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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 23, Issue 12 - Dec 2007
Volume 23, Issue 11 - Nov 2007
Volume 23, Issue 10 - Oct 2007
Volume 23, Issue 9 - Sep 2007
Volume 23, Issue 8 - Aug 2007
Volume 23, Issue 7 - Jul 2007
Volume 23, Issue 6 - Jun 2007
Volume 23, Issue 5 - May 2007
Volume 23, Issue 4 - Apr 2007
Volume 23, Issue 3 - Mar 2007
Volume 23, Issue 2 - Feb 2007
Volume 23, Issue 1 - Jan 2007
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Short- and Long-term Load Carrying Capacity of Geogrid-encased Stone Column - A numerical investigation
Lee, Dae-Young ; Song, Ah-Ran ; Kim, Sun-Bin ; Yoo, Chung-Sik ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 5~16
The stone column method is widely used in Europe as an alternative to conventional pile foundations. Several benefits of using the stone column method include sound performance, low cost, expediency of construction, and liquefaction resistance among others. Recently, geosynthetic-encased stone column approach has been developed to improve its load carrying capacity through increasing confinement effect. Although such a concept has been successfully applied in practice, fundamentals of the method have not been fully explored. This paper presents the results of an investigation on the load carrying capacity of geogrid-encased stone column using a series of 2D finite element analyses. A parametric study was then conducted for influencing factors such as effect of geogrid encasement, encasement length, geogrid strength, among others. The results of the analyses indicated improved short- and long-term load carrying capacity of the geogrid-encased stone column method has advantages over the conventional stone column method without encasing.
A Study of Obtaining Reliable Travel Time Information in Downhole Seismic Method
Bang, Eun-Seok ; Lee, Sei-Hyun ; Kim, Jong-Tae ; Kim, Dong-Soo ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 17~33
Downhole seismic method is widely used for obtaining shear wave velocity profile of a site because it is simple and economical. Determining accurate travel time of shear wave is very important to obtain reliable result in downhole seismic method. In this paper, comparison study of various travel time determination methods was performed. Numerical study and model chamber test were performed for effective comparison study. Signal traces were acquired by performing downhole test at each numerical simulation and soil box test. Travel time data for each signal traces were determined by using six different methods and Vs profiles were evaluated. Comparing travel time data and Vs profiles with the reference value, the first arrival picking method proved to be ambiguous and unreliable. Other methods also did not always provide accurate results and the magnitude of error was dependent on the signal to noise ratio. Cross-correlation method proved to be the most adequate method for the field application and it was verified additionally with field data.
Axial Behavior of Non-Displacement Tapered Piles in Sand
Paik, Kyu-Ho ; Lee, Jun-Hwan ; Kim, Dae-Hong ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 35~45
It is known that the response of piles is affected by the shape of pile as well as soil conditions. In order to investigate the characteristics of the axial responses and bearing capacities of non-displacement tapered and cylindrical piles in sands, 12 model pile load tests using a calibration chamber were conducted on model tapered and cylindrical piles, which were specially manufactured to measure the base and shaft load capacities independently. Results of the model tests showed that the shaft load of tapered piles continuously increased with pile settlement, whereas the shaft load of cylindrical piles reached ultimate values at a settlement equal to 4% of pile diameter. Therefore, taper piles have greater shaft loads than cylindrical one at the same settlement. It is also observed that the total load capacity of tapered piles is lower than cylindrical piles for dense sand but is greater than that of cylindrical piles for medium sand. The ultimate unit base resistance of tapered piles was greater than that of cylindrical piles for lateral earth pressure ratio greater than 0.4, and the shaft resistance was greater than that of cylindrical piles irrespective of lateral earth pressure ratio.
Improvement Scheme of Simplified Liquefaction Potential Evaluation for a Dredged and Reclaimed Ground
Jung, Min-Hyung ; Kim, Ju-Hyun ; Jeong, Sang-Guk ; Lee, Song ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 47~57
In this study, the analysis of density characteristics of some dredged and reclaimed ground sites, which is necessary for liquefaction evaluation of a dredged and reclaimed ground, was conducted. From analyzing a simplified liquefaction potential evaluation using SPT-N values which have been applied as domestic earthquake-resistant design criterion, improvement scheme is suggested. Based on the analysis result of density characteristics, it was found out that the relative density and the intial N-value ranged respectively
. In the case of applying Liao & Whitman's equation to correct effective overburden pressure, liquefaction resistance of the upper ground that is relatively weaker than that of lower ground is overestimated. So, Skempton's equation is recommended. And the N value with depth which is applied for design process should be estimated by the exponential equation,
Comparative Study on Cross-anisotrupic Elasticity of Granular Soils Based on Lab-scale Triaxial Experiment and Discrete Element Analysis
Jung, Young-Hoon ; Lee, Jae-Hoon ; Chung, Choong-Ki ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 59~68
The comparative study using the lab-scale experiment and the discrete element analysis is attempted to analyze the cross-anisotropic elasticity of granular soils. The lab-scale experiment consists of the small stress-controlled triaxial cyclic tests and the bender element tests. In the discrete element analysis the simulations of lab-scale cyclic tests are conducted in the various directions. Good agreement between the experimental data and the simulation on the elastic properties in the axial and shear directions confirms the usefulness of the discrete element method. The comparative analysis of the difference in the experimental data and the simulation of radial cyclic tests shows that the discrete element method can successfully be used to check the reasonable magnitude of each measurement in the experiments.
