• 한국지진공학회논문집
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• 제28권1호
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• pp.33-39
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• 2024

Understanding the behavior of soil under cyclic loading conditions is essential for assessing its response to seismic events and potential liquefaction. This study investigates the effect of non-plastic fines content (FC) on excess pore pressure generation in medium-density sand-silt mixtures subjected to strain-controlled cyclic direct simple shear (CDSS) tests. The investigation is conducted by analyzing excess pore pressure (EPP) ratios and the number of cycles to liquefaction (Ncyc-liq) under varying shear strain levels and FC values. The study uses Jumunjin sand and silica silt with FC values ranging from 0% to 40% and shear strain levels of 0.1%, 0.2%, 0.5%, and 1.0%. The findings indicate that the EPP ratio increases rapidly during loading cycles, with higher shear strain levels generating more EPP and requiring fewer cycles to reach liquefaction. At 1.0% and 0.5% shear strain levels, FC has a limited effect on Ncyc-liq. However, at a lower shear strain level of 0.2%, increasing FC from 0 to 10% reduces Ncyc-liq from 42 to 27, and as FC increases further, Ncyc-liq also increases. In summary, this study provides valuable insights into the behavior of soil under cyclic loading conditions. It highlights the significance of shear strain levels and FC values in excess pore pressure generation and liquefaction susceptibility.

• 한국지반공학회논문집
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• 제28권2호
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• pp.33-42
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• 2012

본 연구에서는 토립자의 입경과 입도분포가 불포화토의 흙-수분특성에 미치는 영향을 검토하고자 하였다. 이를 위해 축이동기법이 적용된 시험장치를 이용하여 현장에서 채취한 새만금실트에 대해 함수특성시험을 실시하였다. 비교를 위해 주문진 표준사에 대해서도 시험을 실시하였다. 시험으로부터 측정된 모관흡수력과 체적함수비를 토대로 van Genuchten 모델에 대한 흙-함수특성곡선을 추정하였다. 추정된 함수특성곡선의 비교분석결과 포화체적함수비, 잔류체적함수비 그리고 공기함입치 모두 모래보다 실트에서 더 높게 나타났으며, van Genuchten 모델의 계수 ${\alpha}$, $n$, $m$ 모두 실트보다 모래에서 더 크게 나타났다. 이는 불포화토의 흙-함수특성곡선은 흙의 구조적 특성(간극크기, 형태, 분포)과 밀접한 관계를 가지며 상대적으로 입경이 크고 입도분포가 불량한(다시 말해, 간극크기가 크고 간극분포가 균등한) 조립토일수록 포화체적함수비, 잔류체적함수비, 그리고 공기함입치가 작고, 모관흡수력 변화에 따른 체적함수비의 변화율이 크며, 따라서 전이 영역의 범위가 좁게 나타나는 경향이 있다는 것을 보여준다.

• 한국지반환경공학회 논문집
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• 제6권1호
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• pp.23-31
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• 2005

실트폰드는 크기가 55만평의 인공연못 안에 두께가 3~20m의 초연약점토가 침전되어 있었다. 1990년대 중반에 매립이 시작되었다. 매립 전 시료채취 및 다양한 종류의 원위치시험을 수행하였다. 실트폰드에 침전되어 있는 흙은 극도로 연약하기 때문에 모래 포설장비를 이용하여 모래를 전 지역에 균등하게 살포하였다. 대단히 주의 깊은 시공에도 불구하고 모래 포설시 대규모 전단파괴가 발생하였다. 따라서 파괴지역에 보강을 위하여 가로가 900m이고 세로가 700m인 고강도 보강매트를 포설한 후 재차 모래를 포설하여 매립을 완료하였다. 매립의 성공은 수중 콘관입시험으로 확인하였다.

