• Geomechanics and Engineering
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• v.17 no.6
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• pp.565-572
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• 2019

Spatial variability is an inherent characteristic of soil, and auto-correlation length (ACL) is a very important parameter in the reliability or probabilistic analyses of geotechnical engineering that consider the spatial variability of soils. Current methods for estimating the ACL need a large amount of laboratory or in-situ experiments, which is a great obstacle to the application of random field theory to geotechnical reliability analysis and design. To estimate the ACL reasonably and efficiently, we propose a micro-structure based numerical simulation method. The quartet structure generation set algorithm is used to generate stochastic numerical micro-structure of soils, and scanning electron microscope test of soil samples combined with digital image processing technique is adopted to obtain parameters needed in the QSGS algorithm. Then, 2-point correlation function is adopted to calculate the ACL based on the generated numerical micro-structure of soils. Results of a case study shows that the ACL can be estimated efficiently using the proposed method. Sensitivity analysis demonstrates that the ACL will become stable with the increase of mesh density and model size. A model size of $300{\times}300$ with a grid size of $1{\times}1$ is suitable for the calculation of the ACL of clayey soils.

• KCID journal
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• v.5 no.1
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• pp.75-82
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• 1998

A multivariate regression analysis for compression index and com- pressibility ratio of clayey soils in regard to some soil indices, i.e natural water content, Atterberg limits, and in-situ void ratio, was presented to estimate the primary consolidation s

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2003.08a
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• pp.315-322
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• 2003

최근 들어 시화호 주변에 연구개발 및 주거를 목적으로 하는 사업지구가 활발하게 계획 또는 시공되고 있는데, 모든 건설공사에서와 마찬가지로 안전하고 경제적인 설계 및 시공을 위해서는 실내 및 현장지반조사를 통하여 지반의 공학적 특성에 대한 정확한 평가가 반드시 선행되어야 한다. (중략)

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.1
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• pp.102-105
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• 2001

This study has been done to investigate the characteristics of the wall materials of a earthen house ; the core-wall of a wood-frame house and the mud-wall of a all-wall house. A series of tests is carried out to study the physical properties of wall materials which are picked from existing earthen houses. The core-wall materials are composed of sandy soil or clayey soil with low plasticity. The mud-wall materials are sandy soil with well compaction effect. It is confirmed that the wall materials are common soils which are easily picked from the residential quarter.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.3
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• pp.211-216
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• 1986

To establish a suitability grouping system of paddy soils for double or multiple cropping with rice which is intensively practiced in the southern parts of Korea, a few basic experiments were carried out for two years. The results are summarized as follows; 1. The potential productivities of the paddy soils which were tested without any fertilizer in the pots of subsoil samples by the double cropping of rice and other upland crops were resulted that the soils of "Moderately well drained" fine silty textured were the highest while the soils of "Poorly drained" sandy were the lowest, and the productivities could be clearly comparable according to the differences of soil conditions. 2. The decomposability of organic matter also was higher in the soils of "Moderately well drained" than the "Imperfectly drained". The coarse loamy and coarse silty textured soils were high in the upland condition and in the early stages of submerging while the fine loamy and fine silty textured soils were high at the late stage of submerging in the rates of organic matter decomposition. 3. The days to be reached to tillable condition after rainfall in fine loamy textured soils were about 5 days earlier than the clayey soils. The period of tillable condition of fine clayey soils with "Moderately well drained" was the longest and that of the fine loamy textured soils was the shortest. But the soils with "Imperfectly drained" were not clear among soil textural classes. 4. The lower the ground water table the higher was the productivity indices. The variation of ground water table in the medium textured soils was higher than the both of coarse and fine textured soils among "Moderately well drained". But it was observed the opposite in the soils of "Imperfectly drained".

