• 화약ㆍ발파
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• 제21권4호
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• pp.23-35
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• 2003

본 연구에서는 남원지역 화강암을 대상으로 각 방향에 따른 물성간의 상관관계와 역학적 이방성을 규명하고자 하였다. 화강암의 수평, 수직축의 방향별 물성치는 일축압축강도 및 압열인장강도와 선형관계를 나타내었으며, 초음파 속도 측정 결과 수직방향은 나머지 두 수평방향 보다 약 10∼15% 정도 빠르게 나타났다. 이러한 속도 차이의 원인은 주로 암석 내에 존재하는 미세균열의 발달형태에 따르는 것으로 판단되며, 이는 현미경관찰 결과와 매우 일치함을 알 수 있었다. 점하중시험에 의한 점하중강도지수(Is(50)) 측정결과, 화강암의 경우 일축압축강도와 점하중강도지수의 비는 18∼20에 해당하는 것으로 나타났다. 일축압축강도와 점하중강도지수. 슈미트해머 반발치. 압열인장강도와 좋은 상관관계를 나타내었으며, 이중 점하중강도지수가 가장 높은 상관관계를 보였다. 이로부터 알 수 있듯이 점하중 강도지수가 일축압축강도를 추정하는데 가장 유효한 도구임을 확인할 수 있었다.

• Computers and Concrete
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• 제22권6호
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• pp.563-572
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• 2018

Uniaxial compressive strength test and uniaxial compression creep one were produced on four groups of twelve concrete specimens with different hole number by RLW-2000 rock triaxial rheology test system. The relationships between horizontal holes and instantaneous failure stress, the strain, and creep failure stress, the strain, and the relationships between stress level and instantaneous strain, creep strain were studied, and the relationship between horizontal holes and failure mode was determined. The results showed that: with horizontal hole number increasing, compressive strength of the specimens decreased whereas its peak strain increased, while both creep failure strength and its peak strain decreased. The relationships between horizontal holes and compressive strength of the specimens, the peak strain, were represented in quadratic polynomial, the relationships between horizontal holes and creep failure strength, the peak strain were represented in both linear and quadratic polynomial, respectively. Instantaneous strain decreased with stress level increasing, and the more holes in the blocks the less the damping of instantaneous strain were recorded. In the failure stress level, instantaneous strain reversally increased, creep strain showed three stages: decreasing, increasing, and sharp increasing; in same stress level, the less holes the less creep strain rate was recorded. The compressive-shear failure was produced along specimen diagonal line where the master surface of creep failure occurred, the more holes in a block, the higher chances of specimen failure and the more obvious master surface were.

• Geomechanics and Engineering
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• 제32권5호
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• pp.495-502
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• 2023

In this study, stress relaxation tests were carried out by keeping silt type soil specimens under different strain levels. Decreases in the stress values with time data was collected to better understand the effect of the strain level on the relaxation properties of soil specimens. In addition, the stress relaxation effect on the uniaxial compressive strength (UCS) values of the specimens was investigated with a series of tests. According to the results obtained from this study, the UCS values of the silt specimens significantly vary as a result of the stress relaxation effect. The UCS values were determined to increase with an increase of relaxation strain level to a threshold value. On the other hand, the UCS values were found to be affected adversely in case of high stress levels at the initiation of the relaxation, which are close to the peak level.

• 터널과지하공간
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• 제10권1호
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• pp.70-79
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• 2000

입자수, 압력, 온도일정의 앙상블(NPT-ensemble) 분자동력학(MD) 시뮬레이션을 이용하여 300$^{\circ}$K에서 $\alpha$-quartz의 결정축에 따른 일축압축강도를 계산하고, 자연산 $\alpha$-quartz 단결정 코아를 제작하여 일축압축강도시험을 실시하였다. $\alpha$-quartz 단결정 코아에 대한 일축압축시험에서 측정된 결과에 의하면 재하 방향이 c축에 평행한 경우가 수직인 경우보다 높은 강도를 나타내지만, MD 시뮬레이션에서 계산된 완전무결함 $\alpha$-quartz의 경우 이와 반대의 결과를 보이고 있다. 두 경우 모두 재하방향에 따른 강도 이방성을 보이고 있으나, 그 이유는 서로 다르다. MD 시뮬레이션에 의해 계산된 무결함 $\alpha$-quartz의 강도 이방성은 결정구조의 차이에 기인하는 것으로 사료된다. 이에 반해 일축압축시험을 통해 측정된 $\alpha$-quartz의 강도 이방성은 결정성장과정에서 생기는 주상 미세결함에 의해 영향을 받는다.

• 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.

