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디지털 이미지 코릴레이션 기법으로 평가한 평면변형률 시험의 단부 구속 효과
장의룡,추윤식,이원택,정충기 한국지반공학회 2008 한국지반공학회논문집 Vol.24 No.7
The plane strain test can reproduce the real field condition and failure behavior precisely over other laboratory shear tests. Accordingly, this test has been utilized to investigate the shearing behaviors associated with overall failure behavior and local deformation of soils. However, most plane strain tests have been carried out with restrained end plates due to difficulties in manufacturing the equipment and also performing it. This restraint induces different results with real field because of shear stress on end plates. In this study, plane strain tests with/without bottom plate restraint were performed on Jumunjin-sand. The measurement of overall and local deformation was accomplished by digital image correlation technique as well as external LVDT. By applying digital image correlation method using two consecutive images captured through the transparent wall, local deformation behavior of various parts inside the specimen was estimated. And the formation and development of shear band caused by the restrained effect of end plate and the deformation mechanism of sand under plane strain condition were examined.
장의룡,정영훈,정충기 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.1
To incorporate micromechanical characteristics of soils into geotechnical design and simulation, the optimal size of the Representative Volume Element (RVE) needs to be provided. This study aims to determine the RVE of a soil specimen axially compressed under plane-strain conditions. The strain field was computed from the linear displacement field measured via the digital image analysis technique. The increments of the local strains under pre- and post-failure conditions were statistically compared. The results showed that the deformation of the soil specimen was homogeneous until the axial stress reached the peak. The tested hypothesis suggested that under pre-failure conditions the optimal RVE was 10.5 mm×10.5 mm, occupying 12% of the analyzed domain and 2% of the entire specimen area, while under post-failure conditions the RVE could not be attained with a certain level of uniformity.
평면변형률 시험에서 이미지 해석을 통한 사질토의 전단면 특성 평가
장의룡,정영훈,김준영,정충기 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.4
Shear banding, the localization of deformation into thin zones, has a quite practical relevance, as stability and deformation characteristics of earth structures are controlled by the soil behavior within the shear band. In this study, for understanding occurrence and developed pattern of shear band, plane strain compression tests were performed on three soils with different particle-size distribution under various conditions. Digital images were captured during the experiments; then, deformation of a specimen was evaluated by digital image analysis technique. The characteristics of a shear band were evaluated from the state shortly after post-peak occurrence to critical state. Additionally, the statistical procedure was developed to determine the reasonable thickness of a shear band.
사질토의 변형 측정을 위한 최적의 디지털 이미지 해석 기법
장의룡,정영훈,정충기 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.12
To measure the soil deformation, two common techniques of the digital image analysis—Particle Image Velocimetry (PIV) and Digital Image Correlation (DIC)—have been used. To generally apply these techniques to the soils, the accuracy of these techniques should be evaluated under various conditions. In this study, the influence factors including the image resolution, the degree of displacement and deformation, the size of pixel subsets, and analysis techniques were analyzed. The deformation of an idealized particle assembly using the discrete element method was measured by the digital image analyses, and then the results were compared with the actual deformations. To conduct the optimal digital image analysis, various factors are systematically analyzed in terms of the degree of the displacement and the deformation.
흙의 변형 측정을 위한 디지털 이미지 해석 기법의 최적화 및 정확도 평가
김준영,장의룡,정충기 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.7
고체 역학 및 유체 역학 분야에서 대상 물체의 변형, 변위 및 속도를 측정하기 위하여 디지털 이미지 해석 기법이 개발, 사용되고 있다. 지반 공학에서도 흙을 포함한 지반 구조물의 변형을 관측하기 위하여 Particle Image Velocimetry (PIV)와 Digital Image Correlation (DIC) 기법이 실내 시험 및 모형 시험 등에 적용되기 시작하는 추세이다. 이미지 해석은 시료의 종류 및 크기, 카메라 해상도, 해석 범위, 이미지 해석 조건에 영향을 받으므로, 다양한 조건에서의 정밀도를 평가하여 합리적으로 최적 조건을 결정할 필요가 있다. 본 연구에서는 디지털 이미지 해석 결과에 영향을 미치는 다양한 요소를 정리하였다. 그리고 높은 정확도의 해석 결과를 얻을 수 있는 최적의 이미지 해석 조건을 결정하는 절차를 제안하였으며 최종적으로 제안된 절차의 적용성을 점성토 시료에 대하여 검증하였다.
