• The Journal of Engineering Geology
• /
• v.19 no.1
• /
• pp.9-14
• /
• 2009

In this work applicability of a sharp-interface model to well-scale problems is examined. In coastal areas one of the main concerns in groundwater development is saltwater intrusion. To determine the saltwater intrusion at a well one needs to evaluate the saltwater content from a pumping well. We conducted laboratory sand-tank experiments to determine if a sharp-interface model can simulate the saltwater content of a pumping well. Lateral saltwater intrusion experiments and freshwater lens experiments are conducted. A partially penetrating well and a fully penetrating well are used. Comparison between numerical results and observation results indicates that the sharp-interface model can determine saltwater contents reasonably well. We conclude that a sharp-interface model can be applied to well-scale groundwater flow problems in coastal areas.

• Journal of Korea Water Resources Association
• /
• v.50 no.6
• /
• pp.387-395
• /
• 2017

Sea level rise, accompanied by climate change, is expected to exacerbate seawater intrusion in the coastal groundwater system. As the salinity of saturated groundwater increases, salinity can increase even in the unsaturated soil above the groundwater surface, which may cause crop damage in the agricultural land. The other adverse impact of sea level rise is reduced unsaturated soil thicknesses. In this study, a composite model to assess impacts of sea level rise in coastal agricultural land is proposed. The composite model is based on the combined applications of a three dimensional model for simulating saltwater intrusion into the groundwater and a vertical one dimensional model for simulating unsaturated zone flow and transport. The water level and salinity distribution of groundwater are calculated using the three dimensional seawater intrusion model. At some uppermost nodes, where salinity are higher than the reference value, of the 3D mesh one dimensional unsaturated zone modeling is conducted along the soil layer between the ground water surface and the ground surface. A particular location is judged salinized when the concentration at the root-zone depth exceeds the tolerable salinity for ordinary crops. The developed model is applied to a hypothetical agricultural reclamation land. IPCC RCP 4.5 and 8.5 scenarios were used as sea level rise data. Results are presented for 2050 and 2100. As a result of the study, it is predicted that by 2100 in the climate change scenario RCP 8.5, there will be 7.8% increase in groundwater saltwater-intruded area, 6.0% increase of salinized soil area, and 1.6% in increase in water-logging area.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.90-90
• /
• 2019

본 연구에서는 SWASH(Simulating WAves till SHore) 모형의 염분분포 해석의 정확성을 평가하기 위해 Goswami et al.(2007)의 모형실험을 재현하였다. SWASH모형은 Delft 대학에서 개발된 비정수압수치모형으로 연직방향으로 층(layer)을 나누어 자유수면변위를 정확하게 예측하고 표준 ${\kappa}-{\varepsilon}$ 난류모델을 이용해 염분, 온도 및 침전물 등의 난류확산을 계산한다. 우선 Goswami et al.(2007)의 모형실험 중 정상상태의 모형실험을 이용해 층수에 따른 수치모형의 정확도를 평가하였다. SWASH 모형의 층수를 늘리며 수치모의를 수행한 결과, 층수가 늘어날수록 종, 횡 방향의 염분농도 분포가 정확하게 나타나는 것을 확인하였다. 추가로 SWASH 수치모형을 이용해 염수침투 및 후퇴 상태의 모형실험도 수치모의하였다. 염수의 공급에 따라 시간에 따른 염분농도 분포가 변화하는 것을 확인하였다. 또한 연직방향의 층수가 많은 경우 모형실험의 결과와 비교적 잘 일치하는 것을 확인할 수 있다. 따라서 연직방향의 층수를 늘려감에 따라 수심방향으로 더 정밀한 염분분포 해석이 가능하다는 것을 알 수 있다. 그러나 연직방향으로 많은 층을 나눈 경우 계산시간이 증가하기 때문에 수심이 작거나 연직방향의 염분농도 분포가 중요하지 않은 경우라면 적절한 층수(5~10 layer)를 고려해 수치모의를 수행하는 것이 시간과 비용측면에서 더욱 경제적이라고 할 수 있다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.1
• /
• pp.56-63
• /
• 2016

