Study on the evaluation method of in-situ deformation-strength characteristics of sand ground

点击翻译按钮获取中文摘要

The following results were obtained from the experimental and analytical research aimed to study the rational procedures to evaluated the stress-deformation behavior of sand ground.1. After a series of experiment, using hollow cylinder torsional shear test apparatus, assuming that a sand possess inherent and induced anisotropic mechanical properties, the following facts were pointed out. 1) Although shear strength was not affected by the induced anisotropy in this study, it is affected by the inherent anisotropy. The angle of shear resistance showed its minimum value when the direction of major principal stress deviates 75'from the direction parpendicular to the bedding plane of the test specimen. 2) In both shear and volumetric deformation behavior, considerable effects of inherent anisotropy was observed. As to the induced anisotropy, the decline of rigidity against shear deformation was largest when the deviation of current principal stress direction from the previous one is 75゜ . 3) Strain path was observed to deviate to the direction of bedding plane due to the inherent anisotropy, and to deviate to the direction away from the previous loading direction.2. A constitutive model for sand having anisotropic mechanical properties based on the concept of multi-directional sliding surfaces was examined its validity. 1) The model, which bases on the postulation that the resistance against shear deformation is the lowest on the bedding plane and appropriate shear deformation behavior is able to be characterized for every potential sliding surface, was proved valid to evaluate the anisotropic deformation behavior of sand. 2) Adopting Masing's rule to model the Bauschinger's effect on the shear deformation behavior on potential sliding surface, characteristics of strain path direction, effect of induced anisotropy on shear behavior and so forth were proved to be evaluated practically well by the constitutive model.