• Geomechanics and Engineering
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• v.17 no.3
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• pp.247-252
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• 2019

Modulus of deformation of soil is an essential parameter used for design analysis of foundations, despite its importance; little attention is paid to developing empirical models for predicting the sensitivity of deformation moduli to other parameters that obtained from the pressuremeter tests. Various methods of analysis used to predict the horizontal at rest pressure from pressuremeter testing ($P_o$), these values showed distinctive variations, five methods used to evaluate the values of horizontal at rest pressure, these values been used to evaluate the modulus of elasticity using three methods of analysis. The values of modulus showed distinctive increase when the values of horizontal at rest pressure increase for the same pressuremeter test, these increases may reach to 65%. This sensitivity of the moduli to values of horizontal lead the author to propose some reliable methods of analysis for both the horizontal at rest pressure and the modulus of deformation from pressuremeter testing.

• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.39-49
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• 2018

In this study, aimed at determining the elastic modulus of deep mixed samples, 320 test specimens were developed by mixing 8%, 10%, 12%, and 14% of stabilizer mixture in the granular conditions of clay, sand and gravel. Uniaxial compression tests were carried out using these specimens, and the uniaxial compression strength and strain were analyzed to determine the secant elastic modulus and tangent elastic modulus. Laboratory test results showed that the uniaxial compression strength of all deep mixed samples increased with increasing curing time and stabilizer mixing ratio, and that the secant elastic modulus and the tangen elastic modulus also increased. The increase of the elastic modulus according to the curing period turned out greater in the tangent elastic modulus than in the secant elastic modulus. In order to measure elastic modulus with changes in stabilizer mixing ratio, the correlation coefficient between the elastic modulus for stabilizer mixing ratio of 8% and that of 10%, 12% and 14% was calculated respectively by the specimen condition. The elastic modulus tended to increase as the grain size in a deep mixed specimen increased. The distribution of grain size that had the greatest effect appeared when the composition ratio of sand was high. On the other hand, the increase in the elastic modulus was larger in the sand specimens than in the clay and gravel specimens. Based on these results, it is suggested that a pertinent soil parameter of the deep mixed ground in the field may be obtained by the particle size distribution and the mixing ratio of stabilizer of the deep mixed soil.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.428-435
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• 2011

In general, thickness of the sublayers under track is designed based on concept of vertical soil reaction value or vertical stiffness. However, this design method cannot take consideration into soil-track interaction under repetitive load, traffic condition and velocity of the train. Furthermore, the reinforced roadbed soils experience complex behavior that cannot be explained by conventional stress-strain relation expressed as soil reaction value k. The reinforced roadbed soils also can produce cumulative permanent deformation under repetitive load caused by train. Therefore new design method for the sublayers under track must be developed that can consider both elastic modulus and permanent deformation. In this study, a new design concept, a rule-of-thumb, is proposed as the form of design monograph that is developed using elastic multi-layer and finite element programs by analyzing stress and deformation in the sublayers with changing the thickness and elastic modulus of the sublayers and also using data obtained from repetitive triaxial test. This new design concept can be applied to design of the reinforced roadbed before developing full version of design methodology that can consider MGT, axial load and the material properties of the layers. The new design monograph allows the user to design the thickness of the reinforced roadbed based on permanent deformation, elastic modulus and MGT.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.113-122
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• 1990

In case of repeated wheel-loads are acted on subbase course material, field test is generally executed to get the design standard, but the study shows dynamic properties of soils especially under repeated loads, which have not been well known to us. We try not only to obtain yield stress and elastic modulus of soil in terms of rheological model interpretation but also to investigate the influence of the repeated loads. Yield stress of soil induces hardening until approaching critical value along with the increase in number of cycle, whereas the change in modulus of elasticity with respect to the number of cycle greatly depends on the strength of repeated stress, if weak in strength of repeated stress, the modulus of elasticity increases along with the number of cycle, while if strong, it tends to decrease.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.157-165
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• 2000

The applicability and performance of HMS-25 as the railroad roadbed materials were evaluated through the model and laboratory tests. The uniaxial compression test of HMS-25, model soil box test, and combined resonant column and torsional shear test were performed for static and dynamic analysis of railroad roadbed. The uniaxial compression test result of HMS-25 shows steady increase in strength due to hardening chemical reaction between HMS-25 and water. The result of model soil box test reveals that railroad roadbed of HMS-25 is better than that of soil in several aspects such as bearing capacity and settlement. The combined resonant column and torsional that shear test result indicates that shear modulus of HMS-25 increases with the power of 0.5 to the confining pressure and that shear modulus increases with the increase of curing period.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.237-249
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• 2002