• Computers and Concrete
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• 제23권4호
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• pp.267-272
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• 2019

In order to study the effect of moisture on the compressive strength of low-strength hollow concrete blocks, an experimental study was carried out on 96 samples of locally manufactured hollow concrete blocks collected from three different locations. Uniaxial compression tests were conducted on dry specimens and three types of saturated specimens with moisture contents of 30%, 50% and 80% respectively. The range of moisture content adopted covered the range within which the concrete block samples are saturated in the dry and monsoon seasons. The compressive strength of low-strength hollow concrete blocks decreases with increase in moisture content and the relationship between compressive strength of hollow concrete blocks and their moisture content can be considered to be linear. However, the strength degradation of 30% moist concrete blocks with respect to dry blocks is relatively low and can be considered to be comparable to dry concrete blocks. A formula indicating the relationship between the moisture content and compressive strength of low-strength hollow concrete blocks is also proposed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.53-54
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• 2015

As the result of uniaxial compression strength test on the CLMS mixing BFS and SS with BFS 4000, it required to determine the desired strength through increasing unit quantity of cement in mixing process because of dramatic strength deterioration of strength according to increasing replacing rate. In this study's result, regardless of differences in fine aggregates used, in order to get uniaxial compression strength in the scope exceeding criteria of minimum strength for applying to the field, the most reasonable combination was to mix replacing BFS with fineness of 6000 in 30%. For the CLMS mixing BFS and SS, in order to improve flow ability by securing quantity of minimum unit and to repress bleeding rate with securing uniaxial compress strength considering the field applicability, regardless of differences in fine aggregates used, to mix BFS over 6000 in 30% was most effective.

• 터널과지하공간
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• 제6권2호
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• pp.101-121
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• 1996

The thermomechanical characteristics of rocks such as temperature dependency of strength and deformation were experimentally investigated using Iksan granite, Cheonan tonalite and Chung-ju dolomite for proper design and stability analysis of underground structures subjected to temperature changes. For the temperature below critical threshold temperature $T_c$, the variation of uniaxial compressive strength, Young's modulus, Brazilian tensile strength and cohesion with temperature were slightly different for each rock type, but these mechanical properties decreased at the temperatures above $T_c$ by the effect of thermal cracking. Tensile strength was most affected by $T_c$, and uniaxial compressive strength was least affected by $T_c$. To the temperature of 20$0^{\circ}C$ with the confining prressure to 150 kg/$\textrm{cm}^2$, failure limit on principal stress plane and failure envelope on $\sigma$-$\tau$ plane of Iksan granite were continuously lowered with increasing temperature but those of Cheonan tonalite and Chung-ju dolomite showed different characteristics depending on minor principal stress on principal stress plane and normal stress on $\sigma$-$\tau$ plane. The reason for this appeared to be the effect of rock characteristics and confining pressure. Young's modulus was also temperature and pressure dependent, but the variation of Young's modulus was about 10%, which was small compared to the variation of compressive strength. In general, Young's modulus increased with increasing confining pressure and increased or decreased with increasing temperature to 20$0^{\circ}C$ depending on the rock type.

• Structural Engineering and Mechanics
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• 제67권5호
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• pp.505-516
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• 2018

In this paper, the effects of particle size and model scale of concrete has been investigated on the failure mechanism of PFC2D numerical models under uniaxial compressive test. For this purpose, rectangular models with same particle sizes and different model dimensions, i.e., $3mm{\times}6mm$, $6mm{\times}12mm$, $12mm{\times}24mm$, $25mm{\times}50mm$ and $54mm{\times}108mm$, were prepared. Also rectangular models with dimension of $54mm{\times}108mm$ and different particle sizes, i.e., 0.27 mm, 0.47 mm, 0.67 mm, 0.87 mm, 1.07 mm, 1.87 mm and 2.27 mm were simulated using PFC2D and tested under uniaxial compressive test. Concurrent with uniaxial test, direct shear test was performed on the numerical models. Dimension of the models were $75{\times}100mm$. Two narrow bands of particles with dimension of $37.5mm{\times}20mm$ were removed from upper and lower of the model to supply the shear test condition. The particle sizes in the models were 0.47 mm, 0.57 mm, 0.67 mm and 0.77 mm. The result shows that failure pattern was affected by model scale and particle size. The uniaxial compressive strength and shear strength were increased by increasing the model scale and particle size.

• 터널과지하공간
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• 제31권6호
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• pp.440-459
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• 2021

최근 대형 로드헤더가 국내 터널현장에 도입되면서 해외 제조사의 굴진율 예측모델에 대한 관심이 증가하고 있다. 현재 주로 사용되는 해외모델은 압축강도로부터 굴진율을 예측하고 있는데, 암석 시험편의 직경 대 길이의 비율이 1.0인 시편을 일축압축시험으로 사용하고 있다. 일반적으로 시편의 형상과 치수는 강도에 영향을 미치는 것으로 알려져 있다. 본 기술보고에서는 직경 대 길이 비율에 따른 암석강도의 변화에 대한 기존 연구사례를 조사하였다. 그 형상효과에 대한 원인을 이론적으로 고찰하였다. 이를 토대로 국내 예정된 암종에 대해서 길이 비율에 따른 강도의 변화 양상을 예측하고 굴진율 수정모델을 제시하였다.