• 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 Korea Concrete Institute
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• v.27 no.1
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• pp.29-35
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• 2015

Recent studies to develop Very Large Floating Structure(VLFS) has shown that the construction procedure of the structure needs to acquire precast concrete module connection system using prestressing. However, the loads occurring on water are complex combinations of various condition, so the safe and stable performance of the module joints and bonding materials are key to the success of the construction. Therefore, micro-silica mixed aqua-epoxy development was introduced in Part 1 using a bonding material developed in this study. The performance of the micro-silica mixed aqua-epoxy(MSAE) applied joint of concrete module specimens connected by prestressing tendon was evaluated to verify the usability and safety of the material. RC beam, spliced beam connected by prestressing tendon and MSAE, and continuous prestressed concrete beam were tested for their initial cracking and maximum loads as well as cracking procedure and pattern. The results showed that the MSAE can control the stress concentration effect of the shear key and the crack propagation, and the maximum load capacity of MSAE joint specimens are only 5% less than that of continuous RC specimen. The details of the study are discussed in detail in the paper.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.245-254
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• 2006

Using a natural gradient tracer test, the characteristics of hydrodynamic dispersion according to each depth of a fractured rock were studied, and the effective porosity and longitudinal dispersivity of the fractured rock were estimated. The difference of vertical hydrodynamic dispersion was identified by concentration breakthrough curves linear regression analyses of bromide concentrations according to depths versus time, and hydraulic fracture characteristics at two intervals of the monitoring well. Higher concentration and faster arrival time at GL- 18 m depth (RQD 13%, average joint spacing 2 cm, TCR 100%) than at GL- 25 m depth (RQD 41%, average joint spacing 7 cm, TCR 100%) resulted from shorter distance and more fractures. Tracer was transported through the 1 st fractures until the arrival of its peak concentration and through the 2nd fractures or matrix diffusion after the arrival of its peak concentration. The increase/decrease slopes of bromide concentration versus time were 3.46/-1.57 at GL-18 m depth and 3.l9/-0.47 at GL- 25 m depth of the monitoring well. So the faster bromide transport was confirmed at GL- 18 m depth with more fractures. The concentration increment of bromide was fitted by a Gaussian function and the concentration decrement of bromide was fitted by an exponential function. Effective porosity and longitudinal dispersivity estimated by CATTI code were 10.50% and 0.85 m, respectively.

• The Journal of Engineering Geology
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• v.15 no.4 s.42
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• pp.407-421
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• 2005

This study aims to investigate hydrogeological properties of the central area from Yangjeong-Dong to Sujeong-Dong in Busan Metropolitan City. For this study, pumping tests were carried out in the bedrock aquifer of Yangjeong-Dong and the unconsolidated aquifer near Busanjin railway station. The pumping test in the bedrock aquifer containing the Dongrae fault revealed specific hydraulic characteristics with respect to the fault. The pumping test in the unconsolidated aquifer revealed the hydrogeologic properties of both coastal landfill and fine sediments. It was found that the Moench's sphere-shaped dual-porosity model fits the bedrock aquifer, whereas the Neuman's uncofined aquifer model accords with the unconsolidated aquifer. The average transmissivity and storage coefficient of the bedrock aquifer are $2.75{\times}10^{-5}m^2/s\;and\;6.41{\times}10^{-5}$ and those of the unconsolidated aquifer are $8.24{\times}10^{-4}m^2/s\;and\;3.70{\times}10^{-3}$, respectively. On the other hand, slug tests gave average transmissivity and storage coefficient values of $9.84{\times}10^{-4}m^2/s\;and\;1.21{\times}10^{-2}$, respectively.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.11-18
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• 2010

The contamination of a suite of heavy metals were evaluated in water and sediments of urban stream, Tancheon down the stream. Tancheon is a urban stream which goes all the way across the urban area where various pollution sources are present. The sixteen study sites from seven different areas were designated down the stream. The heavy metal levels of the streams were detected in the order of Zn>Cu>Ni>Pb>Cd>Cr>Sb. There was a difference in the relative order of the concentration ranking in lake sediments. There is a trend that the heavy metal levels are higher at the sites where the construction causes inflow of soil particles to stream. Toxicity tests using pore-water in sediments were conducted for samples collected in some study sites, and pore-water in one site was proven to be toxic to Japanes medaka (Oryzias latipes). The reason may be the fecal pollution rather than heavy metal effect. Strong odor was detected in the sediment whose pore-water samples showed ecotoxicity. We did not observed the increasing concentration of heavy metals down to stream since the soil texture varied in the stream area of our study. Further study is needed to find quantitative relations between the level of contamination and its eco-effect.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.1
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• pp.75-82
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• 1997

