• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6C
• /
• pp.349-358
• /
• 2008

In performing the reliability analysis for predicting the settlement with time of alluvial clay layer at Kobe airport, the uncertainties of geotechnical properties were examined based on the stochastic and probabilistic theory. By using Terzaghi's consolidation theory as the objective function, the failure probability was normalized based on AFOSM method. As the result of reliability analysis, the occurrence probabilities for the cases of the target settlement of ${\pm}10%,\;{\pm}25%$ of the total settlement from the deterministic analysis were 30~50%, 60%~90%, respectively. Considering that the variation coefficients of input variable are almost similar as those of past researches, the acceptable error range of the total settlement would be expected in the range of 10% of the predicted total settlement. As the result of sensitivity analysis, the factors which affect significantly on the settlement analysis were the uncertainties of the compression coefficient Cc, the pre-consolidation stress Pc, and the prediction model employed. Accordingly, it is very important for the reliable prediction with high reliability to obtain reliable soil properties such as Cc and Pc by performing laboratory tests in which the in-situ stress and strain conditions are properly simulated.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1996.03a
• /
• pp.251-258
• /
• 1996

• Korean Journal of Agricultural Science
• /
• v.25 no.2
• /
• pp.235-246
• /
• 1998

This study was performed to find the effect of parameters of numerical analysis model. To find the parameters of numerical analysis model, triaxial test and consolidation test were conducted and the results were compared and analyzed with various methods. Preloaded ground was analyzed with Hyperbolic and Modified Cam-Clay models. Hyperbolic model analysis result was good agreement with measured lateral displacement, and Modified Cam-Clay model agreed more than Hyperbolic model with settlement. When the parameters of models were changed, change of settlement on center of embankment and of maximum lateral displacement on distance 5m from end of embankment were compared. On Hyperbolic model the parameter K has large influence on settlement and lateral displacement. On Modified Cam-Clay model the parameters ${\Gamma}$ and M have large influence on settlement and lateral displacement, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.1
• /
• pp.221-228
• /
• 2003

In land reclamation construction using marine clay, a measure of material function, that is, the relation between void ratio-effective stress and permeability, is very important aspect for the prediction of self-weight consolidation behavior. But reclaimed ground has very high water content, so there are many difficulties in the laboratory test for measuring material function. For this reason, some researches are carried out using slurry cconsolidometr to measure material function. In this study, material function was measured using slurry consolidometer, and to overcome the shortcoming of researches using slurry cosolidometer, an equation for the prediction of material function was proposed on the basis of column test's parameter. Material function was determined through low stress consolidation test and permeability test, and it also was calculated with the equation using column test parameter. The continuity of material function could be confirmed through these tests. Material function is easily determined with the equation proposed in this study, and can be used for the prediction of self-weight consolidation behavior.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.1
• /
• pp.75-81
• /
• 2000

The anisotropy of soils has an important effect on stress-strain behavior. In this study, an attempt has been made to implement artificial neural network model for modeling the stress-strain relationship and predicting the undrained shear strength of normally consolidated clay with varying consolidation pressure ratios. The multi-layer neural network model, adopted in this study, utilizes the error back-propagation loaming algorithm. The artificial neural networks use the results of undrained triaxial test with various consolidation pressure ratios and different effective vertical consolidation pressure fur learning and testing data. After learning from a set of actual laboratory testing data, the neural network model predictions of the undrained shear strength of the normally consolidated clay are found to agree well with actual measurements. The predicted values by the artificial neural network model have a determination coefficient$(r^2)$ above 0.973 compared with the measured data. Therefore, this results show a positive potential for the applications of well-trained neural network model in predicting the undrained shear strength of cohesive soils.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.3
• /
• pp.35-40
• /
• 2007

