• 한국해안해양공학회지
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• 제16권1호
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• pp.18-26
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• 2004

SCP공법(Sand Compaction Pile Method)은 안벽구조물 하부 지반이 연약할 경우에 압밀침하 속도를 증가시키고, 침하를 감소시키며, 지지력을 증대시키기 위하여 널리 적용되어 왔다. SCP 개량지반은 연약지반에 타설된 모래말뚝과 주변 연약지반으로 구성된 복합지반을 형성한다. 이와 같은 복합지반의 설계 및 해석 시 가장 중요한 요소는 치환율에 따른 응력분담비이다. 본 연구에서는 수치해석기법을 사용하여 복합지반에 대한 응력분담비 특성을 검토하였다. 치환율에 따른 응력분담비는 상수 값이 아니라 연약지반의 깊이, 압밀과정에 의존한다. 또한 하중재하 단계에 응력분담비는 복합지반의 응력전이 특성에 의하여 증가하며, 재하 완료 직후에는 치환율에 따라 2.5∼12의 값을 가진다. 그러나 과잉간극수압이 소산되어 점토지반의 유효응력이 증가되는 압밀과정 동안에는 감소하여 압밀 완료 후에는 치환율에 관계없이 2.5∼6정도 범위로 수렴한다.

• Composites Research
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• 제30권1호
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• pp.7-14
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• 2017

In this paper, the inter-lamina shear strength (ILSS) of multi-wall carbon nanotube (MWNT) reinforced carbon fiber reinforced plastics (CFRP) and thin-ply composites were verified under low earth orbit (LEO) space environment. CFRP, MWNT reinforced CFRP, thin-ply CFRP and MWNT reinforced thin-ply CFRP were tested after aging by using accelerated ground simulation equipment. The used ground simulation equipment can simulate high vacuum ($2.5{\times}10^{-6}torr$), atomic oxygen (AO, $9.15{\times}10^{14}atoms/cm^2{\cdot}s$), ultraviolet light (UV, 200 nm wave length) and thermal cycling ($-70{\sim}100^{\circ}C$) simultaneously. The duration of aging experiment was twenty hours, which is an equivalent duration to that of STS-4 space shuttle condition. After the aging experiment, ILSS were measured at room temperature ($27^{\circ}C$), high temperature ($100^{\circ}C$) and low temperature ($-100^{\circ}C$) to verify the effect of operation temperature. The MWNT and thin-ply shows good improvement of ILSS at ground condition especially with the thin-ply. And after LEO exposure large degradation of ILSS was observed at MWNT added composite due to the thermal cycle. And the degradation rate was much higher under the high temperature condition. But, at the low temperature condition, the ILSS was largely recovered due to the matrix toughening effect.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1214-1223
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• 2009

In this study, a composite behavior of stone columns reinforced in soft ground, Sabkha, have been evaluated by a series of field measurements and numerical analysis. Field loading tests were performed to verify the effect of the composite ground reinforced by stone columns in Kayan, Saudi. The settlement measured in the field test was compared with the settlement calculated by the Priebe method and the numerical analysis using ABAQUS. It is found that the settlement estimated using the Priebe method significantly overestimated the settlement measured in the field test. In addition, it is confirmed that consideration of confinement effect exerted by surrounding stone columns in a numerical simulation is indispensable to estimate the settlement of composite ground.

• 한국지반공학회논문집
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• 제25권8호
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• pp.23-32
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• 2009

본 연구에서는 모래 다짐말뚝 공법의 설계 및 시공단계에서 침하거동 예측에 활용될 수 있는 합리적이고 간편한 해석기법을 제안하였으며, 모델 계수값들은 유전자 알고리즘에 근거한 최적화 과정을 통하여 구할 수 있다. 제안된 기법의 검증을 위하여 0(무치환), 20, 36 및 56%의 다양한 모래 치환율에 대한 SCP 복합지반의 침하거동에 관한 실내압밀실험이 수행되었다. 제안된 모델은 각 치환율에 대하여 간극비-대수응력 관계 및 시간-압축 관계에서 계측값과 매우 일치되는 경향성을 보였다.