• Geomechanics and Engineering
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• 제22권3호
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• pp.219-226
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• 2020

Unconfined compression test (UCT) is widely conducted in laboratories to evaluate the mechanical behavior of frozen soils. However, its results are sensitive to the initial conditions of sample creation by freezing as well as the end-surface conditions during loading of the specimen into the apparatus for testing. This work compared ice samples prepared by three-dimensional and one-dimensional freezing. The latter created more-homogenous ice samples containing fewer entrapped air bubbles or air nuclei, leading to relatively stable UCT results. Three end-surface conditions were compared for UCT on ice specimens made by one-dimensional freezing. Steel disc cap with embedded rubber was found most appropriate for UCT. Three frozen materials (ice, frozen sand, and frozen silt) showed different failure patterns, which were classified as brittle failure and ductile failure. Ice and frozen sand showed strain-softening, while frozen silt showed strain-hardening. Subsequent investigation considered the influence of fines content on the unconfined compression behavior of frozen soil mixtures with fines contents of 0-100%. The mixtures showed a brittle-to-ductile transition of failure patterns at 10%-20% fines content.

• 한국농공학회지
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• 제35권3호
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• pp.130-139
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• 1993

In order to evaluate the long-term permeability performace of the geotextiles, for five different combination of geotextiles and soils the long-term column test method The results obtained are as follows; 1.The gradient range of the initial stage of the long-term permeability curves varied with respect to the soil types, while that of the final stage varied according to the interaction of the soil/geotextile system. 2.The time required for a given soil/geotextile system to reach a interactive stable stage was measured ahout 100 hours for the standard sand and 150 to 600 hours for the silty content soils, respectively. 3.There were no differences between the plain woven geotextile and the non-geotextile in the long-term permeability performance. 4.As the silt content increased, the long-term performance of the geotextiles decreased, and the limiting silt content was about 15%. 5.The thickness and area density of the geotextiles did not influence on the variation of the seepage quantities. 6.The ayerage slope and the transition time of the long-time flow curve were calculated. 7.In order to evaluate the mechanism of soil/geotextile system more perfectly, the gradient ratio test or the hydraulic conductivity test is required.

• Journal of Applied Biological Chemistry
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• 제63권3호
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• pp.175-180
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• 2020

본 연구에서는 재배 환경에 따른 산수유나무의 지표성분인 loganin 및 morroniside을 함량 분석을 통한 상관관계 구명하고자 하였다. Loganin 및 morroniside 함량은 UPLC에 의해 동시 분석되었다. 토양 데이터의 Mg²⁺ 함량과 pH가 loganin 함량에 가장 큰 영향을 미치는 것으로 나타났으며 Mg²⁺, Na⁺ 함량, pH, 염도, silt 비율, 점토 비율이 morroniside 함량에 가장 큰 영향을 미치는 것으로 나타났다. 결론적으로 Mg²⁺ 함량, pH, 점토비율은 산수유 지표성분인 morroniside 및 loganin 함량에 높은 영향을 미치는 것으로 나타났다. 이러한 결과들은 산수유나무의 최적의 재배환경요건에 대한 기초자료로 이용될 수 있을 것으로 기대된다.

• 지질공학
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• 제27권1호
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• pp.91-101
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• 2017

단층물질은 불균질하고 복잡한 메커니즘에 의해 생성되기 때문에 지역, 암종 및 구성 성분에 따라 다양한 특성을 보인다. 본 연구에서는 단층물질의 물리 역학적 특성을 규명하기 위해 국내에 분포하는 단층물질 109개를 채취하여 각종 실내시험을 실시하고, 지역, 암종 및 구성 성분에 따른 물리 역학적 특성(단위중량, 비중, 공극률, 자갈함량, 실트/점토 함량, 점토광물 함량, 내부마찰각 및 점착력)을 분석하였다. 암종별 물리 역학적 특성은 편마암의 경우 단위중량($17.1kN/m^3$)과 비중(2.73)에서 가장 높은 중앙값을 보이며, 화강암은 공극률(45.5%), 편암은 자갈함량(20.0 wt.%)과 점착력(38.1 kPa), 천매암은 실트/점토 함량(54.4 wt.%), 점토광물 함량(37.7 wt.%)과 내부마찰각($38.2^{\circ}$)에서 가장 높은 중앙값을 보인다. 구성 성분별 물리 역학적 특성은 단층점토가 공극률과 실트/점토 함량을 제외한 모든 인자에서 파쇄암 및 손상대보다 낮은 값을 보이는 것으로 나타났다.

