• Wind and Structures
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• v.6 no.2
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• pp.127-140
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• 2003

An investigation into the effect of corner cuts on the Strouhal number of rectangular cylinders with various dimensional ratios and various angles of attack is described. The Strouhal number given as a function of corner cut size is obtained directly from the aerodynamic behavior of the body in a uniform flow through a series of wind-induced vibration tests. For a quick verification of the validity of the Strouhal numbers obtained in this way, they are compared with the approximated the Strouhal numbers based on Shiraishi's early research. The test results show that the Strouhal number of the model with various corner cuts has a fluctuating trend as the angle of attack changes. For each cutting ratio as the angle of attack increases at each cutting ratio above $15^{\circ}$, the Strouhal number decreases gradually, and these trends are more evident for larger corner cut sizes. However, a certain corner cut size which is effective in reducing the wind-induced vibration can be identified by larger Strouhal numbers than those of other corner cut sizes. Three distinct characteristics of Strouhal number variation can be identified in three regions which are termed as Region I, II, and III based on the general trend of the test results. It is also found that the corner cut is effective in one region (Region-II) and less effective in another one (Region-III) when only the vortex-induced vibration occurs.

• Journal of the Mineralogical Society of Korea
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• v.6 no.2
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• pp.145-155
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• 1993

Mineralogical, textural, and chemical changes of chlorite by weathering in anorthosite in the Sancheong district were stucdied using X-ray diffraction, scanning electron microscopy, and electron microprobe analysis. Chlorite in anorthosite corresponds to ferroan clinochlore with IIb structural type. It weatheres firstly to regularly mixed-layered chlorite/vermiculite(C/V) and then, to halloysite without the intermediate stage of vermiculite. Clinochlore packet cleaves and transforms to several thin packets of C/V, which subsequently change to halloysite developint fan-sharped structures by large volume increase. Direct halloysitization of C/V is attributed to the rapid weathering of anorthosite.

• Tunnel and Underground Space
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• v.14 no.2
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• pp.108-120
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• 2004

Dynamic analysis has been increased recently to analyze the effect of the blasting vibration on the rock mass as well as the surrounding structures. The major input parameter far the general dynamic analysis, however, is merely the blasting pressure which can be obtained from the blasting pressure-time history curves. But in case of the complicate geological condition it is not simple to apply the blasting pressure on the numerical analysis because e ground vibration characteristics should be obtained considering the complexity of ground condition. Therefore the authors tried to use the blasting vibration waveform as an input data This vinylation frequency could be obtained from the test blasting in the Pasir mine, Indonesia. Through the dynamic numerical analysis on the slopes in Pasir, the current situation of this slope could be simulated precisely.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.288-295
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• 2005

Many mechanical defects originated from various geological causes make rock mass exhibit anisotropic characteristics. Understanding how the stress distribution occurs in anisotropic rock mass is, therefore, very important for the design of footings on rock and rock structures. In this study, the patterns of elastic stress distribution, developed by acting line load on the surface, in transversely isotropic was investigated. The influence of joint stiffness, joint spacing, and dip angle on the stress distribution was examined. By assuming the Mohr-Coulomb criterion as joint slip condition, the development of joint slip zone was also discussed.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.507-510
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• 2007

Piston cores retrieved from the western Ulleung Basin, East Sea were analyzed to examine the potential for hydrocarbon generation and to determine the hydrocarbon indicators. 2D multi-channel reflection seismic and Chirp data were also investigated for mapping and characterizing the geophysical hydrocarbon indicators such as BSR (bottom simulating reflector), blank zone, pock-mark etc. High organic carbon contents and sedimentation rates that suggest good condition for hydrocarbon generation. High pressure and low temperature condition, and high residual hydrocarbon concentrations are favor the formation of natural gas hydrate. In the piston cores, cracks generally oriented to bedding may indicate the gas expansion. The seismic data show several BSRs that are associated with natural gas hydrates and underlying free gas. A number of vertical to sub-vertical blank zones were well identified in the seismic sections. They often show the seismic pull-up structures, probably indicating the presence of high velocity hydrates. Numerous pockmarks were also observed in the Chirp profiles. They may indicate the presence of free gas below the hydrate stability zone as well.

