• 한국지반공학회논문집
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• 제22권8호
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• pp.129-136
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• 2006

단단한 모래 입자와 연약하고 작은 고무 입자로 이루어진 Engineered Soil의 변형률에 따른 거동을 분석하기 위한 시험을 수행하였다. 파의 전파, $K_{o}$ 재하, 삼축 시험을 이용하여 단단한 입상 재료에서 연약한 입상 재료의 전이 거동을 파악하기 위해 다른 모래부피비를 가진 Engineered Soil을 준비하였다. 미소, 중간 및 대변형 변형계수는 단단한 입자의 부피비에 따라 직선 관계가 아닌 것으로 나타났다. 대신 변형계수들은 모래부피비가 $sf=0.6{\sim}0.8$ 사이의 threshold 값을 초과할 때 급격하게 증가하였다. 이는 단단한 입자들의 침투 네트워크(percolating network)의 형성을 나타낸다. 내부마찰각은 단단한 입자의 부피비가 증가함에 따라 증가한다. 반대로, 첨두 강도에서의 축변형률은 연약한 입자의 함유에 따라 증가하며, 모래부피비가 60% 이하인 Engineered Soil에서는 첨두 강도를 관찰 할 수 없었다. 연약한 입자의 존재는 하중 체인(farce chain)의 형성을 바꾼다. 연약한 입자들이 높은 하중 전달 체인(chain)의 역할을 못할 지라도, 단단한 입자 하중 체인의 뒤틀림 방지의 중요한 역할을 수행한다.

• 한국지반공학회논문집
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• 제24권2호
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• pp.87-97
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• 2008

단단한 모래 입자와 연약한 고무 입자로 이루어진 Engineered soils을 고결화 시킨 후 $K_o$ 상태에서의 거동 특성을 분석하였다. 고결화 효과에 따른 영향 및 모래부피비에 따른 영향을 파악하기 위하여 다양한 모래부피비를 가지는 비고결화 및 고결화 시료를 준비하여, 수직 응력에 따른 변형 및 탄성파 속도를 측정하였다. 탄성파 속도 측정은 벤더 엘리먼트와 PZT 엘리먼트를 이용하였다. 고결화 이 후 응력에 따른 수직 변형율의 기울기는 이중 선형 관계를 보이며 고결화 결합 파괴 이후에는 비고결화 시료와 비슷한 기울기를 가진다. 정규화된 수직 변형량은 응력에 따라 capillary force, cementation, decementation 구간으로 나눌 수 있다. 근접장 내에서 측정된 전단파 신호의 첫 번째 움직임은 압축파의 도달과 일치하였다. 고결화에 의해 탄성파 속도는 수직 응력의 증가 없이 급격한 증가를 보였으며, 고결화 이후 추가적인 응력 증가에도 일정한 값을 보였다. 고결화 파괴 후 지속적인 수직 응력의 증가에 따라 탄성파속도는 증가하였다. 고결화는 비고결화 시료에서 나타나는 유사고무, 유사모래, 전이 3가지의 거동을 방해한다. 고무-모래 혼합재의 고결화 결합의 파괴 메커니즘은 모래부피비에 따라 다르며 낮은 모래부피비의 시료는 입자 모양의 변화가, 높은 모래부피비 시료에서는 입자 구조의 변화가 고결화 결합의 파괴가 주요한 원인이다. 본 연구를 통해 연약한 고무 입자와 단단한 모래 입자의 혼합재인 Engineered soils의 거동은 고결화 및 고결화 파괴에 따라 비고결화 시료와 구분됨을 알 수 있었다.

• 한국토양비료학회지
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• 제44권2호
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• pp.316-319
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• 2011

Biopiles which offer the potential for cost-effective treatment of contaminated soils are above-ground, engineered systems that use oxygen to stimulate the growth and reproduction of aerobic bacteria for degradation of the petroleum constituents adsorbed to soil in excavated soils. This technology involves heaping contaminated soils into piles and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. Inside the biopile, microbially mediated reactions by blowing or extracting air through the pipes can enhance degradation of the organic contaminants. The influence of a aeration system on the biopile performance was investigated. Air pressure made to compare the efficiency of suction in the pipes showed that there were slightly significant difference between the two piles in the total amount of TPH biodegradation. The normalised degradation rate was, however, considerably higher in the aeration system than in the normal system without aeration, suggesting that the vertical venting method may have improved the efficiency of the biological reactions in the pile.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권4호
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• pp.32-39
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• 2013

This research focused on the effects of heavy metals on the biomonitoring activity of genetically engineered bioluminescent bacteria, Pseudomonas putida mt-2 KG1206. KG1206 was exposed to single or binary mixtures of different heavy metals as well as soils contaminated with heavy metals. In case of single exposure with different inducer pollutant, the toxicity order was as followings : As(III) > Cd, As(V) >> Cu, Cr(VI). The toxic effects of the binary mixtures was compared to the expected effect based on a simple theory of probabilities. The interactive effects were mostly additive, while in few cases antgonistic and synergistic mode of action was observed for some concentration combinations. No considerable correlation was found between the total metal contents in soils and the bioluminescence activity of each sample. However, statistically significant differences (p = 0.0102) were observed between two groups, classified based on arsenite contamination. These results demonstrate the usage of recombinant bioluminescent microorganism in biomonitoring and the complex interactive effects of metals.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 추계학술대회
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• pp.153-162
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• 2000

