  • In this study, the blast-induced vibration effects on the structural stability of the adjacent tunnel and the stability were estimated with respect to the allowable peak particle velocity (PPV). The blasting distance from the tunnel satisfying the allowable PPV was estimated based on the analytical solutions, United States Bureau of Mines (USBM) suggestions, and the equations used in the subway in Seoul. The allowable blasting distance was estimated by using finite difference analysis (FDA) and the behavior of the concrete lining and rock bolts was examined and the stability of those was estimated during the blast. Research results show that the blast-induced vibration effects on the structural stability are negligible for the concrete lining but relatively large for the rock bolts.

Characterization of Tensile Strength of Anisotropic Rock Using the Indirect Tensile Strength Test (간접인장강도시험을 통한 이방성 암석의 인장강도 특성)

  • 김영수;정성관;최정호
    • Journal of the Korean Geotechnical Society
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    • v.18 no.5
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    • pp.133-141
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    • 2002
  • Isotropic rock and anisotropic rock have different tensile strength which has the greatest influence on rock failure. In this study, elastic modulus of anisotropic rock is obtained through uniaxial compression test, and tensile strength and tension failure behavior are analyzed through indirect tensile strength test. Stress concentration factor of a specimen at the center is obtained from anisotropic elastic modulus and strain by indirect tensile strength test. Theoretical solutions for tensile strength of isotropic and anisotropic rock are compared. Stress concentration factor of anisotropic rock is either higher or lower than isotropic rock depending on the inclination angle of bedding plane. The use of stress concentration factor of isotropic rock resulted in overestimation or underestimation of tensile strength.

Comparison and Analysis of Mechanical Performance Evaluation Methods for Geosynthetics (토목합성재료의 역학적 성능평가방법 비교, 분석)

  • 전한용;금재호;김홍관;김유겸;변성원
    • Proceedings of the Korean Fiber Society Conference
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    • 2003.04a
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    • pp.364-365
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    • 2003
  • 토목합성재료는 지반위에 전폭으로 연결되어 사용되고 하중도 전장 및 전폭으로 전달되므로 인장강도 역시 전장 및 전폭으로 시험하는 것이 바람직하나 시험기의 용량 및 시험편 파지장치의 기술적 제약 상 전폭시험이 불가능하다. 현재 국내에서는 그래브 및 스트립 상태인 소폭으로 시험한 후 m당 인장강도로 환산하여 시공설계에 적용하고 있으므로 실제 재료의 설계 시 인장강도와 측정된 인장강도간에 차이가 있다. 그러나 미국, 유럽 등에서는 광폭시험편을 준비하여 인장강도를 측정함으로써 이러한 오차를 최소화하고 있다. (중략)

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Effect of Moisture on Tensile Strength in Sand (모래의 인장강도에 미치는 함수비의 영향)

  • Kim, Tae-Hyung
    • Journal of the Korean Geotechnical Society
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    • v.18 no.3
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    • pp.13-21
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    • 2002
  • An extensive tension experiment was carried out to examine the variation of tensile strength in moist sand having moisture contents in the range of 0.5% < w < 4.0% with newly developed direct tension apparatus. It was observed that tensile strength of sand varied as functions of moisture content, relative density, presence of fines, and level of precompression. Tensile strength increases with increasing moisture content and fines, and this trend is more noticeable at increasing relative densities. However, the influences of relative density and fines on the tensile strength are substantially dependent on the water content. These effects are reduced at low moisture levels (w < 0.5%). The precompression effects also depend on the water content but less on the duration and level of the precompression.