• The Journal of Engineering Geology
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• v.7 no.1
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• pp.53-62
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• 1997

Fracture mechanics properties of rock materials can he applied to predict the distribution of natural fractures in rock masses, and also to assess the safety of rock slopes and underground structures. In this study, rock fracture toughness and other fracture rrechanics properties of sorne lithologies showing apparently rock-property-controlled distribution of natural fractures were measured. Propagation behaviors of natural and experirnental fractures were also characterized both qualitatively and quantitatively, in terns of the propagation types and sorne statistical parameters. It was concluded that the application of fracture mechanics theories to the ge6logic materials should be based on the geological background and evidences.

• Wind and Structures
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• v.11 no.5
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• pp.413-426
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• 2008

A wind tunnel study has been carried out to determine the influence of spacing between buildings on wind characteristics above rural and suburban type of terrain. Experiments were performed for two types of buildings, three-floor family houses and five-floor apartment buildings. The atmospheric boundary layer (ABL) models were generated by means of the Counihan method using a castellated barrier wall, vortex generators and a fetch of roughness elements. A hot wire anemometry system was applied for measurement of mean velocity and velocity fluctuations. The mean velocity profiles are in good agreement with the power law for exponent values from ${\alpha}=0.15$ to ${\alpha}=0.24$, which is acceptable for the representation of the rural and suburban ABL, respectively. Effects of the spacing density among buildings on wind characteristics range from the ground up to $0.6{\delta}$. As the spacing becomes smaller, the mean flow is slowed down, whilst, simultaneously, the turbulence intensity and absolute values of the Reynolds stress increase due to the increased friction between the surface and the air flow. This results in a higher ventilation efficiency as the increased retardation of horizontal flow simultaneously accompanies an intensified vertical transfer of momentum.

• Journal of Soil and Groundwater Environment
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• v.7 no.2
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• pp.23-33
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• 2002

There are two case history. One is the case of 3 wells-group well system-drilled and artificially hydrofractured for dewatering to help to excavate and treat deep building foundation. The recoveries of groundwater of 3 wells are increased 29%, 42% and 110% respectively through hydrofracturing. Simultaneous pumping test reveals that 3 wells are geohydrologically interconnected considering lowered specific capacity comprising influence of additional drawdown effect by other 2 wells compared to single well test. Response time effect during single well test shows that dorminant lineaments are more expandable to other geological structures. The other one is the case of 28% increasing of groundwater productivity for domestic use by hydrofracturing.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.535-542
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• 2000

The investigated cut-slope is located in Odong-Ri, Hoebuk-Myun, Boeun-Gun and composed of quartzite and phyllitic rocks (approximately 80 meters in length and 25 meters in height). During the investigation, the groundwater which was inferred to the natural pipe of slope was continuously flowing in the upper part of slope. The investigation for discontinuity properties in this area was carried out to decide the rock mass rating and strength parameters. To analyze the stability of cut-slope, lower equal-area hemisphere projection method was used. And laboratory test was done to evaluate engineering properties of soil which was sampled in the non-failure and failure area The inferred causes of cut-slope failure are the geometric relationship between the orientation of cut-slope and geological structures such as joints, faults which is distributed in the slope. And direct cause of failure is the increase of water content due to the heavy rainfall.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.807-814
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• 2004

Land seismic reflection survey has been increasingly demanded in various civil engineering works because of its own ability to delineate layers, water table, to detect cavities or fracture zones, to estimate seismic velocities of each layer. However, our shallow subsurface structures are very complex. The relatively thin layer(mostly soil) to the wavelength directly followed by a basic rock with high impedance used to generate complicated surface waves, kind of channel waves with high amplitude that is dominate in entire seismograms and hence the useful reflection events will be almost hopelessly immersed in the undesired surface waves. Thus, it would seem that the use of traditional seismic survey could not be likely to provide in itself a satisfactory information about our exploration targets. This paper hence introduces an efficient measuring strategy illustrating a properly controlled arrangement of the vertical single force sources commonly used, yielding a very sharply elongated form of P-energy with a minimum of S radiation energy, what we call, P-beam source. Abundant experiments of physical modeling showed that in that way the surface waves could be enormously reduced and the reflection events would be additive and thus reinforced. Examples of field data are also illustrated. The contribution of P-beam source will be great in civil engineering area as well as in general geological exploration area.