• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.245-254
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• 2006

Using a natural gradient tracer test, the characteristics of hydrodynamic dispersion according to each depth of a fractured rock were studied, and the effective porosity and longitudinal dispersivity of the fractured rock were estimated. The difference of vertical hydrodynamic dispersion was identified by concentration breakthrough curves linear regression analyses of bromide concentrations according to depths versus time, and hydraulic fracture characteristics at two intervals of the monitoring well. Higher concentration and faster arrival time at GL- 18 m depth (RQD 13%, average joint spacing 2 cm, TCR 100%) than at GL- 25 m depth (RQD 41%, average joint spacing 7 cm, TCR 100%) resulted from shorter distance and more fractures. Tracer was transported through the 1 st fractures until the arrival of its peak concentration and through the 2nd fractures or matrix diffusion after the arrival of its peak concentration. The increase/decrease slopes of bromide concentration versus time were 3.46/-1.57 at GL-18 m depth and 3.l9/-0.47 at GL- 25 m depth of the monitoring well. So the faster bromide transport was confirmed at GL- 18 m depth with more fractures. The concentration increment of bromide was fitted by a Gaussian function and the concentration decrement of bromide was fitted by an exponential function. Effective porosity and longitudinal dispersivity estimated by CATTI code were 10.50% and 0.85 m, respectively.

• The Journal of the Convergence on Culture Technology
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• v.8 no.1
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• pp.507-512
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• 2022

The subjects of the study are the sedimentary rock slope of the Mesozoic Gyeongsang Supergroup, which has a high risk of failure. The rocks of the slope shall be sandstone, siltstone and dacite, and discontinuities shall develop beddings, shear joints, extension joints, and dacite dyke boundary planes. The type and scale of failure varies depending on the type of rock and the strike/dip of the discontinuities, but the planar failure prevails. Based on the face-mapping data, SMR, physical and mechanical testing of rocks, the critical equilibrium analysis, all representative sections required a countermeasure method because the acceptable safety factor during dry and rainy seasons were far below Fs=1.5 and Fs=1.2. After applying the countermeasure method, both the dry and wet conditions of the slope exceeded the allowable safety factor. In particular, the face-mapping data of the slope-face, the geological cross-sections of several representative sections perpendicular to the slope-face, and the critical equilibrium analysis and the presentation of countermeasure methods that have been reviewed based on them are expected to be reasonable tools for the slope stability.

• The Journal of Engineering Geology
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• v.4 no.1
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• pp.13-28
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• 1994

Hydrogeologic characteristics of crystalline rock including discontinuities is defined by the hydraulic data from the in situ test and by analytical method. Methodology and procedure of the in situ test are used in accordance with test purpose, site condition and characteristics of host rock Hydraulic conductivities in crystalline rock including discontinuifies such as fractured zone and joint, are defined by packer test and slug test. The results indicate Hvorslev' s theory of ground water flow in NX borehole, that the shorter of test interval is, the higher hydraulic conductivity is. This is an indicafion of the fact that the hydraulic rneasured were governed by scale effect of test interval, even at same borehole. According to the result of packer tests in two boreholes, it is understood that hydraulic conductivifies show variations according to the effect of as order of tests. In the comparison of hydraulic conductivifies from both of open borehole tests, the results are relatively well correrated in values. The hydraulic conductivity in the test intervals induding hydrogeologically significant discontinuity shows relatively higher value of hydraulic conductivity in vertical distribution of full depth.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.196-210
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• 2000

This study was aimed to verify the validity of the flexural toughness evaluation method of steel fiber reinforced shotcrete(SFRS) currently being adopted by Korea Highway Corporation(KHC). Total 33 beam specimens using six different kinds of steel fiber products were prepared at tunnel construction sites and flexural toughness tests were executed at laboratory. Equivalent flexural strengths and toughness quotients were evaluated from the tests following the KHC guide iud these were compared with the quality grades determined under the guides proposed by ASTM, ITA and EFNARC. To discard the disadvantage that the toughness quotient could be influenced by flexural strength when following the KHC guide, a modification substituting the designed flexural strength for the flexural strength in the toughness quotient calculation formula was proposed to rate the quality of SFRS more adequately.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.44-51
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• 2003

Changes of the hydraulic conductivity resulting from the redistribution of stresses by underground excavation are examined using the strain-dependent hydraulic conductivity modification relation, where the modulus reduction ratio and induced strain are the major parameters. The modulus reduction ratio is defined in terms of RMR(Rock Mass Rating) to represent the full gamut of rock mass condition. Though shear dilation has the effect on the modification of hydraulic conductivity, the extent of it depends on RMR When the extensional strain is applied to a fracture, the hydraulic conductivity increases with the decrease of RMR Loading configuration has the effect on the modification of hydraulic conductivity, where the differential stress mode with a magnitude of the minimum principal stress $($\sigma$_x)$ fixed and a magnitude of the maximum principal stress $($\sigma$_y)$ varied is found to exert the greatest effect on the change of hydraulic conductivity.

