• Geotechnical Engineering
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• v.14 no.3
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• pp.123-134
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• 1998

To analyse the stability of a slope composed of waste material produced in a closed lead mine, numerical modeling has been carried out in two dimension using FLAC, finite difference program. The research was focused on the effect of the earthquake as well as a rise of water table upon slope stability. The numerical results have shown that the slope would not be safe against earthquake event and that the increase of pore pressure due to a rise of water table up to the ground level may result in a failure of the slope. On the basis of numerical analyses and site investigation, two sorts of measures have been taken. In short term, removal of a part of materials deposited on the top of the pile is required to increase immediately safety factor of the slope even a little. In ling term, it is necessary to repair drainage facilities and dam which covers waste material so that the slope is prevented from failure in a radical manner. It has been confirmed by numerical analyses that an improvenment of the stability can be in a great extent expected after such measures have been performed.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.81-92
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• 2011

In order to understand evaluation of the seismic stability of a fill dam, we made chambers of 1:100, 1:70, and 1:50 (the ratio of the miniature), considering the law of similarity based on drawings of three representative cross sections. And we measured an increase in acceleration, excess pore water pressure, and vertical/horizontal displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the stability and interaction between the ground, the structure, and fluids based on the measurements. As a result, we could observe that displacement of the target cross section was relatively small compared to the allowed level of 30 cm, ensuring proper stability for an earthquake. Regarding the acceleration measurements, the increase rate was 20% for Hachinohe wave and Ofunato wave but 30% for the artificial wave. With respect to the excess pore water pressure, it was lower than 1 (which is the permissible ratio for liquefaction) ensuring proper stability as well.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.2-11
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• 2006

In the processes of hydrological cycle, when precipitation reaches the ground surface, water may become surface runoff or infiltrate into soil and then possibly further percolate into groundwater aquifer. A part of the water is returned to the atmosphere through evaporation and transpiration. Soil moisture dynamics driven climate fluctuations plays a key role in the simulation of water transfer among ground surface, unsaturated zone and aquifer. In this study, a one-layer canopy and a four-layer soil representation is used for a coupled soil-vegetation modeling scheme. A non-zero hydraulic diffusivity between the deepest soil layer modeled and groundwater table is used to couple the numerical equations of soil moisture and groundwater dynamics. Simulation of runoff generation is based on the mechanism of both infiltration excess overland flow and saturation overland flow nested in a numerical model of soil moisture dynamics. Thus, a comprehensive hydrological model integrating canopy, soil zone and aquifer has been developed to evaluate water resources in the plain region of Huaihe River basin in East China and simulate water transfer among precipitation, surface water, soil moisture and groundwater. The newly developed model is capable of calculating hydrological components of surface runoff, evapotranpiration from soil and aquifer, and groundwater recharge from precipitation and discharge into rivers. Regional parameterization is made by using two approaches. One is to determine most parameters representing specific physical values on the basis of characterization of soil properties in unsaturated zone and aquifer, and vegetations. The other is to calibrate the remaining few parameters on the basis of comparison between measured and simulated streamflow and groundwater tables. The integrated modeling system was successfully used in the Linhuanji catchment of Huaihe plain region. Study results demonstrate that (1) on the average 14.2% of precipitation becomes surface runoff and baseflow during a ten-year period from 1986 to 1995 and this figure fluctuates between only 3.0% in drought years of 1986, 1988, 1993 and 1994 to 24.0% in wet year of 1991; (2) groundwater directly deriving from precipitation recharge is about 15.0% t of the precipitation amount, and (3) about half of the groundwater recharge flows into rivers and loses through evaporation.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1257-1271
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• 2014

The hydraulic deterioration of the drainage system in tunnel linings is one of the main factors governing long-term lining-ground interactions during the lifetime of tunnels. Thus, in the design procedure of a tunnel below the groundwater table, the possible detrimental effects associated with the hydraulic deterioration should be addressed. Hydraulic deterioration in double-lined tunnels can occur because of reasons such as clogging of the drainage layer and drain-pipe blockings. In this study, the coupled mechanical and hydraulic interactions between linings due to drain-pipe blockings are investigated using the finite-element method. A double-lined structural model incorporating hydraulic behavior is developed to represent the coupled structural and hydraulic behavior between the linings and drainage system. It is found that hydraulic deterioration hinders flow into the tunnel, causing asymmetric development of pore-water pressure and consequent detrimental effects to the secondary lining.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.399-403
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• 2005

Slope angle, ground water table and thickness of soils are the key factors affecting landslide stability. However examining the factors such as thickness of soils; geological structure, slope angle, and height, in order to use the global landslide susceptibility forecasting analysis is very expensive and time consuming effort. So most researchers prefer to use the simplest methods such as the C strata and the USGS methods. In this research thickness of soils was calculated using these two methods and stability analysis was performed with the thickness of soils calculated by the two methods at the SINMAP based on ArcView 3.2. The two safety factor maps were compared with the past landslide records. The thickness of soils calculated by USGS method showed more unstable safety factors.

