• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.65-76
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• 2009

The unsaturated characteristics of Korean weathered granite soils have been studied to investigate the influence of saturated permeability, rainfall intensity and soil-water characteristic curve (SWCC) on the slope stability. The upper, average and lower SWCCs were estimated from the publication and experimental results using the statistical concept. The roughly estimated SWCC can be used for the soils without experimental results by relating SWCC with the particle size distribution curve. An appropriate ratio between the saturated permeability and the rainfall intensity ($k_s$/i) was also suggested for practical use in designing the slopes by investigating the time-dependent variation of slope instability during the rainfall. The slope stability was deteriorated from the initiation of rainfall and recovered again after the factor of safety reached the critical value. The FS of the slope decreased at first and then increased after reaching the critical value during the rainfall. As a result, the slope instability was not related with an absolute rainfall intensity but with the ratio between the saturated permeability and the rainfall intensity. In case of the upper SWCC, the critical condition occurred when the ratio between the saturated permeability and the rainfall intensity was in the range of $1.0{\sim}2.0$.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.98-105
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• 1997

Compacted clay materials are often used to form barriers for waste disposal by means of landfill. The performance of clay barrier depends on its permeability characteristics under the site environments. The study discusses permeability characteristics of 4 types of permeants through a compacted clayey soil. Permeabilities are measured using the modified rigid-wall permeater and with water, PEG, Ethanol, and TCE, ranging 80 to 3.4 of dielectric constants. Results of the study are as follows : 1) Absolute permeabilities of Ethanol and TCE that their dielectric constants are lower than that of water are $K=1.0{\times} 10^{-12} cm^2$, and $5.8{\times} 10^{-12} cm^2$, respectively, that is, 1.67, and 9.67 times of permeability of water, respectively. Absolute permeability and dielectric constant of water are $K=6{\times} 10^{-13} cm^2$, and 80, respectively. 2) Changes in absolute permeability of Ethanol and TCE converge to a constant after 3.5 pore volume of permeant flows through the clay sample. This can be explained that diffuse double layer of clay is no longer reacted with permeants and contracted their pores. However there is no change in absolute permeability when water is used as a per-meant. 3) It is found that absolute permeability in reversely proportional to the value of dielectric constant of the permeants. Change in absolute permeability of the permeants with 40 or over of dielectric constant is not significant. However change in absolute permeability of the permeant with 30 or lower dielectric constant is abruptly increased. 4) A lower absolute permeability of PEG is found because of its high viscosity.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.149-149
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• 2011

