• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1571-1580
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• 2008

Subsea tunnels that link land to island and among nations for transportation, efficient development of limited surface and pursuit of economic development should be designed to support pore water pressure on the lining. It is generally constructed in the bed rock of the sea bottom. When the tunnel excavation face meets fractured-zones below sea bottom, collapse may occur due to an increase of pore water pressure and large inflow. Such an example can be found in the Norwegian subsea tunnel experiences in 1980's. In this study hydraulic behavior of tunnel heading is investigated using numerical method based on the collapse of Norwegian subsea tunnel. The effect of pore water pressure and inflow rate were mainly concerned. Horse-shoe shaped model tunnel which has 50 m depth from the sea bottom is considered. To evaluate hydraulic performance, parametric study was carried out for varying relative permeability. It is revealed that pore water pressure has increased with an increase of sea depth. Especially, at the fractured-zone, pore water pressure on the lining has increased significantly. Inflow rate into tunnel has also increased correspondingly with an increase in sea depth. S-shaped characteristic relation between relative permeability and normalized pore water pressure was obtained.

• Journal of Environmental Science International
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• v.22 no.8
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• pp.953-963
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• 2013

Reliable long-term streamflow forecasting is invaluable for water resource planning and management which allocates water supply according to the demand of water users. Forecasting of seasonal inflow to Andong dam is performed and assessed using statistical methods based on hydrometeorological data. Predictors which is used to forecast seasonal inflow to Andong dam are selected from southern oscillation index, sea surface temperature, and 500 hPa geopotential height data in northern hemisphere. Predictors are selected by the following procedure. Primary predictors sets are obtained, and then final predictors are determined from the sets. The primary predictor sets for each season are identified using cross correlation and mutual information. The final predictors are identified using partial cross correlation and partial mutual information. In each season, there are three selected predictors. The values are determined using bootstrapping technique considering a specific significance level for predictor selection. Seasonal inflow forecasting is performed by multiple linear regression analysis using the selected predictors for each season, and the results of forecast using cross validation are assessed. Multiple linear regression analysis is performed using SAS. The results of multiple linear regression analysis are assessed by mean squared error and mean absolute error. And contingency table is established and assessed by Heidke skill score. The assessment reveals that the forecasts by multiple linear regression analysis are better than the reference forecasts.

• Journal of Korea Water Resources Association
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• v.52 no.7
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• pp.451-461
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• 2019

The dam reservoir inflow prediction is utilized to ensure for water supply and prevent future droughts. In this study, we predicted the dam reservoir inflow and analyzed how seasonal weather forecasting affected the accuracy of the inflow for even multi-purpose dams. The hindcast and forecast of GloSea5 from KMA were used as input for rainfall-runoff models. TANK, ABCD, K-DRUM and PRMS models which have individual characteristics were applied to simulate inflow prediction. The dam reservoir inflow prediction was assessed for the periods of 1996~2009 and 2015~2016 for the hindcast and forecast respectively. The results of assessment showed that the inflow prediction was underestimated by comparing with the observed inflow. If rainfall-runoff models were calibrated appropriately, the characteristics of the models were not vital for accuracy of the inflow prediction. However the accuracy of seasonal weather forecasting, especially precipitation data is highly connected to the accuracy of the dam inflow prediction. It is recommended to consider underestimation of the inflow prediction when it is used for operations. Futhermore, for accuracy enhancement of the predicted dam inflow, it is more effective to focus on improving a seasonal weather forecasting rather than a rainfall-runoff model.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.249-258
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• 2014

Phytoplankton species composition and ecological index (diversity, evenness, richness and dominance) were analysed from April 2013 to March 2014 at 10 stations of cupped oyster, Crassostrea gigas culture area in Iwon coast, Korea. Seasonal and positional variation of phytoplankton standing crops, biomass, dominant species and water quality were distinctively different according to occasionally inflow of Iwon dam reservoired water. The composition of phytoplankton species were Bacillariophyceae 98, Dinophycease 22, Chlorophycease 13, Cyanophyceae 8, Silicofalgellate 4, Euglenophyceae 2, Cryptophyceae 1 species. The most dominant species was Bacillariophyceae as 64.0%. The highest biomass of phytoplankton recorded in September as $40,910{\times}10^3$ cell/L at the station 1, near from inland water inflow area. Ecological indices (diversity, richness, evenness, and dominance index), used for structural change of phytoplankton community and water quality (temperature, dissolved oxygen, salinity) showed difference of spatiotemporal property also.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.22-28
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• 2004

A mathematical model has been developed to evaluate the capability of sea water exchanges under tidal and diffusive environments and has been verified through comparison with numerical experiments. From the mathematical analysis, this study presents the rates of sea water exchanges due to the tidal inflow and diffusion process. The port characteristic length $L_p$ is the most significant evaluation index.

