• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.49-58
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• 2004

The cone pressuremeter test (CPM) is a new in-situ test which combines a standard cone penetration test with a pressuremeter. The cone pressuremeter tests in clay are presented and analyzed. An analytical solution of CPM incorporated non-linear soil behavior with no volume change is presented, and curve fitting technique is proposed to make use of both the loading and unloading portions of the pressuremeter test. The proposed method is accomplished by putting greater emphasis on the unloading portion. Twenty CPM tests are analyzed using the proposed method, and the derived undrained shear strength of soil is compared with other tests such as field vane tests and laboratory tests. The interpreted soil parameters had resonable values when compared to other in-situ and laboratory test results. The cone pressuremeter has provided reliable measures of undrained shear strength using curve fitting method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.33-40
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• 1988

In this study, effects of the density of soil and the confining pressure applied to the soil sample on the elastic moduli of subgrade soils are experimentally analyzed. Through investigation of subgrade materials of domestic expressways, five typical types of subgrade soils are selected for the experiments. A series of unconsolidated undrained triaxial tests is performed on samples prepared with various water contents and densities at the confining pressures of 1.02, 2.04, and $3.06kg/cm^2$. Initial tangent modulus is inferred from the unloading-reloading portion of the stress strain curve obtained during an individual loading-unloading-reloading test. As a result of the analysis, it is found that the effect of the confining pressure on the elastic modulus of subgrade material is well consistent with the equation proposed by Janbu, and that the elastic modulus can be related to the dry unit weight expressing the Janbu constants as exponentiial functions of it. It is also found that the water content has little effect on the elastic modulus for the samples with the degree of saturation less than 70%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5654-5663
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• 2015

In the unsaturated soil, suction, the negative pore water pressure leads to increases of the yield stress and the plastic shear stiffness of the soil skeleton due to the growth in interparticle stress. Therefore, in this study, the stress-strain relationship based on cyclic elasto-plastic constitutive model extended for unsaturated soil considering the 1st and the 2nd yield functions was induced in order to account for these effects of suction under the dynamic loading condition such as the earthquake. Through the program code considering this relationship and the routine of the cyclic loading with the reversion of loading direction, the numerical simulation of the cyclic triaxial test under the unsaturated condition would be possible. It is expected that the results of this study possibly contribute to the accuracy improvement on the prediction of unsaturated soil behavior under the dynamic loading condition.

• Journal of the Korean Geosynthetics Society
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• v.8 no.1
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• pp.25-32
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• 2009

In reclaimed loose sandy layer with dredged soil, liquefaction by the small scale earthquake coud be occurred easily. A study has been carried out to investigate the Liquefaction characteristic on Saemangeum dredged sandy soil, and compared with other results from the literature investigation. A series of undrained cyclic triaxial compression tests were performed on dredged sandy soil of Seamangeum area. The tests were performed at the three different initial relative densities(namely 30%, 50%, 70%), different cyclic stress ratio and different consolidation stress condition. The results of this study showed that cyclic stresses (${\sigma}_d$) increased linearly with increase of consolidation ratio, but the stress ratios (${\sigma}_d/2{\sigma}^{\prime}{_c}$) were almost same. The stress ratios were increased almost linearly with increase of relative density. Compared with other sandy soil, Saemangeum dredged sandy soil showed relatively weak liquifaction characteristics.

• Geotechnical Engineering
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• v.13 no.4
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• pp.177-198
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• 1997

Since decomposed granite soil shows various characteristics of shear behavior dependent on initial conditions such as weathering degree and grain breakage, it is nacessary to invert ligate stress -strain relationship and changes of shear characteristics for different initial conditions. Associated with abovefnentioned view, direct shear tests, and triaxial compression tutsts(Ef, CD) were carried out in this study for undisturbed and disturbed compacted weathered granite samples obtained from 4 construction work sites with the various weathering degree and components of parent rocks. The deformation behavior of undisturbed samples under small confining stress shows hardening to softening, which is similar to that of over nsolidated clay whereas disturbed weathered granite soils do hardeningfonstant regardless of weathering degree, which is also similar to sedimentary clay. Conventional direct shear-tests for undisturbed samples show a tendency to overestimate cohesion. It is possidle to approximate stress ratio(q/p') and volumetric increment ratio(dv/ds) in the triaxital compression tests by an equation, ($dv/d\varepsilon,=\alpha(M-\eta))$ irrespective of moisture content, weathering degree and disturbance.