The vertical drain method recently being used in Korea is divided into the sand drain method, the pack drain method, the paper drain method, and the PBD method according to the drainage. However, these methods generate the disturbed zone called the smear zone when the drainage is penetrated into the in-situ ground. The characteristics of the smear zone generated cause the problems that the coefficient of permeability decreases and the consolidation time becomes longer than expected in the design. Although the size of the smear zone is a very important factor directly influencing the degree of consolidation, in the existing studies, the general value for the size of the smear zone proposed has been used in the design. However, the size of the smear zone proposed by the existing studies cause a loss of economical efficiency because of the inaccuracy of the design. Hence, in this study, the characteristics on the size of the smear zone were analyzed by carrying out the three dimensional numerical analysis and the method to determine the conversion size of the smear zone considering the change of the coefficient of permeability was proposed in order to consider the change of the coefficient of permeability in the actual design.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.38 no.3
• /
• pp.429-438
• /
• 2018

Cone and T-bar penetrometers have been frequently used to estimate the undrained shear strength of clay. For small-size model tests, miniature penetrometers should be used but their correlation factors have not been well published. In this study, a testing setup was developed to derive empirical factors of the miniature cone and T-bar penetrometers. A 350mm-diameter chamber and kaolin clay were utilized to prepare soil specimens consolidated under four different pre-consolidation pressures controlling undrained shear strength. Two miniature cones with two diameters of 10-mm and 16-mm and a T-bar penetrometer with 10-mm diameter were used to investigate boundary effect, penetration rate effect, and diameter and shape effect. Unconsolidated-undrained triaxial tests were carried out with samples taken from the specimens to measure undrained shear strength. Finally, empirical factors for the penetrometers were constructed to correlate tip resistance to undrained shear strength.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.5
• /
• pp.89-98
• /
• 2008

In this study, the behaviour of an unsaturated soil was analyzed by performing $K_0$ consolidated triaxial tests. Unsaturated triaxial tests were performed with matric suctions for weathered soils and stress paths under consolidation and stress-strain relationships under shear were obtained. As a result, the $K_0$ value decreased as the matric suction increased. Besides, both isotropic and $K_0$ conditions had similar shear strength envelopes at the same matric suction. Especially, strength parameters could be obtained by stress variables used in the critical state theory more reasonably than by those of Mohr circles at failure.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1078-1085
• /
• 2005

1990년 이래 낙동강 하구 서쪽지역인 서부산과 인근 지역에서는 대단위 지반조성공사가 수행되었다. 이 지역에서는 부산점토라고 명명된 점성토가 20-70m의 두께로 상당히 두텁게 형성되어있다. 최근에 들어 정교한 지반조사가 수행됨에 따라 이 지역의 점토에 대한 공학적 특성이 효과적으로 밝혀졌지만, 점토의 특성을 면밀히 규명하기 위해서는 여전히 많은 과제가 남아있다. 본 논문에서는 부산신항 지역에서 점토에 대하여 다양한 방법으로 투수계수를 구하여 투수특성을 규명하고자 한다. 이를 위하여 수평 및 연직방향의 배수에 의한 일정변형률(CRS) 압밀실험, 표준압밀실험 및 압밀 중에 변수위 투수실험이 실내실험으로 이루어 졌으며, 현장실험으로 CPTU에 의한 소산실험 및 Casagrande형 피에조미터에 의한 소산실험이 실시되었다.이들 결과를 서로 비교하여 합리적인 실험결과를 분석하며, 이점토에 대한 깊이별 투수계수 및 투수 이방성을 규명하고자 하였다.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.42 no.4
• /
• pp.115-123
• /
• 2000

This study compared the degree of consolidation by hyperbolic, curve fitting , Asaoka's and methods using values measured with a theoretical curve in consideration of smear effect and well resistance. The degree of consolidation by the Hyperboilc method was underestimated than the degree of consolidation by Curve fitting. Asaoka's , and Monden's methods. The typical range of the coefficient of horizontal consolidation was Ch=(2-3)Cv in the case considering smear effect and well resistance, and Ch =(0.5-2.1) Cv in the case disregarding smear effect and well resistance. The degree of consolidation obtained by ground settlement monitoring was nearly the same value when the coefficient of smear zone permeability by back analysis was shown to be half that of in-situ and the diameter of the smear zone was shown to be double that of mandrel. By increasing the diameter reduction ratio of the drain, the time of consolidation was delayed. The effect of well resistance showed that the case of a small coefficient of permeability was much more than in the case of a large coefficient of permeability . It was recommended that when designing diameter reduction of a drain, well resistance should be considered.