• Geomechanics and Engineering
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• 제5권4호
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• pp.331-342
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• 2013

The major factors that control the performance of reinforced soil structures is the interaction between the soil and the reinforcement. Thus it is necessary to obtain the accurate bond parameters to be used in the design of these structures. To evaluate the behavior of flyash + clay soil reinforced with a woven geotextile, 36 Unconsolidated-Undrained (UU) and 12 reinforced Consolidated-Undrainrained (CU) triaxial compression tests were conducted. The moisture content of soil during remolding, confining pressures and arrangement of geotextile layers were all varied so that the behavior of the sample could be examined. The stress strain patterns, drainage, modulus of deformation, effect of confinement pressures, effects of moisture content have been evaluated. The impact of moisture content in flyash + clay backfills on critical shear parameters was also studied to recommend placement moisture for compaction to MDD. The results indicate that geotextile reinforced flyash + clay backfill might be a viable alternative in reinforced soil structures if good-quality granular backfill material is not readily available.

• 한국지반공학회논문집
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• 제20권6호
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• pp.85-94
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• 2004

동반논문에서는 사질토의 취성적 응력-변형률 관계와 전단시 팽창을 고려할 수 있는 구성모델을 제안하였다. 본 연구에서는 제안된 모델의 계수를 체계적으로 결정하기 위하여 실수형 유전자 알고리즘에 근거한 최적화 기법이 적용되었으며, 이를 통하여 구성모델에 필요한 주요 계수값들을 결정할 수 있었다. 본 연구에서는 제안된 모델을 검증하기 위하여 풍화토시료에 대한 $K_0$ 압밀 삼축시험을 수행하였다. 또한 조립토에 등방압축 삼축시험결과를 이용하여 제안된 모델을 검증하였다. 이러한 시험자료들에 대하여 제안된 모델은 취성적 응력-변형률 관계 및 체적의 팽창과 같은 실제 유효응력 거동을 합리적으로 모델하는 것이 가능하였다. 이로부터 제안된 모델이 풍화토 및 조립토와 같은 사질토의 거동에 적합한 것으로 판단된다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권3호
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• pp.21-26
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• 2008

염화아연($ZnCl_2$)으로 표면개질된 코코넛 입상활성탄(Granular Activated Carbon, GAC)의 질산성질소 제거제로서의 적용가능성을 알아보기 위해 두 가지 질산성질소 농도(25 mg/L, 50 mg/L) 조건에서 수중에서의 질산성질소 흡착능력을 평가하였다. 표면개질된 코코넛 입상활성탄의 질산성질소 흡착은 반응초기에 빠르게 진행되어 10분 이내에 흡착율이 50%에 이르렀고 흡착평형에 소요된 시간은 1시간 이내였다. 염화아연으로 표면개질된 코코넛 입상활성탄의 질산성질소 흡착 원리를 조사하기 위해 네 가지 속도 모델들(유사 일차 모델, 유사 이차 모델, Weber & Morris의 입자내 확산 모델, 그리고 Bangham의 공극 확산 모델)을 각 모델의 속도 상수(k)에 따라 적용하였다. 그 결과, 본 연구의 흡착속도는 공극 확산 단계에 의하여 결정되는 것으로 사료되며 유사 이차 모델을 따르는 것으로 나타났다.

• Geomechanics and Engineering
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• 제17권5호
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• pp.439-444
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• 2019

It is generally known that high strength soil is indicative of well-graded particle size distribution. However, there are some special cases of firm ground despite poor grade distribution, especially a specific gap-graded soil. Based on these discoveries, this study investigated the development of an additive of gap-graded soils designed to increase soil strength. This theoretical concept was used to calculate the mixed ratio required for optimal soil strength of the ground sample. The gap-graded aggregate was added according to Plato's polyhedral theory and subsequently calculated ratio and soil strength characteristics were then compared to characteristics of the original soil sample through various test results. In addition, the underground stress transfer rate was measured according to the test conditions. The test results showed that the ground settlement and stress limit thickness were reduced with the incorporation of gap-graded soil. Further field tests would confirm the reproducibility and reliability of the technology by using gap-graded soil to reinforce soft ground of a new construction site. Gap-graded soil has the potential to reduce the construction cost and time of construction compared to other reinforcing methods.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.241-252
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• 2010