Influence of Taper Angle on Axial Behavior of Tapered Piles in Sand
Paik, Kyu-Ho ; Lee, Jun-Hwan ; Kim, Dae-Hong ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 69~76
Axial behavior of tapered piles is affected by taper angle, stress state of soils, soil frictional angle and pile-soil interface friction angle. In this paper, a series of model pile load tests were performed using a calibration chamber in order to investigate the effect of taper angle on the axial response of cast-in-place tapered piles in sand. According to results of the tests, as taper angle of piles increased, the shaft load capacity of piles increased but its base load capacity decreased. The unit base load capacity of piles increased with increasing taper angle for medium sand but decreased for dense sand. The ratio of shaft to total load capacity increased with increasing taper angle and with decreasing relative density of soils. The test results also showed that total load capacity per unit pile volume increased with increasing taper angle for medium sand, but it decreased for dense sand. Therefore, it can be stated that tapered piles are economically more beneficial for medium sand than for dense sand.
Analysis and Evaluation of CPT Cone Factor for Undrained Shear Strength Estimation of Pusan Clay
Park, Young-Hwan ; Kim, Min-Ki ; Kim, Chang-Dong ; Lee, Jun-Hwan ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 77~85
In order to estimate undrained shear strength and evaluate cone factors, various in-situ and laboratory test results at new harbor construction area near Pusan were analyzed. To evaluate Nk values and equation applicable in Korea, measured and theoretical cone factors were compared based on the test results. For comparison, various analytical solutions were adopted and used. Adopted methods include cavity expansion solutions of Baligh (1975) and Yu (1993) and steady state solutions of Teh and Houlsby (1991) and Yu et al. (2000). According to the result of comparison, cavity expansion solutions were found to be reasonable for the CPTu-based undrained shear strength evaluation.
Ground Behavior and Reinforcing Methods of NATM Tunnel through Deep Weathered Zone
Chun, Byung-Sik ; Song, Seung-Hoon ; An, Jung-Whan ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 87~95
This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analyses of failure rate and vertical stress ratio show that the tunnel for which the height of the cover (H) was higher than four times the diameter, can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than that obtained by Ring-cut split method. In addition, the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.
Effect of pH Level on the Characteristics of a Landfill Clay Liner Material
Jung, Soo-Jung ; Lee, Yong-Su ; Kim, Tae-Hyung ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 97~106
In this study, experiments are conducted to find out the effect of waste leachate on landfill clay liner system. Tensile test, hydrometer analysis and crack pattern test were conducted on sand-bentonite mixtures with different pH values of water. The tensile strength of specimen compacted with pH 9 of water is smaller than that of specimen compacted with for pH 3 and 6 of water. That is, the higher the pH value, the smaller the tensile strength, because a higher pH solution decreases flocculation phenomenon. The percent finer also increased with high pH value in particle size distribution of fine grained soil (<0.075 mm), because the velocity of particles settling decreases. This trend becomes the clearer as the content of bentonite, becomes the larger, because the higher pH value decreases flocculation structure of fine soils. The results of the crack pattern tests also showed the effect of pH values of water.
Resistance Factors for Drilled Shafts Embedded in Weathered Rock
Yoon, Hong-Jun ; Jung, Sung-Jun ; Kim, Myoung-Mo ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 107~116
Load and Resistance Factor Design (LRFD) method is being used increasingly in geotechnical design practice worldwide, and is expected to completely replace the current Allowable Stress Design (ASD) method in the near future. LRFD has advantages over ASD in that it allows the design of superstructures and substructures at a consistent reliable level by quantification of failure probability based on reliability analysis. At present, resistance factors for cast-in-place piles embedded in rocks are determined by AASHTO only for the intact rock conditions. In Korea, however, most of the bedrocks in which piles are embedded are heavily weathered. Thus, this study will try to determine the resistance factors of heavily weathered rocks (so-called intermediate goo-materials). To this aim, reliability analysis was carried out to evaluate the resistance factors of cast-in-place piles embedded in intermediate geo-materials in Korea. Pile load test data of 21 cast-in-place piles of 4 construction sites were used for the analysis. Depending on the method which calculates the pile capacities, the resulting resistance factors ranged between 0.1 and 0.6.
