• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1512-1519
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• 2005

In this study, the potential for liquefaction in the Incheon international airport was calculated by appling the standard penetration test data and laboratory test data to the modified Seed & Idriss(2001) method. The analysis was performed on the non-plastic silty layer and silty sand layer which within the depth of 20m, below 20 of the standard penetration value(N), and the ground water level. Also, each set of data was mapped by using GIS(geographic information systems) and the factor of safety for the potential for liquefaction was obtained by overlapping those layers. As a result, it was found that there exist potential hazard zone for the liquefaction partially. So, the additional detailed assessments for those are thought to be necessary.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1229-1233
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• 2010

Subsurface investigation results obtained from soils with strong heterogeneity sometimes show a high level of uncertainty about stratigraphy and mechanical characteristics. In these cases, important engineering judgments are dependent on the personal experiences of engineers. However, many of such problems can be solved by applying appropriate statistical approaches. This study introduces the outlier analysis as a one of the statistical solutions and a simple case study is presented as an example.

• 한국해양공학회지
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• 제28권1호
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• pp.47-54
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• 2014

When an anchor penetrates and is installed under a seabed, a portion of the mooring line connected to the anchor is also embedded under the seabed. This embedded mooring line affects the capacity of the anchor in two ways. First, the frictional resistance that occurs between the mooring line and the seabed reduces the pulling force acting on the anchor. Second, the embedded part of the mooring line forms a reverse catenary shape due to the bearing resistance of the soil, so that an inclined pulling force is applied to the anchor. To evaluate the mooring line's effect on the capacity of an anchor in sand, centrifuge model tests were performed using two relative sand densities of 76% and 51% while changing the anchor depths. The test results showed that the load is reduced much more in deep and dense sand, and the inclination angle of the load is lower in shallow and loose sand.

• Environmental Engineering Research
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• 제17권2호
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• pp.111-116
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• 2012

This study investigates the complete removal of nitrate and the recovery of valuable ammonium salt by the combination of nanoscale zero-valent iron (NZVI) and a membrane contactor system. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The main end-product of nitrate reduction by NZVI was ammonia, and the solution pH was stably maintained around 10.5. Effective removal of ammonia was possible with the polytetrafluoroethylene membrane contactor system in all tested conditions. Among the various operation parameters including influent pH, concentration, temperature, and contact time, contact time and solution pH showed significant effects on the ammonia removal mechanism. Also, the osmotic distillation phenomena that deteriorate the mass transfer efficiency could be minimized by pre-heating the influent wastewater. The ammonia removal rate could be maximized by optimizing operation conditions and changing the membrane configuration. The combination of NZVI and the membrane contactor system could be a solution for nitrate removal and the recovery of valuable products.

• 한국해양공학회지
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• 제36권1호
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• pp.11-20
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• 2022

Generally, tsunamis are generated by the rapid crustal movements of the ocean floor. Other factors of tsunami generation include landslides on coastal and ocean floor slopes, glacier collapses, and meteorite collisions. In this study, two numerical analyses were conducted to examine the formation, propagation, and deformation properties of landslide tsunamis. First, LS-DYNA was adopted to simulate the formation and propagation processes of tsunamis generated by dropping rigid bodies. The generated tsunamis had smaller wave heights and wider waveforms during their propagation, and their waveforms and flow velocities resembled those of theoretical solitary waves after a certain distance. Second, after the formation of the landslide tsunami, a tsunami based on the solitary wave approximation theory was generated in a numerical wave tank (NWT) with a computational domain that considered the stability/steady phase. The comparison of two numerical analysis results over a certain distance indicated that the waveform and flow velocity were approximately equal, and the maximum wave pressures acting on the upright wall also exhibited similar distributions. Therefore, an effective numerical model such as LS-DYNA was necessary to analyze the formation and initial deformations of the landslide tsunami, while an NWT with the wave generation method based on the solitary wave approximation theory was sufficient above a certain distance.

• 한국해양공학회지
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• 제27권6호
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• pp.90-94
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• 2013

This paper reports the results obtained for there flection and transmission coefficients on rubble mound breakwaters in Busan Yacht Harbor. A2D physical model test was conducted in the wave flume at the Coastal Engineering Research Laboratory at Pusan National University, Busan, South Korea. In this study, physical model tests were completed to further our understanding of the hydrodynamic processes that surround a rubble mound structure subjected to irregular waves. In particular, the reflection and transmission coefficients, as well as the spectrum transformation, were analyzed. This analysis suggests that with an increase in wave height around a rubble mound, the reflection coefficient drastically increases at each water level (HHW or MSL or LLW). Moreover, when the water level changes from HHW to LLW, the reflection coefficient is suddenly reduced. A further result of the analysis is that the transmission coefficient strongly drops away from the rear of the structure. Finally, in regard to the rubble mound breakwater in Busan Yacht Harbor, a consideration of the reflection and transmission coefficients plays an important role in the design.

