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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 18, Issue 6 - Dec 2002
Volume 18, Issue 5 - Oct 2002
Volume 18, Issue 4 - Aug 2002
Volume 18, Issue 3 - Jun 2002
Volume 18, Issue 2 - Apr 2002
Volume 18, Issue 1 - Feb 2002
Selecting the target year
A Fully Coupled Hydrogeomechanical Numerical Analysis of Rainfall Impacts on Groundwater Flow in Slopes and Slope Stability
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 5~16
A hydrogeomechanical numerical model is presented to evaluate rainfall impacts on groundwater flow in slopes and slope stability. This numerical model is developed based on the fully coupled poroelastic governing equations for groundwater flow in deforming variably saturated geologic media and the Galerkin finite element method. A series of numerical experiments using the model developed are then applied to an unsaturated slope under various rainfall rates. The numerical simulation results show that the overall hydromechanical slope stability deteriorates, and the potential failure nay initiate from the slope toe and propagate toward the slope crest as the rainfall rate increases. From the viewpoint of hydrogeology, the pressure head and hence the total hydraulic head increase as the rainfall rate increases. As a result, the groundwater table rises, the unsaturated zone reduces, the seepage face expands from the slope toe toward the slope crest, and the groundwater flow velocity increases along the seepage face. From the viewpoint of geomechanics, the horizontal displacement increases, and the vertical displacement decreases toward the slope toe as the rainfall rate increases. This may result from the buoyancy effect associated with the groundwater table rise as the rainfall rate increases. As a result, the overall deformation intensifies toward the slope toe, and the unstable zone, in which the factor of safety against shear failure is less than 1, becomes thicker near the slope toe and propagates from the slope toe toward the slope crest. The numerical simulation results also suggest that the potential tension failure is likely to occur within the slope between the potential shear failure surface and the ground surface.
Modulus and Damping Properties of Kaolinite Using Ultrasonic Testing
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 17~24
The objective of the present research is to evaluate the wave propagation velocity and attenuation characteristics of kaolin clay specimens using ultrasonic testing. Test specimens with known initial micro-fabric were prepared using a two-stage slurry consolidation technique. For a known state of stress conditions, initial void ratio, and micro-fabric, a series of experiments were conducted to evaluate the longitudinal wave propagation velocity and associated damping behavior. The effects of major variables involved in ultrasonic testing of cohesive soil were considered in this study. Ultrasonic velocity was not correlated to the microfabric structure under the given consolidated pressure whereas ultrasonic attenuation was affected by the microstructural properties of the specimen.
The Soil Particles Distributions and Fractal Dimension
;;;Baveye, Philippe C.;
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 25~32
The fractal dimension that was evaluated with soil components from the traditional particle-size distribution(PSD) curve was analyzed using the results of Wu et al.(1993) and Bittelli et al.(1999). In order to find the change of the variation of fractal dimension with the upper and lower limit, three limit values(200
, and 125
) were chosen, and these results of fractal dimension analysis were compared to the result that was evaluated in the whole range of the soils. The results showed that it is possible to evaluate fractal dimension from the traditional PSD curve with the soil contents, and it showed that Bittelli et at.(1999)'s upper and lower limit value was more reasonable than Wu et al.(1993). Equations that were presented by Bittelli et at.(1999) also showed a good agreement with the analytical results in the silt domain.
Numerical Analysis of the Effects of Stress Anisotropy and Tunnel Excavation Shape on Initial Elastic-wall Displacement
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 33~42
Ground reaction curve is a very important information for evaluating the side wall displacements and installation time of the tunnle support. The ground reaction curve can be estimated by analytical closed form solutions derived on the supposition of circular section and isotropic stress condition. The conditions of stress field and tunnel configurations, however, are quite different in practice. Therefore, it is necessary to investigate the effects of stress anisotropy and tunnel configurations in order to use simply in practical design. This paper describes a study of influence factors in the ground reaction curve. In order to evaluate the applicability of analytical closed form solution in practical design, two sets of parametric studies were carried out by numerical analysis in elastic tunnel behaviour: one set of studies investigated the influence of the K and the other set investigated the influence of the tunnel configurations such as circular and horse-shoe shape. In the studies, K value varies between 0.5 and 3.0, initial ground vertical stress varies between 5～30MPa far each K values. The results indicated that the self-supportability of ground is larger in the ground having lower K value. However, it is suggested that the applicability of closed form solution may not be adequate to determine directly the installation time of the support and self-supportability of ground. It is necessary to consider stress anisotropy and tunnel configurations.