Reliability Analysis of Slopes Using ANN-based Limit-state Function
Cho, Sung-Eun ; Byeon, Wi-Yong ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 117~127
Slope stability analysis is a geotechnical engineering problem characterized by many sources of uncertainty. Some of them are connected to the uncertainties of soil properties involved in the analysis. In this paper, a numerical procedure for integrating commercial finite difference method into probabilistic analysis of slope stability is presented. Since the limit-state function cannot be expressed in an explicit form, the ANN-based response surface method is adopted to approximate the limit-state function and the first-, second-order reliability method and the Monte Carlo simulation technique are used to calculate the probability of failure. Probabilistic stability assessments for a hypothetical two-layer slope and the Sugar Creek embankment were performed to verify the application potential to the slope stability problems. The examples show the successful implementation and the possibility of the extension of the proposed procedure to the variety of geotechnical engineering problems.
The Characteristics of Sedimentation and Self-Weight Consolidation for Dredged Soil Depending on Fines Content
Lee, Bum-Jun ; Lee, Moo-Cheol ; Lee, Song ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 129~135
In order to analyze the effect of fines content on sedimentation and self-weight consolidation characteristics of dredged soil, a series of self-weight consolidation tests with different fines content were conducted. From the experimental test results on dredged soils, it was found that the coefficient of sedimentation and consolidation is correlated with water content. And it is related to fines content as well. So, in this study, correlation between fines content and the coefficient of sedimentation and consolidation has been proposed. And it is expected that the coefficient of sedimentation and consolidation can be estimated by the percentage of fines content.
Required Time for Isotopic and Ko Consolidation of Marine Clay in Triaxial Cell
Lee, Kyeong-Jun ; Jung, Du-Hwoe ; Im, Jong-Chul ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 137~147
Isotropic (instant loading) and Ko (gradual increase loading) consolidation tests were conducted in triaxial test equipment using cylindrical sample (5.0 cm in diameter and 10.0 cm in height) on two marine clay deposits. The duration of primary consolidation was estimated by two curve fitting methods using measured strain. A differential equation of consolidation for drainage in the radial and vertical direction was solved by the implicit finite difference scheme. The results of two curve fitting methods were compared with the numerical solutions to evaluate the appropriate axial loading rate of Ko consolidation and the primary consolidation periods. In addition, primary consolidation periods of the samples with a diameter of 35 mm and a height of 70 mm were calculated. The relation of radial and vertical consolidation coefficients is also presented.
A Study on the Availability of Pohang's Mudstone as a Reclamation Material
Lee, Kyu-Hwan ; Jung, Dae-Suck ; Yang, Tae-Sun ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 149~158
Recently, the selection of procurement material for reclamation or road at Pohang area is getting harder. so, it is attempted that mudstones are used for road base material and harbor reclamation. But there is no example that use mudstone to reclamation and the features of the reclaimed land using mudstones have not been made clear yet. We will make clear these features-especially the water absorption and softening, slaking behavior and the geological mechanism, so we will obtain the method to forecast a land subsidence and a decline of land strength. In this study, we examined the adaptedness judgment of mudstones as a reclamation material for road basis material or harbor reclamation material through the laboratory test and pilot test.
Unconfined Compressive Strength of Fiber-reinforced Cemented Sands by Fiber Reinforcement Form
Park, Sung-Sik ; Kim, Young-Su ; Lee, Jong-Cheon ;
Journal of the Korean Geotechnical Society, volume 23, issue 8, 2007, Pages 159~169
The behavior of fiber-reinforced cemented sands (FRCS) was studied to improve a brittle failure mode observed in cemented sands. Nak-dong River sand was mixed with ordinary Portland cement and a Polyvinyl alcohol (PVA) fiber. A PVA fiber is widely used in concrete and cement reinforcement. It has a good adhesive property to cement and a specific gravity of 1.3. A PVA fiber has a diameter of 0.1 mm that is thicker than general PVA fiber for reinforced cement. Clean Nak-dong River sand, cement and fiber at optimum water content were compacted in 5 layers giving 55 blows per layer. They were cured for 7 days. Cemented sands with a cement/sand ratio of 4% were fiber-reinforced at different locations and tested for unconfined compression tests. The effect of fiber reinforcement form and distribution on strength was investigated. A specimen with evenly distributed fiber showed two times more strength than not-evenly reinforced specimen. The strength of fiber-reinforced cemented sands increases as fiber reinforcement ratio increases. A fully reinforced specimen was 1.5 times stronger than a specimen reinforced at only middle part. FRCS behavior was controlled not only by a dosage of fiber but also by fiber distribution methods or fiber types.