• 한국환경과학회지
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• 제9권2호
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• pp.125-129
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• 2000

As one of the fundamental survey to evaluate purification capacity of pollutants at the tidal flat sediments, we studied vertical environmental characteristics in three tidal flat sediments, Chunjangdae, Eueunri and Gyewhado. These are dissmilar to external feature in each other. The results of this study may be summarized as followed; As the results of particle analysis, Eueunri tidal flat fediment located in Keum river estuary consists of 98.98% as silt & clay, Chunjangdae tidal flat sediment located in SeocheonGun consists of 97.99% as sand. And Gyewhado tidal flat sediment located in Saemankeum in Saemankeum area consists area consists of 32.81% as silt & clay and 67.19% as sand. The concentration of organic pollutants(I.L., COD, POC, PON) in Eueunri tidal flat sediment which highly content of silt & clay were 3~4 times higher than others. The concentration of organic pollutants at each layer were slightly increase goes with deepen layer. The linear correlation between I.L. and COD, POC, PON were obtained. Correlation coefficients were in range of 0.821~0.940. Also the correlation between pH and COD, POC, PON were high(>r=0.9). Filteration rate in Chunjangdae tidal flat sediment was 0.01584cm/s as mean value, but the other were almost nothing filtered off.

• Ocean Science Journal
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• 제42권3호
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• pp.165-170
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• 2007

The structure of the nematodes communities has been studied in the sediments on two sites located outside and under the layer of Ahnfeltia tobuchiensis (Kanno and Matsubara 1932; Makijenko 1970). Bottom sediments at the stations were represented by sands with a different degree of silting. Specific structure of nematodes at the stations was significantly different under the similar environmental conditions (water depth, dissolved oxygen saturation, salinity, temperature of the bottom layer and organic carbon content inside of the sediment). Nematodes dominated (75.7 %) in meiobenthos community under the layer of A. tobuchiensis where concentration of silt particles was 12 %. Representatives of the family Comesomatidae were dominant. Low index of species diversity and high Simpson domination index were detected in this community. Under a layer of A. tobuchiensis with the thickness of 30 cm concentration of the silt particles was 5.39 %; nematodes density was low and made 32.1 % of the general density of meiobenthos. Species of the families Xyalidae and Monoposthiidae were dominant. Outside of A. tobuchiensis, field percentage of silt particles was minimal (3.1 %) and representatives of families Cyatholaimidae and Axonolaimidae dominated. The specific structure of nematodes in this type of the ground is characterized by high index of species diversity and low level of domination.

• The Korean Journal of Ecology
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• 제20권2호
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• pp.133-143
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• 1997

From 1984 to 1989 reclaimed coastal lands in Choongnam Province of the western coast of Korea were studied for soil texture at three sites(Daeho, Hyundai A and Hyundai B) and for desalination one site(Hyundai B). The soil textures of varied sites in Hyundai A were horizontally similar and composed of 39-40% clay, 40-49% silt and 8-14% sand. But those in Da돼 and Hyundai B differed horizontally in the same area and vertically at the same site. Soil texures of Da돼 were composed of 15-17% clay, 30-45% silt and 40-55% sand and those of Hyundai B were composed of 22-45% clay, 26-49% silt and 17-31% sand. The measured electrical conductivity(EC), which represents whole salt content of the reclaimed soil, decreased year by year. The vertical distribution of the EC changed temporally and spatially in the upper zone above a 50 cm depth but not in The lower zone below a 50 cm depth. The EC valus of the soil were inversely proportional to the magnitued of annual precipitation, evaporation and the numbers of rainy days with r equalling -0.97. But the annual decrease of the EC was directly proportional to climatic factors with r=0.7. Salt in the reclaimed land was leached out by the percolative action of surplus rain water, or moved up by evaporation and carried away by running rain water. The running out of the salt on the soil surface was most efficiently carried out over 10 mm precipitation per day.