• 한국해안해양공학회지
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• 제5권2호
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• pp.143-150
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• 1993

이중 주파수(Dual Frequency)를 사용한 Prototype형 천해 지층 탐사기를 사용하여 얻은 탐사 기록지가 제시되었다. 이중 주파수로는 3.5/100KHz 혹은 15/100KHz를 이용해서 고주파수에 의한 고해상도(High Resolution)을 얻고 동시에 저주파수(3.5~15KHz)에 의한 심층 투과력을 높이는데 본 연구의 목적이 있다. 특히 탐지하는 목표물이 Fresnel 반경에 비해서 매우 작을 때는 쌍곡선형 회절무늬(Hyperbolic Diffraction)가 나타나기 때문에 쉽게 목표물을 찾을 수 있다. 감쇠상수가 큰 모래층은 작은 감쇠상수를 갖고 있는 점토보다 지진파의 투과력을 약하게 만든다. 이와같이 이중 주파수의 동시 운용은 해저 지질. 모래와 점토(Silt/Clay) 분포 오니토 및 해양고고학 유물 탐사에 크게 활용할 수 있다.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 2003년도 한국해안해양공학발표논문집
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• pp.344-352
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• 2003

Sediment plumes arising from various coastal works can cause detrimental effects on the coastal ecosystem in various manners. Although the most active countermeasure against the plumes is to restrict the works to specified time periods known as environmental windows (Reine et al., 1998), silt screens have been widely used for reducing the spreading of suspended sediments (SS) generated by coastal works. (omitted)

• 한국물환경학회지
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• 제22권1호
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• pp.140-144
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• 2006

This study was performed to investigate the effect of organic characteristics and feed water solution chemistry on membrane fouling index such as Silt Density Index (SDI) and Modified Fouling Index (MFI). Specifically, Aldrich humic acids (AHA) and Suwannee river humic acids (SHA) were used in SDI/MFI experiments. Higher SDI values were observed with increasing organic concentration. AHA with larger molecular weight (MW) and SUVA (${\approx}UV_{254}/TOC$) resulted in higher SDI values, compared to SHA. The feed solution chemistry (i.e, pH, ionic strength, and hardness) also affects SDI values to some degree. In particular, SDI increased with increasing hardness ($Ca^{2+}$) concentration for AHA. Unlike SDI, the MFI developed on the basis of particle cake filtration theory, was not accurately assessed due to internal fouling by organics such as pore adsorption and subsequent pore blocking.

• 한국지반공학회논문집
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• 제28권6호
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• pp.53-61
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• 2012

본 연구의 목적은 연약지반에 대한 미생물의 고결화 메커니즘을 확인하기 위함이다. 연약지반에 대한 미생물의 고결화 메커니즘을 확인하기 위해서 6가지 미생물 조건(무처리, 일반농도처리, 고농도처리, 상층액처리, 2X 고농도처리, 25% 시료 고농도처리)으로 실험되어졌다. 전자현미경(SEM, EDX)과 X선 분석 회절기(XRD)를 이용하여 실트질시료와 느슨한 모래시료의 분석을 수행하였으며, 일반농도처리 시료에 비교하여 25% 시료 고농도처리 시료에서 입자와 입자 사이에 탄산칼슘이 더욱 명확히 관찰되어졌다. 이러한 연구결과를 바탕으로 연약지반에 대한 미생물 고결화 반응을 확인할 수 있었다.

• 수산해양교육연구
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• 제19권1호
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• pp.1-7
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• 2007

The purpose of this study was to investigate geochemical characteristics of surface sediments in the Keum river estuary adjacent to coastal area. For this study we collected the 21 surface sediments samples. Mean size of surface samples was $3.24{\sim}6.65{\phi}$ on inner estuary and was $2.15{\sim}3.42{\phi}$ on outside estuary. Surface samples were composed of silt on inner estuary and were composed of sand which was more larger than $4{\phi}$ on outside estuary. Most major elements except CaO, $Na_2O$ showed good relationships between variation of contents and grain size. Contents of $Al_2O_3$, $Fe_2O_3$, MgO, $K_2O$, $TiO_2$, $P_2O_5$ and $M_nO$ were increased predominately owing to the variation of mean size of surface samples. Contents of Co, Cr, Cu, Li, Sr, Zn, La, Ce, Pb, Rb, Nd have a good relationships with grain size but Ba, Th, Sm have not. All of major and minor elements contents except $K_2O$ and Ba were less than world mean contents of shallow surface sediments but apprehend a high pollution possibility on silt sediments in the estuaries.

• 한국제4기학회지
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• 제20권1호
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• pp.1-8
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• 2006

인천 국제공항 고속국도 건설을 위하여 영종북 갯벌에서 많은 시추 조사가 이루어졌다. 이 시추 자료를 분석하여 이 갯벌 퇴적물의 수직 구조를 검토했다. 영종북 갯벌의 퇴적층 두께는 대략 30m이고, 하부로부터 기저 사력층, 하부 점토층, 중부 실트층, 중부 점토층, 상부 실트층이 차례로 퇴적되어 있었다. 황갈색의 반고 화된 산화대는 $-3{\sim}-5m$ 고도에서 중부 점토층 윗면 혹은 중부 점토층 내에서 나타났다. 산화대 윗면을 선현세 갯벌층과 현세 갯벌층 간의 부정합면으로 인정하기에는 퇴적 단면 구조의 해석상 어려운 점이 많았다.

