• The Journal of Engineering Geology
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• v.24 no.1
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• pp.39-52
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• 2014

Limestone caves that consist of main passages and branches are formed by a variety of processes, and have the characteristic of developing with a preferred orientation controlled by discontinuities such as bedding, joints, and faults around the cave. However, it is difficult to analyze a representative orientation from various orientations. To interpret the overall development orientation of limestone caves, this study proposes new development orientation analysis methods, termed the Average Span Ratio Method (ASRM) and the Individual Development Ratio Method (IDRM), using the weighting of persistence. Nine limestone caves in Korea were randomly selected for testing the new methods. The methods show a stronger development orientation for limestone caves than that obtained by traditional methods, which consider only the distribution of development orientations. Based on an analysis of the relationship between the average span and the dip angle of bedding, it is confirmed that shallowly dipping bedding is a major contributor to the expansion of span in limestone caves. In addition, using scan-line survey data acquired in the field, we perform an RMR analysis of stability of the ground around limestone caves.

• Proceedings of the KSEG Conference
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• 2005.04a
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• pp.157-164
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• 2005

BIPS와 Televiewer를 이용하여 10개의 지하수 관측공에서 획득된 1,591개 불연속면을 분석하여 지하수 유동과의 관계를 비교${\cdot}$분석하였다. 연구지역 내의 지형은 산계가 잘 발달된 계곡형 지형이며, 수계의 발달은 매우 미약하다. 연구지역 주변에는 북북동-남남서 방향의 양산단층과 동래단층이 발달되어 있으며, 연구지역 내에는 EW방향의 선구조도 발달되어 있다. 지하수공내에서 조사된 불연속면의 주 방향은 위성사진에서 판독된 선구조의 방향과 대부분 일치한다. 지구통계기법을 이용하여 작성된 지하수위 등고선도에서 추정된 지하수 유동방향과 유향${\cdot}$유속기에서 측정된 지하수 유향은 거의 일치하지만, 단열암반에 발달된 불연속면의 방향과 지하수 유동방향은 2가지로 해석되었다. 첫째는 단열암반에 발달된 불연속면의 방향과 지하수 유동방향이 잘 일치하는 경우(BH-01, 03, 04, 12공), 둘째는 불연속면의 방향과 지하수 유동방향이 잘 일치하지 않는 경우(BH-02, 05, 07, 11) 이다. 지하수 유동방향이 불연속면의 방향과 일치하지 않는 경우는 지형의 변화에 더 영향을 받는 것으로 나타났다. 따라서 단열암반 내에서 지하수의 유동은 단열의 방향성에 영향을 받지만, 지형의 특성에도 큰 영향을 받는다.

• The Journal of Engineering Geology
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• v.11 no.2
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• pp.191-203
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• 2001

We investigate mechanical anisotropy dependent of rock fabric and its relationship with microcracks in the Pocheon Granite. Uniaxial compressive strengths range from 177MPa to 212MPa and the elastic constants are 48GPa-62GPa. The tensile strengths are 6.9MPa~8.5MPa and ultrasonic wave velocities range between 3,200m/sec and 3,700m/sec, indicating that mechanical anisotropy is strongly dependent of rock fabric. The minimum anisotropy ratio is 14% and the maximum is 24%, depend on the mechanical properties. The preferred orientations of microcracks are closely related with the directions of rock fabric. The preferred orientations of microcracks in feldspar are governed by the direction of mineralogical axis and are different from the directions of rock fabric. However, microcracks in quartz grains are very long and parallel to the directions of rock fabric, indicating that directions of rock fabric may be governed by the preferred orientations of microcracks in quartz grains. The preferred orientations of microcracks measured by differential strain analysis and microscopic observation are slightly different. That may be caused by different methodology. Lengths and numbers of microcrack are measured by microscopic observation. However, differential strain analysis measures the widths of microcracks.