A Study on the Selection System of Waterproof Method by Using Database
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 43~59
In this study, database systems which were used to select the waterproof method according to leakage patterns of underground structures were built by performing pilot tests, reviewing literatures, and analysing the gathered data statistically. The database was built by using check lists which consisted of 5 major items and 73 subdivided items, and 26 major parameters according to 4 classified grades were determined on the base of survey which considered various in-situ conditions. The database of waterproof methods was comprised of 10 methods which were applied in Korea. From the database of waterproof methods, application ranges and design conditions of waterproof methods were suggested. From the results of study, database system consists of parameters selection database, waterproof method database, and design condition database. From the results of pilot tests, when the database of waterproof methods was applied to design stage, saving time and reducing mistakes for selecting waterproof method were gained. In addition, when the database of waterproof methods was applied to construction stage, effects such as evaluation of applicability of waterproof method, improvement of constructability and post management were expected.
Injection Characteristics of Cement Grouting Waterproof by Model Tests
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 61~72
In this study, model tests were performed to evaluate the injection characteristics of cement grouting which was used as waterproof method for leakage of underground structures. To simulate in situ condition, model tests were performed with varying the ground conditions such as the kinds of test soils, soil density, water content, etc. and the injection conditions such as kinds of injection materials, injection pressure, injection quantity, injection velocity, etc. From the results of model tests, the major factors influencing the permeability of injection material were determined to be the kinds of soils and soil density. To obtain optimal injection effects, injection should be performed after investigating the condition of backside ground accurately,
Profiling Stress History(OCR,
p) of Marine Clay Using Piezocone Penetration Test
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 73~81
Various CPT-based prediction models far profiling stress history of marine clay at the southern part of the Korean peninsula were investigated by using both statistical analysis and case history study. Preconsolidation pressures(
p) and overconsolidation ratio(OCR) estimated by empirical correlations and cone penetration tests were compared with those of laboratory odometer test results. Stress history of marine clay determined by odometer test results was in general overconsolidated at below 10m depth from the mudline, whereas marine clay at below l0m depth from the mudline which has an around 0.3 overconsolidation ratio showed variable stresses and unstable states. Preconsolidation pressures were computed by both empirical methods of the Chen and Mayne(1996) and theoretical method of Konrad and Law(1987). It is estimated that Chen and Mayne(1996)'s prediction method based on pore water pressure is more reliable than any other prediction methods, and their method proved to be the most reliable for overconsolidation ratio estimation. However, it is recommended that Mayne & Holtz(1988) and Mayne & Bachus(1988) methods are more suitable than any other methods for predicting the overconsolidation ratio at an underconsolidated (OCR<1) clay. For these reasons, rather than making use of existing prediction models, development of site specific empirical correlations which considers local characteristics and site conditions may be required due to different local stress history and variable soil properties.
Soil Properties in Relation to Elastic Wave
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 83~101
Elastic waves provide an important information about the soil mass in the near-surface. Soil properties in relation to elastic wave parameters are clarified to facilitate the application of geophysical technique to soil characterization. As an example, experiments are performed to gain further insight into the behavior of unsaturated particulate materials using bender elements. The small strain stiffness is continuously measured on specimens subjected to drying, and changes in stiffness are related to changes in interparticle forces such as capillarity, bonding due to ion sharing, buttress effect due to fine migration, and cementation due to salt precipitation. The rate of menisci regeneration is studied after a perturbation as well. Finally, several phenomena associated with the evolution of capillary forces during drying are identified.
