• 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 Geotechnical Society
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• v.16 no.3
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• pp.89-89
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• 2000

The shear behavior of any interface is a function of the fundamental properties of both materials at the interface. This study aimed at investigating the effect of planar surface roughness on the stress-horizontal displacement curve at theinterfaces composed of various geomembrane textures and granular materials. In addition, the extent of surfacialscarring on smooth geomembranes against granular materials during shearing induced by plowing effect was studied. It wasobserved that the displacements required to achieve peak and residual interface resistance, and the stress-displacementcurve at the interface vary greatly with the surface roughness of geomembrane. Quantification of surface roughnessvariations on smooth geomembrane due to plowing effect showed that the surfacial scarring during shearing by the soilparticles is directly related to both the normal stress and the angularity of the soil particles at the interface. The findingsof this study can be used to provide the useful information for the design and selection of counterface materials.

• Geomechanics and Engineering
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• v.4 no.4
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• pp.251-262
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• 2012

Triaxial tests are essential to estimate the shear strength properties of the soil or rock. Normally triaxial tests are carried out on samples of 38 mm diameter and 76 mm height. Granular materials, predominantly used in base/sub-base construction of pavements or in railways have size range of 60-75 mm. Determination of shear strength parameters of those materials can be made possible only through triaxial tests on large diameter samples. This paper describes a large diameter cyclic triaxial testing facility set up in the Geotechnical Engineering lab of Indian Institute of Science. This setup consists of 100 kN capacity dynamic loading frame, which facilitates testing of samples of up to 300 mm diameter and 600 mm height. The loading ram can be actuated up to a maximum frequency of 10 Hz, with maximum amplitude of 100 mm. The setup is capable of carrying out static as well as dynamic triaxial tests under isotropic, anisotropic conditions with a maximum confining pressure of 1 MPa. Working with this setup is a difficult task because of the size of the sample. In this paper, a detailed discussion on the various problems encountered during the initial testing using the equipment, the ideas and solutions adopted to solve them are presented. Pilot experiments on granular sub-base material of 53 mm down size are also presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.448-456
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• 2010

The mechanical behavior of granular soils is affected by particle bonding including natural cementation. This study addresses a simple model of small strain stiffness and salt concentration based on wave measurements of salt-cemented particulate media. Published models of artificially cemented soils with different curing methods and several types of cementation agents are reviewed. Glass beads with the median diameter of D50 = 0.5mm are prepared in rectangular cells using the water-pluviated method in salt water with different concentrations. Piezo disk elements and bender elements embedded in the cell are used for the measurements of compressional and shear waves. The relationships between elastic wave velocities and salt concentration show an exponential function. The measured small strain stiffness matches well the predicted small strain stiffness based on micromechanics for simple cubic monosized sphere particles. This study demonstrates that the salt concentration in salt-cemented specimen may be evaluated by using elastic wave velocities.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.69-78
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• 1993

A testing system has been developed to evaluate the seasonal variation of the resilient modulus of granular subgrade soils. Two sites were successfully instrumented with soil moisture-temperature cells to monitor over a period of one year, the field temperature and moisture content underneath the pavement. Multiple regression equations were developed to determine the resilient modulus under environmental conditions. It is noted that the use of the effective resilient modulus at the location of the Average Depth of Significant Stress (ADSS) provides a reasonable basis for determining subgrade properties. In addition, a theoretical model has been developed to predict the resilient modulus due to the change of temperature and moisture condition.

• Journal of the Korean Geotechnical Society
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• v.21 no.4
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• pp.13-20
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• 2005

In this study, consolidation test and numerical analysis were performed with the aim of investigating the characteristics of consolidation behavior of mixed soil with the amount and particle shape of inserted materials. Mixed soil was made up of matrix (dredged clay) and inserted material (crashed oyster shell and/or sand). The concept of stress share ratio was introduced to evaluate the consolidation characteristics of mixed soils. And the finite differential numerical analysis was carried out by applying the Mikasa's consolidation theory. From the results of experiments and numerical analysis, it was verified that mixed soil consolidation behavior is affected by changes in inserted material. When a similar amount of granular material was inserted, the compressibility of the clay matrix of oyster shell mixed soil was smaller than that of sand mixed soil.

