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Abstract
The studies in this thesis have focused on two interrelated areas: (1) experimental investigation on strain-rate effects, creep behaviour and stress relaxation of remoulded Hong Kong marine deposits (RHKMD); (2) examination and development of time-dependent constitutive models and applications of these constitutive models in fully coupled consolidation analyses of geotechnical structures on soft ground.
A large number of tests on remoulded BKMD have been conducted. These tests include (a) conventional triaxial tests shearing at various strain rates (ranging from ±0.15%/h to ±15%/h), (b) triaxial creep tests (both drained and undrained creep), and (c) triaxial stress relaxation tests. The strain rate-dependency, creep and stress relaxation behaviour of RHKMD are investigated extensively and systematically.
From the experimental investigation, it is found that the remoulded HKMD exhibits viscous effects, albeit not as pronounced as those of other natural sensitive clays.
In both undrained compression and extension multi-staged triaxial creep tests, the log([special characters omitted])-log(t) relationship at lower stress levels is linear, and the slopes of these lines are dependent on current deviator stress as well as stress history. From the drained triaxial creep test results, two empirical equations are proposed for the relationships of deviator and volumetric strains versus time. In the FE modelling, the foundation soil is considered as an elastic visco-plastic material described by the EVP model. The so-called abnormal increase of porewater pressure after the completion of loading may result from either the Mandel-Cryer effect or viscous effects, or both of them depending on boundary conditions.
The FE program with the 3-D EVP model is also used to analyse porewater pressure responses and deformation in clay underneath an island—Tarsiut Island in the Canadian Beaufort Sea. Yin and Graham's (1999) 3-D EVP model is extended in this thesis. A framework of a 3-D EVP model for anisotropically consolidated clay is proposed. This model is based on the original Cam-clay model and the concept of “equivalent time”. The constitutive relationship is formulated. The validity of the model is then briefly verified by comparing model predictions to test results. (Abstract shortened by UMI.)
