• 한국지반공학회논문집
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• 제18권4호
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• pp.75-83
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• 2002

본 연구에서는 준설토, EPS 그리고 고화재를 혼합한 경량혼합토의 역학적 특성을 일축 및 삼축압축시험을 통하여 고찰하였다. 역학적 특성은 다양한 준설토의 초기 함수비, EPS 함유율, 시멘트 함유율 그리고 양생압력에 대한 경량혼합토의 압축강도에 대하여 연구하였다. 삼축압축상태에서 EPS를 함유한 경량혼합토의 압축강도는 유효구속압에 의존 하지 않는 것으로 나타났다. EPS 함유율이 감소할수록($A_E$<2%) 그리고 시멘트 함유율이 증가할수록($A_c$>2%) 삼축압축강도-변형 거동특성은 극한 압축강도를 지나 급격한 압축강도의 감소를 보이는 시멘트 혼합토의 압축강도-변형 거동특성과 유사한 것으로 나타났다. 200kpa 이상의 압축강도를 요구하는 개량지반에 본 경량혼합토를 적용하는 경우에서 적절한 준설토의 초기함수비, EPS 함유율은 각각 약 165%~175%이상 그리고 3%~4%이상으로 제시할 수가 있었다. 삼축 및 일축압축상태에서 극한 압축강도는 시멘트 함유율이 2%이상에서 거의 증가하지 않음으로서 한계 시멘트 함유율은 2%로 제시할 수가 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.189-196
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• 2002

According to the Korean Design Code for port and harbor facilaties, bearing capacity of rubble mound under eccentric and inclined load is calculated by the simplified Bishop method, and strength parameters are recommended to be c=0.2kg/$\textrm{cm}^2$ and ø=35$^{\circ}$for standard rubble if the compressive strength of parent rock is greater than 300kg/$\textrm{cm}^2$, quoting from research results by Jun-ichi Mizukami(1991), But this facts have never been certified in Korea because there was not large-scale triaxial test apparatus until 2000 in Korea. Firstly in Korea, the large-scale triaxial test (sample diameter, 30cm and height, 60cm) on the rubble originated from porous basalt rock in North-Cheju was accomplished. Then strength parameters for basalt rubble produced in North-Cheju are recommended to be c=0.3kg/$\textrm{cm}^2$ and ø=36$^{\circ}$if the compressive strength of parent rock is greater than 400kg/$\textrm{cm}^2$.

• KCI Concrete Journal
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• 제13권1호
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• pp.19-25
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• 2001

Based on the orthotropic hypoelasticity formulation, a constitutive material model of concrete taking account of triaxial stress state is presented. In this model, the ultimate strength surface of concrete in triaxial stress space is described by the Hsieh's four-parameter surface. On the other hand, the different ultimate strength surface of concrete in strain space is proposed in order to account for increasing ductility in high confinement pressure. Compressive ascending and descending behavior of concrete is considered. Concrete cracking behavior is considered as a smeared crack model, and after cracking, the tensile strain-softening behavior and the shear mechanism of cracked concrete are considered. The proposed constitutive model of concrete is compared with some results obtained from tests under the states of uniaxial, biaxial, and triaxial stresses. In triaxial compressive tests, the peak compressive stress from the predicted results agrees well with the experimental results, and ductility response under high confining pressure matches well the experimental result. The reinforcing bars embedded in concrete are considered as an isoparametric line element which could be easily incorporated into the isoparametric solid element of concrete, and the average stress - average strain relationship of the bar embedded in concrete is considered. From numerical examples for a reinforced concrete simple beam and a structural beam type member, the stress state of concrete in the vicinity of talc critical region is investigated.

• 콘크리트학회지
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• 제11권2호
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• pp.197-208
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• 1999

고강도 콘크리트는 기둥부재에서 그 사용효과가 극대화될 것이 예상되지만, 아직 고강도 콘크리트를 사용한 기둥의 연성특성과 최대강도효과에 대한 구체적인 자료가 부족한 실정이다. 띠근 보강된 콘크리트 기둥은 삼축압축상태가 되며, 고강도 콘크리트의 연성을 증가시키므로 이에 대한 많은 연구가 필요하다. 본 연구에서는 축하중을 받는 띠근보강 고강도 콘크리트 기둥부재의 횡보강효과에 의한 극한강도와 변형율 특성에 대하여 정성적 평가와 정량적 평가를 수행하는 것을 목적으로, 삼축압축상태하의 콘크리트 파괴이론과 기존의 실험결과들을 활용한 통계적기법을 이용하였다. 그 결과 콘크리트 강도, 띠근의 항복강도 및 간격비, 체적비 등을 변수로 고려하는 띠근의 횡보강응력 산정식, 최대압축강도 추정식 그리고 변형율 특성식을 제안하였다. 또한 제안된 식들은 실험결과를 적절히 예측하고 있음을 확인하였다.