송도 지역 실트질 점성토 고화처리를 위한 최적 배합 조건
김준영,장의룡,정충기,장순호 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.5
Recent increase of large scale construction near costal area has also increased the application of soft ground treatment. As a result, solidification with cement and lime which increases stability and durability of soils, is frequently used for surface layer stabilization in soft ground site. While stabilization of very soft clay with high plasticity and compressibility has widely been studied, studies on silty clay with low plasticity and compressibility are relatively rare. In this study, after stabilizing low plasticity silty clay of Songdo area with cement and lime under various water contents, mixing ratio, and curing time, uniaxial compression test and plate load test were performed. Strength properties from both tests were considerably consistent. And trackability of construction equipment on the treated surface layer of dredged land was estimated. Finally, optimum mixing condition for Songdo silty clay was proposed.
GIS를 이용한 서울 시범 지역에서의 부지고유 지진 응답의 정밀구역화
선창국,정충기,천성호,장의룡 한국방재학회 2007 한국방재학회논문집 Vol.7 No.5
As computer technology has been rapidly advanced, geographic information system (GIS) is recently used in many disciplines. In this study, for a model area in Seoul, seismic hazard potential relating to site effects, which are influenced by the subsurface geotechnical conditions, was estimated using the GIS tool. The distribution of pre-existing borehole drilling data in Seoul metropolitan area was examined for the regional estimation of site-specific seismic responses at the model area. Spatial geo-layers across the entire model area were predicted by constructing a GIS-based geotechnical information system (GTIS). A microzonation of site period (TG) for estimating site-specific seismic responses at the model area was performed within the GTIS. The spatial microzoning map of TG indicated seismic vulnerability of two- to four-storied buildings in the model area. Furthermore, a site classification map for determining the design ground motion was established based on the TG within the GTIS. This informed that most of location in the model area was categorized into current site classes C and D. This seismic microzonation framework for the model area could be applicable particularly in the entire Seoul metropolitan area based on the pre-existing borehole data. 컴퓨터 기술이 급속히 발전됨에 따라, 최근에는 많은 분야에서 지리정보시스템(GIS)이 활용되고 있다. 이 연구에서는 서울 내의 한 시범 지역을 대상으로 지하 지반 조건에 따라 영향을 받는 부지 효과에 관련된 지진 피해 가능성을 GIS 기법을 이용하여 평가하였다. 시범 지역에서의 지역적 부지고유 지진 응답의 평가를 위하여 서울 대도시 지역에 대한 기존 시추 조사 자료의 분포를 파악하였다. GIS 토대의 지반 정보 시스템(GTIS)을 구축하여 시범 지역 전체에 대한 공간 지층 정보를 예측하였다. 서울 시범 지역의 부지고유 지진 응답 예측을 위한 부지 주기(TG)의 정밀구역화를 GTIS 내에서 수행하였다. 공간 분포 정밀구역화 지도로부터 시범 지역 내 2 층에서 4 층 건물들의 지진 취약성을 확인하였다. 또한, GTIS 내에서 TG 분포를 토대로 설계 지반 운동 결정을 위한 지반 분류 지도를 작성하였으며, 그로부터 대상 시범 지역 부지의 거의 대부분이 현행 지반 분류 C 와 D로 분류됨을 확인하였다. 이와 같은 서울 시범 지역에 대한 지진 정밀구역화 적용 구조 체계는 특별히 기존 시추 자료를 활용하여 대도시 서울 지역 전체에 대해 적용 가능할 것으로 판단된다.