• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.57-66
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• 2006

In this study, the centrifuge model tests were carried out to evaluate the stress concentration ratio, the deformation modes of piles and the ground movement in clay deposit improved by SCP and GCP piles with changing the replacement ratio(20%, 40%, 60%) under flexible loading. Based on the results obtained, it was shown that the stresses acting on GCP was larger than those acting on SCP with the same replacement ratio. It was evaluated that the average stress concentration ratio of soft clay ground improved by GCP was slightly larger than that of SCP when the replacement ratio is 40%. Only expansion failure occurred in GCP, whereas SCP showed the expansion and shear failure simultaneously.

• Journal of the Korean Geotechnical Society
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• v.22 no.4
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• pp.21-30
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• 2006

In this study, centrifuge model tests were performed to investigate the stress concentration ratio, bearing capacity and deformation modes of piles in clay ground improved by granular piles with two types of pile (CSCP, SCP) and various replacement ratios (0, 20, 40, 60%). According to the results of tests, the load ratio of ground improved by SCP and CSCP proportionally increased as replacement ratio increased. It shows that average normalized load of ground improved by CSCP is higher by about $8{\sim}21%$ than by SCP. As a result of rigid loading tests, it was evaluated that average stress concentration ratio of CSCP is higher than that of SCP. Only expansion failure occurred in CSCP, whereas SCP showed the expansion and shear failure simultaneously.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.83-92
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• 2021

In this study, effective porosity measurement, electron microscope (SEM) observation, X-ray diffraction analysis (XRD), slaking, swelling, and unconfined compression strength according to water immersion were analyzed to evaluate the properties of mudstone with high porosity in Pohang. As a result of the test for 16 square samples (5 cm), the effective porosity was 14.67% on average, higher than porosity of general mudstone, and electron microscope observation confirmed that the porosity was actually high. As a result of X-ray diffraction analysis, the swelling clay mineral content was 2.3~4.1%, which was lower than the results of previous studies in Pohang. The slake durability index was 37.73~87.73%, showing low to medium durability, which was lower than the results of previous studies. It was confirmed that the swelling property rapidly expanded to 1.79~1.82% of maximum swelling strain in the major axis direction for 30 minutes. As the properties of decreasing the unconfined compression strength according to water immersion, the samples rapidly weathered after 10 minutes of water immersion, and the strength decreased. It was confirmed that the results of previous studies related to mudstone in Pohang were different. This is judged to be due to the high porosity of mudstone in study.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.23-32
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• 2016

This study evaluates landslide susceptibility using statistical analysis by SVM (support vector machine) and the illite index of clay minerals extracted from ASTER(advanced spaceborne thermal emission and reflection radiometer) imagery which can be use to create mineralogical mapping. Landslide locations in the study area were identified from aerial photographs and field surveys. A GIS spatial database was compiled containing topographic maps (slope, aspect, curvature, distance to stream, and distance to road), maps of soil properties (thickness, material, topography, and drainage), maps of timber properties (diameter, age, and density), and an ASTER satellite imagery (illite index). The landslide susceptibility map was constructed through factor correlation using SVM to analyze the spatial database. Comparison of area under the curve values showed that using the illite index model provided landslide susceptibility maps that were 76.46% accurate, which compared favorably with 74.09% accuracy achieved without them.

• Journal of the Mineralogical Society of Korea
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• v.17 no.4
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• pp.299-307
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• 2004

Surfactant adsorption by two montmorillonite types with different interlayer cations of Ca and Na was characterized by examining the time dependence of surfactant behavior on the clay surfaces. Surfactants with different micelle concentration were conducted in our experiment to observe a nonequilibrium activity of cationic surfactant on the clay over reaction periods ranging from 0.1 min to 11 days. As compared with Ca-montmorillonite (SAz), a more active intrusion of surfactant molecules into the interlayers was found in Na-montmorillonite (SWy). During a short 'initiation' stage, the basal spacing of SWy montmorillonite increased rapidly with logarithmic time. For SAz montmorillonite, however, the abrupt basal spacing increase occurred at the later stage of the reaction. From the result, the difference in the adsorption behavior exhibited by the two montmorillonite types partly results from their intrinsic nature, that is, inorganic cations originally existing on the clay surfaces. Additionally, the micelle concentration of surfactants affects the development of organo-montmorillonite, especially, in the intercalant formation and stabilization under nonequilibrium.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.41-50
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• 2007

