Equivalent time and elastic visco-plastic modelling of geomaterials

The concepts of equivalent time, reference time line etc. are introduced and a simple one-dimensional elastic visco-plastic model (1-D EVP) is derived. Yin and Graham's 1-D EVP model and its verification are also introduced. The creep data of a marine clay and a soft salt rock are used to examine the loading-history independence of equivalent time and creep strain rate. It is shown that the general 1-D EVP model will approach to the elastic line and the reference time line (elastic-plastic line) when the creep parameter ψ/V approaches to zero.