| The stress-strain behaviors of saturated clays are time-dependent. This thesis mainly focuses on both experimental and constitutive modeling studies of the time-dependent stress-strain behaviors of two clayey soils.;Firstly, the time-dependent behaviors of the SMB soils are examined by Multi-Stage Loading (MSL) oedometer tests, Constant Rate of Strain (CRSN) oedometer tests, and step-changed undrained triaxial CRSN tests. From the test data, creep, swelling and strain rate effects are observed and discussed. In MSL oedometer tests, it is found that SMB soils exhibit considerable viscous behaviors. The sand content exerts an indispensible impact on soil behaviors in terms of compression and time (or strain rate)-dependency. In CRSN tests, the strain rate effect is examined by step-changed strain rate, in both oedometer and undrained triaxial conditions.;Secondly, the time-dependent behaviors of the HKMD soils are examined using MSL oedometer tests, 1D relaxation tests (in both loading and unloading stages) and settling column tests. In MSL oedometer tests, both the creep and swelling behaviors of HKMDs are less obvious compared with SMBs. In 1D relaxation tests, the viscosities of HKMDs are observed in both creep and swelling regions. The time-dependent large-strain behavior is studied by settling column tests of HKMDs.;In the constitutive modeling of the time-dependent stress-strain behaviors, a new Elastic Visco-Plastic model considering swelling (EVPS model) is proposed. The model considers the contribution of swelling strain rate to the total strain rate, so that the unloading/reloading loop can be simulated. The 1D EVPS model is calibrated by the oedometer test in 1D straining, and then the model is verified by simulating the stress-strain behaviors of SMBs in CRSN oedometer tests and 1D relaxation tests.;Based on the classical plasticity and the framework proposed in Yin and Graham (1999), a 3D EVPS model is developed. Eight parameters are needed to construct the model for a specific soil. The 3D EVPS model has been adopted to simulate triaxial undrained CRSN tests on different SMB specimens. |