The results from normally consolidated isotropic drained and undrained triaxial compression tests (NCIU and NCID) on sand with high silt content were presented in this paper. The experiments were performed on specimens of Nak-dong River sand with 63% silt content under effective confined pressures, 100 kPa to 400 kPa. From test results, Sandy silt became initially compressive but eventually appeared to provide dilatancy response throughout the entire stress-strain curve The behavior of sandy silt was more difficult to characterize than that of clay and sand due to lower plastic characteristic. Especially, the samples exhibited dilatancy development during shear after failure. The shear behavior and shear strength parameters of sandy silt can be determined as stress-strain behaviors are described by the Mohr-Coulomb failure criterion. The shear behaviors were observed increasing dilatancy volume change tendency with strain-softening tendency after failure. In this paper, the behavior of dilatancy depends on not only sand content but also fine content with low-cohesion during shear in the samples of sandy silt.

• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.249-259
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• 2009

The objective of this research was to find out the physical properties, such as dispersion and coagulation, of soil minerals depending on the types and concentrations of the cations in aqueous solution. Hwangto samples were obtained from 90 to 130 cm from surface at Jangdong-ri, Donggang-Myon, Naju, Chonnam Province. The clay fraction (< $2\;{\mu}m$) was separated by sedimentation method from the bulk soils. Both Hwangto and clay fractions, and the same samples after removal of amorphous and crystalline iron oxides were used in this experiment. The effect of 4 cations ($Na^+$, $K^+$, $Mg^{2+}$, $Ca^{2+}$) and their concentrations on settling speed and basal spacing of the minerals were observed to examine the physical properties of the soil and clay minerals. Hwangto mainly consisted of quartz, and the clay fractions consisted of kaolinite, illite, and vermiculite. The bulk soils contained 16.3 mg/kg of amorphous iron oxides and 436 mg/kg of crystalline iron oxides. Clay fractions were dispersed better than bulk soils due to their smaller particle size than that of the bulk samples in the aqueous solution. The bulk and clay samples were dispersed better when iron oxides were removed because of coating of minerals by the iron oxides. Clay minerals were settled faster as the charge and the concentration of cations added increased. The d-spacing of kaolinite and illite did not change when 4 types of cations were added. The d-spacing of vermiculite showed $14.04\;{\AA}$ when divalent cations were added while that of vermiculite showed $13.9\;{\AA}$ when monovalent cations were added. It may be attributed to the hydration radii of cations. This study indicated that both coating of iron oxides on minerals and types and concentrations of cations affect dispersion of minerals in solution and d-spacing of expanding clay minerals such as vermiculite.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.247-256
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• 2003

FEM analyses which are based on modified Cam-clay theory have been generally used in such cases as analyses of stability and displacement fur embankment construction on soft clays. However, the Modified Cam Clay Model can generate some problems in anisotropic stress conditions of field because the critical state theory has been developed through many laboratory tests in isotropic conditions. Thus, the applicability on the prediction of undrained shear strength and pore water pressure which was based on the critical state theory was evaluated by triaxial tests and numerical analyses in isotropic and anisotropic conditions. Used samples often come out in domestic area, together with general low plastic clays which are showing dilatant behavior in shearing process. They were evaluated by laboratory tests and FEM based on MCCM. From the results of test and numerical analysis, the predictions of undrained strength in low plastic clays well coincided with each other in both isotropic and anisotropic conditions. However, the generation of porewater pressure was often overestimated during undrained shearing in anisotropic conditions. The results can generate the errors in the prediction of stress path of field sites during loading such as construction of embankment on soft clays because the field is subjected to anisotropic conditions during loading.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.317-320
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• 2002

The compression index, $C'_c$ and the swelling index, $C'_s$ which are obtained from the e-log p curve of the consolidation test, are used to calculate the consolidation settlement. In this research, $C'_c$ and the two new methods of $C'_s$ i.e. $C'_{s1}$, $C'_{sm}$ for remolded clays were examined with the $({\omega}_0-{\omega}_p)$ and $(e_0-e_p)$ which are satisfied with the condition and the type of soil. Moreover, the relationships of $C'_{s1}$, and $C'_{sm}$ versus $C'_c$ were obtained.