This study investigates the application of dilatometer test for evaluating the deformation characteristics of granular soil. $K_D$ is the most sensitive to the stress history among CPT and DMT measurements, and $E_D$ and $q_c$ are observed to be similarly affected by the stress history. The coefficient of at-rest earth pressure($K_0$) is an indirect measure evaluating the stress history of granular soil. A relation using only DMT indices provides appropriate prediction of $K_0$ values. Although penetration of dilatometer inevitably induces the failure of cementation bonds, $E_D$ reflects the deformation characteristics of undamaged cementation relatively well. Therefore, a slightly better prediction of M value for cemented sand is achieved by using $E_D$ rather than $q_c$. Because of the weaker particle strength of calcareous sand compared than quartz sand, the majority of sand particles adjacent to dilatometer probe will be crushed during penetration. The particle crushing will induce the less contraction of the dilatometer membrane during penetration, consequently, the smaller $K_D$ and $E_D$ of calcareous sand.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.172-181
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• 2001

Upflow anaerobic sludge blanket (UASB) system employs granular sludge to treat various wastewaters including landfill leachate. CH$_4$ production of the granules determines overall performance of a UASB reactor. Sludge granules are developed by self-granulation of microorganisms and dynamic balance between granule growth and decay results in coexistence of granules with different sizes in the reactor. In this study, granules taken from a laboratory-scale UASB reactor were classified into 4 groups based on their diameters and their Physicochemical characteristics we were investigated. Each group was analyzed for settling ability, specific methanogenic activity (SMA), and elemental content. Settling ability was proportional to granule diameter. suggesting effective detainment of larger granules in the reactor. When acetate or glucose was used as a substrate, all groups showed relatively slight difference in SMA. However SMA with a volatile fatty acid mixture showed significant increase with granule diameter, suggesting better establishment of syntrophic relationship in larger granules. Larger granules showed higher value of SMA upon environmental changes (i.e., PH, temperature, or toxicant concentration). Comparative analysis of elemental contents showed that content (dry weight %) of most tested elements (iron, calcium, phosphorus, zinc, nickel. and manganese) deceased with granule diameter, suggesting importance of these elements for initial granulation. Taken together, this study verified experimentally that Physicochemical Properties of granules are related to granule size distributions. Overall results of physicochemical characterization supports that larger.

• 한국지반공학회지:지반
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• 제8권2호
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• pp.81-96
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• 1992

본 문은 Lade의 단일항복면 구성모델(single work-hardening model)을 선정하여 사질토의 거동해석에 필요한 토질매개변수를 실내시험을 하여 구하는 과정에서 필연적으로 발생하는 실험오차가 해석결과에 미치는 영향을 분석하였다. 연구방법으로서는 백마강 모래에 대하여 등방압축-팽창시험과 구속압력을 달리한 일련의 배수삼축시험을 하고 이 시험자료를 이용하여 회귀분석을 근거로, 본 연구에서 개발된 토질 매개 변수 결정 프로그램에 의해 기찬매개변수를 결정하고 그 평균치에서 표준편차를 증감시켜 축방 향변형률에 대한 축차응력 및 체적변형률의 상계 및 하계 범위를 밝힘으로서 각 토질매개변수의 민감도를 규명하였다. 그 결과 토질매개변수결정 프로그램의 실용성이 크다는 것을 화인하고 Lade의 단일항복면 구성모델의 예측능력이 좋다는 것을 알았다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.314-323
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• 2010

