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Recognition of the Phanerozoic “Young Granite Gneiss” in the central Yeongnam Massif
송용선,이호선,박계헌,Ian C.W. Fitzsimons,Peter A. Cawood 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.1
Up to now, all the high-grade gneisses of the Koreanpeninsula have been regarded as Precambrian basement rocksand presence of the Phanerozoic high-grade metamorphic rockshave remained unknown. However, such granite gneiss is discoveredthrough this study from the central Yeongnam massif nearGimcheon. SHRIMP zircon U-Pb age determinations on the granitegneiss, having well-developed gneissic foliations and migmatitictextures, reveal concordant age of ca. 250 Ma indicating the EarlyTriassic emplacement of this pluton, which is in contradict to theprevious belief that it is a Precambrian product. Even though thegranite gneiss reveals well-developed gneissic foliations and somezircons show rather low Th/U ratios, the metamorphic age hasnot been determined successfully. However, the age of metamorphismcan be constrained as middle Triassic considering theabsence of any evidences of metamorphism from the nearbygranitic plutons having emplacement ages of ca. 225 Ma. EarlyTriassic emplacement and subsequent Middle Triassic metamorphismof the granite gneiss from the Yeongnam massif bear aremarkable resemblance to the case of South China block. Wesuggest the possibility that Early to Middle Triassic metamorphismof the Korean peninsula might be products of the intracontinentalcollisional events not directly related with the EarlyTriassic continental collision event.
연약지반에서 보강옹벽의 안정성을 위한 적정 치환영역의 사례 연구
송용선,이병식 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 논문집 Vol.11 No.6
연약지반에 시공되는 보강토옹벽과 개비온옹벽에 대해서 옹벽의 안정성을 확보하기 위해 필요한 적정 치환영역을 유한요소해석을 통해 검토하였다. 해석은 연약토층의 압밀단계를 포함하여 시공순서를 모사하는 단계별 해석방법으로 수행되었다. 적정 치환영역의 제안을 위한 첫 단계로 치환깊이를 변화시킨 경우들에 대해서 시공단계에 따른 벽체 및 주변 지반의 거동을 조사하는 일련의 해석을 수행하였다. 이들 해석결과를 문헌연구를 통하여 설정한 옹벽의 안정성을 보장할 수 있는 벽체변위, 지반의 침하량 및 전단변형율 등의 한계값과 비교, 평가하였다. 그 결과, 본 연구에서 검토한 지반조건에서 벽체의 높이가 변하는 경우에 대한 적정 치환영역을 벽체의 높이에 대한 치환깊이의 비로 나타내는 시공표준도를 제안하였다 For the cases of constructing reinforced earth and gabion walls on the soft ground, an appropriate replacement area of soft ground required to maintain the stability of walls was investigated by FEM analyses. Incremental analyses were performed in FEM, in which construction sequences including consolidation of soft soil layer were simulated. As a first step to suggest the appropriate replacement area, a series of analyses for cases varying the replacement depth were conducted to examine the behaviors of wall and adjacent ground according to the construction sequence. The analysis results were, then, evaluated with the proper limiting values of displacements of wall, settlements and shear strains of ground to guarantee the stability of walls, which were specified based on the literature review. Consequently, the typical construction drawings could be suggested, in which appropriate replacement areas for varying wall heights for the ground condition investigated in this study were represented in terms of the ratio of replacement depth to the height of wall.