• Journal of the Korean GEO-environmental Society
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• v.3 no.2
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• pp.5-14
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• 2002

In this study, stress-deformation characteristics of buried pipe are studied. A numerical model, i.e., Egg-Cam Clay is introduced for the analysis of soft clay. Cam Clay model has a difficulty in analyzing soft clay that has two properties of shrinkage and swelling. Egg-Cam Clay model is modified format of Cam Clay model. In addition, Mohr-Coulomb model using finite element method is employed to verify effects of the geogrid, EPS geofoam. Stress deformation of several cases of pipe and other reinforcemnt material combinations are analyzed. Geofoam and geogrid have positive effects on the deformation characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.167-176
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• 1991

Finite element programs are developed, adopting the hyperbolic model and the Cam-clay model. In the hyperbolic model, a new model taking into account the volume change during shear is proposed and a new technique considering the density change underneath a footing is proposed. And a computing algorithm considered as more reasonable than existing one is presented. In the Cam-clay model, the deveoloped program is applied to sand, the case not recorded much, and then it is tried to analiza the behavior of sand from the viewpoint of the critical state concept. For this, the conventional CD triaxial compression tests and the footing model tests are carried out. The results are improved by 60 percent by using the modified hyperbolic model proposed. When the Cam-clay model is applied to sand, a model reflecting the overconsolidation effects and a computing algorithm accounting for the strain softening are needed. The results obtained by using the Cam-clay model are not much influenced by the value of the initial poisson's ratio, but those of the modified hyperbolic model are much influenced by that. So th values of the initial poisson's ratio must be selected deliberately in the numerical analysis.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.89-99
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• 2001

In this study, the numerical analysis of piezocone penetration and dissipation tests has been conducted using the Modified Cam-Clay model, which is generally used in soil mechanics. The Modified Cam-Clay model and related mathematical equations in finite element derivation have been formulated in the Updated Lagrangian reference frame to take the large displacement and finite strain nature of piezocone penetration into consideration. The cone tip resistance, the pore water pressure, and the dissipation curve obtained from the finite element analysis have been compared and investigated with the experimental results from piezocone penetration test performed in Yangsan site. The numerical results showed good agreement with the experimental results; however, the better numerical simulation of the continuous and deep penetration needs further research.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.45-59
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• 1983

This study aims at investigating the deformation and strength characteristics on reconsolidated-remoleded saturated clay sampled at the downstream of Young-san river, in Cheollanamdo through a series of both drained and underained triaxial tests by means of the critical state concept. Among several constitutive equations developed so far, the Cam-clay model, the modified Cam-clay model and the dilatancy model are used. The prediction of strains is obtained and the value of prediction is compared with that of observation. For the clay specimen, the prediction of volumetric strain on the dilatancy model is well consistent with the observation and the prediction of shear strain on the modified Cam-clay model coincides exactly with the observation.

• Korean Journal of Agricultural Science
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• v.25 no.2
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• pp.235-246
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• 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 GEO-environmental Society
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• v.1 no.1
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• pp.5-12
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• 2000

Mudstone, found Du-Ho Dong and around there in Po-Hang, is used as construction material. When it is exposed to the air and contacts with water, the strength is decreased rapidly and then it causes a lot of problems. In the field, clay soils with $K_o$ condition have anisotropic characteristics which behave differently according to the change of principal stress direction. In this study, $K_o$ consolidation is performed to make the completely weathered mudstone under the same conditions of construction place. Then, the triaxial compression test is performed at different shear velocity and anisotropy by sampling degree and the stress - strain behavior is shown the strain softening behavior. The stress - strain relationship from triaxial compression test is compared with the prediction value of Cam-clay model. From the results of tests, $K_o$ value decreases with the increase of sampling degree. Generally the behavior of $K_o$ consolidated specimen shows work-softening characteristic. The trend of behaviour of the measured is nearly to same to the predicted by Cam-clay model. But the measured value of deviator stress is very higher than the predicted. Therefore, Cam-clay model was not appropriate to the completely weathered mudstone consolidated with $K_o$ condition in Pohang region.

• Journal of the Korean Geotechnical Society
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• v.36 no.4
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• pp.5-15
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• 2020

This paper proposes a revised Modified Cam Clay type failure surface based on the critical state theory. In the plane of the mean effective and von Mises stresses, the original Modified Cam Clay model has an elliptic failure surface which leads the critical-state mean effective stress to be always half of the pre-consolidation mean effective stress without hardening and evolution rules. This feature does not agree with the real mechanical response of clay. In this study, the preconsolidation mean effective stress only reflects the consolidation history of the clay whereas the critical state mean effective stress only relies on the currenct void ratio of clay. Therefore, the proposed failure surface has a distorted elliptic shape without any fixed ratio between the preconsolidation and critical state mean effective stresses. Numerical simulations for various clays using failure surfaces as yield surface provide mechanical responses similar to the experimental data.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.247-256
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• 2003

FEM analyses which are based on modified Cam-clay theory have been generally used in such cases as analyses of stability and displacement fur embankment construction on soft clays. However, the Modified Cam Clay Model can generate some problems in anisotropic stress conditions of field because the critical state theory has been developed through many laboratory tests in isotropic conditions. Thus, the applicability on the prediction of undrained shear strength and pore water pressure which was based on the critical state theory was evaluated by triaxial tests and numerical analyses in isotropic and anisotropic conditions. Used samples often come out in domestic area, together with general low plastic clays which are showing dilatant behavior in shearing process. They were evaluated by laboratory tests and FEM based on MCCM. From the results of test and numerical analysis, the predictions of undrained strength in low plastic clays well coincided with each other in both isotropic and anisotropic conditions. However, the generation of porewater pressure was often overestimated during undrained shearing in anisotropic conditions. The results can generate the errors in the prediction of stress path of field sites during loading such as construction of embankment on soft clays because the field is subjected to anisotropic conditions during loading.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.61-70
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• 2008

In this study, undrained triaxial (CU) tests were performed on low-plastic silt of Nakdong River in order to investigate the undrained shear behavior of low-plastic silt. In experimental results, the deviator stress showed the hardening behavior after reaching its yield stress like the tendency of common sand, and the pore water pressure was gradually decreased to critical state after the maximum value. In the effective stress paths, regardless of consolidation stress or overconsolidation ratios, both a critical state line (CSL) and a phase transformation line (PTL) exist in the effective stress path that is similar to the case of sand. The behavior of low-plastic silt was predicted by the Modified Cam-Clay (MCC) model, the Jordan and the Elman-jordan model that is artificial neural network model. According to predicted results, the overall undrained shear behavior of low-plastic silt could not be predicted with the MCC model, but the Jordan and Elman-Jordan model showed well-matched experiment results.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.79-89
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• 2004

An elastic-plastic-viscous constitutive model was proposed based on a simple formulation scheme. The anisotropic modified Cam-Clay model was extended for the general stress space for the plastic simulation. The generalized viscous theory was simplified and used for the viscous constitutive part. A damage law was incoporated into the proposed constitutive model. The mathematical formulation and development of the model were performed from the point of view that fewer parameters be better employed. The creep behaviors with or without creep rupture were predicted using the developed model for cohesive soils. The model predictions were favorably compared with the experimental results including the undrained creep rupture, which is an important observed phenomenon for cohesive soils. Despite the simplicity of the constitutive model, it performs well as long as the time to failure ratio of the creep rupture tests is within the same order of magnitude.