• Journal of the Korean earth science society
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• v.26 no.8
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• pp.828-835
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• 2005

The purpose of this study is to clarify the landform development of fluvial terrace and the soil characteristics occurring on the terrace deposit. In order to achieve the purpose, the characteristics of soil profiles, the physic-chemical properties of soils that are developed on terrace deposits and X-ray diffraction analysis of clay were investigated. The horizon of Al in the high fluvial surface is silt clay loam of red (2YR 4/6). The soil structure is a developed granular structure. The horizon of B1 is silt clay reddish-brown (2.5YR 4/6). The soil structure is a medium subangular blocky structure. This red soil structure is made on heavy textured and compactly packed parent materials of high terrace sediments and usually has A-B-C profile. In most cases, clay accumulations in B-horizon and clay cutans on ped surfaces are observed, which mean the formation of agrillic horizon. As the result of this study, soils derived from fluvial terrace deposits on high fluvial surfaces are considered paleo-red soil which were developed by pedogenese-strong desilicification and rubefaction and strong leaching of bases- under warmer bio-climatic condition during in the old Pleistocene period.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.2
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• pp.108-115
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• 1991

A field experiment was conducted to evaluate the effects of cattle compost application on the change of soil physical properties and their relationship to yield performance of selected main forage crops. Maize(CV. Suweon 19) and sorghum hybrids(CV. Pioneer 9'31) as a summer crops and winter rye were grown on newly reclaimed red yellow soils(Fine loamy, Typic Hapludults) under different application rate of cattle compost associated with chemical NPK fertilization, from Oct. 1986 to Sept. 1989. Experimental field was laid down as a split plots design with four replications. The results obtained are summarized as follows: 1. Cattle compost application reclaimed soil physical propeties, such as formation of granular structure and water holding capacity, and it result in a great increase of plant growth and the rate of dry matter accumulation. 2. While cattle compost treatment reduced the portion of soild phase of the three phase constituents of soils, it increased the portion of air phase and liquid phase comparatively. 3. Organic matter, N, P, K, and mineral content in soil were markedly increased in the plot treated with compost. 4. Cattle compost application increased fodder production both in maize-rye and sorghum hybrids-rye cultivation. Annual dry matter yield of maize-rye cropping was 2183(NI'K only), 2425(NPK+compvst 3000 kg) and 2800kg/lOa(NPK + compost 6000kg/10a).

• Geomechanics and Engineering
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• v.5 no.3
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• pp.241-261
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• 2013

The bearing mechanism of pile during installation and loading process which controls the deformation and distribution of strain and stress in the soil surrounding pile tip is complex and full of much uncertainty. It is pointed out that particle crushing occurs in significant stress concentrated region such as the area surrounding pile tip. The solution to this problem requires the understanding and modeling of the mechanical behavior of granular soil under high pressures. This study aims to investigate the sand behavior around pile tip considering the characteristics of sand crushing. The numerical analysis of model pile loading test under different surcharge pressure with constitutive model for sand crushing is presented. This constitutive model is capable of predicting the dilatancy of soil from negative to positive under low confining pressure and only negative dilatancy under high confining pressure. The predicted relationships between the normalized bearing stress and normalized displacement are agreeable with the experimental results during the entire loading process. It is estimated from numerical results that the vertical stress beneath pile tip is up to 20 MPa which is large enough to cause sand to be crushed. The predicted distribution area of volumetric strain represents that the distributed area shaped wedge for volumetric contraction is beneath pile tip and distributed area for volumetric expansion is near the pile shaft. It is demonstrated that the finite element formulation incorporating a constitutive model for sand with crushing is capable of producing reasonable results for the pile loading problem.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.55-61
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• 2005

Dynamic compaction is a ground improvement technique which is particularly effective for loose granular soils. It has also been used successfully to the cohesive soils with high void ratio, and wastes and fills. For the design of dynamic compaction method, prediction of depth of improvement is very important. The depth of improvement is influenced not only by compaction energy but also by many parameters such as grid spacing, soil property, degree of saturation and site conditions. Based on the test results, the depth of improvement were evaluated with considering compaction energy, soil type and ground water level.