• Journal of the korean society of oceanography
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• v.33 no.3
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• pp.41-52
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• 1998

A seasonal circulation pattern in the eastern Yellow Sea (EYS) is suggested from the water mass analysis and geostrophic calculation using the hydrographic data collected by National Fisheries Research and Development Institute during the years of 1970 to 1990. This research focuses on the presence of inflow of warm (and saline) waters into EYS in summer. EYS is divided into two regions in this paper: the west coast of Korea (WCK) and the central Yellow Sea (CYS). In CYS, waters are linked with warm waters near Cheju Island in winter, but with cold waters from the north in summer (in the lower layer). It is not simple to say about WCK because of the influences of freshwater input and tidal mixing. Nevertheless, water mass analysis reveals that along WCK, waters have the major mixing ratios (40-60%) of warm waters in summer, while the dominant mixing ratios (50-90%) of cold waters in winter. Such a seasonal change of water mass distribution can be explained only by seasonal circulation. In winter, warm waters flow northward into CYS and cold waters flow southward along WCK. In summer, warm waters flow northward along WCK and cold waters flow southward into CYS. This circulation pattern is supported by both statistical analysis and dynamic depth topography. Accordingly, Yellow Sea Warm Current may be defined as the inflow of warm waters to CYS in winter and to WCK in summer.

• Ocean and Polar Research
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• v.28 no.2
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• pp.153-161
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• 2006

To investigate inflow path of the East Sea Intermediate Water (ESIW) into the Ulleung Basin, hydrographic data surveyed in July 2005 were analyzed. The ESIW was characterized by the Salinity Minimum Layer (SML) within a depth range of 100 to 360 meters. Averaged potential temperature and salinity of the SML were $1.835^{\circ}C$ and 34.049 psu, respectively. Mean potential density $({\sigma}_{\theta})$ of the SML was 27.221 with a standard deviation of 0.0393. On isopycnal surfaces of 27.14 and 27.18 $({\sigma}_{\theta})$ which correspond to upper layers of the ESIW, the coastal low salinity water was separated from the offshore low salinity water by the relatively warm and saline water which might be affected by the Tsushima Warm Current Water. Relatively cold and fresh water, however, intruded into the Ulleung Basin from the region of Korean coast on isopycnal surfaces of 27.22 and 27.26 which was lower layer of the ESIW. The salinity distribution in the isopycnal layer of $27.14{\sim}27.26$ with acceleration potential on 27.22 up surface also showed clearly that the low salinity water flowed from the coastal area and intruded into the Ulleung Basin. This implies that the ESIW flows ken the north to the south along the east coasts of Korea and spreads into the Ulleung Basin in summer.

• Journal of Environmental Science International
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• v.14 no.4
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• pp.397-404
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• 2005

In order to study the temporal variations of nutrients and chlorophyll-a in the Bottol Bada, three field observations were carried out on 20, 23 and 26 July, 2004. The low N:P values exhibit nitrogen deficiency during the periods of observation. This result is not representative of typical summer environment in the southern coast of Korea. The possible mechanisms are as follows: 1) The freshwater inflow was not sufficient for the supply of nitrogen because the total precipitation was 11.9 mm in July, 2004. This amount is no more than $5\%$ in normal precipitation in July. 2) There was an inflow of oceanic water under the subsurface into the Bottol Bada. Even though the oceanic water comprises more nutrients, it produces the stratification between the surface and the subsurface water and seems to prevent the supply of nutrinets to the surface layer. 3) The high chlorophyll-a concentration of $1.2 {\cal}ug/L$ was shown near the narrow channel between Gae-do and Geumo-do. This seems to be resulted from the inflow of water from Gamak Bay.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.463-473
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• 2017

Bentonite swells when it comes into contact with water and makes it a viscous fluid. Thus it is widely used in civil engineering works for waterproofing. Utilizing the properties of bentonite, the slurry shield TBM supports excavated face with pressurized slurry as well as transporting excavated muck. When bentonite is in contact with seawater, due to the change of double layer thickness, its expandability and viscosity are lowered. This may cause problems for excavation stability and muck discharge due to the increase of sea water inflow when Slurry TBM is used under sea water conditions. In this study, the change of slurry condition caused by the inflow of sea water during tunnel excavation with Slurry TBM was investigated and a slurry management guideline was proposed. For this purpose, a laboratory test was carried out based on the slurry management criterions applied in the field, and a method applicable to the field where sea water is affected has been proposed.

• KCID journal
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• v.7 no.1
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• pp.8-18
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• 2000

The variations of water quality due to inflow of sea water by gate operation were observed in Sihwa Lake. The distributions and concentration of salinity, temperature, dissolved oxygen, nutrient were investigated from Feb. 1997 to Jul. 1998. The salinity