Both quick cyclic and slow cyclic shear tests are performed on saturated sand to investigate the process of liquefaction under the condition of constant mean principal stress. Special tests with varying amplitude of cyclic shear stress are also performed to estimate the change in excess pore water pressure during irregular cyclic loading. The pore water pressure increment during each loading cycle may be expressed as a function of the shear stress and the normal stress on the shear plane. This relation is likely to be applicable to the case of irregular cyclic loading which simulates the actual timehistory of shear stress during an earthquake. The number of stress cycles required to cause the initial liquefaction may also be expressed in terms of the ratio of cyclic shear stress to normal stress. In so far as the sand and glass beads used here are concerned, the pore water pressure tends to increase during unloading and vice versa at the time when initial liquefaction occurs, and the angle of internal friction mobilized at that time has a close relation with the true angle of friction of granular materials.

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Sand fabrics were fixed with polyester-resin without disturbing the spatial arrangement of granular particles, Thin sections prepared from thus fixed sand specimens were studied under the optical microscope to find the preferred orientations and spatial relations of constituting grain particles with the following conclusions: (1) The characteristics of configuration relations of nonspherical particles are determined not only by the shape of particles but by the method of compaction. which are composed of flat or elongated particles indicate strong anisotropic feature of fabric character. (2) The initial fabric of granular material as sand has important influences on the mechanical properties such as mobilized stress ratio and secant deformation modulus.

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The purpose of this paper is to prove rigorously the known relation between shape factors for cohesion and surcharge by the method of limit analysis under the assumption that soil is rigid, perfectly plastic. Relation between bearing capacity factors for cohesion and surcharge determined in the general stress state, i.e., in three-dimensional state, is derived by examining the nature of complete solution in limit analysis. On the basis of the derived relation, the known relation between the two shape factors of bearing capacity is proved rigorously.

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