• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.3-14
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• 2000

Anisotropic consolidation, shear, a transportational component during or after deposition each may produce anisotropic fabrics, which result in the anisotropic properties of soils. Nevertheless, the isotropically consolidated compression triaxial tests are commonly used in practice to determine the strength of the anisotropically consolidated soils because of their practicality and simplicity. In this paper the effects of anisotropic consolidation on the strength properties of soils are discussed. For the sandy soils consolidated under a constant vertical consolidation pressure, the deformation modulus decreases with decreasing consolidation pressure ratio($\sigma$$\sub$3c/'/$\sigma$ sub 1c/'), but the liquefaction resistance increases. For the saturated cohesive soils, both the undrained shear strength and undrained creep strength decrese with decreasing the consolidation pressure ratio. When the in-situ strength properties of the anisotropically and normally consolidated soils are determined by the isotropically consolidated tests, the undrained shear strength and creep strength of saturated cohesive soils as well as the deformation modulus of sandy soils are measured to be higher than the rear in-situ values. This, therefore, could lead to a dangerous judgement in stability analysis

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.685-692
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• 2000

Vertical drain used improvement soft clay is made of not only decreasing construction time but also increasing the ground strength during some decades. As, it is applied to improvement soft clay with vertical drain, it is designed by the result that is caused by oedemeter test ignored anisotropic of the ground related to consolidation conditions. When we are expected consolidation conditions, the most important factors is soil of compaction and water permeability. Above all, anisotropic of the ground permeability show the results which differ between vertical and radial drainage. Recently, We study for radial consolidation coefficient and permeability coefficient that utilized Rowe Cell Consolidation and permeability tester but, it dont use well because of not only a supply lack also difficulty of test. The paper experimented with searching anisotropic of the ground so there are Rowe Cell test, standard consolidation tester and modified standard consolidation test that have pohang's soft clay ground. Therefore, we find anisotropic of the ground and a tester of easy use more than before. We made a comparison test result between the devised tester and Rowe Cell tester, Also, we learned average degree of consolidation for partial penetrating vertical drains. We were found relations as effective stress-void and effective stress-permeability coefficient through those tests.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.7-14
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• 2003

This study has investigated the feasibility of caissons for accelerating consolidation (C.A.C.) constructed in clays with anisotropic permeability by improving the former study on C.A.C. in isotropic clays. Analytical solutions for excessive pore water pressures of two-dimensional consolidation equation and average degrees of consolidation with varying time factors have been provided by considering anisotropic permeability. With varying anisotropic permeability ratios of 5, 10, and 50, consolidation times required for reaching the average degree of consolidation of 90% for C.A.C. at the section of $\xi$=0.1 are shorter than those for conventional caissons by 8, 13, and 47 times, respectively. C.A.C. is more effective in reducing consolidation time as anisotropic permeability ratio increases. This study provides also plots for average degrees of consolidation versus the width to depth ratios of analyzed sections and permeability ratios, which will enable engineers to determine easily average consolidation settlements.

• Geotechnical Engineering
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• v.12 no.2
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• pp.95-106
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• 1996

In this study, a constitutive model which can describe the anisotropic and plastic behaviors of natural cohesive soils, was developed based on anisotropic bounding surface theory. The model was fomulated by the concepts of the improved anisotropic bounding surface function, nonassociated flow rule with new plastic potential function, anisotropic hardening rule, and new mapping rule governing the plastic behavior inside bounding sutraface. Comparing with the results of Ku consolidation and triaxial shearing tests, the predictions by the proposed model agree quite well with real soil responses.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.823-830
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• 2004

Consolidation tests under various deformation modes were performed to investigate the effect of deformation modes on the coefficient of consolidation in the normally consolidated clay in remolded and undisturbed clay. The degree of soil anisotropy was evaluated using cross-anisotropic elasticity theory suggested by Graham et al.(1983). Experimental results showed that the vertical compressibility was larger than the horizontal compressibility by $12{\sim}21%$ for the remolded clay and by $23{\sim}60%$ for the undisturbed clay, respectively. The results of a series of consolidation tests under the specific deformation modes showed that the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 3 dimensional strain condition due to different deformation mode. Furthermore, the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 1 dimensional horizontal strain condition by $40{\sim}60%$ in undisturbed clay, which clearly emphasized the significant effect of soil anisotropy on the rate of consolidation. Consequently, it can be concluded that the anisotropic deformation modes of soils, especially naturally deposited clays, should be taken into account for more accurate evaluation of the coefficient of consolidation.