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.3
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• pp.1-8
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• 2002

Clayey paddy soils should be mixed with other good coarse soils to be used as a material for the lining, or, embankment. However, it has been difficult to separate soil particles from each other because of the internal cohesion in the soil gradation(separation) characteristics of the fine soil were investigated by various laboratory tests including the slaking durability test. Degradation rate of the soil were dependent upon the clay content and the initial water content before the submergence. The amount of degradations decreased as initial water content increased with exponential functions. The dried specimens separated into the particles after 24 hours of the submergence and specimens which water contents were less than 10% also separated into the particles after 2, or 3 days of the submergence. Compaction curves and the unconfined strength were not varied before and after the submergence. However, unconfined strength decreased as water content increased.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.87-96
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• 2002

The strain holding test(SHT) or the sell-boring pressuremeter test(SBPT) has been effectively utilized to determine the horizontal coefficient of consolidation$(c_h)$ of clayey soils. However, a commonly used procedure proposed by Clarke et al.(1979) can lead to an erroneous estimation of $(c_h)$ because of its simplified assumptions. This paper deals with numerical analyses based on realistic test conditions of the generally accepted testing procedure, and .using the most commonly used type of pressuremeter. The effects of pressuremeter geometry, partial drainage during cavity expansion, and the cavity strain level for the holding test are investigated with the radial distributions of the initial excess pore pressure and their dissipation rate. Based on the results of the numerical analyses, the curve of the time factor for the 50% degree of consolidation($T_{50}$) needed to estimate $(c_h)$ is proposed. Comparisons are made between $(c_h)$ values estimated from the SHT or the SBPT and those obtained from other in situ and laboratory tests performed at two sites in Korea. These results suggest the improved capability of the $T_{50}$ curve proposed herein.

• Journal of the Korean Geotechnical Society
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• v.27 no.6
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• pp.49-61
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• 2011

This paper presents the applicability of rheological models for describing fine-laden debris flows and analyzes the flow characteristics as a function of grain size. Two types of soil samples were used: (1) clayey soils - Mediterranean Sea clays and (2) silty soils - iron ore tailings from Newfoundland, Canada. Clayey soil samples show a typical shear thinning behavior but silty soil samples exhibit the transition from shear thinning to the Bingham fluid as shear rate is increased. It may be due to the fact that the determination of yield stress and plastic viscosity is strongly dependent upon interstructrual interaction and strength evolution between soil particles. So grain size effect produces different flow curves. For modeling debris flows that are mainly composed of fine-grained sediments (<0.075 mm), we need the yield stress and plastic viscosity to mimic the flow patterns like shape of deposition, thickness, length of debris flow, and so on. These values correlate with the liquidity index. Thus one can estimate the debris flow mobility if one can measure the physical properties.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.21-27
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• 2012

Estimating the thermal conductivity of clayey soils is important for enhancing the performance of geoengineering structures in cold regions and clay barriers for nuclear waste repositories, but specimen disturbance, saturation, and heat boundary conditions of the test apparatus hinder reliable measurements of the thermal conductivity of saturated clayey soils. This paper presents the results of an experimental study carried out using modified consolidation tests with the needle probe method to measure thermal conductivity. Experimental consolidation tests with saturated kaolinite were performed to investigate the effect of effective stress and dry density on thermal conductivity for saturated kaolinite. In addition, thermal conductivity of soil particles were thoroughly investigated and experimental results were used to evaluate the accuracy of the models to predict thermal conductivity.

• Geotechnical Engineering
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• v.8 no.4
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• pp.17-30
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• 1992

Constitutive relations for lightly overconsolidated state of clayey soils. as well as normally consolidated state of those, play an important role in the analyses of geotechnical structures in clay deposits. For the practical point of view, a constitutive model applicable to lightly overconsolidated soils should be developed to easily evaluate the model parameters, and to precisely predict the various behavior of OC soils. For that purpose, a constitutive model for the lightly overconsolidated soil behavior has been proposed to rep- resent the undrained behavior which can be normalized using equivalent pressure, p. , Yielding within the initial yield surface is modeled exclusively using the given normally consolidated model parameters only. Furthermore, the proposed model can be applied to consider the effects of overconsolidation, secondary consolidation, and stress relaxation. The measured behavior in undrained triaxial tests has been Predicted easily and precisely in comparison with other models.