• 터널과지하공간
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• 제2권2호
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.821-832
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• 2008

The hazard warning levels are necessary for the rational design and safety construction of underground space, as mountain and urban tunnel. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the critical strain of rock mass, which is defined as a ratio between uni-axial compressive strength and the Young's modulus. The concept of critical strain guidelines is introduced in this study for the assessment of tunnel safety during excavation. Moreover, in this paper, the critical strain properties of sedimentary rock in Korea has investigated and analysed in detail by Lab. test, as the uniaxial and triaxial compression tests. Finally, critical strain properties of sedimentary rock on uniaxial and triaxial stress condition is discussed the relationship of failure strain values, uniaxial and triaxial compression strengths, confining pressure and Young's modulus.

• Geomechanics and Engineering
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• 제17권2호
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• pp.215-225
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• 2019

The mechanical behavior of rock is essential to estimate the capacity and long-term stability of $CO_2$ storage in deep saline aquifers. As the depth of reservoir increases, the pressure and temperature that applied on the rock increase. To answer the question of how the confining pressure and temperature influence the mechanical behavior of reservoir rock, triaxial compression experiments were carried out on brine-saturated sandstone at elevated temperature. The triaxial compressive strength of brine-saturated sandstone was observed to decrease with increasing testing temperature, and the temperature weakening effect in strength enhanced with the increase of confining pressure. Sandstone specimens showed single fracture failures under triaxial compression. Three typical regions around the main fracture were identified: fracture band, damaged zone and undamaged zone. A function was proposed to describe the evolution of acoustic emission count under loading. Finally, the mechanism of elevated temperature causing the reduction of strength of brine-saturated sandstone was discussed.

• 한국지반환경공학회 논문집
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• 제14권8호
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• pp.5-9
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• 2013

본 연구에서는 저에너지, 친환경적인 방법의 지반개량을 목적으로 하는 유기산재의 지반개량재로서의 강도특성을 모색하였다. 이에 유기산재를 활용하여 재령 28일까지의 일축압축강도시험 및 삼축압축시험을 통한 흙의 강도 변화에 대해 분석하였다. 유기산 재료를 첨가한 점토의 강도는 재령이 길어질수록, 유기산재 혼합비가 커질수록 전반적으로 증가하는 경향을 나타내었다. 유기산계 지반개량재 혼합에 따른 점토의 강도 증진 효과를 파악하는데 있어서, 일축압축강도시험과 삼축압축시험 결과를 통해 유기산재가 지반개량재로 쓰였을 때 가져오는 강도 증대효과가 있다는 것을 알 수 있었다. 결과적으로, 실내시험을 통해 지반개량에 있어 유기산계 지반개량재의 활용가능성을 볼 수 있었다. 향후 세부적인 시험과 현장시험이 좀 더 명확한 강도증진을 규명하는데 도움이 될 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.137-154
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• 2006

The reliable pushover analysis of RC structures requires a realistic prediction of moment-curvature relations, which can be obtained by utilizing proper constitutive models for the stress-strain relationships of laterally confined concrete members. Theoretical approach of Mander is still a single stress-strain model, which employs a multiaxial failure surface for the determination of the ultimate strength of confined concrete. Alternatively, this paper introduces a simple and practical failure criterion for confined concrete with emphasis on introduction of significant modifications into the two-parameter Drucker-Prager model. The new criterion is only applicable to triaxial compression stress state which is exactly the case in the RC columns. Unlike many existing multi-parameter criteria proposed for the concrete fracture, the model needs only the compressive strength of concrete as an independent parameter and also implies for the influence of the Lode angle on the material strength. Adopting Saenz equation for stress-strain plots, satisfactory agreement between the measured and predicted results for the available experimental test data of confined normal and high strength concrete specimens is obtained. Moreover, it is found that further work involving the confinement pressure is still encouraging since the confinement model of Mander overestimates the ultimate strength of some RC columns.

• 터널과지하공간
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• 제9권3호
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• pp.221-229
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• 1999

수치모델링을 통한 암반구조물 설계 및 안정성 평가에서 가장중요한 것은 현지암반의 파괴조건계수, 압축강도, 탄성계수 등이다. 본 연구에서는 기 연구된 문헌들과 150 set의 삼축압축자료들을 비교분석함으로써 입력자료의 적용성을 제안하였다. Hoek-Brown이 제시한 신선암의 암종별 파괴조건계수와 삼축실험자료의 분석에 의한 파괴조건계수 사이에는 많은 차이가 있었다. 그러나, 압축강도의 변환식들은 RMR에 따라 모두 유사한 거동을 보여 주었다. 한편, 탄성계수의 변환식들은 식의 선택에 따라 많은 차이가 나는 것으로 분석되었으나, Nicholson 등의 제안식이 각 사례들과 대비하여 더 현실적인 것으로 분석 되었다.