• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.347-355
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• 2008

In this paper single degree of freedom macro-element model was presented to investigate the interaction between soil and the deep foundation under the lateral loads. It was made by modelling each component related to the soil-structure interaction and combining them into one piece. It enhanced the conventional method that was not able to break down the interaction components in piece due to the usage of simple spring element for interaction. A proposed macro-element classified the stress components in relation to the interaction into frictional and compressive resistance. Each component was modelled using the classical plasticity theory, and finally combined in parallel. An example study was carried out using the proposed macro-element for deep foundation embedded in three layered cohesive soil. It showed improved results compared to the conventional method by producing additional information of the interaction components as well as the overall behavior of foundation.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.481-488
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• 1999

This study, investigates the existing theoretical backgrounds in order to examine the behavior of lateral flow owing to the plasticity of soils when unsymmetrical surcharge is worked on polluted soils by the increase of water content compares and analyzes the results measured through model tests. Unsymmetrical surcharge is increased at regular intervals to soil tank made up the polluted soils and then the amounts of settlement, lateral displacement and upheaval are observed. Critical surcharge was decided ｑ$\sub$cr/= 3.42 C$\sub$u/ similar to those had proposed Terzaghi and JHI, and the value of ultimate capacity was decided ｑ$\sub$ult/= 7.71 C$\sub$u/ similar to that of Tschebotarioff and JHI.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.677-684
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• 2000

Piezocone test as well as Dilatometer tests are used worldwide to evaluate the engineering properties of clay soils. The common strong point of the two tests is that they can estimate, by the identical test equipment, various properties of soils, which are the unit weight of soils of OCR, K$\sub$o/, undrained shear strength(s$\sub$u/), coefficient of consolidation(c$\sub$h/) and soil classification etc,. A series of the two types of field tests are performed in this study on marine clays with low plasticity at Inchon International Airport construction site to estimate various properties of the soils such as s$\sub$u/, OCR, and c$\sub$h/, which are then compared each other as well as with the results of reference tests. The comparisons show that the way of interpretation is the most critical factor in obtaining confidential results for a certain engineering property for both tests.

• Journal of Microbiology and Biotechnology
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• v.16 no.11
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• pp.1661-1677
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• 2006

Rhizobium and related genera are soil bacteria with great metabolic plasticity. These microorganisms survive in many different environments and are capable of eliciting the formation of nitrogen-fixing nodules on legumes. The successful establishment of symbiosis is precisely regulated and requires a series of signal exchanges between the two partners. Quorum sensing (QS) is a prevalent form of population density-dependent gene regulation. Recently, increasing evidence indicates that rhizobial quorum sensing provides a pervasive regulatory network, which plays a more generalized role in the physiological activity of free-living rhizobia, as well as during symbiosis. Several rhizobia utilize multiple, overlapping quorum sensing systems to regulate diverse properties, including conjugal transfer and copy number control of plasmids, exopolysaccharide biosynthesis, rhizosphere-related functions, and cell growth. Genomic and proteomic analyses have begun to reveal the wide range of functions under quorum-sensing control.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.2
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• pp.64-72
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• 1995

A series of cubical triaxial tests with three independent principal stresses was per- formed on Baekma river sand( # 40~100). It was found that the major principal strain at failure remained approximately constant for b values larger than about 0.3 for both the drained and undrained condition, and thereafter increased as b value decreased. The test results showed that the direction of the strain increment at failure form acute angles with the failure surfaces for both the drained and undrained condition. The results were thus not in agreement with the normality condition from classic plasticity theory. Howev- er, it was found that the projections of the plastic strain increment vectors on the octahe- dral plane were perpendicular to the failure surface in that plane. Failure strength in terms of effective stress anlaysis was greatly influenced by the variation of intermediate principal stress and so was failure criterion. The effective stress failure surfaces for both the drained and undrained condition were estimated quite well by use of Lade's failure criterion.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.1
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• pp.93-101
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• 1997

This paper presents yield surfaces and hardening laws for describing the state of an unsaturated soil under isotropic compression and suction changes. The yield surface is formulated within the framework of hardening plasticity using two independent sets of stress variables : the excess of total stress over air pressure and the suction. And the application of the yield surfaces and hardening laws are confirmed from the result of the experiment. To this end a series of suction-controlled isotropic tests are conducted on clayey soils. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. The specimens are compacted using a half of Proctor compaction energy with 5 % lower of water content than the optimum moisture contents. From test results, existence of the yield surfaces and an application of hardening laws to samples are confirmed by comparison between test and predicted results. And it is confirmed that LC yield locus is extened with the total plastic deformations induced by suction or stress changes, however, SI yield locus is only extended with the plastic deformations by induced suction changes.

