Normalized cyclic undrained triaxial stress-strain relationships of undisturbed sandy specimens are discussed in this paper. Cyclic undrained triaxial strengths defined by axial strain amplitudes and developments of excess pore water pressure are analyzed. A simplified equation for evaluating cyclic undrained triaxial strength of sands is derived. Based on the empirical normalized strength equation, a relationship between strength for a uniform cyclic loading and that for a random cyclic loading is obtained. A simplified method for evaluating an equivalent uniform loading strength for a random loading is proposed using a strength curve through uniform cyclic loading tests.

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This paper describes and discusses practical performance for undisturbed sand samples obtained by a sand sampler, such as evaluation of sample quality, treatment procedure for samples, specimen preparation procedure for laboratory tests, sample transportation and other problems involved in sand sampling.Volumetric change (=density change) and structural disturbance of sand samples, which may take place during the process from sampling to laboratory tests were discussed and examined based on various field and laboratory tests results. From the study, the following important conclusions were obtained : -1) Density change takes place for clean sand during the above process, however, structural disturbance having an effect on shear response of solis can be ignored.2) Density change during the above process can be negligible for naturally deposited silty sand (fine content more than 10%) and structural disturbance can be evaluated from the axial strain at failure in unconfined compression tests.3) Specimen placement directly from the sampling tube to the laboratory apparatus should be adopted for laboratory strength tests. In order to make this operation easier, clean sand should be frozen at the site.

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The construction control has been recently recognized as one of the most important matters in a series of design procedures of the earth works such as embankment and excavation in which the small safety factor is generally adopted since the modification of design is comparatively easy during the works. The small safety factor means the severe conditions in the construction field, therefore the good method to evaluate the present degree of safety and to predict the successive failure is needed indispensably in order to control the works well and to take the appropriate countermeasures immediately if necessary. In connection with the problem of the large-sized excavation, this paper describes the study to find the method predicting the failure during the works. The items to be measured in a field and the reasons for them are firstly discussed and the valid prediction method of using values of the lateral displacement of the earth retainning structure and the earth pressure on it at the bottom of excavation is shown. After that, how to utilize the measured results in engineering practice is examined and the diagrams for construction control are proposed, in which many actual data in the recent construction fields of the large-sized excavation in Japan were used.

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The shear mechanism of granular materials has been studied from a microscopic point of view in order to derive their macroscopic stress-strain relationship. For this purpose, simple shear tests were carried out using a pile of aluminium rods to simulate granular materials in a two-dimensional state. In the analysis, granular materials are considered to be an assembly of a unit element composed of two particles, which is named "two particles model". According to this model, the sliding displacements between two particles across the potential sliding plane were formulated by considering the mechanism of disappearance and generation of angles of interparticle contacts. A new stress-strain equation was derived from the relationship of these sliding dispacements, and compared with the results of cyclic simple shear tests on aluminium rod mass. Furthermore, stress-strain characteristics of a sand under cyclic loading were explained by the proposed equation.

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Simple shear deformation under vertical pressure of granular materials which consist of cohesionless rigid grains, is considered. Based on the mechanics of the relative motion of the grains or families of grains at the microlevel, and by considering the corresponding rate of frictional losses, a simple energy equation is obtained, on the basis of which the phenomena of initial densification, subsequent dilatancy for a dense sample, and the net amount of densification which accompanies cyclic shearing, are explained.

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This paper presents a simple elasto-plastic theory for anisotropic granular materials as a preliminary one incorporating inherent anisotropy and anisotropic yielding. While several elasto-plastic thoeries for granular material have been proposed by several investigators, most of these theories are isotropic concerning deformation, strength and yielding. Recently, however, it has been found that granular materials have, in general, different deformabilities and strengths for the different directions and their yielding performances are not isotropic but anisotropic. While this theory involves several parameters, the present author is not able to establish the definite functions of all of these parameters with respect of stress, void ratio, inherent anisotropy or so. By using some assumptions, several calculation by this theory were performed.

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