• Geomechanics and Engineering
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• 제28권2호
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• pp.117-133
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• 2022

Determination of the mechanical behaviour of jointed rock masses has been a challenge for rock engineers for decades. This problem is more pronounced for non-persistent jointed rock masses due to complicated interaction of rock bridges on the overall behaviour. This paper aims to study the effect of a non-persistent joint set configuration on the mechanical behaviour of rock materials under both uniaxial and biaxial compression tests using a discrete element code. The numerical simulation of biaxial compressive strength of rock masses has been challenging in the past due to shortcomings of bonded particle models in reproducing the failure envelope of rock materials. This problem was resolved in this study by employing the flat-joint contact model. The validity of the numerical model was investigated through a comprehensive comparative study against physical uniaxial and biaxial compression experiments. Good agreement was found between numerical and experimental tests in terms of the recorded peak strength and the failure mode in both loading conditions. Studies on the effect of joint orientation on the failure mode showed that four zones of intact, transition to block rotation, block rotation and transition to intact failure occurs when the joint dip angle varies from 0° to 90°. It was found that the applied confining stress can significantly alter the range of these zones. It was observed that the minimum strength occurs at the joint dip angle of around 45 degrees under different confining stresses. It was also found that the joint orientation can alter the post peak behaviour and the lowest brittleness was observed at the block rotation zone.

• 수완나부미
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• 제6권1호
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• pp.27-65
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• 2014

Flourishing in the Central Dry Zone of Burma during a period from the mid-eleventh to the late-thirteenth century A.D., the historical kingdom of Pagan was one of the major Buddhist centers in Southeast Asia. The significance of Pagan as an important pilgrimage site of the region, where numerous relics of the Buddha were enshrined, had been maintained until long after the fall of its civilization. It is evident that the artistic influences of Pagan, particularly in the architectural and decorative domains, had been transmitted to various other Buddhist civilizations in the area. This study provides a detailed analysis on the relationships between the mural tradition of Pagan and those of its neighboring civilizations in Thailand-of the Ayutthayā, Lānnā and Sukhothai schools-dating from after the Pagan Period in the fourteenth century to the sixteenth century. Surprisingly, as the analysis of this study has suggested, such relationships seemed to be trivial, more on a minor stylistic basis than on substantial ideological and iconographic grounds. They suggest that transmission of the complex idea and superb craftsmanship of the mural tradition would not have been maintained adequately at Pagan after its civilization, probably due to the lack of royal patronage. It would have been extremely difficult for foreign pilgrims who visited Pagan after its dynastic period to appreciate the surviving murals of this lost tradition in terms of their complex programs and associated symbolism. Also, there had been a new center of the Sinhalese Buddhism firmly established in the Martaban area of lower Burma since the mid-fourteenth century that outcompeted Pagan in terms of supplying the new Buddhist ideas and tradition. Its fame spread wide and far among the Buddhist communities of Southeast Asia. Later, these Buddhist communities also established direct contact with Sri Lanka. The Sukhothai murals and the Ayutthayā murals in the crypt of Wat Rātchaburana, dating from the fourteenth/fifteenth century, show obvious Sri Lankan influence in terms of artistic style and Buddhist iconography. They could be a product of these new religious movements, truly active in Southeast Asia during that time.

• 지질공학
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• 제25권2호
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• pp.215-225
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• 2015

염수로 충진된 부산시 낙동강 델타지역에 염수오염을 방지하고 지하수자원을 확보할 수 있는 인공함양 실증시설의 구축을 목적으로, 고심도 피압대수층에 담수 주입시험을 실시하였다. 연구지역은 두꺼운(두께 10~21 m) 점토층이 가압층으로 분포하며, 두꺼운 하부모래층(두께 31.5~36.5 m)과 자갈층(두께 2.8~11 m)이 주대수층을 이루는 피압대수층을 형성하고 있다. 시험 전 실시한 전기전도도(EC) 검층결과 연구지역은 약 7~44 mS/cm의 EC 분포를 보이며, 15~38 m 사이에 담수와 염수의 전이대가 존재하였다. 수온은 5 m 심도까지는 10~15.5℃이었으나, 5 m 심도부터는 15.5℃에서 50 m 심도까지 17℃로 일정하게 증가하고 있었다. 담수 주입시험에서 총 62시간 동안 370 m³/day의 주입유량으로 약 950 m³의 담수가 주입되었으며, 주입공 OW-5의 40 m 심도에서 CTD Diver를 이용하여 담수체의 형성을 확인하였다. 주입 후 EC 및 온도 검층을 통해 주입된 담수체가 24시간 이상 유지되는 것을 확인하였고, 21일 경과 후 실시한 검층에서도 담수체의 존속이 확인되었다. 또한 OW-5공 주입시험보다 20일전에 실시된 1차 주입시험 주입공 OW-2에서도 아직 담수체의 영향이 남아있는 것으로 확인되었다. 그리고 OW-2와 5에 주입된 담수와 염수의 관계는 점이적이 아닌 뚜렷한 경계(Sharp Boundary)를 이루고 있었다. 따라서 주입된 담수가 염수 내에서 일정한 공간을 차지하며, 원상태의 수질을 상당기간 유지할 수 있다는 것을 파악하였다. 향후 인공함양 시설을 구축하여 장기적인 담수 주입을 통해 이 델타지역에 담수체를 형성시키는 실증연구를 수행한다면, 염수로 오염된 해안대수층을 대체수자원 확보의 공간으로 활용할 수 있을 것으로 사료된다.