A field study was performed to test effectiveness of a bloluminescent genetically engineered microorganism (GEM) for bioremediation process monitoring and control. The study employed Pseudomonas fluorescens HK44 that was the first strain approved for field application in the U.S. for bioremediation purposes. HK44 contains lux gene fused within a naphthalene degradative pathway, allowing this GEM to bioluminesce as it degrades naphthalene as well as substituted naphthalenes and other polycyclic aromatic hydrocarbons (PAHs) , Results showed that HK44 was maintained in both PAH-contarninated and uncontaminated soils even 660 days after inoculation. HK44 was able to produce bioluminescence in response to PAHs in soil. Although effectiveness of chemical remediation was not assessed due to heterogeneous distribution of contaminants, decreased concentration of naphthalene was shown in the soils, Taken together, HK44 was useful for in situ bioremediation process monitoring and control. This work is so far the only field release of a GEM for bioremediation purposes.

• 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.

• Geomechanics and Engineering
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• 제19권1호
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• pp.1-9
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• 2019

Shallow failures occur frequently in both engineered and natural slopes in expansive soils. Rainfall infiltration is the most predominant triggering factor that contributes to slope failures in both expansive soils and clayey soils. However, slope failures in expansive soils have some distinct characteristics in comparison to slopes in conventional clayey soils. They typically undergo shallow failures with gentle sliding retrogression characteristics. The shallow sliding mass near the slope surface is typically in a state of unsaturated condition and will exhibit significant volume changes with increasing water content during rainfall periods. Many other properties or characteristics change such as the shear strength, matric suction including stress distribution change with respect to depth and time. All these parameters have a significant contribution to the expansive soil slopes instability and are difficult to take into consideration in slope stability analysis using traditional slope stability analysis methods based on principles of saturated soil mechanics. In this paper, commercial software VADOSE/W that can account for climatic factors is used to predict variation of matric suction with respect to time for an expansive soil cut slope in China, which is reported in the literature. The variation of factor of safety with respect to time for this slope is computed using SLOPE/W by taking account of shear strength reduction associated with loss of matric suction extending state-of-the art understanding of the mechanics of unsaturated soils.

• 대한환경공학회지
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• 제27권5호
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• pp.507-512
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• 2005

본 연구에서는 유전자 재조합 발광균주, Pseudomonas putida mt-2 KG1206을 이용하여 토양에 오염된 m-toluate 탐지 방법 및 적용 가능성에 대해 조사하였다. KG1206은 톨루엔 계열 화합물의 중요 중간 분해물질인 m-toluate 및 benzoate가 직접 생물 발광 유도제로 작용하며, 또한 톨루엔 계열 화합물들이 간접 유도제로서 발광 활성을 나타내었다. 토양에 오염된 유도제 오염원 검출을 위해 발광 균주 9.9 mL에 에탄올 추출물 0.1 mL을 첨가하여 조사하였다. 생물발광에 근거하여 작성된 m-toluate 검량선은 대략 $R^2>0.97$ 이상의 상관관계가 관찰되었다. 토양에 임의 오염된 m-toluate(직접 발광유도제)는 정립한 방법에 따라 발광활성에 근거하여 추측하였고, 기기분석치와 통계적으로 유의한 것으로 조사되었다. 본 연구 결과를 통해서 특정 화합물에 대해 발광을 생산하는 유전자 재조합 균주가 특정 오염원에 오염된 지역의 관리를 위한 수단으로 사용할 수 있는 가능성을 확인할 수 있었다.

• Geomechanics and Engineering
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• 제22권3호
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• pp.207-217
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• 2020

Slope reliability analysis and risk assessment for spatially variable soils under rainfall infiltration are important subjects but they have not been well addressed. This lack of study may in part be due to the multiple and diverse evaluation indexes and the low computational efficiency of Monte-Carlo simulations. To remedy this, this paper proposes a highly efficient computational method for investigating random field problems for slopes. First, the probability density evolution method (PDEM) is introduced. This method has high computational efficiency and does not need the tens of thousands of numerical simulation samples required by other methods. Second, the influence of rainfall on slope reliability is investigated, where the reliability is calculated from based on the safety factor curves during the rainfall. Finally, the uncertainty of the sliding mass for the slope random field problem is analyzed. Slope failure consequences are considered to be directly correlated with the sliding mass. Calculations showed that the mass that slides is smaller than the potential sliding mass (shallow surface sliding in rainfall). Sliding mass-based risk assessment is both needed and feasible for engineered slope design. The efficient PDEM is recommended for problems requiring lengthy calculations such as random field problems coupled with rainfall infiltration.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2002년도 춘계 국제 학술대회
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• pp.9-12
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• 2002

Diffusive transport of volatile organic compounds(VOCs) and their degradation by bacteria in unsaturated soils are couple by poorly understood mass transfer kinetics at the gas/water interface. Determination of the fate of VOCs in unsaturated soil is necessary to evaluate the feasibility of natural attenuation as a VOC remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOC transport, microbial activity, and sorptive interaction in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOC transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations form diffusion experiments using toluene as a representative VOC in well-defined soil columns that contained a toluene degrading bacterium, Pseudomonas Putida, as the sole active microbial species. The coefficient for gas-liquid mass-transfer, K$\sub$LA/, was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be important parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils.