• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.5-15
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• 2011

Recent increase of large scale construction near costal area has also increased the application of soft ground treatment. As a result, solidification with cement and lime which increases stability and durability of soils, is frequently used for surface layer stabilization in soft ground site. While stabilization of very soft clay with high plasticity and compressibility has widely been studied, studies on silty clay with low plasticity and compressibility are relatively rare. In this study, after stabilizing low plasticity silty clay of Songdo area with cement and lime under various water contents, mixing ratio, and curing time, uniaxial compression test and plate load test were performed. Strength properties from both tests were considerably consistent. And trackability of construction equipment on the treated surface layer of dredged land was estimated. Finally, optimum mixing condition for Songdo silty clay was proposed.

• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.49-55
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• 2006

Quick lime made from limestone that are deposited abundantly in Korea has excellent potentials for stabilization of clayey soils. If Korea is able to take advantage of its abundant supply, economical efficiency could be achieved through mass production as well as being able to take advantage of utilization of natural resources. For stabilizing of clayey soil with lime, it is necessary to determine the required quantities of lime firstly and to evaluate the degree of stabilization with lime content. In this test, the quantity of lime required for 2 clayey soils which located in Seunggok and Bugok province respectively, and for 2 clay minerals-kaolinite and montmorillonite-were determined by ASTM C 977-92 and were evaluated for solidification of each samples with changing lime contents by Atterberg limit test and pH test. It was also evaluated for the improvement of each sample with lime content and curing time. The sample which added lime content determined by ASTM C 977-92 increased plastic limit, unconfined compression strength, and decreased pH in increasing trend.

• Geotechnical Engineering
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• v.11 no.1
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• pp.41-50
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• 1995

In situ clay soils with Ko condition have anisotropic characteristics, varying the response according to the principal stress direction upon loading. But because of their practicality and simplicity, consolidated isotropic undrained compression tests are commonly used in practice to determine the behavior of cohesive soils. In this study to investigate the anisotropic characteristics and the effects of consolidation stress states on the response of normally consolidated clay soils during shearing, triaxial compression and extension tests after consolidating the undisturbed clay soil samples, which are obtained as a block sample to normalized consolidation states under isotropic or Ko state, were carried out. As a result of tests, the anisotropy of the undrained strength was confirmed. Comparing the soil responses between isotropic and Ko consolidation, the undrained strength by isotropic consolidation is overestimated because of its higher mean consolidation pressure. And isotropic consolidation reduces the anisotropy of soil response and influences on the stress-strain behavior and pore pressure response because the animotropic soil structure is partially collapsed during isotropic consolidation process. Also, OCR in overconsolidated soils is decreased by isotropic consolidatiorL Friction angle in eztension is higher than that in compression, but regression analysis shows that friction angle with cohesion in extension is almost the same as that without cohesion in compresslon.

• Korean Journal of Food Science and Technology
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• v.15 no.3
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• pp.295-301
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• 1983

The mechanical models representing the theological property of traditional Korean noodles; i.e. wheat flour noodle and wheat-sweet potato starch noddle, were investigated from the data obtained by creep and creep recovery test using a tensile tester. The rheological behavior of the noodle products could be expressed by the 6-elements Voigt model. The instantaneous elasticity, retarded elasticity, retardation time, retarded viscosity and Newtonian viscosity of the noodle products were evaluated. With the increasing cooking time, 4-elements Burger's model was applicable to represent the mechanical behavior of wheat-sweet potato starch noodle.

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.21-28
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• 2013

This study proposed optimum lime contents for clayey soils consisting of representative clay minerals, Kaolinite and Na-Bentonite, according to optimum lime content method (ASTM C 977-22) by means of ground improvement method of clayey soils. As geotechnical properties, the variations of atterberg limits and unconfined compressive strength were analyzed and Ca-ion and micro-structure along elapsed time were observed for lime-added clayey specimens. The test results show that optimum lime content method provides an appropriate methodology for ground improvement of clayey soils and the variation of $Ca^{2+}$ might be a good index to predict the rate of ground improvement for clayey soils with lime addition.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.169-178
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• 2002

The stress~strain characteristics of geosynthetics reinforced clayey soil were investigated by triaxial compression tests. All the tests were peformed either on unreinforced or reinforced soils under fully drained condition after having been consolidated isotropically or anisotropically to the required level of effective stresses by the small increment of 0.05kgf/$cm^2$. The anisotropically consolidated drained tests were performed to simulate the in-situ condition of reinforced soil structures such as reinforced soil wall, abutment and embankment which are generally in the anisotrpic state. From a series of tests it was ffund that the behavior of the anisotropically consolidated reinforced clayey soils was very different from stress~strain characteristics of consolidated reinferced clayey soils. It was found especially that the initial Young's moduli of anisotropically consolidated reinforced clayey soils were higher than those of isotropically consolidated reinforced clayey soils. It was found also that the reinforcement effect in anisotropically consolidated reinforced soils developed at a much lower level of axial strain(0.01%) compared with isotropically consolidated ones(about 1.0~5.0%).

