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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Geotechnical Society
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Journal DOI :
Korean Geotechical Society
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Volume & Issues
Volume 24, Issue 12 - Dec 2008
Volume 24, Issue 11 - Nov 2008
Volume 24, Issue 10 - Oct 2008
Volume 24, Issue 9 - Sep 2008
Volume 24, Issue 8 - Aug 2008
Volume 24, Issue 7 - Jul 2008
Volume 24, Issue 6 - Jun 2008
Volume 24, Issue 5 - May 2008
Volume 24, Issue 4 - Apr 2008
Volume 24, Issue 3 - Mar 2008
Volume 24, Issue 2 - Feb 2008
Volume 24, Issue 1 - Jan 2008
Selecting the target year
The Analysis of Permeability Coefficient and the Evaluation of Equations of Permeability Coefficient for an Unsaturated Soils
Lim, Seong-Yoon ; Lyu, Tae-Jin ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 5~13
The coefficient of permeability for a soil can be determined by the direct or the indirect method. The direct method of permeability can be performed either in the laboratory or in the field. The indirect method can be predicted from the soil-water characteristic curve. In this study, the coefficient of permeability for an unsaturated soil was determined by the modified apparatus of steady-state method (Klute, 1972) and was predicted from the equations of Brooks & Corey (1964) and van Genuchten (1980). The experimental results were compared with predicted coefficient of permeability and the applicability of the two equations (from Brooks & Corey, van Genuchten) was reviewed.
Modeling Direct Shear Test of Crushed Stone Using DEM
Cho, Nam-Kak ; Yoo, Chung-Sik ; Lee, Dae-Young ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 15~23
In this study, modeling shear characteristics of a coarse material mainly containing crushed stones were implemented using PFC2D, a commercially available code based on DEM(Discrete Element Method). Using the DEM code, this study provides the methodology considering the shear characteristics due to a irregular grain shape, GSD(Grain Size Distribution) and porosity of coarse material which are not effectively incorporated in conventional continuum numerical codes. Direct shear test was simulated for the GSD and porosity generated sample using the code and the simulated results showed very good agreement with the laboratory test results. The current modeling approach can be applied to other coarse materials having various GSD and porosities. Using such application, prediction of the strength characteristics of coarse material in field scale would be possible, which is limited in laboratory scale so far.
Experimental Study on the Triaxial Compressive Behaviour of Unsaturated Compacted Silt under Various Suction Levels
Kim, Young-Seok ; Oka, Fusao ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 25~35
It has been recognized that the behaviour of unsaturated soil plays an important role in geomechanics. However, up to now, only a few experimental data are available for the technical difficulties related to both volume changes and suction measurements. In this study, the volume changes of unsaturated compacted silty soil were monitored with proximeter during various triaxial compression tests, which gave a realistic estimation in the volume changes of unsaturated soil sample. From the test results, the behaviours of wetting-induced collapses are observed during the drainage/water absorption tests. Under exhausted-drained conditions during shearing, the shear strength increases with an increasing initial suction. On the other hand, the volume changes become small with an increase in the initial suction. And, the volumetric strain during shearing is independent of the confining pressure.
A Study on the Physical Characteristics of Grout Material for Backfilling Ground Heat Exchanger
Choi, Hang-Seok ; Lee, Chul-Ho ; Choi, Hyo-Pum ; Woo, Sang-Baik ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 37~49
A geothermal heat pump system is a preferable alternative energy system in Korea because it uses the heat energy of the earth, which is environmentally friendly and inexhaustible. In order to characterize the thermal conductivity and viscosity of grout materials used for backfilling ground heat exchangers, nine bentonite grouts, one marine clay from Boryung, and cement grouts adapted in the United State have been considered in this study. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or filler (silica sand). In addition, material segregation can be observed when the viscosity of grout is relatively low. The marine clay turns out to be unsuitable for backfilling the ground heat exchanger due to its insufficient swelling potential. The saturated cement grouts appear to possess much higher thermal conductivity than the saturated bentonite grouts, and the reduction of thermal conductivity in the cement grouts after drying specimens is less than that in the case of the bentonite grouts. Maintaining the moisture content of grouts is a crucial factor in enhancing the efficiency of ground heat exchangers.
