Both vertical and horizontal samples of undisturbed fibrous peat, which were obtained by maintaining the axes of thin-walled tubes parallel to the vertical and horizontal directions in peat ground, were used in this investigation. These samples contained organic matter in the amount of 10%-80%. After normal isotropical consolidation of the samples in the triaxial cell, undrained compression and extension tests with pore water pressure measurement were performed, and the influences of confining pressure, loading path, amount of organic matter and fabric anisotropy on the undrained shear behavior of peat were investigated. Test results indicate that the undrained shear behavior of saturated peat can be discussed based on the principle of effective stress, in the same manner as inorganic soils. However, as the anisotropic fabric of fibrous peat which had formed during accumulation still remained after the isotropic consolidation, anisotrpic shear behavior was observed ; the undrained deformation-strength properties observed in the compression test were considerably distinct from those obtained in the extension test. Moreover, it was also found that the normally consolidated fibrous peat had a cohesion intercept due to the effect of tension in the fibers, and undrained-strength parameters were found to be greater than those of inorganic soils.Furthermore, based on the test results, the authors proposed a new method of predicting stress-strain behavior of peat under triaxial compression and extension conditions.

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When repeated loads are applied to a foundation, the deformation of the foundation soil may increase significantly in comparison with the case of static load applications. For this reason an unconventional calculation in the case of repeated loading needs to be made for estimating the deformation of the soil. Among the various types of repeated loads some typical examples are earthquake forces, vehicle loads and oil storage tank loads.Specially-devised consolidation tests under static and repeated loading were performed on remolded saturated cohesive soil samples. The samples under repeated loading conditions were more compressible than those under static loading conditions, and the difference in compressibility or settlement between these two loading conditions seems to be due to secondary compression and the change in soil particle structures.As the settlement of the foundation under repeated loading is caused and governed primarily by the magnitude of total load, the loading period, the load increment ratio and the number of load cycles, it is suggested that all of these factors should be considered in predicting the settlement induced by repeated loading. In this paper, therefore, we aim at presenting some basic data and an interpretation of the consolidation of clay under repeated loading. In addition, based on a simplified method for prediction, a case study of settlement calculation is shown for an oil tank foundation on clay. The necessity of repeated oedometer tests and their analysis is emphasized by comparison of settlement under cyclic loading with that under static loading.

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The Pasternak Foundation concept, a refinement of the Winkler Foundation theory, is briefly stated and its shortcomings pointed out. The concept is extended to take into account material nonlinearity and body forces using an analytical approach. The paper is concluded by an examination of the proposals of Meyerhof and Hanna regarding the behaviour of two layer soil systems.

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This paper presents a stability analysis of vertical cohesive slopes with a finite length (perpendicular to cross sections of slopes). The method of analysis is based on three-dimensional limit equilibrium techniques and variational calculus. The shapes of three-dimensional critical failure surfaces were determined exactly and found to be split cylinders with curved end caps. Then the three-dimensional factors of safety were calculated as the functions of the ratio of failure length to vertical slope height. These factors of safety were higher than the two-dimensional factors as indicated by Baligh and AZZOUZ (1975), etc. The method of analysis of this study could be extended to any inclined cohesive slope. The solutions obtained here give the least upper bound of the problem in limit analysis. In practice they can be applied to evaluate the end effects of vertical cuts or excavations in clays in narrow areas.

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Two new improved-efficiency techniques for soil sampling by in situ freezing were used to obtain undisturbed samples of saturated alluvial volcanic soils, locally termed "Shirasu", from Kagoshima city, Japan. Undrained cyclic triaxial tests were conducted on the undisturbed alluvial Shirasu samples obtained from a depth of 5.4 to 6.0 m at site A, and from a depth of 8.4 to 10.5 m at site B, after they had been thawed. For studying the effects of sample disturbance, undrained cyclic triaxial tests were also conducted on the reconstituted specimens. The liquefaction resistance in the field was estimated based on the laboratory tests. Based on the above studies it was shown that (1) two new developments in the technique of sampling by in situ freezing were successfully achieved in the field, and (2) compared with the liquefaction resistance of the undisturbed samples, that of the reconstituted samples from site A, all of which had about the same density, was about 45 to 50% of the value for undisturbed samples, and that of the reconstituted samples from site B, with relative density 13 to 20 percentage points higher than that of undisturbed samples was about 62 to 67%.