청정 에너지원으로 높은 잠재력을 가지고 있는 가스하이드레이트는 상업적 기술개발이 미확보된 상태임에도, 우리나라에서 부존이 직접적으로 확인되었기 때문에 에너지원으로서 그 중요성이 부각되고 있다. 현재 전세계적으로 가스하이드레이트 개발 및 생산에 관한 연구가 활발히 진행되고 있으며 이에 대한 기초자료로서 가스하이드레이트가 함유된 퇴적층의 물성자료가 필요하다. 이에 따라 본 연구에서는 입도 분포별 총 5가지의 미고결 시료를 대상으로 투과도, p파속도, 전기비저항 측정을 수행하였다. 연구에 사용된 미고결 시료는 Hama#5($774{\mu}m$), #6($485{\mu}m$), #7($258{\mu}m$), #8($106{\mu}m$) 4가지와 Hama#6과 Hama#7을 1:1($371{\mu}m$)로 혼합하여 사용하였다. 실험에 사용된 장비는 가스하이드레이트를 인공적으로 생성시키기 위해 퇴적층을 모사할 수 있는 고압셀과 자료획득장비, 유체 주입장비, 온도 유지장비이다. 또한 투과도 측정에는 차압계, 전기비저항 측정에 RLC meter, p파속도 측정에 음파 송수신장비를 사용하여 각각의 물성을 측정하였다. 실험과정을 단계별로 요약하면 먼저 시료를 고압셀에 충진한 뒤 주입된 물의 양으로부터 공극률을 측정하고, 절대 투수계수를 측정하였다. 그 후, 메탄가스를 주입하여 퇴적층 내 수포화도(water saturation)를 잔류상태(irreducible saturation)로 유지시키고 메탄가스를 추가적으로 주입하여 원하는 압력까지 가압한 뒤 온도를 $1^{\circ}C$로 낮추었다. 가스하이드레이트의 생성은 급격한 압력강하로부터 알 수 있다. 최종적으로 가스하이트레이트가 함유된 퇴적층의 상대 투수계수를 측정하기 위해 메탄가스를 주입하였고 각각의 측정장비를 통해 전기비저항 및 p파 속도를 측정하였다.$V_g$, $V_h$, $V_w$, $V_ss$는 각각 가스의 부피, 하이드레이트의 부피, 물의 부피, 모래의 부피이다. 또한 수포화도, $S_w=\frac{V_w}{V_v}$이며 하이드레이트 포화도, $S_h=\frac{V_w}{V_v}$, 가스 포화도, $S_g=\frac{V_g}{V_v}$로 정의된다. 본 실험의 결과 투과도는 가스의 부피비, $\frac{V_g}{V}=nS_g$에 민감한 반응을 보였으며, 비저항은 공극수의 부피비, $\frac{V_w}{V}=nS_w$에 민감한 반응을 보였다. 또한 p파 속도는 고체의 부피비, $\frac{V_s+V_h}{V}=n(1-S_h)$에 민감한 반응을 보였다. 이러한 실험의 결과는 가스하이드레이트 개발, 생산 연구에 있어 기초 물성자료로 활용되는데 도움을 줄 것이다.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.83-93
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• 1997

The purpose of the study is to analyze the sensitivity of the parameters that affect the runoff and water quality in the studied drainage basins. SWMM model is applied to the four drainage basins located at Namgazwa and Sanbon in Seoul and Gray Haven and Kings Creek in the USA. first of all, the optimum values of the parameters which have least simulation error to the observed data, are detected by iteration procedure. These are used as the standard values which are compared against the procedure. These are used as the standard values which are compared against the varied parameter values. In order to catch the effectiveness of the parameters to the computing result, the parameters are changed step by setp, and the results are compared to the standard results in flowerate and quality of the sewer. The study indicates that the discharge is greatly affected by the types of runoff surface, i.e., impervious area remarkably affects the peak flow and runoff volume while the surface storage affects the runoff volume at mild sloped basins. In addition, the major parameters affecting the pollution concentrations and loadings are the contaminant accumulation coefficient per unit area per time and the continuous dry weather days. Furthermore, the factors that affect the water quality during the initial rainfall period are the rainfall intensity, transport capacity coefficient and its power coefficient. Consequently, in order to simulate the runoff-water quality, it is needed to evaluate previous data in the research performed for the studied basins. To accurately estimated from the tributary areas and the rational computation methods of the pollutants calculation should be introduced.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.245-253
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• 2001

To investigate the effects of hydromechanical and textural characteristics of sediment deposits on the cultivation of Manila clam, Ruditapes philippinarum surface and sub-surface core sediments were collected seasonally in Gomso tidal flat. Grain size distribution were analyzed to investigate the annual variation of sediment texture. In winter unimodal distribution of grain size with the peak at $5\phi$ is dominant However, during the summer sediment texture become a little bit coarser and grain size distribution shows the peaks at $4\~5 \phi$. Optimum sediment texture for the cultivation of manila clam, R. philippinarum was found to be sandy silt in which mean Brain size was between 4 and $5 \phi$ with the sand content less than $50\%$ and clay content of $5\~10\%$. Mechanical and hydrological characteristics of sediment deposits were also studied in the laboratory and the results were applied to the numerical simulation for the behavior of surface sediment subjected to the cyclic loading from sea-water level change. Results of numerical simulation illustrate that the permeability of sediment had to be maintained in the range of $10^{-11}\sim10^{-12}m^2$ to ensure the proper sedimentological environment for the cultivation of manila clam, R. philippinarum. The deposits of virtually impermeable mud layer, with the threshold thickness of 4 cm, would be very hazardous to clam habitat.