건설기술과 산업의 발전에 따라 구조물은 대형화되어 가고, 건설공사의 급격한 팽창으로 골재 수용량이 급증함에 따라 천연골재자원은 점차 부족현상을 면치 못할 처지에 있다. 또한, 무리한 천연골재의 채취는 자연환경을 훼손시킬 뿐만 아니라 자연보호 측면에서도 심각한 공해문제로 대두되고 있어 공급량 부족현상은 날로 심화되고 있다. 이에 세계 몇몇 나라에세는 산업부산물을 이용한 골재 생산으로 공해예방과 폐기물 활용방법을 연구하고 있다. 산업부산물중 플라이 애쉬 생산량은 전 세계적으로 매년 약 2억여톤에 달하고 있으나 이중 일부만 활용되고 있는 실정이다. 이와같은 부산물을 활용하기 위한 일환으로 산업부산물인 PFA(Pulverized Fuel Ash)로 만든 인공경량골재의 년생산량이 영국은 600,000$m^3$, 미국은 300,000$m^3$이며, 매년 증가주세에 있다. 고성능 경량골재 콘크리트는 단위중량의 증가없이 내구성과 강도를 향상시켜 실용화 측면에서 경제적인 효과가 있으며, 플라이 애쉬로 만든 경량골재는 시멘트와의 친화력이나 접착면에서 우수한 것으로 알려져 있다. 본 시험에 사용한 골재는 플라이 애쉬로 만든 인공경량 조골재와 강모래이고, 결합제로서 프틀랜드 시멘트를 사용하였다. 부수적인 결합재로서는 플라이 애쉬, 슬래그, 실리카 흄을 사용하였으며, 고성능 경량골재 콘크리트를 개발코자 재령 28일과 180일의 압축강도가 각각 50MPa와 60MPa가 되도록 배합설계를 하였다. 본 연구에서는 플라이 애쉬, 슬래그, 시리카 흄과 같은 산업부산물을 혼입했을때 경량골재 콘크리트의 압축강도, 휨강도, 동탄성계수, 공극체적, 공극률, 단위중량, 공극 크기별 분포등의 변화를 실험적으로 구명하여 재반 구조용 콘크리트에 활용하기 위한 기초자료를 마련코저 한다.있어 특정한 발육단계의 난포 사망기전을 연구하기 어렵다. 또한 난포는 생체 내에서 다양한 호르몬을 동시에 분비하기 때문에 특정한 난소국부호르몬이 사망기전에 미치는 영향을 조사하기 힘든 점이 있다. 최근 들어 난포체외배양이 다양하게 개발되면서, 이러한 어려운 점을 극복할 수 있게 되었다. 본 논문은 각 발육단계의 난포를 절단해 체외배양하면서, apoptosis DNA 절단 현상을 이용하여 각종 난소국부 호르몬들이 난포발육단계별로 사망기전에 미치는 영향을 요약해 보였다. 난포는 발육하면서 점차 복잡한 호르몬 경로를 생존을 위해 필요로 한다. Prevulatory난포생존에 필요한 난소국부호르몬들은 early antral 단계의 난포에서는 그 미치는 영향이 감소되다가 preantral단계의 난포에서는 영향을 전혀 미치지 못했다. 단지 예외는 cGMP처리로써, 세포내 cGMP수준을 일정하게 유지시켜주는 것이 난포발육단계에 무관하게 생존에 중요한 인자로, 장래 연구는 난포 세포내의 cGMP수준을 조절하는 기작을 규명하는데 있을 것이다.인정되지 않았다. 7. 농지보전 처리구인 배수구와 초생수로구는 비처리구에 비해 낮은 침두 유출량과 낮은 토양유실량을 나타내었다.구보다 14% 절감되는 것으로 나타났다.작용하는 것으로 사료된다.된다.정량 분석한 결과이다. 시편의 조성은 33.6 at% U, 66.4 at% O의 결과를 얻었다. 산화물 핵연료의 표면 관찰 및 정량 분석 시험시 시편 표면을 전도성 물질로 증착시키지 않고, Silver Paint 에 시편을 접착하는 방법으로도 만족한 시험 결과를 얻을 수 있었다.째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰 자기폭풍일수록 현저했다. 주상에서 관측된 이러한 특성은 서브스톰 확장기 활동이 자기폭풍의 발달과 밀접한 관계가