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Normalized undrained shear strengths from direct simple shear (DSS) tests conducted on 50 different clays are compared with strengths determined from triaxial shear tests. The DSS strength is typically observed to be an intermediate strength between triaxial compression and extension. Normally consolidated and overconsolidated data are included in the study. Numerous important factors were not considered including : strain rate, sensitivity, different laboratories, sampling disturbance, and others. Nevertheless, approximate trends are observed between DSS strengths and data from companion triaxial compression and triaxial extension tests.

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When a loose sand is subjected to a cyclic rotation of principal stress axes during an undrained test, excess pore water pressure is generated. To study the nature of pore pressure build-up, several series of laboratory tests were conducted using a hollow cylindrical torsion shear apparatus. Tests were conducted employing different kinds of cyclic loading schemes in which specimens were subjected to cyclic shear stresses with or without continuous rotation of principal stress axes. Based on the test results, accumulated shear work per unit volume was calculated at each stage of shear stress application, and its correlation with the pore water pressure was examined.It was found that, at each state of shear stress alteration, there exists a unique relationship between the shear work and the pore water pressure, independent of the shear-stress history. This observation enables contour lines of equal shear work to be drawn in the stress space.

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Stress-induced anisotropy or fabric in granular masses is discussed on the basis of biaxial compression tests performed on two-dimensional assemblies of oval cross-sectional rods. The fabric of granular mass depends at least on three basic fabric elements : the distribution of the contact normals, the shape of the particles, and the shape of the associated voids. These are discussed in order to define the corresponding anisotropy in terms of a second-rank fabric tensor. It is shown that the principal axes of the fabric tensor rotate gradually toward the principal axes of the stress tensor during the course of monotonic deformation. Generation of new contacts in the direction of the maximum principal compression is closely related to the formation of column-like load paths in that direction and is a major process which leads to the stress-induced anisotropy. The stress-induced anisotropy due to the formation of elongated voids seems to be a contributing factor to the post-peak failure of the material.

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Finite element computations for earth pressure problems of retaining wall are performed, considering the wall friction and the mode of wall deflection together with the deformation and strength characteristics of soil. A method to describe the frictional behavior between soil and wall is firstly proposed using an elastoplastic joint element, and its validities are confirmed by analyzing the slip behavior between two solid elements. Active and passive earth pressure problems are than analyzed by using a constitutive model for soil obtained on the basis of the extended concept of "Spatially Mobilized Plane" and the elastoplastic joint element proposed here. The computed variations of earth pressure with wall displacement in active and passive states explain well the influence of the wall friction and the wall deflection. The computed distributions of earth pressure where the modes of wall deflection are different agree with the tendencies known empirically. Furthermore, the failure zone and the zone of lower factors of safety derived from the present analysis correspond to the slip plane and the plastic wedge in the theories of plastic equilibrium.

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Two series of tests using miniature pressuremeter and torsionmeter were carried out on sand specimens in a triaxial chamber in which stress boundary conditions were fully controlled. The deformation moduli estimated based on the elasticity theory were compared with those obtained from triaxial tests subjected to various types of stress path starting from its isotropic consolidation state.The results showed that the deformation moduli corresponding to the Young's modulus E, Poisson's ratio ν and shear modulus G depend on stress path and stress level of the specimens. The deformation moduli estimated from the pressuremeter tests and torsionmeter tests were in the range of those estimated from triaxial tests under various conditions of stress paths.On the sandy deposits, the deformation moduli estimated from the pressuremeter and the torsionmeter tests could not be widely used for engineering practices simply because the pressuremeter and the torsionmeter can provide only limited stress conditions.

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A transmissivity tensor is an available expression of hydraulic parameters for groundwater flow analysis in fractured material. Although components of tensor are related to geometrical and physical properties of cracks, its concept can be applied to anisotropic porous material as well.A closed from drawdown equation concerning a fully penetrating well into an anisotropic confined aquifer has already been obtained by Papadopulos (1965). He also proposed a method for determining components of tensor based on the Theis type curve method. But it has been said that individual differences frequently occur when it is applied to pumping test analysis.The authors derived a graphical method for determining the tensor from the Papadopulos solution. The method described in this paper is based on the Jacob procedure. We can, therefore, easily determine not only components of tensor but also a storage coefficient without individual differences. Its application to an actual pumping test shows availability of this method for analysis of a pumping test in a mountainous area.

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