The previous study has shown that the geometrical arrangement of contact surfaces between the grains could have an important bearing on the mechanical properties of granular materials. In an attempt to represent this effect in a quantitative manner, summations of projected areas of contact surfaces of YZ- and XY-planes, being denoted by S_x and S_z respectively, is shown to be an useful index. Particularly, the ratio S_z/S_x which is determined by microscopic analyses of thin sections is believed to be one of the most important fabric features to determined some mechanical properties of granular sands. The ratio S_z/S_x has close relations with mobilized stress ratio as well as dilatancy rate. The maximum value of S_z/S_x at peak stress is determined not only by initial fabric but also by some other properties of granular particles. The process of fabric reconstruction is continuous and no gap can be observed between granular fabrics formed at pre-peak stress and those formed at peak stress. This continuous reconstruction of the initial fabric with the increase of axial strain is mostly due to the sliding along unstable contacts between grain particles and partly due to the rotation of grain particles.

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Strain-controlled cyclic torsion tests were run on a saturated sand using a triaxial torsion apparatus in which the vertical piston was designed so that its cross sectional area was equal to that of the specimen. In the first series of tests, a cyclic twist was applied while keeping the principal stress ratio constant. In these tests liquefaction did not occur and failure was associated with the development of a large amount of shear strain. In the second series of tests, a sample was consolidated anisotropically and then subjected to a cyclic twist while preventing entry of the cell water. This produced the situation in which the lateral expansion of the sample was completely confined. In these tests liquefaction did occur and the sample consolidated anisotropically was found to develop pore pressure faster than the sample consolidated isotropically. Such difference in the potentiality of pore pressure development was accounted for by the fact that the lateral stress was gradually increased during cyclic loading until the principal stress ratio became equal to unity at the onset of liquefaction. The concept of the principal stress ratio change during cyclic loading was used to account for the difference in liquefaction potential between the normal type of a cyclic triaxial test and a simple shear test.

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An equivalent lumped system for analysis of structures founded upon stratum of soil had been proposed by the author and R.V. Whitman (1968) and introduced by R.V. Whitman (1968). A series of laboratory tests has been carried out to check upon the applicability of the proposed approximate system, which show a good agreement with the system from an engineering point of view. Dunkerley's formula has also been applied with respect to the fundamental frequency of buildings on stratum, and checked upon by the laboratory tests.

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This technical note provides a theoretical analysis of finite length beams on soil subjected to general loadings and given end support conditions. The principle of virtual work was employed to formulate the stiffness matrix of the soil-structure interaction problem. Numerical methods such as finite element analyses were employed, and the results from the examples indicated that the proposed method gave results close to those solved using Harr's approach.

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