Effects of wetting and ageing on 1D elasto-viscoplastic behaviour of cement-mixed clay and model simulation

The combined effects of wetting, the viscous property and ageing on the one-dimensional (1D) compression characteristics of kaolin were evaluated. Two series of special constant-rate-of-strain (CRS) 1D compression tests, with sustained loading at intermediate stages, were performed on kaolin with and without cement-mixing. Most of the air-dried specimens were made partially or fully saturated at intermediate stress levels. The effects of the degree of saturation, the wetting process period, the stress level at which wetting was made, the strain rate during loading and the over-consolidation history applied by compaction during the preparation of the specimens were evaluated. The effects of wetting, viscous property and ageing, observed in the experiments, were significant and complicated. A non-linear three-component elasto-viscoplastic model, that had been modified to take into account the effects of wetting, was further modified to account for the ageing effects. The effects of wetting and ageing were described by a decrease and an increase in the inviscid yield stress at a fixed irreversible strain in the plastic component. The viscous property changed from the basic type, Isotach to TESRA as the ageing effects due to cement-hydration developed. The stress–strain relations and the time histories of stress and strain, during complicated loading and wetting histories applied in the experiments, were successfully simulated by the modified model.