• The Journal of Engineering Geology
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• v.22 no.3
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• pp.275-281
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• 2012

Thermal distribution in soils must be considered in engineering designs and constructions, including estimates of frost heave and thaw settlement, infrastructure in cold regions, and geothermal systems. Because thermal conductivity is a key parameter for evaluation of thermal distribution in soils, it must be accurately estimated. The thermal conductivity of fine-grained soils has been widely studied in recent years; however, few studies have reported a reliable method for experimental measurement. The present study presents the results of an experimental investigation of the thermal conductivity of a saturated kaolinite-silica mixture with respect to the variation of dry density. Thermal conductivities were measured in Constant Rate of Strain (CRS) consolidation tests, and the experimental data were analyzed to evaluate the accuracy of the new measurement system. In addition, we present an evaluation method for predicting thermal conductivity in fine-grained soils.

• Journal of the Korean GEO-environmental Society
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• v.3 no.3
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• pp.15-25
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• 2002

The permeability coefficient is one of the fundamental engineering properties of soft clays. Consolidation process as well as migration of pollutants in soil are affected the permeability coefficient, which generally decreases with the reduction in void ratio during consolidation. After Kozeny(1927) and Carman(1956), many researchers have proposed the relationships between void ratio and permeability in such forms as; (1) log e - log k(1+e), (2) e - log k, or (3) log e - log k. Constant rate of strain (CRS) tests was performed with undisturbed samples obtained at Kunsan and Kimhae deposits, which are representative Korean marine clay. From the results of the tests, the relationships were found valid for Kunsan and Kimhae clays. The experimental correlation $C_k=0.5e_o$ was satisfied with Kimhae clay but not with Kunsan clay.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.459-469
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• 2002

We have remolded marine clay sample collected along the vertical and horizontal directions and investigated the characteristics of the consolidation constants by SCT and CRSC methods. We have studied also on consolidation chracteristics and application for weathered granite soil using SCT and CRSC methods for undisturbed and disturbed samples. As the result, values of pre-consolidation stress, compression index, excessive pore pressure, pore water pressure ratio of the marine-clay were different due to different test methods(SCT and CRSC) and sampling directions(vortical and horizontal directions). Disturbed and undisturbed samples of the weathered granite soil have showed similar change aspect like marine clay during over-consolidatied and normally consolidatied stages.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.93-105
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• 2000

일정변형률압밀사시험의 효율성 및 적용성을 구체화하기 위해 인공시료 또는 한정된 지역에서 채취한 불교란 점성토 시료가 아닌 광범위한 지역에서 채취한 불교란 점성토 시료에 대해 시험을 실시하였다. 시료채취의 대상지역은 우리나라의 서해안에서 동해안에 이르는 13개 지역이며, 29개의 불교란 자연시료를 채취하여 일정변형률압밀시험을 113회 실시하였다. 또한, 비교하기 위해 표준압밀시험도 병행하였다. 시험결과로부터 얻어진 압밀정수에 대한 공학적 특성을 고찰하였고, 회기분석을 통해 통계식을 제안하였다. 두 시험법에 의해 산출된 압밀정수를 비교 분석한 결과 수압비가 20% 이내인 범위에서는 일정변형률압밀시험의 변형률 속도가 압밀시험의 정수에 미치는 영향은 거의 없는 것으로 나타났다. 압축지수 및 압밀계수는 일정면형률시험의 결과 값이 표준압밀시험의 결과 값보다 크게 산출되었으나 일관성을 보였다. 또한, 선행압밀압력에 있어서는 두 시험법에 Cassagrande의 방법을 적용할 경우 서로 일치하는 것으로 나타났다. 본 연구로부터 일정변형률압밀시험을 사용하여 표준압밀시험에 상용하는 상호관계식 개발의 타당성을 확인할 수 있었다.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.279-295
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• 2014

A series of one-dimensional consolidation tests and triaxial creep tests were performed on Nansha clays, which are interactive marine and terrestrial deposits, to investigate their time-dependent behaviour. Based on experimental observations of oedometer tests, normally consolidated soils exhibit larger secondary compression than overconsolidated soils; the secondary consolidation coefficient ($C_{\alpha}$) generally gets the maximum value as load approaches the preconsolidation pressure. The postsurcharge secondary consolidation coefficient ($C_{\alpha}$') is significantly less than $C_{\alpha}$. The observed secondary compression behaviour is consistent with the $C_{\alpha}/C_c$ concept, regardless of surcharging. The $C_{\alpha}/C_c$ ratio is a constant that is applicable to the recompression and compression ranges. Compared with the stage-loading test, the single-loading oedometer test can evaluate the entire process of secondary compression; $C_{\alpha}$ varies significantly with time and is larger than the $C_{\alpha}$ obtained from the stage-loading test. Based on experimental observations of triaxial creep tests, the creep for the drained state differs from the creep for the undrained state. The behaviour can be predicted by a characteristic relationship among axial strain rate, deviator stress level and time.