• The Journal of the Petrological Society of Korea
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• v.18 no.4
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• pp.293-305
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• 2009

The Gilan-Cheongsong area, which is in contact with Yeongyang and Uiseong Blocks of Gyeongsang Basin, Korea, consists of Precambrian metamorphic rocks, Triassic Cheongsong granite, Cretaceous sedimentary rocks(Iljik, Hupyeongdong, Jeomgok Formations), and Cretaceous igneous rocks(andesite, quartz porphyry, felsite). In this area are developed faults trending in (W)NW, NNW, ENE, NS, (N)NE directions which are representative in the Gyeongsang Basin. We analyzed the geometric and kinematic characteristics of fracture systems to inquire into movement history and sense of these faults in this area. This study suggests that these faults were mainly strike-slip movement. The orientations of fracture sets show ENE, NNW, (W)NW, (N)NE, NS in descending order of frequency. Their prolongation presents (W)NW, NNW, ENE, (N)NE, NS in descending order of predominance, and also agrees with that of faults in this area. The development sequence and movement sense of fracture sets are summarized as follows; (1) (W)NW: dextral shearing $\rightarrow$ (2) (W)NW and NNW: conjugate shearing(the former: dextral, the latter: sinistral) $\rightarrow$ (3) NNW: dextral shearing $\rightarrow$ (4) (W)NW: sinistral shearing $\rightarrow$ (5) ENE: dextral shearing $\rightarrow$ (6) ENE and NS: conjugate shearing(the former: sinistral, the latter: dextral) $\rightarrow$ (7) (N)NE: sinistral shearing, and this result is closely associated with the development sequence and movement sense of faults developed in this area.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2001.03a
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• pp.177-187
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• 2001

암반사면의 안정성은 암반 내에 발달한 불연속면의 방향성과 파괴특성에 지대한 영향을 받는다. 두 조의 연속성이 좋은 절리가 발달한 암반의 거동을 해석하기 위해 FLAC의 FISH 언어로 작성된 편재 절리모델을 사용하여 절리암반사면의 안정성을 평가하였다. 해석 결과는 절리의 간격과 방향성을 달리하면서 수행된 UDEC 해석과 저면 마찰 모델 시험결과와 비교하였다. UDEC 해석과 저면 마찰 모형시험 의해 발생된 파괴면의 형상은 유사하였으며, 이 결과로부터 편재절리모델에 의한 FLAC 해석에서의 파괴면은 두 조의 교차하는 절리를 따라 계단식으로 파괴면이 발생함을 추정할 수 있었다.

• Tunnel and Underground Space
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• v.10 no.4
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• pp.497-505
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• 2000

The surveyed area is mainly distributed by the sedimentary rocks, tuffs, and esites in Cretaceous age and acidic and basic dikes are intruded in these rocks. The principle discontinuities are represented by beddings, joints and faults. The trends of the beddings of sedimentary rocks develop as E-W direction in the start area. However, they are gradually bending and finally their trends are N-S direction in terminal area. In the sedimentary rocks the 3∼4 joint sets are distributed and in dikes joints are more scattered. The majority of joints are highly dipped. Sampo fault which has NE-SW trend makes a valley and NW trending normal faults are well developed at 50k+600 to 51k+000 area. During the construction of tunnel the orientation of discontinuities will not significantly influence on the stability of excavation. Since the rock mass is extensively jointed, the overbreak in tunnel wall may be placed.

• The Korean Journal of Petroleum Geology
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• v.1 no.1 s.1
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• pp.53-62
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• 1993

The geologic structure of the Yongil Bay was studied in detail based on high resolution seismic profiles. The seafloor trends NE to SW with a deeper part off the Kuryong Peninsula. The seafloor is rather smooth due to the Quaternary fluvial deposits in the lower part and muddy sediments in the upper part. The seafloor off Umockri is very irregular due to erosion where Tertiary sedimentary rocks crop out. The underlying basement rocks were strongly deformed with faults and folds. High-angled reverse faults mostly trend N-S and NNW-SSE and are indicative of westward thrusting. Normal faults in NW-SE and WNW-ESE directions occur locally. Large folding structures trend NE-SW nearshore area of Umockri. The geologic structure suggests that the bay was subject to compressional stress regimes trending E-W and/or NW-SE prior to the early Late Miocene.

