• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6C
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• pp.377-384
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• 2006

Theoretical and experimental study of the unconfined penetration (UP) test was conducted to suggest a new test method (referred to as IUP, Improved Unconfined Penetration) for determination of the tensile strength of compacted sand-bentonite mixtures. The tensile strength of compacted mixtures can be calculated from limit analysis based on the theory of perfect plasticity. The measurement errors in new test method were reduced by improving the UP device. Preliminary experiment results indicate that the tensile strength increases with increasing the disk size, loading rate and pH level. In addition, the disk diameter with 25.4 mm and the loading rate with 0.5%/min~1%/min are most suitable condition for the IUP test. The reliability of IPU test was verified by through the fact that good agreement between the IUP and conventional split tensile test results is observed.

• 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.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.293-308
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• 1999

이 논문에서는 패널, 깊은 보 그리고 전단벽과 같이 평면응력상태하에 있는 철근콘크리트 구조물의 비선형 유한요소해석에 있어서의 직교이방성 콘크리트 구성 모델의 적용성을 보여준다. 등가의 일축 변형을 개념을 토대로 콘크리트의 구성 관계가 주변형률 축과 일치하고 하중이력에 따라 회전하는 직교하는 축에 대해 제시된다. 제안된 모델은 이축 압축응력상태와 인장-압축 응력상태에서 각각 압축강도의 증가와 인장 저항력의 감소효과를 보여주는 이축 파괴영역의 정의를 포함한다. 인장균열이 발생한 후, 콘크리트의 압축강도의 감소효과가 제시되고, 인장강화효과로 알려진 철근에 의해 지지되는 콘크리트의 인장응력이 고려된다. 평균응력과 평균변형률 개념을 사용하여 힘의 평형, 적합조건 그리고 철근과 철근을 둘러싼 콘크리트 사이의 부착응력-슬림 관계를 토대로 인장강화효과를 모사하기 위한 모델이 제안된다. 유한요소 모델에 의한 예측은 유용한 실험자료와의 비교에 의해 입증된다. 이 논문에서는 해석결과와 이상화한 전단 패널실험으로부터 얻어진 실험값의 비교연구가 수행되고, 제안된 모델의 타당성을 보여주기 위해 서로 다른 응력상태하의 전단 패널 보와 벽체의 힘-변위 관계를 평가하였다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2000.11a
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• pp.3-8
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• 2000

현재 재료의 기계적 특성을 평가하기 위한 가장 표준화된 방법은 일축인장시험이다. 일축인장시험은 다양한 기계적 물성을 제공하나, 일정 크기 이상의 시편을 요구하므로 실제 산업현장에서 사용되고 있는 구조물의 안전성 평가에 이용하기 어렵다. 이러한 단 점을 개선할 수 있는 시험법으로 최신압입시험법이 제안되었다.(중략)

• Magazine of the Korea Concrete Institute
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• v.8 no.2
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• pp.129-138
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• 1996

Localization of concrete is a phenomenon such that the deformation of concrete is localized in finite region with softening behavior and it governs ultimate load of concrete. In this Paper, concrete under strain localization was modeled with localization region and non-localization region and lc~calization behavior was formulated based on averaging concept of heterogeneous material. By using the formulation, the localization phenomena of concrete under uniaxial loadings were well predicted. The analytical results show that size of localization region of concrete under uniaxial compression is three times of maximum aggregate size and the size effect of concrete is well predicted. The use of tension-softening curve obtained from direct tension test is suitable for well prediction of localization of concrete under uniaxial tension.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.215-225
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• 2008

In order to investigate the influence factors to compressive and tensile strength of basalt in Cheju Island, rock samples of Pyosenri basalt, trachy-basalt and scoria were taken from Seoguipo-Si Seongsan-Eup area, and a series of uniaxial compressive strength test and Brazilian test were carried out. Especially, these tests were performed in consideration of the loading speed, the moisture content in rock sample, and the anisotropy of rock strength. The uniaxial compressive strength was increased gradually as the loading speed rose. The increasing quantity of uniaxial compressive strength had a difference in each rock types. Also, the strength was decreased with increasing the moisture contents in rock sample by pore water. As the result of test considering the anisotropy of rock strength, the compressive strength in condition of failure occurred parallel to stratified layer is decreased about 12-26% more than that in condition of failure occurred inclined to stratified layer.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.5-15
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• 2022

In this study, to propose simplified methods for estimating the cohesion and internal friction angle of volcanic rocks in Jeju Island using uniaxial compressive strength and/or Brazilian tensile strength, the estimated values of cohesion and internal friction angle from triaxial and uniaxial compression tests and Brazilian tests were compared in terms of estimation accuracy. This study proposed simplified methods for estimating the cohesion and internal friction angle using the uniaxial compressive strength and/or Brazilian tensile strength of volcanic rocks in Jeju Island. According to the findings, among the proposed simplified methods, the method using uniaxil compressive strength was most desirable to accurately estimate the cohesion and internal friction angle of volcanic intact rocks in Jeju Island.

• 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.

• Journal of the Korean Geotechnical Society
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• v.36 no.2
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• pp.17-28
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• 2020

With respect to the tensile strength of volcanic rocks in Jeju Island, a comparative study was conducted using the existing research results and the test results performed in this study. In addition, the characteristics and effectiveness of the cohesion and internal friction angle estimated from the Brazilian tensile strength and unconfined compressive strength of Jeju volcanic rocks were investigated. As results, the Brazilian tensile strength of Jeju volcanic rocks was closely related to absorption, and decreased exponentially as the absorption increased. It was confirmed that the internal friction angle was closely related to the ratio of unconfined compressive strength to Brazilian tensile strength (σ_c / σ_t), and increased logarithmically as the ratio of σ_c / σ_t increased. In addition, the ratios of σ_c / σ_t of Jeju volcanic rocks were in the range of 5~20 depending on the magnitude of internal friction angle. In the case of cohesion, it was closely related to the absorption and Brazilian tensile strength. The cohesion exponentially decreased as the absorption increased, such as the relation between the Brazilian tensile strength and absorption. It was confirmed that there was a linear relation between the cohesion and Brazilian tensile strength.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.139-146
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• 2008

The characteristics of the biaxial flexural tensile strength of concretes was compared to that of the uniaxial strength. The uniaxial and biaxial strengths in this study were obtained from the classical modulus of rupture test and the biaxial flexural test recently developed by Zi and Oh and Zi et al., respectively. Three different sizes were considered to investigate the effect of the size of aggregates. To estimate the stochastic aspect of the strength, 32 specimens were used for each test. The average biaxial flexural fracture strength was about 20% greater than the uniaxial test. At the same time, the coefficient of variation for the biaxial test was 18% greater than the uniaxial test. This means that the probability of the biaxial cracking can be greater than the uniaxial cracking.