This experiment was compared and analyzed between the original surface paint through chloride penetration, neutralization, freeze-thaw and chemical corrosion resistance measuring internal structure and volume of voids in order to evaluate the effect of increase in durability of the newly modeled nano synthesized polymer paint painted on concrete surface which results improvement on air permeability to increase the durability of concrete structures. The test result of measuring volume of void and inner structure, concrete, spreaded with nano synthesized polymer paint, showed decreasing trend of pore volume in the range of less than $0.1{\mu}m$ and more than $0.3{\mu}m$. Also, using an electron microscope inside showed tightness of hydration texture. Chloride penetration depth of concrete, painted with nano synthesized polymer paint, was decreased more than 92% compared to non-painted concrete and 70% with water-based epoxy painted concrete. Especially, chemical corrosion resistance test set with aqueous solution of 5% sulfuric acid, non-painted concrete and water-based epoxy painted concrete showed weight loss of 4% after dipping for 12 days. On the other hand, concrete painted with nano synthesized polymer paint showed 1.7% weight loss under the same condition. Also, it showed great result of appearance under the criteria of Tsivilis et al.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.29 no.4
• /
• pp.106-116
• /
• 1987

미국 Utah주의 huntington 화력발전소에서 냉각수를 사용하고 버리는 염분농도가 4mmhos/cm 정도로 높아 자연하천으로 그대로 방류 시킬 수 없으며, 미 환경법에 따라 안전처리후 방류할 수 있다. 따라서 이 염분발생 처리방법의 하나로 보리, 밀, 옥수수, 감자 그리고 알팔파등 사료작물의 관개용수로 이용할 수 있는 방법이 장기간 시험연구되고 있다. 현재로서는 이 방법이 경제적인 것으로 평가되고 있으나 장기적으로 이 염분폐수로 인한 토양의 성질변화 작용의 생산량 감소등에 미치는 영향을 구명하기 위해서 1977년에 시작하여 8년 연속 연구사업으로 진행되고 있다. 본 논문에서는 지난 8년간(1977~1984년)의 관측.조사자료를 이용하여 염분 관개용수가 장기적으로 생산량 추정과 계획예측을 위한 자발성과 토양수분변화를 추정할 수 있는 모형에 의하여 연구한 결과를 요약하면 다음과 같다. 1. EC 4mmhos/cm의 염분 관개용수로 8년간 장기간 추출한 결과, 추출용수의 양에 관계내 염분축적은 예상보다 서서히 진행되었으며, 이 염분축적이 작물의 생산량 감소의 주원인은 아니었다. 2. 지난 2년간의 관측 결과, 염분 관개용수에 함유된 10ppm정도의 요소가 작물 특히 보리, 옥수수, 감자등의 생산량 감소의 주원인 것으로 판단된다. 염분용수 진개구에는 하천수 보다 20배가 많은 요소가 축적돼 있었으며, 이는 요소가 토양내에 잘 침투되며, 토양으로 부터 요소를 용달시키려는 염분을 용달시킬 때 보다 후러씬 더 많은 용달용수를 필요로함을 뜻한 작물들의 면요소성을 구명하기위한 모형개발이 요구된다. 3. 염분관개용수로 관개할 때 보리, 옥수수, 감자등의 작물 생산량과 풍작물 생산량은 현저하게 감소하였다. 보리, 옥수수의 염분용수에 의한 생산량과 하천수에 의한 생산량과의 비는 풍건물의 경우 0.6, 매물의 경우 0.5였으며 감자의 경우는 0.2이하였다. 4. 염분용수 관개구와 하천수 관개구의 모든작물에서 풍건물 생산량과 축배량 사이에는 강한 직선적인 관계를 보였다. 보리, 감자의 작물 생산량과 축배량사이에도 선형의 관계가 성립되었으나, 밀과 옥수수의 매물 생산량과 축배량사이에는 곡선적인 관계를 나타내었다.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2005.05a
• /
• pp.59-64
• /
• 2005

Although experimental analysis for groundwater sample at wells located systematically are very effective to delineate seawater intrusion region at coastal area, this method is restricted in few wells and time. We have conducted electrical resistivity sounding at 30 points in the study areas to analyze the region of seawater intrusion and found the boundary between salt wedge and fresh water lens from the analysis results of geostatistical method using variogram for one-dimensional inversion results. The methodology adopted in this study would be useful for finding the seawater intrusion region and evaluating quantitatively.