• Water for future
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• v.7 no.2
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• pp.75-82
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• 1974

본시험은 관개 및 배수 설계를 위한 기초자료 제공을 목적으로 토양수분 및 지하수위의 변화상태를 구명하고자 하는 것으로 카나다 퀴백(Quebec) 지방 저지대의 대표적인 2종의 태양인 점토와 사질로움 토양에 대해서 일차적으로 지표, 지하배수간의 토양수분과 지하수위의 변화를 연구분석한 것으로 그 결과를 요약하면 다음과 같다. 1. 2종의 토양(점토, 사질로움)에 있어서 공히 토양수분은 지표로부터 지하로 내려갈수록 증가되는 상태를 나타냈으면 이는 하층토로 내려감에 따라 팽창된 치밀한 토양 조직을 가지고 있음을 시사하며 2. 동기에 있어서는 지표로부터 12inch 깊이의 토양수분이 더 깊은 18inch나 24inch 깊이의 토양수분보다 증가된 상태를 유지하였다. 이는 토양내의 빙결막이나 지표면의 눈 또는 어름에 영향으로 생각되며 이 경향은 점토질 토양에서 보다 토양내 빙결막으로의 수분 이종을 조장해주는 투수 계수가 큰 사질로움 토양에서 더 높았다. 3. 양식험구 공히 지표에서 얕은 지하 0∼3inch 이내의 토양수분은 항우를 전후해서 급격한 변화를 가져왔다. 여기에서 수분의 급상승은 호우시나 표층토가 하층토의 토양수분에 영향을 주는 항우이전에 포장용수량(Field capacity)에 달했기 때문에 급항하는 지표면의 물 분자가 열에너지에 의해 증발산되고 천층에 산재한 초, 수근에 의해 소비되는 때문인 것으로 사료된다. 4. 지하수위하의 토양수분은 포화에 달하여 거의 일정할 것으로 기대되었지만 실제로 많은 변화를 가져왔다. 이들 변화에는 부분적으로 토양사극이 지하수위하이라도 채워지지 않았거나(Capillary pressure가 작을 시) 혹은 관측기간 중에 토양의 융기와 수축에 기인된다고 생각된다. 5. 지하배수구가 지표배수구에 비해 지하수위항하가 빨랐음은 물론 사질로움 토양에서는 보다 높은 투수계수로 인해서 지하수위의 항하가 점토질 토양에서 보다 훨씬 빨랐음을 보여주고 있다.표시할 수 있다.된다.acid $0.41{\sim}0.65%$, 오미자는 malic acid $1.51{\sim}3.90%$, citric acid $2.40{\sim}3.92%$로 주요 유기산이 있다. 타닌은 물보다 에탄올 추출물이 다소 함량이 높았으며 특히 오갈피는 $3.35{\sim}3.85%$로 매우 높은 함량이었다.a 6 cases, etc. 2. The retroperitoneal space including kidneys were the most commonly involved site (43.5%), of which Wilms' tumor was the commonest. 3. About 2/3 of tumors developed under the age of 6 and the commonest lesion was Wilms' tumor and the next being neuroblastoma, teratoma, ovarian cyst and so forth. 4. In all tumors except ovarian tumor and choledochal cyst, male was more frequently affected. 5. In plain abdomen 75% of neuroblastoma crossed the mid line while in Wilms' tumor only 2 cases (14%) showed midline cross. Calcific density was 입력불가 in all 6 cases of teratoma (100%) as dense and discrete ossification, in 3 case of neuroblatoma (38%) characteristically in diffuse stippled appearance and in one case