• Journal of Plant Biology
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• v.16 no.3_4
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• pp.1-6
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• 1973

The distribution of plant communities along the Bukhan Riverside in Chun-seong was studied by means of the methods fo Curtis and Pattern. The communities were arranged in a single-dimensioned ordination on the basis of the importance values of the persistent species. Leading dominant species, form the 'low' level to the 'high' levels of the ordination gradient, were Phalaris arundinacea, Salix gilgiana, Artemisia feddei, Zoysia japonica, Pennisetum japonicum, and Arundinella hirta. These species from a continuum from the river to the dry grassland depending upon available soil-moisture. Standing crops in terms of dry weight and the nitrogen content of the above-ground parts of these species showed a good relationship with gradients of available soil-moisture.

• Economic and Environmental Geology
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• v.25 no.4
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• pp.373-378
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• 1992

Ores of the Nohwa Pyrophyllite Deposits are composed mainly of pyrophyllite, kaolinite (dickite), quartz, pyrite, alunite and diaspore, etc. Alunite ore zone is located in the middle-lower parts of the deposits. Alunite ore zone with thickness of 20~30 cm is divided into two parts according to alunite contents: reddish and white greyish zone in the upper and lower parts, respectively. And the reddish alunitic ore has higher contents $Al_2O_3$, $K_2O$, $Na_2O$ and Ig.loss than the white greyish alunitic ore. Perhaps alunitization of the deposits occurred in the vicinity of paleo-ground water table. EPMA data shows that sodium replaces potassium considerably in alunite structures and that the hydrothermal solution probably contains considerable amounts of sodium.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.401-409
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• 2003

Recently, the development of underground structures is to be inevitably necessary due to the increase in population and traffic volume that has caused to the limit of urban land use and the heavy traffic jams. Therefore, underground structures such as subway, underground shopping centers, lifeline facilities and so on, have been increasingly constructed, On the other hand, several social problems have occurred during construction, i.e., ground subsidence, noise, and vibration. Therefore, safer and more beneficial methods for underground construction are on the demand. In this research, N.T.R.(New Tubular Roof) method has been modified and utilized for solving those problems and overcoming the difficulties connected with the bored tunnel construction of large underground openings in unfavorable ground, often under the water table, and with overburdens that are too shallow to solve problems of stability using traditional methods. The N.T.R. method has been modified to suit for Korean geotechnical conditions, and was made up for the weak points-the water leakage from walls and tops, the maintenance and the lack of stability-of the conventional methods. This paper dealt with the features and the applicability of N.T.R. Method based on the results from numerical analysis and data from in-situ monitoring system.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.349-356
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• 2015

Although geophysical methods are useful and generally provide valuable information about the subsurface, it is important to recognize their limitations. A common limitation is the lack of sufficient contrast in physical properties between different layers. Thus, multiple methods are commonly used to best constrain the physical properties of different layers and interpret each section individually. Ground penetrating radar (GPR) and shallow seismic reflection (SSR) methods, used for shallow and very shallow subsurface imaging, respond to dielectric and velocity contrasts between layers, respectively. In this study, we merged GPR and SSR data from a test site within the Cheongui granitic mass, where the water table is ~3 m deep all year. We interpreted the data in combination with field observations and existing data from drill cores and well logs. GPR and SSR reflections from the tops of the sand layer, water table, and weathered and soft rocks are successfully mapped in a single section, and they correlate well with electrical resistivity data and SPS (suspension PS) well-logging profiles. In addition, subsurface interfaces in the integrated section correlate well with S-wave velocity structures from multi-channel analysis shear wave (MASW) data, a method that was recently developed to enhance lateral resolution on the basis of CMP (common midpoint) cross-correlation (CMPCC) analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.606-613
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• 2004

One of the major forces that causes landslide is the amount of underground water resulted from rainfall and shear strength. As a result of close study on the landslide area affected by typoon Rusa it is observed that many landslides took place at the interface of rock and soil. Based on this observation that shear strength at the interface played a great role in landslide of the hilly area, two shear strengths were measured on different places, one at the interface between rocks and soil and the other just on soil. The two values thus derived were compared and used to review the safety factor for the hilly areas already collapsed. Back analysis was also used to calculate the ground water table according to the different rock types at the time when degradation happened.