Study on the Evaluation Method of the Engineering Properties of In-situ Sand Grounds

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The following conclusions may be drawn based on the static and cyclic shear tests conducted in the laboratory as well as in the co-operative research of undisturbed sands;(1) Microscopic examination on the deformation-strength properties1. Fabric anisotropy of a granular mass depends at least on the dstribution of contact normals, the shape of particles and the shape of associated voids. These elements were individually discussed to give the corresponding definitions of gabric anisotropy in terms of second-rank symmetric fabric tensor.2. The effect of cyclic shear stress history was estimated considering the mechanism of fabric change under cyclic loading. Introducing this estimation of the effect of shear stress history to the stress-strain model based on the "compounded mobilized planes", various kinds of cyclic true triaxial tests along the rotational stress paths on the octahedral plane were analyzed. The analytical results agreed well with the experimental values.3 The initial fab … More ric of sand has a considerable influence on its strength properties, in particular a predominant influence is exerted in the conditions of a higher density and a lower confining stress.(2) Evaluation of in-situ strength of sand grounds1. The quality of the sample obtained by the in-situ freezing method was judged quite good based on the facts that the sand sample satisfied the requirements for preserving its structure during freezing, and that the evaluation of liquefaction potential based on the cyclic test data for the sample obtained by the in-situ freezing method appeared to be consistent with estimated field behavior of a sand ground.2. The reaults of a deries of cyclic undrained triaxial tests on two kinds of undisturbed sand indicated that natural in-situ sand deposits displayed a significantly anisotropic time history pattern. These anisotropic cyclic deformation performance make a remarkable difference in the cyclic undrained triaxial strength value.3. The feature of anisotropic cyclic deformation-strength properties of relatively clean sand sampled from natural deposit could be reproduced by a suitable sample preparation method which may simulate the block sampling procedure.(3) Examination of undrained cyclic triaxial test methods On the basis of the results of the co-operative undrained cyclic triaxial tests, it is shown that the test conditions such as sample preparation method and specimen shape should be specified at least to minimize the variation of test data. Less