Abstract
The time effects on the stress-strain behaviour of geomaterial consist of effects of loading rate and ageing. The positive ageing effects are analysed based on the results from drained triaxial compression (TC) tests on cement-mixed kaolin and well-graded gravelly soil and incorporated into a non-linear three-component model that can simulate the elasto-viscoplastic behaviour of geomaterials. The inviscid yielding is controlled by the inviscid yield stress that develops basically by irreversible straining and time elapsing following, respectively, a basic inviscid strain-hardening function and an ageing function. The inviscid yield stress may develop additionally by positive interaction between ageing and inviscid yielding following an interaction function, which expresses an additional strength gain by longer ageing at higher shear stress levels. Positive interaction effects are damaged by subsequent irreversible straining following a damage function. These functions are formulated based on experimental results. Illustrative model simulations are presented to describe the structure of the proposed model. The model is validated by simulating drained TC tests exhibiting significant effects of loading rate and ageing.