• 암석학회지
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• 제18권1호
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• pp.19-30
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• 2009

울산시 울주군 언양읍 북부 신흥마을 입구에 북서-남동 방향으로 트렌치된 단면에서 양산단층대의 주단층과 제4기 단층이 관찰되었다. 본 논문은 신흥마을 입구의 트렌치 단면에서 조사된 양산단층대의 기반암 단층(신흥단층)과 제4기 단층(제4기 신흥단층)의 기하학적 운동학적 특성연구로부터 양산단층대 남부의 단층 운동사를 해석하였다 신흥마을 입구 트렌치 단면에서는 단층접촉으로 반복되어 산출하는 백악기 하양층군의 퇴적암류와 유천층군의 화산암류 그리고 이들 기반암류를 부정 합으로 피복하는 제4기 퇴적층 등이 산출하고, 본 연구결과 양산단층대의 형성과 관련된 적어도 2회의 주향-이동 단층운동 (D1, D2)과 이후 적어도 2회의 역-이동 단층운동(D3, D4)이 인지된다 (1) D1 단층운동: 양산단층대의 주 단층을 향하여 퇴적암류의 층리를 고각화시키는 주향-이동 단층운동. (2) D2 단층운동: 고각화된 층리를 단층면으로 하는 우수 주향-이동 단층운동 주요 특징적인 구조요소로서는 북북동 방향의 준 수평적인 우세한 단층조선과 준 수직적인 우세한 단층엽리 등이 있다. 양산단층대의 주요 단층암류는 D2 단층운동에 의해 형성되었다. (3) D3 단층운동: (동) 북동 주향에 (남)남동 내지 (북)북서 방향으로 중각 경사하는 단층면을 갖는 공역성 역-이동 단층운동 주요 특징적인 구조요소로서는 주향 방향의 단층조선을 중첩하는 경사 방향의 단층조선, D2 단층비지에 발달하는 S-C 구조 엽리, 비탈과 평탄 기하의 단층면, 단층운동에 수반된 비대칭 및 끌림 습곡과 붕괴구조 등이 있다. 양산단층대 주 단층면의 방향성은 주로 D3 단층운동에 의해 분산되었다. (4) D4 단층운동: 제4기 퇴적층내에 5-C 구조 엽리의 발달과 함께 제4기 퇴적층을 수 cm 변위시키는 제4기 역-이동 단층운동 양산단층대의 다른 제4기 단층과 같이 D4 단층면은 기반암의 D3 역-이동 단층면의 연장선상에 놓이고, 이들 단층은 동일한(북)북서-(남)남동 방향의 압축응력에 의해 형성되었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제34권3호
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• pp.285-292
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• 2008

Purpose: The present study was performed to evaluate the effect of surface treatment of the cervical area of implant on bone regeneration in fresh extraction socket following implant installation. Materials and methods: The four minipigs, 18 months old and 30 kg weighted, were used. Four premolars of the left side of both the mandible and maxilla were extracted. ${\phi}$3.3 mm and 11.5 mm long US II plus implants (Osstem Implant co., Korea) with resorbable blasting media (RBM) treated surface and US II implants (Osstem Implant co., Korea) with machined surface at the top and RBM surface at lower portion were installed in the socket. Stability of the implant was measured with $Osstell^{TM}$ (Model 6 Resonance Frequency Analyser: Integration Diagnostics Ltd., Sweden). After 2 months of healing, the procedures and measurement of implant stability were repeated in the right side by same method of left side. At four months after first experiment, the animals were sacrificed after measurement of stability of all implants, and biopsies were obtained. Results: Well healed soft tissue and no mobility of the implants were observed in both groups. Histologically satisfactory osseointegration of implants was observed with RBM surface, and no foreign body reaction as well as inflammatory infiltration around implant were found. Furthermore, substantial bone formation and high degree of osseointegration were exhibited at the marginal defects around the cervical area of US II plus implants. However, healing of US II implants was characterized by the incomplete bone substitution and the presence of the connective tissue zone between the implant and newly formed bone. The distance between the implant platform (P) and the most coronal level of bone-to-implant contact (B) after 2 months of healing was $2.66{\pm}0.11$ mm at US II implants group and $1.80{\pm}0.13$mm at US II plus implant group. The P-B distance after 4 months of healing was $2.29{\pm}0.13$mm at US II implants group and $1.25{\pm}0.10$mm at US II plus implants group. The difference between both groups regarding the length of P-B distance was statistically significant(p<0.05). Concerning the resonance frequency analysis (RFA) value, the stability of US II plus implants group showed relatively higher RFA value than US II implants group. Conclusion: The current results suggest that implants with rough surface at the cervical area have an advantage in process of bone regeneration on defect around implant placed in a fresh extraction socket.

