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손실함수가 송도신도시의 최적 압밀층 두께 결정에 미치는 영향
김동휘,이우진,류동우,채영호,박정규 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.8
Spatial estimation of the thickness and depth of the geological profile has been regarded as an important procedure for the design of soft ground. A minimum variance criterion, which has often been used in traditional kriging techniques, does not always guarantee the optimal estimates for the decision-making process in geotechnical engineering. In this study, a geostatistical framework is used to determine the optimal thickness of the consolidation layer and the optimal area that needs the adoption of prefabricated vertical drains via indicator kriging and loss function. From the exemplary problem, different optimal estimates can be obtained depending on the loss function chosen. The design procedure and method considering the minimum expected loss presented in this paper can be used in the decision-making process for geotechnical engineering design.
Nonsyndromic Multiple Basal Cell Carcinomas
김동휘,고효선,전영준 대한두개안면성형외과학회 2017 Archives of Craniofacial Surgery Vol.18 No.3
Basal cell carcinoma (BCC) comprising several lesions is not uncommon, but nonsyndromic multiple BCCs with parotid invasion are rare entities. We present two cases of multiple sporadic, nonsyndromic BCCs, and one of these cases is a unique case of parotid invasion associated purely with actinic keratosis. In Case 1, a 79-year-old female presented with multiple skin lesions on the face and left hand. All lesions were completely removed by surgery. The pathologic results showed lesions consistent with BCC and some lesions consistent with actinic keratosis. After 8 months, the patient presented with skin lesions in bilateral temporal areas and left cheek area. Surgical excision of the lesions was performed, and the biopsy results were squamous cell carcinoma in situ and actinic keratosis. In Case 2, a 43-year-old woman presented with multiple skin lesions on the face, scalp, right chest, abdomen and right leg. All lesions were completely removed by surgery. Pathologic evaluation confirmed the diagnosis of BCC. BCC is rarely metastatic, but it can lead to severe disfiguration or destruction. It is important to diagnose and treat BCC at an early stage.
확률론적 방법에 의한 인천송도지반 압밀침하량의 공간적 분포 평가
김동휘,최영민,이우진 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.9
Because the thickness and depth of consolidation layer vary at every location, the consolidation settlement and time have to be evaluated spatially. Also, for a rational evaluation of the uncertainty of the spatial distribution of consolidation settlement and time, it is necessary to adopt a probabilistic method. In this study, mean and standard deviation of consolidation settlement and time of whole analysis region are evaluated by using the spatial distribution of consolidation layer which is estimated from ordinary kriging and statistics of soil properties. Using these results and probabilistic method, the area that needs adopting the prefabricated vertical drain as well as raising the ground level for balancing the final design ground level is determined. It is observed that such areas are influenced by the variability of soil properties. The design procedure and method presented in this paper can be used in the decision making process for a geotechnical engineering design.
김동휘,김진원,임형덕,김대규,이우진 한국지반공학회 2001 한국지반공학회논문집 Vol.17 No.4
본 논문에서는 경남 양산지역의 퇴적층에서 채취한 불교란 시료를 이용하여 표준압밀시험($IL_{CON}$)과 일정변형률(CRS, Constant Rates of Strain) 압밀시험을 수행한 후 각각의 시험결과를 분석하여 양산점토의 투수특성을 고찰하였다. 이를 위하여 투수계수와 간극비의 관계를 Kozeny(1927)와 Carman(1956) 이후 제안된 많은 연구결과와 비교, 검토하였으며, 시료를 연직방향으로 성형하여 CRS 시험을 수행한 후 횡방향투수계수를 산정하여 양산점토의 투수계수의 이방성을 살펴보았다. CRS시험 결과, 직접적으로 정상류를 발생시켜 누수계수를 측정하는 Rowe cell 시험에 비하여 상대적으로 투수계수의 이방성이 과소평가되는 경향을 보였다. 또한 현장 투수계수에 영향을 미치는 요소들을 살펴보고, 깊이에 따른 투수계수를 고찰하였다.다.
인천 송도국제도시 지층분포추정을 위한 크리깅 방법의 비교연구
김동휘,류동우,이주형,최인걸,김종국,이우진 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.5
Kriging techniques have been used to estimate the spatial distribution of soil layers and soil properties in the geotechnical engineering area. Since the selected kriging technique may provide different values of estimation, the selection of method is important in the geotechnical estimation. In this paper, the spatial distribution of the thickness of consolidation layer of Songdo International City is estimated using simple, ordinary, and universal kriging techniques, and the reliability of estimated results is analyzed. It is shown that the consolidation layer thickness estimated by the simple kriging technique is larger than those by other kriging techniques when the location of estimation is far from the locations where the measured data exist. In this case, the reliability of the simple kriging technique is observed to be lower than those of other techniques. Universal kriging gives a negative value for thickness of consolidation layer in some locations away from the data. It is concluded that the ordinary kriging is the most optimized estimation technique because the reliability of ordinary kriging technique is higher than those of other ones and the consolidation layer thickness estimated by the ordinary kriging locates within the reasonable range.
김동휘,김재정,안신환,이우진 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.6
Geotechnical variability is a complex feature that results from many independent sources of uncertainties, and is mainly affected by inherent variability and measurement errors. This study evaluates the coefficient of variation (COV) of soil properties and soil layers at Song-do region in Korea. Since soil variability is sensitive to soil layers and soil types, the COVs by soil layers (reclaimed layer and marine layer) and the COVs by soil types (clay and silt) were separately evaluated. It is observed that geotechnical variability of marine layer and clay is relatively smaller than that of reclamation layer and silt. And, the highly weathered rock and soil show the higher COVs in the interpretation of the strength parameters of the fresh and weathered rock. And the proposed COV of Songdo area can be used for the reliability-based design procedure.
압축지수의 추정방법이 압밀침하량의 공간적 분포특성에 미치는 영향
김동휘,류동우,김민태,이우진 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.10
In order to investigate the effect of variation characteristics of compression index on the spatial distribution of consolidation settlement, this study presents the estimation methods of the distribution of consolidation settlement and compares the estimated settlements. When the variation of compression index is considerable, the ordinary cokriging is more reliable in estimating the compression index than ordinary kriging because smoothing effect of ordinary cokriging is smaller than that of ordinary kriging. The spatial distribution of consolidation settlement estimated by considering both the variation of compression index and void ratio (CASE-1) is different from that estimated by using the mean value of all soil properties (CASE-2). The settlement of CASE-1 shows the larger variation at short distances rather than that of CASE-2. Whereas the spatial settlement distribution of CASE-1 is affected by the spatial distributions of compression index as well as the thickness of consolidation layer, that of CASE-2 is significantly influenced by the distribution of consolidation layer thickness.