Nonlinearity and anisotropy of soil should be considered for the exact prediction of deformation before the failure state. In this study, a new constitutive model is developed in which the nonlinearity of soil is formulated by Ramberg-Osgood equation and the soil anisotropy is implemented by the cross-anisotropic elasticity. Nonlinear anisotropic model and other models for comparison are used to analyze the simple boundary value problems and the circular footing problem. In the results, the anisotropic ratio of elastic modulus is a key value for the bulk modulus of soil, the coeffcient of earth pressure at rest, and the slope of effective stress paths. Furthermore, it is found that the nonlinearity of soil considering the in-situ stresses has the great influence on the magnitude of settlements.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.587-598
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• 2008

In the trackbed design using elastic multi-layer model, the stress-dependent resilient modulus is an important input parameter, which reflects substructure performance under repeated traffic loading. The resilient moduli of crushed stone and weathered granite soil were developed using nonlinear dynamic stiffness, which can be measured by in-situ and laboratory seismic tests. The prediction models of resilient modulus varying with the deviatoric or bulk stress were proposed (Park et al., 2008). To investigate the performance of the prediction models proposed herein, the elastic response of the test trackbed near PyeongTaek, Korea was evaluated using a 3-D nonlinear elastic computer program (GEOTRACK) and compared with measured elastic vertical displacement during the passages of freight and passenger trains. The material types of the test sub-ballasts are crushed stone and weathered granite soil, respectively. The calculated vertical displacements within the sub-ballasts are within the order of 1mm, and agree well with measured values with the reasonable margin. The prediction models are thus concluded to work properly in the preliminary investigation. The prediction models proposed for resilient modulus were verified by the comparison of the calculated vertical displacements with measured ones during train passages.

• Journal of the Korean Society for Railway
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• v.10 no.3 s.40
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• pp.264-270
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• 2007

Two modulus, strain modulus $(E_v)$ and subgrade reaction modulus $(K_{30})$ are being used as a standard for bearing stiffness in Korea Railroad design. The first is used in Europe and the other is used in Japan. The methodologies to obtain the two modulus are similar in using plate. But testing methods are different in loading to plate. Therefore, according to soil strain range, there should be large gap in not only computations of deformation modulus but also the necessary time to test. At first, this paper focuses on the two kinds of test methods to evaluate bearing stiffness. Secondly, based on elastic theory, the theory to obtain the two coefficients are studied thoroughly. Finally, the correlations between the two coefficients were analyzed and evaluated based on the field test results more than 38 places. The matching values for subgrade and ground between $K_{30}$ and $E_{v2}$ are proposed with the consideration of the proposed strain reduction factor (1.5 for subgrade and 3 for ground) and safety factor, respectively.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.189-197
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• 2003

The treatment and hauling of surplus soils which occur from construction activity are costly and have been demanding a reasonable recycling method. This study presents laboratory test results regarding the mechanistic properties of asphalt stabilized soils. The foamed asphalt equipment which generates the asphalt bubble was used to mix the soil. The marshall stability, indirect tensile test, resilient modulus, creep test and triaxial test(UU) were conducted to find out the performance of the asphalt stabilized soil. The test results were compared with the samples that fabricated in different conditions(the samples without asphalt and the reinforced samples using 2% cement). The inclusion of the asphalt in the soil has improved the marshall stability, resilient modulus and moisture susceptibility, and the addition of the 2% cement has even more increased these properties. The amount of the fines and the optimum moisture contents for mixing affects the mechanistic properties and important parameters for mix design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.193-198
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• 2012

Field and laboratory tests were performed to investigate the swelling(L value) and shrinkage modulus (C value) of soil and rock mixtures using 2 sites. According to test results, when disturbed soil and rock were mixed with same amount (5:5), the maximum density was achieved and showed 19% and 18% increased at each site comparing with the unit weight of rock only. Since measured L values of mixtures were overestimated about 4 to 11% compare to estimated values based on the conventional method. While C values were underestimated about 13~20% compare to conventional values due to the development of compacting equipments and effective construction management. When rock and soil were mixed in the ratio of 5 to 5, the unit weight of the mixture was higher than that of other mixtures and rock or soil only.