• 한국지반공학회논문집
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• 제30권5호
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• pp.25-35
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• 2014

팔공산 주변의 퇴적암은 백악기 후기 화강암질 마그마의 관입에 의해서 접촉변성암인 혼펠스로 변성되었다. 이 혼펠스는 팔공산 화강암체 주변 2.0~3.5km 범위로 분포하고 있으며 퇴적암과 혼펠스의 경계는 명확하지 않다. 본 연구에서는 5개 선별된 지역의 35개 지점에서 채취한 신선한 암석시료에서 350개의 공시체를 성형하여 실내시험을 수행하였다. 시험결과 함수비와 흡수율은 화강암 경계부와 멀어질수록 증가하였지만, 단위중량, 초음파속도, 점하중강도 및 슬레이크 내구성 지수는 감소하였다. 이는 화강암 경계부로부터 멀어질수록 혼펠스의 변성도가 낮아짐을 의미하는데, 거리에 따른 특성치의 변화 및 특성치와의 상관성을 회귀 분석하여 관계식을 제시하였다. 또 시험 결과 중 P파속도와 점하중강도를 바탕으로 혼펠스의 역학적 등급분류 기준을 제안하였다.

• 감성과학
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• 제20권2호
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• pp.117-126
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• 2017

본 연구에서는 직/편물 8종을 대상으로 이들 수직방향과 수평방향 수분이동특성 측정방법에 따른 소재들의 수분이동 특성을 분석하였다. 또한, 8종의 시편의 MMT에 의한 건조특성을 수직 건조 측정 결과와 비교하여 논의하였다. 수평수분이동 방법인 MMT 시험 결과는 수직법인 바이렉 방법의 결과와 유사한 거동을 나타내었다. 대나무, 린넨 및 면/나일론 복합 소재는 드롭법의 흡수시간은 짧았으며, 표면의 낮은 접촉각 및 직물의 높은 다공성에 기인한 것으로 판단되며, 친수성 스테이플 섬유의 구조와 상관이 있을 것으로 보인다. MMT에 의한 건조특성은 니트 및 대나무 직물의 최대 흡수반경이 가장 우수했으며, 수식 건조법에 비해 차이를 나타내었다. MMT 방법의 건조속도는 직물의 두께와 포화수분 흡수율과 높은 상관성을 가졌으며, 회귀계수는 각각 0.9와 0.88이었다. 이는 직물의 두께가 얇을수록 위킹 및 건조특성이 우수하며, 기능성 소재기획시 착용 내구성을 판단하는데 중요함을 의미한다. 또한 상이한 섬유소재, 실 및 구조의 소재에 대한 수분이동특성(위킹, 건조)는 측정 방법에 따라 다른 결과를 나타내었다.

• 한국경제지리학회지
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• 제19권1호
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• pp.33-50
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• 2016

용산구의 동쪽에 위치한 한남동은 부촌으로 알려져 있지만, 실제로는 부촌과 빈촌이 공존하는 장소다. 이 곳은 2000년대까지는 주택가의 성격이 강한 동네였지만, 2000년대 말~2010년대 초 이후 '길'을 중심으로 문화경제적 실천이 집적되면서 새로운 장소, 이른바 창의경제의 장소로 변환되고 있다. 이런 장소의 생산은 다양한 창의계급들이 상이한 구역을 각각 차지하는 양상을 보이며, 그들 사이의 접촉지대에서는 경합과 충돌이 발생하고 있다. 이곳의 한 구역에서는 대기업의 경제자본을 바탕으로 문화적 기획을 왕성하게 전개되는 한편, 다른 구역에서는 창의적 소생산자 혹은 창의적 하층계급이라고 칭할 수 있는 행위자들이 문화자본을 배치하여 우사단길과 한강진길이라는 비공식적 이름의 장소로 형성하는 실천을 수행하고 있다. 결론적으로, 2010년대의 한남동은 상이한 곳들에서 상이한 행위자에 의한 상이한 젠트리피케이션이 발생하면서, 내국인들의 상이한 창의계급이 물리적 위치를 공유하지만 사회적 관계와 소통 네트워크는 거의 부재한 채로 공존하는, 즉, 서로에게 '이방인'이 되는 장소로 생산되고 있다.