• 동굴
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• 제34권35호
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• pp.78-104
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• 1993

Analysis of one sinkhole, the Dodgeville sinkhole, developed in Ordovician dolostones in the Driftless Area of Wisconsin in the Upper Midwest'd Driftless Area reveals homogenous clayey sediment fills reflecting a range of dissolutional processes during the Quaternary or Pre-Quaternary. Granulometric analysis, graphical moments statistics, carbonate minerals, ana sand grain lithology were used to differentiate sinkhole sediment sources and modes of accumulation. Sediments in the dolostone sinkholes developed by dissolution. Sediments contain two major types of sediments : residual redish clay( autogenic sediments) and aeolian silt (allogenic sediments). The massive clay is generated from the weathered dolostone bedrocks as a in situ materials. The loessial silt is mostly derived from transportation of the surrounding surface materials, with some evidences of penetrated deposition. Unlike the collapsed sandstone sinkholes (Oh et al., 1993), dolostone sinkholes reveal homogenous, autogenic clay materials, and a geochemical composition indicative of in situ autogenic karstification. Dolostone sinkhole si1ts (26.9%) and sands (34.9%) are derived from weathered Plattevi1le-Galena dolostones, and contain high carbonate(37.5%), chert (57.2%) and lead ore (3%). Graphical moments statistics for sorting, skewness, and kurtosis indicate that sand grains from dolostones were derived entirely from local bedrock by in situ dissolution. Upper sinkhole sediments are pedagogically very young as carbonate is unleashed. Materials of the sinkhole sediment are definitely inherited from internal dolostones by dissolution and weathering, because not only a granulomatric comparison of dolostone and sandstone sediments demonstrates that they have heterogeneous paticle size distributions, but also 1ithologic analyses displays they differ completely.

• 한국지반신소재학회논문집
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• 제18권1호
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• pp.1-9
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• 2019

본 연구에서는 인공어초의 침하 및 세굴을 저감하고자 다양한 보강재로 보강된 해저 지반의 침하 및 세굴 거동 특성을 알아보았다. 지반에 적용한 보강재는 총 3가지로서 지오그리드(geogrid), 지오그리드-대나무 매트(geogrid-bamboo mat, GBM) 및 해초-지지봉 매트(seaweed-pile mat, SPM)를 각각 보강하여 실험을 수행하였다. 모래, 실트 및 점토 지반에 대해 지지력 실험, 대형 수조 침하 실험, 2차원 흐름 수조 세굴 실험 등 다양한 실내 실험을 수행하였다. 실험 결과 보강재의 보강에 따라 인공어초의 지지력 증진, 침하 및 세굴이 저감되는 효과를 보였으며, 모래나 실트 지반보다 점토 지반과 같은 연약 지반에서 보강효과가 더 크게 나타나는 경향을 보였다.

• Geomechanics and Engineering
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• 제28권3호
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• pp.239-253
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• 2022

Suitable techniques to stabilize organic soil and improve its engineering behaviour are in demand. Despite various alternatives, nano-additives proved to be an effective stabilizer owing to their strength enhancing properties. The study focuses on using nano-silica as a potential stabilizer to improve organic silt. Soil was treated with four dosages of nano-silica namely 0.2%, 0.4%, 0.6% and 0.8% of dry weight of the soil. Nano-silica treated soil showed a strength increase of nearly 25% at a dosage of 0.4% after curing for two hours. Strength of the treated soil improved with age. Strength improved by nearly 62.9% after 28 days of curing and 221.4% after 180 days of curing due to formation of Calcium - Silicate - Hydrate (CSH) gel in the soil matrix. Dosage of 0.6% nano-silica is observed to be the optimum dosage. Coefficient of permeability and compression index showed an increase by 13.32 and 5.5 times respectively owing to aggregation of particles and creation of void spaces as visualized from the scanning electron micrographs. Further model foundation study and numerical parametric studies using PLAXIS 2D indicate that optimized and economic results can be obtained by varying the additive dosage with depth.

• Geomechanics and Engineering
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• 제33권1호
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• pp.113-120
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• 2023

Coastal and offshore structures such as ports and offshore wind farms will often need to be built on fine-grained sediments. Geotechnical properties associated with sediment compressibility are key parameters for marine construction designs especially on soft grounds, which involve clay-mineral dominated fines that can consolidate and settle significantly in response to engineered and environmental loads. We conduct liquid limit tests and 1D consolidation tests with fine-grained soils (silica silt, mica, kaolin and bentonite) and biogenic soils (diatom). The pore fluids for the liquid limit tests include deionized water and a series of brines with NaCl salt concentrations of 0.001 m, 0.01 m, 0.1 m, 0.6 m and 2.0 m, and the pore fluids for the consolidation tests deionized water, 0.01 m, 0.6 m, 2 m. The salt concentrations help the liquid limits of kaolin and bentonite decrease, but those of diatom slightly increase. The silica silt and mica show minimal changes in liquid limit due to salt concentrations. Accordingly, compression indices of soils follow the trend of the liquid limit as the liquid limit determined the initial void ratio of the consolidation test. Diatoms are more likely to be broken than clastic sediments during to loading, and diatom-rich sediment is therefore generally more compressible than clastic-rich sediment.