• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.75-81
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• 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 Geotechnical Society
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• v.18 no.5
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• pp.7-18
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• 2002

Generally, natural soils are affected by one-dimensional consolidation so that the behavior characteristic could be somewhat different from the isotropic consolidation specimen. But, due to experimental difficulties and the lack of equipment, the isotropic triaxial tests are mainly performed in most lab. tests. So it seems to be very effective if it is possible to predict pore water pressure and undrained shear strength in the $K_o$ state as the results of isotropic triaxial consolidation test. In this study, isotropic triaxial consolidation test and $K_o$ triaxial consolidation test were performed and we obtained parameters related to pore water pressure ratio using the Hyperbolic model. And then we predicted the behavior of pore water pressure that occurred in the $K_o$ state from the results obtained in the isotropic triaxial cosolidation test through the equation suggested by Lo(1969). It is possible to seize the validity of Lo(1969) equation. Also, considering undrained shear strength obtained from consolidation method in relation with water content, we find that consolidation method have an effect on undrained shear strength. Finally, using the Wroth(1984) equation that is based on the theory of critical state, undrained shear strength in the $K_o$ state was predicted from that of the isotropic triaxial consolidation test. The usefulness of the equation was verified by comparing the predicted value with experimental results.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.318-326
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• 2008

Recently, a new seismic probe, called "MudFork", has been developed and can be utilized for accurate and easy measurements of shear wave velocities of soft soils. To expand its use to estimate undrained shear strength and density, correlations between those and shear wave velocity were being attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a soft ground site near Incheon, Korea. Also, undisturbed samples were obtained and shear wave velocities of the samples were measured as well as undrained shear strength, using triaxial compression test and bender elements. A simple linear relationship between shear strength and shear wave velocity was obtained, and a tentative relationship between density and shear wave velocity was also defined.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.71-81
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• 1999

A study on the undrained behavior of isotropically consolidated clay-sand mixtures was carried out using the automated triaxial testing apparatus. Overconsolidated ratio, effective mean pressure and clay content( up to 20% bentonite) were the factors varied in the experimental investigation. Undrained behavior(strength and pore water pressure generation during shear in triaxial loading) depends upon overconsolidation ratio, confining pressure and clay content. Significant changes in undrained compression characteristics occurred at around 20% of clay contents in the sand. The test results were analyzed and their behaviors were interpreted within the framework of plasticity constitutive model for clay-sand mixtures. Possible physical bases for the proposed forms are discussed. Validation of the applied model using the laboratory results is also given.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.183-193
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• 1987

After clay particles have been sedimented isotropically, the clay deposits have been consolidated under $K_0$-stress system. Therefore, in order to predict the behavior in-situ of normally consolidated clays, the effect of $K_0$-consolidation should be considered. A series of undrained and drained triaxial compression tests was performed on remolded specimens of clay consolidated under both $K_0$-and isotropic stress systems and the effect of $K_0$-consolidation was investigated. $K_0$-consolidation has much effect on the deviator stress, especially at initial deformation stage of consolidated-undrained tests, but has little effect on the principal effective stress ratio. Thus, the undrained strength behavior of $K_0$-consolidated samples can not be predicted from isotropically consolidated test data. However, the failure envelop, provided by the maximum principal effective stress ratio failure criterion, is unique and curved.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.5
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• pp.1229-1241
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• 1994

This study aims at investigating the undrained behavior of the normally consolidated clay foundation using single hardening constitutive model based on elasticity and plasticity theories. The specimen employed was sampled at Mooan near the down stream of Young San river and remolded into consolidation apparatus. 11 soil parameters for the model was determined from simple tests such as isotropic compression and consolidation undrained triaxial compression tests. FEM program to predict the undrained behavior of the foundation was developed and back analysis was performed to verify prediction ability of the FEM program. Finally plate load test on the 2-dimensional model foundation was carried out in order to compare numerical analysis and observed values on the foundation.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.287-298
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• 2003

The feasibility of using neural networks to model the complex relationship between piezocone measurements and the undrained shear strength of clays has been investigated. A three layered back propagation neural network model was developed based on actual undrained shear strengths, which were obtained from the isotrpoically and anisotrpoically consolidated triaxial compression test(CIUC and CAUC), and piezocone measurements compiled from various locations around the world. It was validated by comparing model predictions with measured values about new piezocone data, which were not previously employed during development of model. Performance of the neural network model was compared with conventional empirical method, direct correlation method, and theoretical method. It was found that the neural network model is not only capable of inferring a complex relationship between piezocone measurements and the undrained shear strength of clays but also gives a more precise and reliable undrained shear strength than theoretical and empirical approaches. Furthermore, neural network model has a possibility to be a generalized relationship between piezocone measurements and undrained shear strength over the various places and countries, while the present empirical correlations present the site specific relationship.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.582-587
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• 1999

This study has been done to investigate the characteristics of synthetic fiber reinforcement sol with fully satruated . To this end, consolidated undrained triaxial test was performed on synthetic fiber reinforcement soil using the soft clay and plypropylene fiber . From the results of test, it was formed that the mixing ratio for weight and the aspect ratio of synthetic fiber have an effect on the shear characteristic of synthetic fiber rinforcement soil. Especially shear paramter C has line relationship for mixing ratio of fiber, and øhas parabolic relationship for mixing ratio of fiber.

• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.1-12
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• 2016

In this study, the impact of sand and weathered granite soil is analyzed by changing the internal temperature from $20^{\circ}C{\sim}70^{\circ}C$C by installing a heating coil inside the triaxial cell. To check the effect on weathered granite soil due to increase of temperature and number of heating-coiling cycles are analyzed by measuring the temperature by using thermometer installed inside the triaxial cell and due to that deviator stress also occurred during the consolidated undrained test. To analyze the effect of weathered granite soil with change of temperature during undrained testing. The deviator stress and pore pressure is measured. As a result, pore pressure increases and the deviator stress decreases with rise of temperature.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.888-895
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• 2006

In this study, anisotropically consolidated undrained shear(CAU) test was performed to examine the variation of the shear strength according to the stress history. The specimen having 30% relative density was homogeniously prepared, and 200KPa of back pressure was applied to increase the B value more than 0.95. To make NC specimens, the vertical stress was applied on the specimen by 100KPa, 200KPa and 400KPa, and to make OC specimens, the vertical stress was applied upto 400KPa and was reduced to 200KPa and 100KPa resulting in OCR 2 and 4 respectively. The test result indicates the shear strength for the OC specimens are slightly higher then that of the NC specimens at the same confining pressure. The elastic modulus varies according to the confining stress and considerably affected by preconsolidation stress.