• Economic and Environmental Geology
• /
• v.42 no.3
• /
• pp.235-246
• /
• 2009

High-saline ground water, whose eclectrical conductivity value ranges from 12,000 to 21,000 $\mu$S/cm, occurs at the small catchment of Gilsan stream near Geum-river estuary dike. These high-saline ground water comes form three different aquifers consisting of two horizons of sand sediments and one weathered zone with top part of unconformity. For these three aquifers showing mutual independence in terms of hydrogeological and hydrogeochemical connection, we examined characteristics of aqifer occurrences and their water chemistry, and observed and analyzed the fluctuations of the ground water level and electrical conductivity. Our study results indicate that the high-saline characteristics of ground water in this study area should not come from dynamic recent seawater intrusion, but might be due to the fossil saline water included and isolated within the paleo-sediments or weathered zone and their upper unconformity part. This high-saline water seems to be now partially mixed and affected by freshwater in the higher inland reach of Gilsan stream.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.4
• /
• pp.413-422
• /
• 2019

A ferrosilicon (FS) by-product was applied into a cementitious binder in concrete substituting the ordinary Portland cement (OPC). The original material characteristic of FS is very identical to silica fume (SF) regarding chemical composition and physical properties such as specific surface area and specific gravity. Therefore, the FS and SF concrete or mortal of which 10% of the material was replaced to total binder weight were fabricated to evaluate the feasibility of using F S as a binder, and the comparative information of OPC, FS and SF concrete was given. The hydration characteristic of FS concrete was analyzed using X-ray diffraction analysis. The FS concrete was beneficial in compressive strength, resistivity against chloride ingress and reducing porosity considering performance of OPC concrete but the advantage was less than using SF. A possibility of alkali-silica expansion was found out from the FS concrete due to the agglomerated size of the silica particles.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.4
• /
• pp.23-30
• /
• 2019

Fiber-Reinforced Cement Composite (FRCC) is known to be effective in mechanical effects such as cracking width control as well as steel anticorrosive effect. In this study, we examined about steel anticorrosive effect by using metal fibers including zinc fibers by accelerated corrosion test. Moreover, it was examined for salt penetration, sacrificial anode effect and formation of electric circuit that was significant effect on the steel anticorrosive effect. As a result, Steel anticorrosive effect was confirmed with mixed metal fibers on FRCC. Especially, In the case of zinc fibers with a high sacrificial anode effect, it was confirmed that the suppression of penetration and corrosion resistance were improved.

• Geophysics and Geophysical Exploration
• /
• v.10 no.4
• /
• pp.361-368
• /
• 2007

In this paper, we suggested the relationship between resistivity of coastal groundwater and NaCl equivalent salinity for the quantitative interpretation the results of surface/borehole resistivity and electromagnetic data. 38 groundwater samples having electrical conductivity higher than about 1,000 ${\mu}S/cm$ were analyzed to derive the empirical relationship between groundwater resistivity and NaCl equivalent salinity. We used Schlumberger chart GEN-8 to convert ion concentration from hydrochemical analysis to the equivalent NaCl salinity, and the portable meter to measure the in situ electrical conductivity of groundwater samples. From the hydrochemical analysis, relationship between the groundwater resistivity $(R_w)$ and equivalent NaCl salinity (Eq_NaCl) is expressed as Eq_NaCl=$5935.3551{\times}R_w^{-1.0993}$, and relationship between the groundwater electrical conductivity (EC) and total dissolved solids (TDS) is expressed as TDS=0.721*EC. We believe these relationships are very useful to assess the seawater intrusion in western and southern coastal area.