Recently, granular soils having a large particle size are frequently used as a filling material in the construction of foundation, harbor, dam, and so on. The shear behavior of this granular soil plays a key role in the stability of structures. For example, soil particle crushing occurring at the interface between structure and soil and/or within soil mass can cause the disturbance of ground characteristics and consequently induce an issues in respect of stability of structures. In order to investigate the shear behavior according to an existence and nonexistence of particle crushing, numerical analyses were conducted by using the DEM(Discrete Element Method)-based software program PFC(Particle Flow Code). Using the crushing model and non-crushing model which were created in this study, numerical analyses of ring shear test were conducted and their results were analyzed and compared. In general, landslide and slope stability are accompanied by a large displacement and consequently not only a peak strength but also a residual strength are very important in the analysis of landslide and slope stability. However the direct shear test which has been commonly used in the determination of shear strength parameters has a limitation on displacement therefore the residual strength parameters can not be obtained. The characteristics of residual shear behavior were investigated through the numerical analyses in this study.

• 한국환경농학회지
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• 제30권2호
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• pp.160-165
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• 2011

시설재배지내의 밀폐공간에서 토양처리농약의 살포 후 농작업으로 작업자의 농약중독 우려가 상존하므로 농약중독예방 방지를 위해 살포농약의 휘산양상과 농작업자 노출량 산정 연구를 수행하였다. 흡착제를 이용한 공기 중 ethoprophos, cardusafos, probenazole의 회수율은 각각 charcoal 흡착제 80.9~121.1%, XAD-4 흡착제가 90.6~99.0% 수준으로 양호하였다. lysimeter에 토양을 혼화처리 한 후 온도별 농약의 휘산은 온도가 높을수록 휘산이 잘되었으며, 특히 수분이 존재 하는 $35^{\circ}C$조건에서는 ethoprophos의 경우 3~5배 휘산량이 증가하였다. 면적 245 $m^2$ 시설하우스 재배포장에서 ethoprophos 입제를 150 g (a.i.) 토양과 혼화처리하고 지면으로부터 50 cm 상층에서 처리 46시간까지 토양처리제인 ethoprophos의 휘산량은 17.8~186.4 ${\mu}g/m^3$이었다. 동일조건에서 cadusafos 180 g a.i./245 $m^2$ 약량을 처리했을 때 처리 39시간째에 최고 농도를 보였으며 46시간까지 공기중농도는 10.0~37.3 ${\mu}g/m^3$이었다. Probenazole은 144 g a.i./245 $m^2$ 약량을 처리했을 때 처리 37시간째에 최고 농도를 보였으며 46시간까지의 공기중 농도는 0.23~1.45 ${\mu}g/m^3$ 수준이었다. 약제처리 후 하우스내 공기중 농약성분의 최대잔류량은 13~39시간 사이에 최대잔류가 되었고 토양처리농약인 ethoprophos 입제와 cadusafos 입제는 휘산성이 높음으로 농작업자 재출입 기간은 살포 후 48시간 이후로 설정해야 할것이다.

• Geomechanics and Engineering
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• 제6권5호
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• pp.487-502
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• 2014

A three dimensional finite element model was used to simulate rapid impact compaction (RIC) in loose granular soils using ABAQUS software for one impact point. The behavior of soil under impact loading was expressed using a cap-plasticity model. Numerical modeling was done for a site in Assalouyeh petrochemical complex in southern Iran to verify the results. In-situ settlements per blow were compared to those in the numerical model. Measurements of improvement by depth were obtained from the in-situ standard penetration, plate loading, and large density tests and were compared with the numerical model results. Contours of the equal relative density clearly showed the efficiency of RIC laterally and at depth. Plastic volumetric strains below the anvil and the effect of RIC set indicated that a set of 10 mm can be considered to be a threshold value for soil improvement using this method. The results showed that RIC strongly improved the soil up to 2 m in depth and commonly influenced the soil up to depths of 4 m.