• Journal of the Korean association of regional geographers
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• v.10 no.1
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• pp.53-66
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• 2004

There are various granite landforms including block stream(natural monument No. 435) within Mt. Biseul, in Daegu city. The Daegyunsa(temple) and community of rhododendron around the summit of the mountain provide visitors many objects o( interest in cultural & ecological heritage. This paper aimed to develope nature trails of various type according to visitor's characteristics. 1) Various granite landforms develope along with the main path up the mountain(block stream-gnamma-exfoliation-poligonal cracking-talus-core stone-sheeting joint-tor-free face-high flat summit). 2) The explanatory note on terminology, origin, characteristics of geomorphic resources are developed in this paper for the first time. 3) In Consideration of the path line of flow of visitor, the best field study sites and the most effective nature trails are designed for visitor. 4) Three nature tails are designed for visitor according to the type and the length of visitor's stay.

• Journal of the Korean association of regional geographers
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• v.14 no.2
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• pp.173-188
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• 2008

In order to make comparative analysis of geomorphological changes caused by urban development, I surveyed the distribution of geomorphological resources of 'Daegu Innovation Town' development plan area. The results are as follow: (1) At the front of small valleys of back-mountains are formed small alluvial fans, and at the side of small valleys are distributed hills connected with back-mountains. (2) As small valley erode laterally hills, vertical bluffs and planner bedrock riverbed are formed, and in some riverbed are appeared mud cracks and ripple marks. (3) The depth of valley in alluvial fan of 'Sinseo District' is 7m. In Sinseocheon valley dissecting alluvial fan, fluvial terraces 2m high above riverbed are distributed. Those terraces were formed while alluvial fan was dissected after last glacial period.

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.25-32
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• 2008

Based on recent studies, the side resistance of rock socketed drilled shafts was affected by unconfined compressive strength of rock, socket roughness, rock types and joints, and initial normal stress. Especially, the socket roughness was affected by rock types and joints, drilling methods, and diameters of pile. In this study, a new roughness measurement system (BKS-LRPS, Backyoung-KyungSung Laser Roughness Profiling System) usable in water was developed. Based on the laboratory model tests, an EMD (Effective Measurement Distances) according to various turbidity was proposed as $EMD=1149.2{\times}T_{b}^{-0.64}$.

• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.5-21
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• 2009

Based on recent studies on rock socketed drilled shafts, it was found that the side resistance of rock socketed drilled shafts is affected by unconfined compressive strength of rock, socket roughness, rock types and joints, and initial normal stress. Especially, the socket roughness is affected by rock types and joints, drilling methods, and diameters. Since existing roughness measurement systems could be conducted only in the air, a new roughness measurement system, which can measure rock socket roughness in the air and also in the water, is needed. However, the development of new roughness measurement system fur civil engineers has been faced with difficulties of electrical applications. In this study, the laboratory verification system far BKS-LRPS (Backyoung-KyungSung Laser Roughness Profiling System) was developed, which can be applied both in the water and air. Based on the laboratory verification, it was found that the improved BKS-LRPS could define effective measurement distances for the conditions reflecting the apparatus and in-situ situations.

• The Journal of the Petrological Society of Korea
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• v.28 no.4
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• pp.251-277
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• 2019

The Gogunsan Archipelago is composed of two island groups; the first group includes Mal-do, Myeong-do, Gwangdae-do, and Bangchuk-do islands consisting of Neoproterozoic rocks, and the second group includes Yami-do, Sinsi-do, Muneo-do, Jangja-do, and Seonyu-do islands consisting of Cretaceous rocks. The first group mainly consists of the Bangchuk formation which can be divided into two layers; the lower layer was more deformed than the upper layer. The former was intruded by mafic and felsic volcanic rocks formed in the volcanic arc tectonic setting 930-890 Ma and the latter was deposited ca. 825-800 Ma. In these islands, large scale folds with east-west fold axes were beautifully formed; the Maldo island fold was designated as natural monument and large scale beautiful chevron fold was developed on the Gwangdae-do island. In addition, there are unique zebra-shaped outcrop formed by a mixing of basic and acidic magma and Independent Gate shaped outcrop formed by coastal erosion. On the other hand, the Yami-do, Sinsi-do, Muneo-do, Jangja-do and Seonyu-do islands consist of 92-91Ma Cretaceous volcanic rocks and, in Sinsi-do island, the Nanshan formation deposited ca. 92 Ma. These Cretaceous volcanic rocks formed by melting of the continental crust by the heat supplied from the uplifting mantle due to the extension caused by a retreat of subducting ocean slab. Yami-do and Sinsi-do islands are composed of rhyolite. In Yami-do island, bands with vertical joint formed by cooling of the bottom part of the lava, are shown. In Sinsi-do island, large-scale vertical joints formed by cooling of lava flow, were developed. The Jangja-bong of Jangja-do island and Mangju-bong of Seonyu-do island are composed of brecciated rhyolite and formed a ring shaped archipelago contributing to the development of marine culture by providing natural harbor condition. They also provide beautiful views including 'Seonyu 8 views' along with other islands. As mentioned above, the Gogunsan archipelago is rich in geoheritages and associated cultural and historical resources, making it worth as a National Geopark.