• 한국농공학회논문집
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• 제59권5호
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• pp.83-91
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• 2017

Recently, ground subsidence frequently occurs in downtown area. The major causes of the subsidence on the subsurface were the damages of the water supply and sewer pipelines and excavation works in adjacent areas, etc. Because of these various factors, it is not easy to analyze the tendency of occurrence of ground subsidence. The purpose of this study is to clarify the effect of ground subsidence by the change of the fine particle content and ground water level and to establish the ground subsidence mechanism. In this study, a model soil-box was manufactured to simulate the failure of the old sewer pipe which is one of the causes on ground subsidence. And a model test was conducted to investigate the effects of fine contents and ground water level on the cavity occurrence. From the test results, firstly the higher the ground water level, the faster the primary cavity is formed as the seepage stress increases. As a result, the secondary cavity and the ground subsidence rapidly progress due to the relaxation of the surrounding ground. The total amount of discharged soil was decreased as the fine content increased.

• 한국농공학회논문집
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• 제64권6호
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• pp.101-112
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• 2022

Extreme precipitation events have recently become a leading cause of disasters. Thus, investigating the variability and trends of extreme precipitation is crucial to mitigate the increasing impact of such events. Spatial distribution and temporal trends in annual precipitation and four extreme precipitation indices of duration (CWD), frequency (R10 mm), intensity (Rx1day), and percentile-based threshold (R95pTOT) were analyzed using the daily precipitation data of 10 observation stations in Chungcheong province during 1974-2020. The precipitation at all observation stations, except the Boryeong station, showed nonsignificant increasing trends at 95% confidence level (CL) and increasing magnitudes from the west to east regions. The high variability in mean annual precipitation was more pronounced around the northeast and northwest regions. Similarly, there were moderate to high patterns in extreme precipitation indices around the northeast region. However, the precipitation indices of duration and frequency consistently increased from the west to east regions, while those of intensity and percentile-based threshold increased from the south to east regions. Nonsignificant increasing trends dominated in CWD, R10 mm, and Rx1day at all stations, except for R10 mm at Boeun station and Rx1day at Cheongju and Jecheon stations, which showed a significantly increasing trend. The spatial distribution of trend magnitude shows that R10 mm increased from the west to east regions. Furthermore, variations in precipitation were very strongly correlated (99% CL) with R10 mm, Rx1day, and R95pTOT at all stations, except with wR10 mm at Cheongju station, which was strongly correlated with a 95% CL.

• 한국농공학회논문집
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• 제58권3호
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• pp.1-12
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• 2016

The objective of this study is to analyze the relationship between stream water quality of TN (total nitrogen), TP (total phosphorus), and BOD (Biochemical Oxygen Demand) and TDI (Trophic Diatom Index) score determined by physico-chemical factors, biomass, and standing crops of epilithic diatoms, and to estimate the required amount of ecological streamflow for good water environment of Trophic Diatom. For the main stream of Chungju dam watershed of South Korea, total 100 field data of 3 years (2008~2010) measured in May and September were used to derive the relationship between water quality and TDI. Trophic Diatom had high correlation (0.55 determination coefficient) with TN. Using the relationship, the required streamflow was evaluated by using the Soil Water Assessment Tool (SWAT) for good Trophic Diatom water environment through T-N water quality maintenance. The SWAT simulated 8 years (2003~2010) stream discharges and T-N water quality along the main stream. From present garde C (score range: 30.0~45.0) to grade A (score above 60.0) of TDI, the May needs additional streamflow of $63.1m^3/sec$ (+36.7 % comparing with the present streamflow of $172.0m^3/sec$) at the watershed outlet.

• 대한환경공학회지
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• 제28권6호
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• pp.661-666
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• 2006

칼슘함량이 낮은 F급 플라이 애쉬와 알칼리 활성화 용액으로 구성된 페이스트의 압축강도 특성에 대한 연구를 수행하였다. 수산화나트륨과 물유리 그리고 물을 혼합하여 제조한 이들 활성화 용액은 매우 높은 $OH^-$ 농도를 가지고 있다. 알칼리 활성화 용액의 조성과 온도는 플라이 애쉬-시멘트 페이스트의 압축강도 발현에 대한 현저한 영향 인자임을 보여주었다. 50 MPa 이상의 압축강도는 플라이 애쉬를 각각 $60^{\circ}C$에서 48시간과 $85^{\circ}C$에서 24시간 양생하여 얻었다. 본 연구결과, F급 플라이 애쉬/NaOH/물유리의 무게 비율 25:8:2와 활성화 용액/플라이 애쉬의 무게 비율 0.6/1.0은 높은 강도를 가진 페이스트를 위한 적정 혼합비율로 나타났다.