The paper focuses on investigating the destructuration process during time-dependent stress-strain evolution. For this purpose, various oedometer tests and triaxial tests on intact and reconstituted samples of soft sensitive Vanttila clay were carried out. Based on experimental observations, a new elastic viscoplastic model, extended from the overstress theory of Perzyna, is developed. The proposed model accounts for inherent and induced anisotropy, interparticle bonds and bond degradation, and viscosity. The determination of model parameters is discussed, demonstrating how all model parameters can be determined in a straightforward way and no additional test is needed for the proposed model compared to the modified Cam clay model. The model is implemented into a finite-element code, which enables coupled consolidation analyses. The model is used to simulate various strain-rate and creep tests under one-dimensional and triaxial conditions on the intact samples of Vanttila clay. The comparisons between exp...