Effect of Fines Content on the Cyclic Shear Characteristics of Sand-clay Mixtures
Kim, Uk-Gie ; Hyodo, Masayuki ; Ahn, Tae-Bong ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 51~59
In this study, cyclic shear characterics of sand-clay mixtures were analyzed. In order to perform cyclic triaxial tests on sand clay mixtures, natural clays with activity and silica sand were mixed variously to reproduce soils with wide range of grain size compositions. Test specimens with various fines contents were prepared by the moisture compaction and pre-consolidation methods, while paying attention to the void ratio expressed in terms of the sand structure and clay structures, and undrained cyclic shear tests were performed. In the test results, cyclic shear strength decreased with increasing of sand granular void ratio below 20% of fine contents. When the granular void ratio of the test specimen exceeded the maximum void ratio of the silica sand, the clay matrix dominated the soil structure, and soil structures were not influenced by compaction energy. It was observed that, the matrix structure of the coarse particles has great effect on the undrained cyclic shear strength characteristics for sand-clay mixtures, and therefore, it is more appropriate to pay more attention to the density of the sand structure, rather than to the fines content.
Deformation Analysis of Shallow Tunnel Using Tunnel Model Test and Computational Analysis
Lee, Jae-Ho ; Kim, Young-Su ; Moon, Hong-Duk ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 61~70
The control and prediction of surface settlement, gradient and ground displacement are the main factors in shallow tunnel design and construction in urban area. For deformation analysis of shallow tunnel due to excavation it is important to identify possible deformation mechanism of shear bands developing from tunnel shoulder to the ground surface. This paper investigaties quantitatively the deformation behavior of shallow tunneling by model tunnel test and strain softening analysis Incorporating the reduction of shear stiffness and strength parameters. The comparison of model tunnel test result and numerical simulation using strain softening analysis showed good agreement in crown settlement, normalized subsidence settlement and developing shear bands above tunnel shoulder. In this study, it is blown that the strain softening modeling is applicable to the nonlinear deformation analysis of shallow tunnel.
Time-dependent Deformation Charateristics of Geogrid Using Wide Width Tensile Test
Yoo, Chung-Sik ; Jeon, Han-Yong ; Kim, Sun-Bin ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 71~80
This paper presents the reusults of wide width tensile tests under sustained and cyclic loads with vairous loading rate on geogrids. A seires of modified wide width tensile tests were conducted to investigate the effect of tensile strain rate on the deformation behavior of the geogrids. In addition, residual deformation characteristics of a geogrid under sustained or cyclic tests were also investigated. The results indicated that the residual deformation of a geogrid is strongly related to the viscous behavior of the geogrid, and the residual deformation can be well described by a hyperbolic curve. Also revealed was that residual deformation of a geogrid when subject to sustained or cyclic load should be described with the framework of viscous behavior.
Feedback Analysis Technique for Tunnel Safety by Using Displacements Measured during the Tunnel Excavation
Park, Si-Hyun ; Shin, Young-Suk ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 81~89
The purpose of this study is to develop a new technique to quickly assess the quantitative stability of a tunnel by using measured displacement at the tunnel construction site. To achieve this purpose, in this study, a critical strain concept was introduced for the first time and applied to an assessment of a tunnel under construction. The new technique calculates numerically the strains of the surrounding ground by using displacements measured during tunnel excavation. The techniques considering the relative displacement, shotcrete, and anisotropic characteristics of ground were newly introduced after reinvestigating the existing analysis technique. In addition, an analysis module was developed based on the proposed analysis technique in this study, and the applicability of the developed module was verified. To verify the module, first of all, the calculated excavation displacements of a cylindrical tunnel by analytic method and commercial programs (Pentagon-3D, Flac-2D) were compared for the confirmation of applicability of commercial programs. Then, the calculated excavation displacements under the same initial condition, both with and without a shotcrete lining, by two commercial programs were compared. finally, we assess the load condition and material properties of in-situ ground by inputting tunnel excavation displacement, which was calculated by a commercial program, into the developed analysis module (FAST-Ver. 1.2, feedback Analysis System for Tunneling), and checked whether the assessed results conform to the originally assumed values.