• Journal of the Korean GEO-environmental Society
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• v.11 no.4
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• pp.25-31
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• 2010

The amount of dredging clay will be greatly increased by the eco-rive project and port development in Korea. Geotechnical engineers have thrown their efforts into the new ways for effective re-uses of the dredging clay such as the material for reclamation, and so on. However, very high initial water content and low strength causes unexpected difficulties in the aspect of trafficablility or time for consolidation. Therefore, the injection of cement stabilizer is used as one of ways to improve reclaimed ground. However, it also makes an argument by heavy metal from cement stabilizer. In this paper constant rate of strain consolidation test and normal consolidation test were performed to investigate behavior characteristics of the consolidation about soil-cement include lean mixed cement to reduce the environmental loads by the cement. The experimental results of consolidation characteristics about soil-cement include lean mixed cement influenced by mixing ratio. Especially it was observed that mixing ratio of 4%~6% leads not only the reduction of consolidation settlement, but time for consolidation.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.87-94
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• 2012

For soils with high void ratios, the inverse method of utilizing results obtained from centrifuge model test was used to find the constitutive relation of effective stress - void ratio - permeability whereas conventional oedometer test and constant rate of strain consolidation(CRS) test about settlement of interface and pore pressure and distribution with time were compared with numerically estimated values to confirm such a constitutive relation as obtained from the inverse method. As results of numerical method, the volumetric ratio and reclamation velocity were obtained for the reclamation condition.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.134-153
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• 1988

This paper was carried out to investigate the existence of a unique stress- strain behavior by obtaining some factors influencing the time dependent stress- strain behavior of clay. The results obtained from this study were summarized as follows ; 1. The relationship between stress ratro and strain in normally consolidated clay was in- dependent on pre-shear consolidation pressure. Therefore, shear strain could be expressed as a function with stress ratio. 2. The constitutive equation of shear strain on Modified Carn Clay Model coincided better with the observed value than Cam Clay Model. 3. The relationships between deviator stress and shear strain, between pore water pressure and shear strain were unified by the mean equivalent pressure. 4. The shear strain contour in norrnally consolidated clay was increased linearly through origin, but that in overconsolidated clay was not in accordance with the result of the former. 5. Because the effective stress path of normally consolidated clay was unified by the mean equivalent pressure, state boundary surface in (e,p,q) space was transformed into two dimensional surface. But it was considered to be suitable that the unified stress- strain in overconsolidated clay be expressed by a function with overconsolidation ratio. 6. The deviator for constant strain was increased linearly with increment of strain rate ($\varepsilon$) on semi-log scale, but pore water pressure was decreased. 7. The behavior of stress relaxation was transformed from linear to curvilinear with inc - rement of strain rate before stress relaxation test, and pore water pressure was increased in total range. 8. The strain of creep was increased linearly with increment of time on semi-log scale. The greater the strain rate before creep test became, the greater the increment of strain of creep became. And the pore water pressure during creep test was increased generally with increment of time on semi-log scale.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.31-41
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• 2008

Consolidation characteristics of reclamated ground with dredged soil and methods of evaluating them are investigated in this paper. For a dredged and reclamated ground with a very high water content, self-weight consolidation being progressed, its consolidation characteristics are difficult to find since it is almost impossible to have a undisturbed sample. In order to overcome such a problem, methods of laboratory tests with disturbed sample were studied to obtain consolidation parameters required to analyze consolidation settlement in practices, using the conventional infinitesimal consolidation theory, were evaluated by carrying out various laboratory tests with disturbed soils such as oedometer test, constant rate of deformation test, Rowe-cell tests with ring diameters of 60 mm, 100 mm and 150 mm and the centrifuge model tests with 40 g-levels. Constitutive relations of void ratio - effective vertical stress - permeability were evaluated by using the inverse technique implemented with the finite strain consolidation theory and results of centrifuge model tests. Design soil parameters related to consolidation such as compression index, swelling index, coefficient of volume change and vertical and horizontal consolidation coefficients were proposed properly by analyzing the various test results comprehensively.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.81-95
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• 2015

The permeability behavior of Ariake clays has been investigated by constant rate of strain (CRS) consolidation tests with vertical or radial drainage. Three types of Ariake clays, namely undisturbed Ariake clay samples from the Saga plain, Japan (aged Ariake clay), clay deposit in shallow seabed of the Ariake Sea (young Ariake clay) and reconstituted Ariake clay samples using the soil sampled from the Saga plain, were tested. The test results indicate that the deduced permeability in the horizontal direction ($k_h$) is generally larger than that in the vertical direction ($k_v$). Under odometer condition, the permeability ratio ($k_h/k_v$) increases with the vertical strain. It is also found that the development of the permeability anisotropy is influenced by the inter-particle bonds and clay content of the sample. The aged Ariake clay has stronger initial inter-particle bonds than the young and reconstituted Ariake clays, resulting in slower increase of $k_h/k_v$ with the vertical strain. The young Ariake clay has higher clay content than the reconstituted Ariake clay, resulting in higher values of $k_h/k_v$. The microstructure of the samples before and after the consolidation test has been examined qualitatively by scanning electron microscopy (SEM) image and semi-quantitatively by mercury intrusion porosimetry (MIP) tests. The SEM images indicate that there are more cut edges of platy clay particles on a vertical plane (with respect to the deposition direction) and there are more faces of platy clay particles on a horizontal plane. This tendency increases with the increase of one-dimensional (1D) deformation. MIP test results show that using a sample with a larger vertical surface area has a larger cumulative intruded pore volume, i.e., mercury can be intruded into the sample more easily from the horizontal direction (vertical plane) under the same pressure. Therefore, the permeability anisotropy of Ariake clays is the result of the anisotropic microstructure of the clay samples.