Strength Change of Concrete with Crushed Oyster Shell by the Addition of Ethylbenzene
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 103~116
The development of contaminated sites often requires foundation concrete to be placed in contact with soils contaminated with organic compounds. There is a common perception that organic compounds affect the setting and hardening of concrete, giving a reduced long-term strength. In this study, unconfined compressive strength tests for concrete cured in Ethylbenzene were performed. The possibility of byproduct to be used for aggregate of concretes as materials of construction was also evaluated by carring out the investigation of the characteristics of the mixture of concrete and crushed oyster shell which is treated as waste material and often illegally disposed at coastal oyster production site. The transformation of strength characteristics was investigated by varying the blending ratio of fly ash.
Slope Stability Analysis Using the Genetic Algorithm
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 117~127
A deterministic approach of slope stability, which is generally corresponding to the model of a simple non-linear function for slopes, is problematic in that it does not account the versatile characteristics of ground layers in an effective way. To resolve this problem, this study proposes a new way of analyzing slope stability, so-called “genetic algorithm method, ” so as to reflect some particular conditions pertaining to the grounds under concern. Similarities and differences in slope stability that may exist between homogeneous and multiple ground layers are examined in a competitive manner, Overall, though similarities deemed a little bit salient, the algorithm method turned out to be very applicable to estimating the validity of slope stability. Furthermore, an additional effort to consider long-standing sequential and dynamic changes in both the amount of rainfall and the underground water level is made in order to improve the results.
Variation of Dielectric Constant of Sand due to Water Content and Measuring Frequency
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 129~139
Dielectric constant measurement has drawn much attention in the investigation of the properties and contaminations of subsurface. In this study, by varying the frequency from 75 kHz to 12 MHz, dielectric constant was measured for the weathered granite soil and Jumunjin sand having different water contents and dry density. The dielectric constant of sand showed the dispersive behavior indicating that dielectric constant decreased with frequency of an electric field. And the dielectric constant of soil increased as water content and/or dry density increased due to the decrease of air portion and/or the increase of amount of water molecules which could contribute to the development of orientation polarization. The dielectric constant of sand showed a linear relationship with the moisture density, considering both water content and dry density. At low frequency, the dielectric constants calculated by Maxwell's, Topp's and CRIM equation deviated from measured values. It could be explained by the fact that those equations did not consider dispersive behavior of dielectric constant with the frequency.
Distribution of Vertical Earth Pressure due to Surcharge Loads Acting on Cantilever Retaining Wall Near Rigid Slope
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 141~152
This paper is the result of the experimental and numerical research on the distribution of vertical earth pressure due to surcharge loads acting on cantilever retaining wall close to a rigid slope with a stiff angle. Centrifuge model experiments were performed with changing the roughness of adjacent slope to the wall, distance between the wall and the slope and gravitational levels. Vertical earth pressures were measured by earth cells embedded in the backfill of the wall. Test results of vertical earth pressures due to surcharge loads were compared with theoretical estimations by using two different methods of limit equilibrium and the numerical analysis. For limit equilibrium methods, the modified silo and the wedge theories, proposed by Chung(1993, 1997), were used to analyze test results. Based on those modified theories, the particular solution with the boundary condition of surcharge loads on the surface of backfill was obtained to find the vertical stress distributions acting on the backfill. FLAC with the hyperbolic constitutive model was also used for the numerical estimation. As a result of comparison of test results with theoretical and numerical estimations, distribution of vertical earth pressures obtained from centrifuge model tests is generally in good agreement with numerical estmated values by using FLAC whereas the wedge theory shows values close to test results in case the distance between the wall and the slope is narrow.
A Study on the System Identification of Tunnel Lining Using Static Deformation Data
Journal of the Korean Geotechnical Society, volume 18, issue 6, 2002, Pages 153~160
A new system identification method based on tunnel deformation data is proposed to find the damage in the lining structure. For this, an inverse problem in which the deformation data and dead load of concrete lining are known a priori is introduced to estimate the degree and location of the damages. Models based on uniform reduction of stiffness and homogenized crack concept are individually employed to compare the applicability and relative advantages of the models. Numerical analyses are peformed for the idealized tunnel structure and the effect of white noise, common in most measurement data, is also included to better understand the suitability of the proposed models. As a result, model 1 based on uniform stiffness reduction method is shown to be relatively insensitive to the noise, while model 2 with the homogenized crack concept is proven to be easily applied to the field situation since the effect of stiffness reduction is rather small.