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1275-1284
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• 2021

This paper presents a machine learning technique applied to prediction of time-dependent local scour around bridge piers in both non-cohesive and cohesive beds. The support vector machines (SVM), which is known to be free from overfitting, is used. The time-dependent scour depths are expressed by 7 and 9 variables for the non-cohesive and cohesive beds, respectively. The SVM models are trained and validated with time series data from different sources of experiments. Resulting Mean Absolute Percentage Error (MAPE) indicates that the models are trained and validated properly. Comparisons are made with the results from Choi and Choi's formula and Scour Rate in Cohesive Soils (SRICOS) method by Briaud et al., as well as measured data. This study reveals that the SVM is capable of predicting time-dependent local scour in both non-cohesive and cohesive beds under the condition that sufficient data of good quality are provided.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.586-597
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• 2022

In this study, a model was developed for the estimating the locational thickness information of the upper clay layer to be used for the consolidation vulnerability evaluation in the Nakdong river estuary. To estimate ground layer thickness information, we developed four spatial estimation models using machine learning algorithms, which are RF (Random Forest), SVR (Support Vector Regression) and GPR (Gaussian Process Regression), and geostatistical technique such as Ordinary Kriging. Among the 4,712 borehole data in the study area collected for model development, 2,948 borehole data with an upper clay layer were used, and Pearson correlation coefficient and mean squared error were used to quantitatively evaluate the performance of the developed models. In addition, for qualitative evaluation, each model was used throughout the study area to estimate the information of the upper clay layer, and the thickness distribution characteristics of it were compared with each other.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.266-273
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• 1999

본 연구에서는 겔캐스팅법의 제조공정 확립을 위하여 분산제의 분자구조가 질화규소 슬립의 점성특성 및 성형체의 상대밀도와 기계적 특성에 미치는 영향을 조사하였다. 슬립과 겔캐스팅 성형체의 제조방법은 기보고된 방법과 동일하게 하였다. 그 결과, 겔캐스팅 슬립의 점성은 분산제의 분자구조와 모노머와 분산제의 구성비율에 크게 의존하였다. PMAA 분산제를 사용한 슬립의 점성은 PAA 및 PAAm 분산제 보다 높은 점도를 나타내었다. 성형체의 상대밀도는 슬립의 농도에 크게 의존하였으며, 분산제양과 모노머의 양변화에는 그다지 변화가 없었다. 그리고, 겔캐스팅 성형체의 기계적 특성은 크게 모노머의 농도에 의존하였으며, 분산제양과 슬립의 농도에는 큰 변화가 없었다.

• Journal of the KSME
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• v.25 no.3
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• pp.236-241
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• 1985

본 고에서는 일반적으로 노즐 부위 열해석에서 무시되는 복사열전달율과 점성소산효과를 수치적 모델을 통하여 그 필요성 여부를 조사한 것이며 다음과 같은 결론을 얻었다. (1)연소실 및 수 렴부위에서는 복사열전달율이 대류열전달율과 같은 차수의 크기로 나타나고 있어서 고 복사율을 갖는 연소가스에서는 특히 중요하다. 특히 최근에 많이 사용되는 연료에는 연소가스에 산화알 루미늄 성분이 증가하는 추세이므로 노즐부위 열해석에는 복사열전달이 차지하는 비중이 커질 것이다. (2)노즐의 확산부위에서는 고속으로 인하여 가스자체의 점성소산이 일어나 특성치 보 정계수 값이 감소한다. 따라서 Bartz의 예측치 보다는 열전달계수의 값이 적어지고 있다. (3) 따라서 노즐수렴부위에서는 일반적으로 Bartz의 예상치보다 높고 확산부에서는 낮은 결과를 얻 었던 실험결과와를 비교할 때 고온고속 노즐에서의 열전달해석은 복사 열전달과 점성열 소산을 고려함으로써 정확하게 될 수 있다. (4)이상 고려된 실험 데이터와 수치모델의 고찰은 노즐내의 침식이 없는 경우이나 실제의 경우 노즐벽 표면에서 화학적 반응이 일어난다. 그러나 이때 발 생될 수 있는 순수한 발한효과는 미미하며 단지 전체적인 단면의 열 해석시 상기에서 예측된 열전달율을 근간으로 화학반응열 및 온도분포를 계산하여야 할 것이다.