• Journal of the Korean Society for Railway
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• v.18 no.4
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• pp.354-362
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• 2015

Since allowable settlement of concrete slab track is about 30mm, a lot of attention must be paid to the settlement of the earthwork (reinforced trackbed, upper subgrade, under subgrade) under the concrete track. To this end, more experimental data should be accumulated through tests for these materials. In this study, we evaluate the long-term settlement of reinforced trackbed and subgrade materials using factors such as repeated loading conditions, water content, and grain size distributions in a large triaxial test and a large oedometer test. In cases in which the performance of the reinforced trackbed layer meets the design criteria, the settlement caused by train load was considerably small. But, when the water content increases in the subgrade, unexpectedly large settlement might occur for certain grain size distributions of the subgrade materials.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.63-70
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• 2011

Expanded Polystyrene (EPS) is a type of geosynthetic material manufactured with various strengths, unit weights, and dimensions. Due to recent advances in research on EPS, the use of EPS has increased dramatically. This super light weight material has a unit weight of approximately $0.16{\sim}0.47kN/m^3$, equivalent to 6.3~15.7 of that of most natural soils with conditions of fill materials. In spite of this advantage, it is noted that no standard method of resilient modulus test on EPS geofoam was reported and no literature on resilient modulus test methods for EPS geofoam exist. The main object of this study was to investigate feasibility of the resilient modulus of EPS when it was applied for flexible pavement. The investigation of the feasibility was completed based on the results from triaxial tests.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.7-15
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• 2022

Most studies have conducted cryogenic triaxial compression tests with frozen specimens prepared in a separate mold by one-directional freezing. This method has the potential to generate residual stress in a frozen specimen and cannot be adopted to simulate the application of the artificial ground freezing method in the field. Therefore, in this study, novel equipment and procedure for the cryogenic triaxial compression test were proposed to overcome the limitations of existing test methods. Therefore, the mechanical characteristics of frozen sand, considering the effect of temperature and confining pressure, were evaluated. As the freezing temperature decreased, the brittleness of frozen sand increased, and the strength increased due to a decrease in the unfrozen water content and an increase in the ice strength. A higher confining pressure resulted in an increase in interparticle friction and the pressure melting phenomenon, which caused strength reduction. Thus, it was found that the mechanical behaviors of frozen sand were simultaneously affected by both temperature and confining pressure.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.89-100
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• 2007

In the companion paper, we provided the novel elastic-plastic constitutive model based on the micromechanics theory. Herein, the elastic and elastic-plastic deformation of granular soils is meticulously analyzed. To guarantee high accuracy of the microscopic parameter, the systematic procedure to evaluate the parameters is provided. The analysis of the elastic response during the isotropic and triaxial compression shows that the stress-level dependency of cross-anisotropic elastic moduli is induced by the power relationship of the contact force in the normal contact stiffness, while the evolution of fabric anisotropy is more pronounced during triaxial compression. The micromechanical analysis indicates that the plastic strains are likely to occur at very small strains. The plastic deformation of tangential contacts has an important role in the reduction of soil stiffness during axial loading.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.27-37
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• 2003

In this research stress-strain behavior of composite geocell-soil systems under triaxial condition and the influence of strength due to the presence of geocell were studied. For the research a series of triaxial tests were carried out on sand specimens confined by flexible-walled single rubber cell. The diameter of all rubber cells placed at the center of the soil sample were 50 mm. Three rubber sizes, i.e. 35, 50 and 70 mm height, were applied to the soil specimen and the size of soil specimen was 50 mm in diameter and 100 mm in height. Three different densities of soil were used for the tests. In general, it was observed that the sand specimen develops an apparent cohesion due to the confinement by the geocell. The magnitude of this cohesion seemed to be dependent to the properties of the geocell material. The test results have shown that the geocell material for this research not only develops the apparent cohesion but also increases the angle of friction whereas geosynthetic material in the references showed only the increase of apparent cohesion. From the application of geocell-soil composites to the hyperbolic model, it was recognized that the determination of the peak strength influences the behavior of the geocell-soil composites.