• The Journal of Engineering Geology
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• v.7 no.2
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• pp.151-159
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• 1997

Since healed microcracks in quartz grain of grantic rocks within the same mass have identical preferred orientations, the oreintations of granitic cores may be determined if the distinctive feature of healed microcracks can be used.In this study, the possibility of determining orientations of granitic cores using healed microcrack orientations were examined using samples from the borehole drilled to 200 m in depth at the Hongcheon. Eight sections whose core recoveries are 100% were selected. Two to six samples were collected in each section and orientations of healed microcracks in each sample were measured. Healed microcracks in samples from each section show almost identical orientations. The error range for sections with only one preferred orientations is within $\pm$5$^{\circ}$, indicating that correct orientations of core can be determined. However, orientations of cores in sections which have 2 or more healed microcrack orientations should be determined using orientations as well as distribution of peaks of orientations. The error range for this case is lager than former one and is within $\pm$15$^{\circ}$. The orientations of joint which is very impontant factor for designing tunnel and slope stability can be determined using healed microcrack orientation in cores.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.115-135
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• 2009

We have studied general orientational characteristics of microcracks distributed in Tertiary crystalline tuff from the northeastern part of the Gyeongsang Basin. 108 sets of microcracks on horizontal surfaces of 6 rock samples from Heunghae-eup and Cheongha-myeon, Pohang-si areas were distinguished by image processing. Those microcrack sets show a distinct linear array in 38 images. Whole domain of the directional angle(${\theta}$)-frequency(N) chart for crystalline tuff can be divided into 20 domains in terms of the phases of the distribution of microcracks. From the related chart, microcrack sets show preferred orientation which are coincident with the direction of vertical common joints. Consequently, the potential for macroscopic vertical joints in a rock body can be inferred from the directional angle showing high frequency in each domain of the related chart. This joint pattern is nearly the same in Mesozoic granites from Seokmo-do, Gwanghwa-gun. From the rose diagram for orientations of microcrack in crystalline tuff, orientations of dominant sets of microcracks in terms of frequency orders reflect representative orientations of maximum principal stress acted on crystalline tuff. Meanwhile, orientations of microcracks in crystalline tuff were compared with those of open microcracks in Bulgugsa granites from the southwestern part of the Gyeongsang Basin, and vertical rift/grain planes from Mesozoic granite quarries in Korea. In regional distribution chart, the agreement of distribution pattern between above two types of microcrack sets and vertical planes suggests that microcrack systems developed in crystalline tuff probably occur regionally in Mesozoic granites in Korea.

• 한국해양학회지
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• v.27 no.1
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• pp.66-77
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• 1992

Tidal sand ridges and sand waves are well developed in the Yellow Sea off Tae-An Peninsula, Korea. Their transport directions were inferred based on high resolution seismic profiles, surficial sediment characteristics and tidal regime. Tidal sand ridges are asymmetric, with long axes parallel to or slightly oblique to the dominant NE-SW tidal current direction. They show steep south and/or southeast flanks, which are in concordance with the apparent direction of internal cross-bedding in the south. Holocene sediments occur in accordance with distributional patterns of tidal sand ridges. These features indicate that Holocene active tidal sand ridges move toward the open sea in southeast, south and southwest direction. Sand waves which are distributed in flat sea floor with depth of about 40-60m show also asymmetric forms with a steep east-to-northeast face. Surficial sediments in the sand wave field are characterized by well sorted fine sands compared with poorly sorted adjacent areas. The sand waves appear to undergo easterly or northeasterly landward movement.