• 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.

• Geotechnical Engineering
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• v.12 no.6
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• pp.153-162
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• 1996

The undrained creep tests with isotropically and anisotropically overconsolidated clays were performed to investigate the effects of anisotropic consolidation on the undrained creep rupture behavior. Results of tests showed that the undrained creep rupture behaviors were iuluenced significantly by stress history including overconsolidation ratio and consolidation pressure ratio$(\sigma_{3c}/\sigma_{le})$. That is. the creep strength of clay increases with the increase of both overconsolidation ratio and consolidation pressure ratio. It, therefore, is dangerous to decide the possibility of creep rupture of clay by the isotropically consolidated creep rupture test in the case of the coefficient of earth pressure lower than 1.0. And the creep strength of clay could be obtained by the equation of the upper yield strength suggested by Finn and Shead(1973) irrespective of both overconsolidation ratio and consolidation pressure ratio.

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.61-70
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• 2000

When clay foundations of embankments are treated with vertical drain, essentially, the strain occurs to vertical direction but the water flow is radial. The initial horizontal permeability and its variation with the vertical compression are key parameters for the choice of the type of drains, their spacing, and affect to the cost of the project. In this study, CRS consolidation test is performed to investigate the anisotropic characteristics of decomposed mudstone soil and direct permeability test is performed on the same specimens. The results of testing show that Ch is larger than Cv. specially, the Cv - $\sigma$v relationship for a soil sample is viewed from three different curve segments corresponding to overconsolidated, transition and normally consolidated states. The anisotropic ratio, rk(kh/kv) is 2.19. Coefficient of permeability in normally consolidated state is related to its void ratio and permeability parameter n. C can be determined from a linear plot of log[k(1+e)] versus log e. The slope, n, of graphs is the same, whereas the vertical intercept, log C, seems to vary somewhat for anisotropic.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.09a
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• pp.73-78
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• 2000

The reinforced soil has been widely used for constructing retaining walls and embankment with steep slope. However, the benefits of soil reinforcing are often-restricted by a lack of good quality backfill material. In this study, plane strain compression tests were carried out to study the effects of preloading on the behavior of geosynthetic-reinforced saturated clay. For the unreinforced and reinforced soil, drained and undrained shearing tests were peformed after anisotropic consolidation in a constant strain rate. A preoading test was carried out by preloading, creep, unloading, aging and undrained shearing after anisotropic consolidation(K=0.3, σ'₃=50 kPa). It was observed that a reinforced clay, Kanto loam, can have a great initial secant modulus in undraind condition by well compaction and over consolidation. The results shown that the increasing of drained strength should be used to apply a large preloading in the case of reinforced clay.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.355-374
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• 2014

An analytical solution of the fully coupled system of equations governing the plane strain deformation of a poroelastic medium with anisotropic permeability and compressible fluid and solid constituents is obtained. This solution is used to study the consolidation of a poroelastic clay layer with free permeable surface resting on a rough-rigid permeable or impermeable base. The stresses and the pore pressure are taken as the basic state variables. Displacements are obtained by integrating the coupled constitutive relations. The case of normal surface loading is discussed in detail. The solution is obtained in the Laplace-Fourier domain. Two integrations are required to obtain the solution in the space-time domain which are evaluated numerically for normal strip loading. Consolidation of the clay layer and diffusion of pore pressure is studied for both the bases. It is found that the time settlement is accelerated by the permeability of the base. Initially, the pore pressure is not affected by the permeability of the base, but has a significant effect, as we move towards the bottom of the layer. Also, anisotropy in permeability and compressibilities of constituents of the poroelastic medium have a significant effect on the consolidation of the clay layer.