• Proceedings of the Korean Geotechical Society Conference
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• 1999.02a
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• pp.36-47
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• 1999

Terzaghi's theory of one-dimensional consolidation is restricted in its applicability to relatively thin layers and small incremental loading. Because it is assumed to infinitesimal strain and linear material function. For this reason, Gibson et al established a rigorous formulation for the one-dimensional nonlinear finite strain consolidation theory. There are some difficulties in the application of finite strain consolidation theory. The developed program consisted of several forms and modules. These forms and modules with graphic-user-interfaced format are used in analysis of consolidation practices. For the purpose of verification of developed program. the results of case study and prediction of developed program are compared. The results of comparison is fairly well with prediction and measured data. And with varying finite strain consolidation parameter, g(e) or λ(e), the sensitivity of predicted values were examined.

• Geotechnical Engineering
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• v.14 no.5
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• pp.181-190
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• 1998

One-Dimensional Nonlinear Consolidation Model(NCM) ivas developed by using an Extended Power Function Model, which could represent the compressibility of soils. A nonlinear finite element program for NCM was developed to analyze the porewater pressure dissipation and the settlement of saturated soils. Parameters used in compressibility model could be easily obtained from conventional oedometer test data. This model has been applied to Yansan-Mulgum area for the comparison with the results of CONSOL program and that of Terzaghi theory. A Good The rates of consolidation predicted by this model and CONSOL were faster than that of conventional Tergaghi theory, for they consider the nonlinear characteristics of soils. Consolidation curves of this model were located between Terzaghi and CONSOL curves. Consolidation curves near drainage boundary, where effective stress valied rapidly, seemed to reflect the variations of compressibility of sails. Consolidation curves near drainage boundary obtained from this model were composed of two parabolic curves. Intersection of the parabolic curves occurred when effective stress reached the value of preconsolidation stress. Moreover, thin model could be used to represent the effect of magnitude of applied load. whereas CONSOL and Terazghi theory could not.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.491-498
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• 2002

Dredged and reclaimed soft clays form slurry state which is very high water content and very low shear strength, experience large self-weight consolidation, nonlinear compressibility and permeability phenomenon would take place. In this case, a material functions which represent variety effective stress-void ratio-permeability relation (especially very low effective stress), are should be determined to predict nonlinear finite strain consolidation phenomenon forehand In this study, large slurry consolidometer with a 380mm diameter and a 1400mm height which is able to consolidation and permeability test, was developed to determine material function of very soft clay with a 500% initial water content clay, self-weight consolidation and low stress level consolidation (1Kpa, 3Kpa, 6Kpa, 12Kpa) was conducted and after each consolidation step permeability test also conducted. after final consolidation step, a constant rate of strain consolidation was conducted with undisturbed sample obtained from the large consolidometer. On the above result, material function was determined and laboratory test was modelled to evaluate its validity, numerical analysis on th field was compared to other method.

• Geomechanics and Engineering
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• v.4 no.4
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• pp.229-241
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• 2012

In this paper, utilizing void ratio-effective stress and void ratio-permeability relationships, a system of two nonlinear partial differential equations is derived to predict the consolidation characteristics of normally consolidated (NC) and overconsolidated (OC) soft clays subjected to cyclic loading. A developed feature of the coefficient of consolidation containing two key parameters is emerged from the differential equations. Effect of these parameters on the consolidation characteristics of soft clays is analytically discussed. It is shown that the ratios between the slopes of e-$log{\sigma}^{\prime}$ and e-log k lines in the NC and OC states play a major role in the consolidation process. In the companion paper, the critical assumptions made in the analytical discussion are experimentally verified and a numerical study is carried out in order to examine the proposed theory.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.92-98
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• 1998

Nonlinear finite element analyses of one dimensional consolidation problem were performed using an anisotropic hardening constitutive model. For the analyses, the anisotropic hardening elasto-plastic constitutive model based on the generalized isotropic hardening(GIH) rule was implemented into a nonlinear finite element analysis program, PLASTIC. In order to preserve the accuracy of the finite element solution for nonlinear problems, an implicit stress integration algorithm was employed. A consistent tangent moduli could also ensure the quadratic convergence of Newton's method. As a result, the nonlinear solution was accurately calculated and was converged to be asymptotically quadratic. In a consolidation problem, the relationship between load and settlement and between settlement and time vertical was analyzed comparing with results using the Cam-clay type model and the final consolidation settlement and the duration of primary consolidation could be evaluated rigorously using the GIH constitutive model.

