• Geomechanics and Engineering
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• v.21 no.2
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• pp.103-109
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• 2020

The inflow rate is of interest in the design of underground structures such as tunnels and buried pipes below the groundwater table. Soil permeability governing the inflow rate significantly affects the hydro-geological behavior of soils but is difficult to estimate due to its wide range of distribution, nonlinearity and anisotropy. Volume changes induced by stress can cause nonlinear stress-strain behavior, resulting in corresponding permeability changes. In this paper, the nonlinearity and anisotropy of permeability are investigated by conducting Rowe cell tests, and a nonlinear permeability model considering anisotropy was proposed. Model modification and parameter evaluation for field application were also addressed. Significance of nonlinear permeability was illustrated by carrying out numerical analysis of a tunnel. It is highlighted that the effect of nonlinear permeability is significant in soils of which volume change is considerable, and particularly appears in the short-term flow behavior.

• Journal of the Korean Society for Railway
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• v.3 no.2
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• pp.84-91
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• 2000

The general concept of reinforced roadbed in the high-speed railway is to cope with the soft ground for the bearing capacity and settlement of foundation soil. The cyclic plate load tests were performed to determine the behavior of reinforced ground with multiple layers of geogrid underlying by soft soil. With the test results, the bearing capacity ratio, elastic rebound ratio, subgrade modulus and the strain of geogrids under loading were investigated. Based on these plate load tests, laboratory model tests under cyclic loading were conducted to estimate the effect of geogrid reinforcement in particular for the high-speed rail roadbed. The permanent settlement and the behavior of earth pressure in reinforced roadbed subjected to a combination of static and dynamic loading are presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.357-364
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• 2002

This paper describes the feasibility of compacting subgrade layer in thicker lifts than currently permitted as 20 cm. This project involved constructing and testing a full scale test section in highway. Soil stiffness in field was evaluated by a nondestructive testing method, called Geogage. Quality control tests and FE Analysis were also conducted. Typical dynamic compaction roller of 11ton weight is applied for full scale test and a Mohr-Coulomb model and Plane strain condition are used for FE Analysis. The results showed that compaction-induced stress and dissipated energy are mainly depend on depth of soil and it could be possible to increase thickness of a lift.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.73-81
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• 2010

The paper presents the application of FE simulations of NATM tunnel using different constitutive models. The results from a series of two dimensional plane strain finite element analyses of medium-liner interaction for NATM are presented. Four types of constitutive models are considered, namely, linear elastic, elasto-plastic Mohr-Coulomb, Hardening-Soil, Soft-Soil model. The design for tunnels requires a proper estimate of surface settlement and lining forces. It is shown that the advanced constitutive model gives better predictions for both ground movement and structural forces.

• Microbiology and Biotechnology Letters
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• v.51 no.3
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• pp.303-305
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• 2023

In this study, we report the complete genome sequence of Priestia megaterium strain HyangYak-01, which was isolated from the rhizosphere soil of Centella asiatica. The genome consists of 5,086,279 bp of sequences with 38.2 percent GC content and 5,111 coding genes. The genome contains several important genes related to plant growth-promoting activities, which were also confirmed with in vitro media assays.

• Journal of the Korean Geotechnical Society
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• v.30 no.5
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• pp.37-46
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• 2014

Geotechnical structures have been analyzed and constructed in various geometry conditions to maintain their stability in accordance with the characteristics of construction design. Shear strengths are generally obtained from triaxial test to apply to design analysis. Geotechnical structures under strip loading, such as earth dam, embankment, and retaining wall, have the strain in a direction, and plane strain condition. Thus, an approximate shear strengths should be applied for stability analysis suitable to ground condition. When applying shear strengths obtained from triaxial tests for slope stability analysis, the evaluation of it may underestimate the factor of safety because the implementation is not suitable for geometry condition. The paper compares shear strengths obtained from triaxial test and plane strain test based on various relative densities using weathered granite soils. Additionally, yield stress is determined by maximum axial strain 15% in triaxial test because of continuous kinematic hardening, but plane strain test can determine a failure point in critical state to evaluate the shear strengths of soils at the second plastic hardening step. This study proposes to perform an appropriate test for many geotechnical problems with plane strain condition.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.69-78
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• 2022

Geotextile tubes are widely used to prevent erosion in coastal areas and to replace the backfill for shore slopes in the reclamation of land using dredged soil. In this study, The triaxial confining pressures were chosen as 10kPa, 50kPa, or 100kPa for the specimens reinforced with geotextile considering the condition in the site. The strain behavior under various compressive stresses was then identified. At strains 0% to 7%, the stress-strain behavior was the same due to the effect of initial strain hardening, in which the force was exerted according to the relaxation of the geotextile regardless of the confining pressure (≤100kPa). At strains of 7% or more, the specimen with the small confining pressure had smaller deformation under load, which increases the tensile resistance provided by the reinforcing geotextile. Brittle fracture was then observed due to strain softening and the deviator stress abruptly decreased. This is different from the phenomenon in which the shear strength increases as the confining pressure increases in general triaxial compression tests. In the geoxtile-confined tests, geotextiles are primarily subjected to tensile displacement. Thereafter, the modulus of elasticity increases rapidly, which exhibits the elastic behavior of the geotextile.

• 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.

• Geotechnical Engineering
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• v.12 no.4
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• pp.21-32
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• 1996

To predict the stress-strain behavior of the soil more approximately, the concept of the critical state soil mechanics was added to the plasticity increment theory in the bounding surface Plasticity model. This model was constituted with two ellipse and one hyperbola in older to describe the behaviour of the isotropically consolidated soil. Thus, this model is very complicate due to the various parameters used. Therefore, the accurate understanding and skill of the theory is required in order to apply this model to the practical geotechnical problems. In the present paper, the bounding surface shape paraiheter R and A, the mapping center parameter C among various parameters used were varied and the results were numerically analized. Finally, each sensitivity with respect to monotonic and cyclic loading was analized and the range of the value of the each parameter was proposed.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1140-1147
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• 2010

To find the soil plug of steel piles shaped by jet grouting, 4 blocks of cement milk with cube of 1.2m were made. 4 open-ended steel piles on the blocks were rested. The inner end part of 2 the piles was not reinforced. Cement milk 65%(SIG-1) and 100%(RJP-1) were filled into the block and height of 4.2 times of inner the pile diameter respectively. And the other the piles were welded 2 steel ring. The filling of the cement milk was an equal method as before(SIG-2 and RJP-2). Also the strain gauges were installed and the static pile load tests were done at the piles all. As a result, list in great order for effect of soil plug was (1)SIG-1, (2)SIG-2, (3)RJP-1, (4)RJP-2. This is because of strength and filling height of cement milk. And the higher the strength is, the greater the confining coefficient is.