괘선/구부림 강공과 종이물성과의 상관관계 II

  • 조신환;오홍석;최대웅;여성국
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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    • 2001.11a
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    • pp.203-203
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    • 2001
  • 패선/구부림 가공은 후가공의 일부분으로서. 박스가공 시 종이에 패션치기와 구부림 공정이 들어가게 되며 이때 종이표면이 약할 경우 금이가는 현상이 발생한다. 본 연구 는 이러한 가공과 다층판지의 물성이 패선/구부림 적성에 영향을 미치는가에 대한 연 구로서 2000년도 추계논문발표시 종이 물성 중 패션/구부림 가공에 영향을 주는 것으 로 표면층의 층간결합력과 내절도 그리고 인장강도가 중요한 변수로 작용하는 결과를 얻었으며 이후 이들 영향인자 중 핵심영향인자의 도출을 위하여 침엽수를 배합하지 않 은 상태에서 상질고지 재생펄프를 고해 처리하여 특성을 향상시켜 실제 공정에서 실험 하였다. 1차 실험은 공정실험 전 예비 실험으로서 재생펄프를 공장 refiner를 사용하여 고해 처리하여 강도향상 효과를 분석하였다. 분석결과 인장강도는 증가하나 내절도 향상은 기대에 미치지 못하는 것으로 나타났다. 이에 따라 1차 공정실험 조건을 부착량을 향상 시켜 인장강도를 침엽수 펄프 배합수준으로 끌어올리는 방법을 선택하였으며 그 결과 패선/구부림 적성이 기존대비 양호한 결과를 얻었다. 즉 인장강도 향상으로 침엽수 펄 프를 대체할 수 있다는 결론을 얻었다. 2차 실험은 부착량 대선 refiner를 사용하여 상 질고지 재생펄프를 고해 처리하여 인장강도를 향상시켜 생산하였다. 실험결과 인장강도 가 침엽수펄프 배합 시 대비 동등이상 수준에 있을 경우 패션/구부린 가공 시 금이가 는 터짐문제는 발생하지 않는 것으로 나타났다. 3차 실험은 두 차례 동안 실시된 공정 실험을 기준으로 refining 처리와 부착량 기준을 설정하고 장시간 생산하여 그 특성을 측정하였다. 실험결과 표면층의 인장강도가 낮아질 때 패선/구부림 적성이 약해지는 경 향을 보였으며 인장강도가 기존 침엽수펄프 배합대비 동등이상일 경우 패선/구부림 가 공적성이 양호하게 나타났으며 실제 가공업체에서도 터짐 문제가 발견되지 않았다. 결론적으로 표면층의 인장강도가 패션/구부림에 가장 중요한 변수로 작용하며 어떠 한 형태로 표면층의 인장강도를 향상시킬 경우 침엽수 펄프는 재생펄프로 대체가 가능 할 것으로 판단된다.

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Influence of Rock Inhomogeneity on the Static Tensile Strength of Rock (암석의 정적 인장강도에 미치는 불균질성의 영향)

  • Cho, Sang-Ho;Yang, Hyung-Sik;Katsuhiko Kaneko
    • Tunnel and Underground Space
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    • v.13 no.2
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    • pp.117-124
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    • 2003
  • The fracture processes under static tensile loading were simulated using a proposed numerical simulation method, based on finite element method and fracture mechanism, and analyzed to verify an influence of rock inhomogeneity on static tensile strength. Static tensile strengths for the specimen models with different spatial microscopic tensile strength when m=5 and m=50 were estimated. These analyses revealed that the static tensile strength becomes closer to the mean microscopic tensile strength at a higher uniformity coefficient and the scatter of the strength data decreases in increasing the uniformity coefficients. Therefore, it could be concluded that rock inhomogeneity has an effect on static tensile strength.

Comparison of Tensile Strengths in Granite Using Brazilian Tests and Hollow Cylinder Tests for Hydraulic Fracturing Test Interpretation (수압파쇄시험 해석을 위한 중공원통 인장시험과 압열인장시험 화강암 인장강도 비교)

  • Jo, Yeonguk;Chang, Chandong;Lee, Tae Jong;Kim, Kwang-Yeom
    • Tunnel and Underground Space
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    • v.23 no.5
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    • pp.362-371
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    • 2013
  • We conducted hollow cylinder tensile strength tests and Brazilian tests in Seokmo granite to measure tensile strength necessary for estimating the magnitude of the maximum horizontal principal stress in hydraulic fracturing stress measurements. Two different pressurization rates were used in hollow cylinder tests. Tensile strengths were determined to be higher at higher pressurization rate, which suggests that tensile strength should be measurement at the same rate used in actual in situ hydraulic fracturing tests. Considering the effect of pressurization rate and specimen size on tensile strength, the hollow cylinder tests and Brazilian tests yield similar results each other. This demonstrates that Brazilian tests can be utilized to produce representative tensile strengths for interpretation of hydraulic fracturing test results.

Bond Strength and Tensile Strength of Polymer-Modified Mortar Using Styrene and Butyl Acrylate (St/BA를 혼입한 폴리머 시멘트 모르타르의 부착강도 및 인장강도 특성)

  • You, Kipyo;Hyung, Wongil
    • Polymer(Korea)
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    • v.38 no.6
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    • pp.820-826
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    • 2014
  • The objective of this study is to find the relationship between the tensile strength of the polymer film and the bond strength and tensile strength of the polymer-modified mortar using styrene (St) and butyl acrylate (BA), and porosity. In the test results, the bond strength and tensile strength of the polymer-modified mortar increased with increases in the tensile strength of polymer film and the fine pore volume.