• Journal of the Korean Geotechnical Society
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• v.17 no.2
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• pp.135-142
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• 2001

사면안정해석을 위해 다공체(porous medium) 이론이 제시되었다. 다공체 이론은 간극수압, 토질입자 및 간극수의 상호작용을 포함하는 여러 가지 지반관련 문제의 이해에 있어 매우 중요하다. 이러한 상호작용은 토질강도 및 변형에 중요한 영향을 미친다. 압밀 예제로서 이러한 모델의 정확도를 첫째로 검증하였다. 사면안정해석에 있어서 토질의 응력 및 강도는 일반적인 구성모델을 포함한 비선형 유한요소해석을 사용하여 정확히 계산되었다. 사면안정해석은 한계상태를 표시하는 파괴면이 나타날 때까지 점차적인 중력의 증가로 실행되었다. 안전율은 증가시킨 중력과 실제사면 중력의 비로서 계산되었다. 제시된 사면 안정 해석 방법의 자세한 사항은 예제를 통하여 설명되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.1
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• pp.13-24
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• 2020

A systematic approach to assess the safety of corrugated steel plate structures has not been established yet. Therefore, an improved safety assessment procedure was proposed in this study by considering the characteristics of corrugated steel plate structures in which the dead load of backfill soil is dominant and the live load effect is minimized. The proposed procedure can consider the combined effect of axial force and bending moment on the safety, based on the Soil-Culvert Interaction (SCI) method, and can differentiate the maintenance scheme according to the calculated plasticity index. There is also an advantage in enhancing the accuracy of assessment, utilizing the measured displacements. Furthermore, improved methods were proposed by discussing various ways for reasonably improving the proposed assessment procedure. The safety of an actual structure and a full-scale test specimen was assessed by applying the proposed procedure. The conventional assessment procedure significantly overestimated the load-carrying capacity, whereas the proposed procedure resulted in a reasonable level of safety. Therefore, the procedure proposed in this study is expected to contribute to the establishment of proper maintenance plan such as the quantitative condition assessment and strengthening of corrugated steel plate structure.

• Journal of Korean Society of Forest Science
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• v.88 no.2
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• pp.255-265
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• 1999

This study deals with forest soil characteristics and their effects on the trafficability of logging vehicles. The study area is the national experimental forest located in Kwangnung. This site has 20m length and is equally divided by 5 surveying ranges with 4m width, on which a tractor(FIATAGRI) attached with logging boogie can drive in 4 driving types, namely 1time-return unload, 1time-return with load of 780-790kg weight of 3 logs, 5 and 10times-return with same load. After one driving type on all surveying ranges, the soil hardness is surveyed 5 times with 3 several type tools, SHM-1 type, lang penetrometer(L-PNTM), and clegg impact soil tester(CIST). A disturbed degree of cover vegetation and sliding conditions of vehicle are also observed. As results, the soil type of the test site was SC by USCS and dry brown forest soil. The cover vegetation is gotten trambled under driving after 3-5 times-return, shrubs leaves are fully fallen and their bark are peeled, and after 10 times-return the cover vegetations were nearly disappeared. The test vehicle has neither slided nor was overthrown. The wheel tracks in the 1-3 ranges, of which unit weight(gd, gt) is high and soil moisture content(MC) is low, were only 1-2cm deep, but those in the 4-5 ranges, of which the gd, gt is low and the MC is high, were 5-7cm deep. In the soil hardness test, which was established in 5 test ranges by types of driving, the more driving times, the higher the hardness. The soil hardness surveyed by L-PNTM has changed slowly and that surveyed by SHM-1 type has risen sharply. In the ranges with higher specific gravity(Gs), higher unit weight, lower MC and higher liquid limit(LL) and plasticity index(PI) was the soil hardness high and the trafficability was good. In the ranges with opposite conditions, also in the ranges of the lower soil hardness, the trafficability must be not good, because the wheel track may be deep. The results from CIST attached with 4kg hammer was not better than expected. So it is recommended to use CIST with 2.5kg or 0.5kg hammer.

• Journal of the Korean Geosynthetics Society
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• v.8 no.3
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• pp.1-7
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• 2009

Earth reinforcement by using geogrids as reinforcing materials are widely applied to several earth structures. The bearing capacity of geogrid reinforced foundation soils is usually examined on based on the rigid plasticity theory or Limit Equilibrium Method. Method of analysis such Limit Equilibrium Method provide no detail information about failure behaviour or strain which develop in the reinforcement or foundation. In this paper the analysis of failure behaviour of strip footing on geogrid-reinforced sand over a soft caly was investigated by using a numerical method. A series of finite element analyses were performed on a geogrid-reinforced strip footing over a soft clay including number of geogrid layers, length, depth. We effectively investigated the failure behaviour and improvement of bearing capacity on the reinforced foundation soil by using FEM program.