Rowe (1962) introduced a new concept called minimum energy ratio principle to get a stress-dilatancy relation of granular materials under axisymmetric stress condition. According to the principle, the slinding contacts are restricted to those with the preferred angle β_c=(π/4)-(φ_μ/2). However, the physical basis of this principle is questioned by many investigators. In this paper, the author investigates this principle only on the basis of equilibrium between interparticle forces with the following results ;(1) Horne's study on Rowe's stress-dilatancy equation is incomplete to clarify the physical meaning of the minimum energy ratio principle. Accordingly, his indication such that the principle could be rigorously established as an equilibrium condition is not acceptable.(2) The minimization of the incremental energy ratio E in Rowe's theory is equivalent to maximize a driving tangential force F_d acting in the same direction as sliding direction and a resisting one F_r in the opposite direction of F_d. The physical ground is not clear.A new and simple concept of shear mechanism of granular materials can be proposed only on the basis of equilibrium between interparticle forces without using the minimum energy ratio principle. The concept is characterized by such a description that the positions of sliding contacts shift as shear stress increases. According to the concept, the development of anisotropy of grain structure during shear and the deformation behaviours under cyclic loadings can be explained well.

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Cracks occuring on the surface or internal parts of fill-type dams have been a matter of great concern for dam engineers, because such cracks sometimes induce internal piping and lead to catastrophic damages of dams. In this paper, the problem of transverse cracks caused by the differential settlements in the longitudinal sections of high embankments is discussed through analytical investigations, and some considerations are given on effective methods for estimating and controlling cracks in the practical design and construction. Numerical analyses are performed by the finite element method assuming that the material is linearly elastic. In the present paper, correlations between the transverse cracks and the configuration of abutment surfaces such as the sharp change of the inclination are first clarified. In practical application of the finite element solutions, it is shown that these are very effective for the prediction of the cracking potential in actual dams. On the basis of above conclusions, a practical method of assessing the possibility of crack generation is proposed taking the tensile strain as a criterion.

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Anisotropic parallel alignment of particles is universally observed not only in river, beach and coastal dune sands but also in artificially deposited sands. Anisotropic shear strength caused by the anisotropic parallel alignment of particles can be observed more clearly in the plane strain condition ε₂=0 than in the symmetrical stress condition σ₂=σ₃. This must be chiefly due to the fact that re-arrangement of particles during shear deformation can be more easily performed in the latter condition than in the former one. Shear strength of sand in a plane strain test has been generally believed to be 10% to 20% greater than that obtained in a triaxial compression test. When the specimen is compressed at a small angle to a bedding plane, however, it is possible that the shear strength in the plane strain test is smaller than that in the triaxial compression test. The effect of anisotropic shear strength cannot be ignored when stability problems and earth pressure problems in plane strain condition are analyzed.

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To evaluate degree of reduction in shear moduli of sands with an increase in shear strain amplitude, dynamic soil tests were performed with use of hollow cylindrical samples applying torsional shearing forces. Two types of soil testing equipments, a resonant-column apparatus and a torsional shear apparatus, were employed. It is pointed out that shear moduli at shear strain amplitude of 10^-4 obtained from these two different equipments agree satisfactorily. Furthermore, extents of reduction in shear moduli with an increase in shear strain amplitude are shown for various sands. These data are compared with those presented by other investigators. On the basis of test results, a simplfied procedure for predicting reduction in shear modulus with an increase in shear strain amplitude is proposed.

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Static undrained triaxial shear tests were performed on the sand specimens overconsolidated to OCR-values of 1.0 to 5.0 under cyclic as well as monotonous loading conditions. It was discovered that pore water pressures and shear strains which developed during undrained shear tests were lower for overconsolidated sand than for normally consolidated sand even when the density of the sand was kept virtually unchanged. To advance a reasonal interpretation for the hardening effect brought about by overconsolidation, the concept of yield loci was introduced, establishing a family of curves in the stress space (effective mean principal stress versus deviator stress plot) which governs the onset of yielding in overconsolidated sand. On the basis of the yield loci thus established the deformation model previously established for normally consolidated sand was modified and generalized so that the pore water pressures and shear strains under irregular loading condition could be predicted for both normally and overconsolidated states.

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Analytical techniques available for numerically solving nonlinear stress-deformation problems of a ground are not applicable to those cases where the highly dilatant materials are involved, as Poisson's ratio ν in these analyses exceeds 0.5, which consequently violates positive definite condition of the stiffness matrix used in these analyses.In a new analytical technique proposed herein volume change of a soil is conceptionally divided into two components : consolidation and dilatancy, which are computed independetly. Through this procedure the new analysis within basically the same framework as the conventional analytical method can readily be applied to any soil materials with arbitrary dilatant behaviors. Analyses carried out for some typical geotechnical problems employing this new technique reveals the effectiveness of the proposed method.

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In order to study the dynamic shear strength of saturated clay, the dynamic simple shear tests were carried out and the dynamic strength was compared with the static strength under various stress conditions.In these experiments, increase of pore water pressure of sample was measured during the test and the effect of pore water pressure on the dynamic shear strength was investigated.It is concluded that the dynamic shear strength decreases in proportion to the number of cycles of repeated shear stress n and increases in proportion to the sustained shear stress Δτ.

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In this technical note, some analytical results of the plane strain consolidation problem of a clay layer with finite thickness are presented in order to complement the authors' previous paper (1976). The boundary conditions of the clay layer considered herein are that the interface is permeable and smooth, impermeable and adherent, and permeable and adherent while the surface is permeable and free from shear stress. The time/settlement relationships for each boundary condition are shown in graphical form which would be useful in foundation engineering.

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