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.29-42
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• 2018

Shale and mudstone in Daegu-Gyungbuk area have low strength and resistance to weathering compared to other rocks. Therefore, it is necessary to evaluate their strength depending on the degree of saturation and crack development. In this study, shales and mudstones were collected from several construction sites in Daegu-Gyungbuk area. Their basic material properties such as porosity, SEM, chemical component, and durability were tested. A porosity (absorptivity) of mudstone was 31% (25%), which was 6 (8) times higher than that of shale. Some mudstone was easily disintegrated with water and it consisted of highly-active clay mineral such as smectite type. These rocks were prepared by small cube specimens for unconfined compression test. An unconfined compressive strength of dry rock was compared with saturated one. Microwave oven was operated step by step to stimulate void water within a saturated rock, which resulted into high temperature and micro crack initiation within rocks. A strength of microwaved rocks was compared with operation time and crack initiation. As a result, the average unconfined compressive strength of dry and saturated shale was 62 and 33 MPa, respectively. The strength of mudstone for each condition was 11 and 4 MPa. When a rock became saturated, its strength decreased by 47% and 64% for shale and mudstone at average. In addition to saturation, a rock was in the microwave for 15 secs, its strength decreased into 49% for shale and 52% for mudstone. When a microwave oven operated up to 20 sec, a rock was crushed into several pieces and its temperature was approximately 200 degrees.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.133-142
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• 2009

This research is performed to estimate quality of trial pavement for construction and analyze effect of fatigue life by using the pay factor. Specially, asphalt content which is difficult to control the pavement quality, is selected by pay adjustment standard factors and pay factor is calculated by asphalt content. This research is also analyzed to present relation of fatigue life according to asphalt content, to evaluate quality of the road pavement by calculating pay factor of sampling trial field mixture 2 times. This research confirms that it is different quality of road pavement according to pay factor changes. To analyze the fatigue life of pavement by using asphalt mixture for trial field. As a result, it is conformed that high pay factor could be high fatigue life of trial field. This means that pay factor using probability theory reflects road pavement fatigue life. Also, this study is included that beam fatigue test manufacturing specimen such as mixing type of plant which purvey asphalt mixture to trial field, compared with fatigue life of trial field. As a result, the fatigue life of specimen that is manufactured by mix type is higher than trial field specimen. This means that performance of road pavement can be reduced by gradation or other effects. Therefore, to exactly evaluate the quality of road pavement, pay factor should be calculated appling various pay adjustment standard factors such as gradation, air-void in U.S. states which is adopted pay adjustment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.9-15
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• 2023

In this study, the lamination performance and strength characteristics of cement-based composite materials according to the laminated specimens manufacturing method were analyzed. As a result of evaluating the buildability according to the layer height, the highest dimensional stability was shown when the layer height was 10 mm in all parts. The mold casting specimen and the printing-Z specimen showed the same compressive strength performance at the age of 28 days. On the other hand, the compressive strength at 28 day of printing-X specimen was the lowest at 71.72 MPa, and 8% lower than that of the mold casting specimen and the printing-Z specimen. The split tensile strength of the laminated specimen may show similar performance to that of the mold casting specimen, but the strength performance may decrease by more than 10% depending on the direction of the layer and the number of layers in the specimen. As a result of the interface analysis of the laminated specimen through X-ray CT analysis, it was confirmed that pores of a certain size were distributed along the interface of the layer.

• The Journal of Engineering Geology
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• v.13 no.2
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• pp.257-266
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• 2003

Jurassic granites of three sites, Pocheon, Geochang and Habcheon, were tested to investigate the effect of microcracks on Physical and mechanical properties of the granites. Fifteen oriented core specimens were used for the physical property test. The test result shows that porosity is almost proportioned to water content. P-wave velocity is the highest in the direction of axis ‘H’, intersection of two major microcrack sets and the lowest in the axis ‘R’, normal to the rift plane. Compressional strength tests were carried out for each core specimen taken parallel with axes ‘R’, ‘G’ and ‘H’, measuring strains. The results revealed a strong correlation between microcrack orientation and other mechanical properties such as rock strength.