• 한국산학기술학회논문지
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• 제13권7호
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• pp.3216-3223
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• 2012

심층혼합처리(deep cement mixing, DCM)공법은 두꺼운 연약지반을 개량하는 공법 중 하나이다. 이 공법은 저소음, 저진동으로 공해가 적고 단시간에 큰 강도를 얻을 수 있는 장점이 있다. DCM공법과 같이 연약지반 개량 후 복합지반이 형성되는 지반의 침하량 산정을 위해서는 응력분담비의 결정이 필요하다. 이 연구에서는 DCM공법으로 개량된 복합지반 거동특성을 이해하기 위하여 모형재하시험을 실시하였다. 모형시험에서 측정한 토압과 침하량, 그리고 기존 제안도표를 이용하여 응력분담비를 산정하였는데 응력분담비는 각각 35.4, 28.6, 27.02로 DCM 개량체에 큰 응력집중이 발생하는 것으로 나타났다. 이러한 결과는 기존 연구결과에 의한 응력분담비(26.52, 32.5)와 비교할 때 유사한 값을 갖는 것으로 나타났다.

• 대한기계학회논문집A
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• 제28권6호
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• pp.807-815
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• 2004

In order to evaluate the static stability of hybrid carbody structures of Korean Tilting Train eXpress(TTX) caused by degradation of composites under ground environments, T300/AD6005 graphite/epoxy composite specimens were exposed to accelerated environmental conditions including ultraviolet radiation, temperature and moisture fer 2000 hours. It was found that the stiffness and strength of composites after aging were lower than those of unexposed specimens, and decreased as the aging time increases. The values of the degraded properties were used in the static analysis to check the static stability of hybrid carbody structures caused by environmental degradation of composites. The results shown that the structural stability of hybrid carbody structures was affected by the degradation of composites after exposure to accelerated aging environments.

• 한국지반공학회논문집
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• 제24권11호
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• pp.143-155
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• 2008

지반앵커는 그라우트가 힘을 받는 형태에 따라 분류되는데 앵커의 인발시 그라우트가 인장을 받으면 인장형 앵커로 압축을 받으면 압축형 앵커로 분류된다. 본 연구에서는 인장과 압축을 동시에 받는 기구를 가진 복합형 앵커를 개발하였다. 현장시험을 위해 연약지반내의 앵커체 내부에 변형률게이지를 설치하였고, 측정된 시험결과를 통해 인장과 압축변형률이 동시에 발생하는 인발저항기구를 관찰할 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.181-188
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• 2004

Composite soil methods among granular pile merhods that we could improve soft ground of fine soil particles by, have permeability as one of fundamental principals. The catual state, that voids of sand or gravel, etc. of granular soil as drainage materials are clogged by fine soil particles, is 'clogging'. In this study, it is analysed that using sand or gravel, etc. of granular soil as drainage materials, experiment are made by clogging tester on several condition.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.241-248
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• 1999

Structural damage during an earthquake is caused by the response of the structure to the ground motion input at its base. The dynamic force produced in the structure are due to the inertia of its vibrating elements. The response of the structure exceeds the ground motion and this dynamic magnification depends on the duration and frequency content of the ground vibration, the soil properties at the site, distance from the epicenter and the dynamic characteristics of the structure. Earthquake load used in this study as a input data was artificially simulated with the design spectrum diagram in the Korean Earthquake Resistant Design Code. This paper presents the seismic analysis of the continuous preflex composite girder bridges according to variation of pier's height and span's length.

• Restorative Dentistry and Endodontics
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• 제5권1호
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• pp.19-23
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• 1979

This experimental study was made to investigate the tensile strength of composite resins to etched enamel surface with a 50% phosphoric acid. Recently extraced 40 maxillary incisors were chosen. These were divied into 4 groups: Group I: Restodent adaptation to the etched enamel surface with 50% phosphoric acid. Group II: Restodent adaptation to only the ground enamel surface. Group III: Hi-pol adaptation to the etched enamel surface with 50% phosphoric acid. Group IV: Hi-pol adaptation to only the ground enamel surface. The results were as follows: 1. The tensile strength of Hi-pol showed much better results than that of Restodent. 2. Hi-pol and Restodent on the ground enamel surfaces showed little difference. 3. Adhesion to enamel increased on the average over 200% after a 50% phosphoric acid etch.