• Geomechanics and Engineering
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• v.4 no.4
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• pp.243-249
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• 2012

In the companion paper, the nonlinear consolidation of soft clays subjected to cyclic loading was analytically investigated. This paper reports the results of an experimental program conducted to verify some critical assumptions made in the analytical study. It, also, includes a numerical study carried out to examine the capability of the proposed theory to determine the consolidation characteristics of soft clays subjected to cyclic loading. Results show that the permeability of the soft clays does not significantly change during the cyclic loading. It is also shown that, compared to the Terzaghi's solution for a linear clay, the inherit nonlinearity of the clay tends to decrease the degree of consolidation due to the smaller rate of dissipation in the excess pore water pressure.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.299-313
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• 2019

This research investigated the nonlinear compressibility, permeability, the yielding due to structural degradation and their effects on consolidation behavior of structured soft soils. Based on oedometer and hydraulic conductivity test results of natural and reconstituted soft clays, linear log (1+e) ~ $log\;{\sigma}^{\prime}$ and log (1+e) ~ $log\;k_v$ relationships were developed to capture the variations in compressibility and permeability, and the yield stress ratio (YSR) was introduced to characterize the soil structure of natural soft clay. Semi-analytical solutions for one-dimensional consolidation of soft clay under time-dependent loading incorporating the effects of soil nonlinearity and soil structure were proposed. The semi-analytical solutions were verified against field measurements of a well-documented test embankment and they can give better accuracy in prediction of excess pore pressure compared to the predictions using the existing analytical solutions. Additionally, parametric studies were conducted to analyze the effects of YSR, compression index (${\lambda}_r$ and ${\lambda}_c$), and permeability index (${\eta}_k$) on the consolidation behavior of structured soft clays. The magnitude of the difference between degree of consolidation based on excess pore pressure ($U_p$) and that based on strain ($U_s$) depends on YSR. The parameter ${\lambda}_c/{\eta}_k$ plays a significant role in predicting consolidation behavior.

• Geotechnical Engineering
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• v.12 no.1
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• pp.5-20
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• 1996

In order to accelerate the rate of consolidation settlement and to gain a required shear strength for a given soft clay deposit, the preloading technique combined with a vertical drainage system has been widely applied. In this'study, the theory of axisymmetric consolidation which considers the variation of compressibility and permeability during the conslidation process, has ben developed. A computer program named AXICON for the analysis of axisymmetric nonlinear consolidation is developed by adopting an explicit finite difference method. Smear and well resistance effects are also considered. The AXICON is capable of analyzing the consolidation behavior of multi -layered deposits and simulates time dependent loading sequence. The results of AXICON are validated with analytical solutions of Hansbo and Barron, and compared with insitu settlements and pore pressures measured in a soft clay deposit.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.133-140
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• 2005

In order to accelerate the rate of consolidation settlement and gain a required shear strength for a given soft clay deposit, vertical drain method combined with a preloading technique has been widely applied. In this paper, a theory of axisymmetric nonlinear consolidation fer drainage-installed deposit, which considers secondary compression (or creep) during primary consolidation, as well as the variations of compressibility and permeability during the consolidation process, has been developed. A computer program named AXICON based on Hypothesis B fur the analysis of axisymmetric nonlinear consolidation was developed by adopting finite difference method. The results of AS(ICON were compared with Hansbo's solution based on Hypothesis A, as well as in-situ settlements and pore pressures measured in test embankment of Ska-Edeby. The results indicated that Hypothesis A usually underestimated the in-situ settlement and Hypothesis B was considered to be logically correct. It was also shown that one may able to appropriately predict the real in-situ behaviors using the proposed program.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.37-43
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• 2007

The interface layer having different consolidation properties and nonlinear material function with permeability needs to be considered to predict consolidation behavior. In this study, interface equation between different layers has been derived and then applied to existing finite difference scheme for conducting consolidation analysis. These results have been compared with those by conventional method in which different layers are converted to single layer having conversion value of properties. Also, although the conventional consoilidation analysis is used to consider non-linearity of the permeability with effective stress, an approximated nonlinear method as a function of consoilidation coefficient with effective stress have been developed and applied to the consoilidation analysis for various cases.