Ageing and Viscous Effects on the Deformation of Clay in 1D Compression

Ageing and viscous effects on the stress-strain behaviour of kaolin and their interactions were evaluated by performing special constant-rate-of-strain 1D compression tests on air-dried and saturated kaolin without and with cement-mixing. The yield stress that was higher than the stress at which curing was made developed by ageing effects associated with cement hydration, which became larger with an increase in the curing period. The stress-strain behaviour of saturated cement-mixed kaolin after monotonic loading continues for some strain range following the start of yielding was rather independent of the stress at which cementation developed. The viscous properties of kaolin was evaluated by measuring the stress jump Δσ_v^' taking place upon a sudden change in the strain rate from (ε˙_v)_before to (ε˙_v)_after at the instantaneous stress σ_v^'. The Δσ_v^'/σ_v^' – log{(ε˙_v)_after/(ε˙_v)_before} relation was linear in all the cases. The slope β, called the rate-sensitivity coefficient, represents the viscous property of clay. The β value of kaolin when dried was about a half of the value when saturated. The effects of cementation on the β value and other aspects of viscous property were evaluated. It is shown that the β value of kaolin when dried was very similar to the values of sand and gravel.