Four types of triaxial compression tests were conducted on fully saturated normally consolidated clays under undrained conditions, in order to serve data for constructing a more general constitutive equation of clay. From the experimental results, we confirm the validity of those empirical equations proposed by Yong and Japp for the behaviors under constant strain rate loading and by Murayama et al. for stress relaxation. Equivalency of those two is clarified and then the empirical equation for creep phenomenon by Singh and Mitchell is derived based on those two equations. This concludes the existence of a unique stress-strain-time relation of clay. Adachi and Okano's constitutive equation was derived by extending Roscoe's original energy theory to be able to explain the time dependent properties of clay based on Perzyna's elasto/viscoplastic continuum and the experimental evidences obtained in this study.

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The rate of consolidation for a clay cylinder with external radial flow of water is usually analyzed by the solution, which is presented by I. Da Silveira as a solution of the consolidation equation of Terzaghi in radial case, independent of the deformation condition of a clay cylinder. However, it is well known from laboratory test results that the rate of K₀-consolidation differs from that of isotropic consolidation.In this study, processes of consolidation for a clay cylinder with external radial drainage are investigated under four conditions as an application of the consolidation theory proposed by H. Yoshikuni. The prepared conditions for calculation of consolidation are as follows; 1) The K₀-consolidation with the average vertical load kept constant. 2) The K₀-consolidation with radial load kept constant. 3) The isotropic consolidation with load kept constant. 4) The no vertical strain consolidation with radial load kept constant.

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The key findings in the previous studies on the deformation of sand are first reviewed to the necessary extent. Then, in summary form, five fundamental postulates are introduced as the bases on which a model of undrained deformation of sand under cyclic loading is to be established. The procedures for assessing pore pressured, shear strains and consequent occurrence of liquefaction during cyclic loading are illustrated on the diagrams based on the above postulates as well as actual data obtained in the static triaxial tests. The undrained performance of sand predicted by the proposed model were compared with several cyclic triaxial test results conducted under various conditions. These include stress and strain controlled tests; static and dynamic tests; and the tests cycles with constant and erratically changing stress amplitude. The comparison disclosed the relevance and applicability of this method of approach.

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Dynamic torsion shear tests on hollow cylindrical samples of saturated sand were conducted by incorporating the test apparatus into an electrohydraulic type loading system in which any desired form of load time history can be applied to the specimen. The acceleration records taken during the recent major earthquakes were used as representative time histories in the test programs. For the several wave forms used relationships were established between the amplitude of shear stress and the residual pore pressures, which may be used to assess the dynamic pore pressures under irregular loading conditions. Finally, the results of dynamic torsion shear tests were compared with the corresponding behavior in dynamic triaxial tests and the correlation between them are discussed.

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The consistency properties of fine grained soils are generally expressed by the plastic limit, the liquid limit and the plasticity index, and especially, Casagrande's plasticity chart based on the plasticity index and the liquid limit is widely used for the classification of soils. However, at present, it is impossible to guess quantitatively the mechanical properties of soils at the classification based on the plasticity chart. Therefore, the authors wish to identify the relation of the consistency properties to the mechanical properties of soils by means of the plastic ratio chart in which the abscissas represent the liquid limit and the ordinates the corresponding plastic ratio. After these considerations, it becomes clear that the plastic ratio as a new index property is effective for evaluating the consistency properties of soils, and the plastic ratio chart is also useful to estimate quantitatively the swelling capacity and the residual strength of soils.

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This paper reports a fundamental study of the characteristics of secondary compression of organic soils by using an oedometer and a triaxial consolidation apparatus.Firstly, the expression of coefficient of consolidation in which secondary compression can be taken is proposed as well as a method of estimation of final settlement including the secondary compression is.Secondly, it is known that the secondary compression rate in triaxial K₀-consolidation test is about twice as large as the one in oedometer test, and we can clearly understand that the side friction in oedometer prevents the progression of secondary compression. Furthermore, it is clarified that the secondary compression rate can be linearly expressed in terms of stress ratio.Finally, the authors point out that shearing and volumetric creep rates in the triaxial consolidation test of permitting lateral strain show a little larger values than those in the K₀-consolidation test of non-lateral strain.

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The immediate and consolidation settlements of a uniformly loaded rectangular area on a overconsolidated clay which is cross anisotropic with respect to its elastic properties are obtained. Tables and graphs are presented for practical use.

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Magnitudes and rates of settlements predicted by the one-dimensional theory seldom coincide with observed values. Of the many attempts made to improve the accuracy of theoretical predictions, Biot's poroelastic three-dimensional theory stands out.This paper presents an attempt made to verify the validity of different theories experimentally. Two circular, one rectangular and one square rigid model footings resting on the surface of saturated clay beds were loaded to an intensity of 0.5 kg/cm². Settlements in and outside the loaded region were recorded. The magnitudes and rates of settlements predicted from various theories were compared with observed values.While there were no significant errors in the magnitudes, rates predicted by the one-dimensional theory were found to be much lower than the observed values and those predicted from Biot's theory were very close.

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