• 자원환경지질
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• 제13권2호
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• pp.91-103
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• 1980

In spite of the fact that the Okcheon system has been rather intensively studied by many geologists since 1945, it still remains as a controversal problem as to its stratigraphy and geologic age. Present study has mainly focused on the upper members of the Okcheon system, namely the Hwanggangri and the Kunjasan formations so as to clarify the lithology, the depositional environment and the tectonic evolution of the formations. The Kunjasan formation lying unconformably over the Hwanggangri formation which is supposed to be a meta-tillite is interpreted as a metamorphosed calcareous argillaceous and/or arenaceous sediments on contract to the idea postulated by some geologists that it was a derivative of silicified Hwanggangri formation. Lithology of the Kunjasan and the Hwanggangri formation is quite different in that the former is white in color, contains few pebbles, and mostly composed of diopside and detrital quartz, whereas the latter is black to dark in color, contains abundant and variable kinds of pebbles, and composed of more argillacous matrix that has been metamorphosed to hornfels. The Hwanggangri and the Kunjasan formations were deposited in the rather deep sea which has transgressed toward northeast from southwest in the late Precambrian time, and the writer (1970) had formerly designated it as Okcheon Paleogeosyncline. With the beginning of Paleozoic era, Okcheon neogeogyncline was formed to the northeast of the old paleogeogyncline area. The transgression of the sea had proceeded toward southwest in which Cambrian strata were accumulated. During this period the area occupied formerly by the paleogeosyncline was uplifted, so that most of the Hwanggangri and the Kunjasan formations were eroded away except in the area close to the neogeosyncline sea coast. This is the reason why the Hwanggangri and the Kunjasan formations are cropped out presently in the area of the vicinity of contact zone of the paleo- and neogeosyncline zones. The age of the Okcheon system has been reconfirmed to be Precambrian from the view of the facts that 1) the Hanggangri formation, the upper member of the Okcheon system is meta-tillite and correlated to the Precambrian tillite in the Yantze basin in China, 2) the Okcheon system has been moderately metamorphosed while other formations of the same age, if it is Paleozoic or later, have not been metamorphosed, and 3) tectonic history and limited areal distribution of the Hwanggangri and the Kunjasan formations is suggestive of Precambian age.

• 자원환경지질
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• 제30권5호
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• pp.395-406
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• 1997

Some RE (Zr, Nb, REE) ore deposits are located in the middle part of the Korean peninsula. Geotectonically, the RE ore deposits situated on the Kyemyeongsan Formation of northern margin of the Okcheon geosynclinal belt and in the transitional zone between Kyeonggi massif and Okcheon belt. The rare metal deposits distributed in Kyemyeongsan Formation which consists of schist and alkaline granite. The alkali granite has suffered extensive post-magmatic metasomatism and hydrothermal processes. The ore contains mainly Ce-La, Ta-Nb, Y, Y-Nb, Ti-Nb-(U), Nd-Th group minerals. Fergusonite, one of Nb-Y rich REE minerals belonging to the A-B oxides, is most common mineral in the rare metal deposits. The fergusonite bearing rocks may be devided into four types by occurrence features and mineral association, that is, zircon type, allanite vein, feldspar type, and fluorite type. Fergusonites show wide variations in optical properties, due to part of differences in their chemical composition (depending on the types), but also the degree of crystalinity of the individual specimens. Fergusonite metamicts enclosed in biotite are generally surrounded by well developed pleochroic haloes. Usually, fergusonite is accompanied with zircon and other REE-bearing minerals. Petrographical and chemical data are presented for fergusonites which collected different types. $Nb_2O_3$ and $Y_2O_3$ contents range from 48.51 to 53.01 wt.% and 29.18 to 42.02 wt.% respectively. Also, $ThO_2$, (1.83~6.93), $UO_2$, (0.17~2.84), ${\sum}RE_2O_3$ (except to Y) (1.11~8.73), and $TiO_2$, (0.19~1.19 wt.%) contents show variational compositions according to fergusonite types. The ${\sum}RE_2O_3$ of fergusonites are positive relation with $Y_2O_3$ and negative relaton with $ThO_2$ and $({\sum}{RE_2O_3}-{Y_2O_3})$. The $Nb_2O_3$ is sightly negative relation with $Ta_2O_3$. Back-scattered electron microscope images (BEI) of fergusonite show the mineral composition and textural feature is very complicated. The variation of Nb, Th and REE content of fergusonite and the modes of occurrence of mineral, suggests that REE may have been mobilized during the circulation of hydrothermal fluids related to contact metamorphism (metasomatism). The chemical variation of the fergusonites with occurrences and mineral association can be related to metasomatism of alkaline fluid was probably the dominant ore-forming process in Chungju district.