Uniformity of Large Gypsum-cemented Specimens Fabricated by Air Pluviation Method
Lee, Moon-Joo ; Choi, Sung-Kun ; Choo, Hyun-Wook ; Cho, Yong-Soon ; Lee, Woo-Jin ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 91~99
The method to prepare the large cemented sand specimen for calibration chamber test by air-pluviation is investigated in this study. The uniformity of cemented specimen is evaluated by performing the CPTs, DMTs, and bender element tests in the calibration chamber. The sand particles, pre-wetted with 0.5% water content, are mixed with gypsum to provide the homogeneous coating of gypsum particles on the grain surface. It was shown that the pre-wetting of particle surface is effective to minimize the potential for segregation between sands and gypsum during air-pluviation. It was observed that the extreme void ratios (
) of the mixture of pre-wetted sand and gypsum powder increase at lower gypsum content while those of the mixture of dry sand and gypsum decrease with increasing gypsum content. It was also shown from the test results that large cemented specimens reconstituted in calibration chamber by rainer system are quite uniform in vertical and horizontal directions.
Experimental Study on Mechanical Properties of Monofilament-reinforced Bottom Ash Mixture for Recycling Dredged Soil
Kim, Yun-Tae ; Han, Woo-Jong ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 101~110
This paper investigates the mechanical characteristics of monofilament-reinforced bottom ash mixtures for recycling dredged soil. Reinforced bottom ash mixture is a lightweight soil added with monofilament in order to increase its shear strength. Test specimens were fabricated by various mixing conditions including monofilament content, its length and its diameter. Then several series of unconfined compression tests and direct shear tests were performed to investigate mechanical characteristics of reinforced lightweight soil. The experimental results indicated that stress-strain behaviors of reinforced lightweight soil were strongly influenced by mixing conditions of monofilament content, its length and diameter. The compressive strength of reinforced lightweight soil generally increased by adding monofilament. In this test, the maximum increase in compressive strength was obtained at 0.5% content and 4cm length of monofilament. These results were similar to those of direct shear tests. The unconfined compressive strength of reinforced lightweight soil with monofilament of 0.25mm in diameter was greater than that of reinforced lightweight soil with monofilament of 0.5mm in diameter.
Characteristic of a Soft Ground Behavior Subjected to Static and Dynamic Loads (A Study on the Model Test)
Kim, Jong-Ryeol ; Kang, Jin-Tae ; Lee, Chi-Yeal ; Part, Yong-Myun ; Jeong, Jea-Hoon ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 111~118
In the study a 2 dimensional model test was executed to grasp the effect of the taking load of equipments on the ground when improving a soft ground like dredging reclaimed ground. The static load and the dynamic load in the consolidated model ground was
respectively. After consolidating far two months by consolidation load of
respectively, the ultimate bearing capacity was
respectively. And the energy price of dynamic load test at the same point as the settlement of static load test indicated
for each consolidation load. When the static load and the dynamic load operated at the same ground condition, the heaving quantity was bigger in the case of the dynamic load than in the case of the static load, and the horizontal displacement quantity the in the case of dynamic load was exhibited very deficiently compared to the quantity in the case of static load test.
Reliability-Based Design of Shallow Foundations Considering The Probability Distribution Types of Random Variables
Kim, Chang-Dong ; Kim, Soo-Il ; Lee, Jun-Hwan ; Kim, Byung-Il ;
Journal of the Korean Geotechnical Society, volume 24, issue 1, 2008, Pages 119~130
Uncertainties in physical and engineering parameters for the design of shallow foundations arise from various aspects such as inherent variability and measurement error. This paper aims at investigating and reducing uncertainty from deterministic method by using the reliability-based design of shallow foundations accounting for the variation of various design parameters. A probability distribution type and statistics of random variables such as unit weight, cohesion, infernal friction angle and Young's modulus in geotechnical engineering are suggested to calculate the ultimate bearing capacities and immediate settlements of foundations. Reliability index and probability of failure are estimated based on the distribution types of random variables. Widths of foundation are calculated at target reliability index and probability of failure. It is found that application and analysis of the best-fit distribution type for each random variables are more effective than adoption of the normal distribution type in optimizing the reliability-based design of shallow foundations.