Limit analysis (upper bound) has been applied for bearing capacity of strip footing on anisotropic and nonhomogeneous clays, by assuming a mechanism similar to Prandtl mechanism but with varying wedge angles. N_c values for different anisotropic coefficients and degrees of nonhomogeneity are given. The results confirm the fact that the bearing capacity of nonhomogeneous and anisotropic clays obtained by assuming a circular slip surface is on the higher side of the actual value.

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Sedimentation mechanism and sediment formation characteristics are examined by use of dilute clay-water mixtures. Direct measurement of the distribution of water content in the mixture is successfully used in the examination. According to the results, the process of soil sedimentation in general comprises three stages.In the first stage, no settling takes place, but flocculation yields flocs. In the second stage, the flocs gradually settle and form a layer of sediment, which undergoes consolidation and reduction of water content. The boundary between the upper settling zone and the sediment is the birth place of new sediment. While the sediment grows, the settling zone becomes thinner and finally vanishes. In the last stage, all of the sediment thus formed undergoes self-weight consolidation and finally approaches an equilibrium state.The water content value at which a mixture changes into sediment is not uniquely determined, but varies corresponding to the mixture's initial water content; the two values are close to each other. That is, soil sediment is not formed at a water content peculiar to the material concerned. This remarkable finding is a reflection of the fact that, even for a clay, countless compression curves exist under very low effective stresses.

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In the stability analysis of the slope with stabilizing piles, the location of the sliding surface is usually determined in advance by field investigations. In this paper, the design method for piles in a row within a slope of such a fixed sliding surface as in landslide has been investigated. That is, studies on the effect of many factors of pile on the slope-stability are carried out for an example of a landslide slope containing stabilizing piles and a new design method is proposed for the stabilizing piles against landslide.The results show that such factors as the interval between piles, the fixity condition of pile head, the pile length above sliding surface, the pile diameter and the stiffness of steel pipe pile have considerable effect on the slope-stability. In the proposed design method, such five factors can be decided systematically. Furthermore, an example of design is shown, in which important factors in pile design are brought out and illustrated.

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Naturally deposited marine clays are usually in overconsolidated state notwithstanding they have not been subjected to release of the overburden because of the additional strength developed by aging effect, such as by secondary compression and chemical bonding. These effects on undrained strength characteristics, such as 1) stress-strain characteristics, 2) overconsolidation ratio, 3) K₀ value and 4) anisotropy in undrained strength are discussed for alluvial marine clays found in the Arabian Gulf and in the Tokyo Bay.It is first shown that clay shows more brittle behaviour as the strength developed by secondary compression and chemical bonding becomes greater. It was found from the study that overconsolidation ratio of the clays investigated can be obtained from the strength ratio between in the field and in normaly consolidated state and that strain value at failure in strength tests shows almost a constant value independing on overconsolidation ratio. In addition, it was strongly suggested that K₀ value and anisotropy in undrained strength (which is a stress induced anisotropy that results from rotation of principal stress during shear) of the clays are independent on overconsolidation ratio and almost the same as the values in normally consolidated state.

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This paper summarizes a theoretical and laboratory investigation to develop a procedure to predict the cyclic undrained stress-strain-time behavior of cohesionless soils under irregular cyclic loading patterns. It was found that the maximum shear strain amplitude induced in sand under a given irregular cyclic loading pattern can be predicted from a knowledge of the stress-strain behavior of the sand for uniform cyclic loading by using the cumulative damage concept. However, the cumulative damage concept cannot adequately predict the strain-time history of sand, and a new analytical method accounting for the deterioration in the stress-strain characteristics of sand was developed to provide this information.Cyclic undrained simple shear tests on sand were performed using uniform and cyclic irregular loadings to confirm the theoretical evaluations. Theoretical results compared with the test results showed good agreement.

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Static finite element analyses and laboratory measurements suggest that the shear modulus of soil in earth dams and embankments increases approximately as the 2/3-power of the distance from the crest, a variation that is also confirmed from field measurements of shear wave velocities in actual earth and rockfill dams. A shear-beam model has been developed and is outlined in this paper that accounts for such an increase of modulus with depth. The main thrust of the paper is to evaluate this model by comparing its predictions with the recorded response of a number of dams and embank-ments subjected to earthquake or man-induced vibrations. It is demonstrated that the model successfully explains observed modal displacement shapes, peak accelerations and seismic coefficients experienced by several Japanese, one American and one European dam, as well as by a large-scale laboratory embankment model. Consequently, the model offers a significant improvement over the classical, homogeneous shear beam model that is presently used to evaluate the seismic safety of earth dams.

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An analytical method due to the hybrid finite element formulation is presented for the multi-dimensional elasto-plastic consolidation analysis. To facilitate a reliable consolidation analysis of K₀-consolidated clay layer, an elasto-plastic analytical model is also proposed, which has a yield function with no singularity satisfying the K₀-strain condition on the K₀-line, followed by showing its reasonableness and advantage in numerical computations.To deal with a more realistic consolidation analysis, the presented method is also characterized by the ability to analyze such cases that the drainage is permitted during incremental loading and that the permeability suddenly changes in the layer.Multi-dimensional elasto-plastic consolidation analysis is carried out for partially loaded ground models. The resulting deformation and stress path behaviors substantiate the validity of the presented analytical technique, which brings out some behaviors reflecting the real mechanism of consolidation of clay.

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Using a true triaxial shear test apparatus, a series of static loading tests were performed in undrained conditions on saturated cubical sand specimens. The three principal stresses were programmed to produce radial stress paths with different directions on the octahedral plane in the three-dimensional stress space. The radial stress paths used consisted of 13 stress paths radiating outwards from the center of the octahedral plane with an angle interval of 15 degrees. As it had been observed previously in drained tests, the effects of inherent anisotropy were noted in the deformation and the pore water pressure buildup characteristics. It was observed that the specimen prepared by vertical deposition exhibited stronger resistance to deformation when loaded vertically in the triaxial stress state of compression than when loaded horizontally in the triaxial stress state of extension. The specimens subjected to loads intermediate between triaxial compression and extension exhibited intermediate resistance.

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This paper discusses a method for calculating the "true" undrained strength ratio, (c_u/p)_SS, of normally consolidated clays measured in a simple shear test. The proposed method assumes that the directions of the principal stress axes during the simple shear test are expressed by the relation proposed by Oda and Konishi (1974). Experimental results obtained from three types of clays confirm that the method gives more reasonable estimates of (c_u/p)_SS and the internal friction angle, φ'_SS, in terms of effective stress measured in the simple shear test compared to other methods. The method also supports Ladd's statement that (c_u/p)_SS should generally be less than (c_u/p)_TC determined from the triaxial compression test due to undrained strength anisotropy (Ladd, 1973). Finally, a significant disadvantage of the method proposed by Duncan and Dunlop (1969) is discussed, and it is pointed out that the Duncan and Dunlop method may predict values of φ'_SS for normally consolidated clay that are excessively high.

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A limited number of laboratory model test results for the ultimate bearing capacity of eccentrically loaded rough surface footing on a sand layer with a rough rigid base at a limited depth have been presented. The model footing has a length-to-width ratio of three. Based on the test results, it appears that the effective area method (Meyerhof, 1953) could be used to predict the ultimate bearing capacity provided that the modified bearing capacity factor, N_γ', can be correctly evaluated.

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