Deformation characteristics of clays at deep position of ground and its time dependency

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In this study, the effect of time dependency on the mechanical characteristics of undisturbed clays is investigated, which is in the Pleistocene deposits at the off-Senshu area in Osaka Bay. Also, the method for predicting deformation of the ground is proposed. The main conclusions are summarized as follows:1. A constant rate of strain consolidation apparatus for semi-high pressure was developed. The consolidation characteristics of undisturbed clays taken from the Pleistocene deposits at the off-Senshu area in Osaka Bay was investigated. Firstly, the effect of such test conditions as strain rate and back pressure on the consolidation characteristics was investigated. It is found that the strain rate significantly affects consolidation yield stresses in the constant rate of strain consolidation tests. Next, a constant rate of strain consolidation apparatus for semi-high pressure could be applicable to the undisturbed clays in the Pleistocene deposits, which have higher yield stresses than the alluvial clays.2. The undrained shear characteristics of the undisturbed clays in the Pleistocene deposits was investigated through mini-triaxial tests. The undrained shear tests of the reconstituted clays were carried out to investigate the "aging" effect on shear characteristics. The linear relationship between logarithmic maximum deviator stresses and void ratios was observed on both the undisturbed and reconstituted clays. It was shown that the effect of initial void ratio on shear strengths can be excluded through using the void index or the e_L.3. A method for determining elasto-viscoplastic parameters for the undisturbed clays in the Pleistocene deposits using mini-triaxial tests and consolidation tests was proposed. The reliability of the determined parameters was investigated through the numerical simulation analysis of deformation behavior in triaxial tests and construction of a man-made island.