On yield stresses and the influence of curing stresses on stress paths and strength measured in triaxial testing of stabilized soils

Studies on the behaviour of stabilized soils under different loading conditions are essential to identify which parameters are relevant in the design of deep mixing, An investigation has been performed on soils stabilized with different types of binders with the purpose of demonstrating the effects of quasi-preconsolidation pressures, i.e., yield stresses that are not primarily linked to previous consolidation pressures but to the cementation taking place, on the strength behaviour of stabilized soil. The effect of stresses applied during curing has also been studied. Drained triaxial compression tests and undrained triaxial compression and extension tests were performed on two stabilized clays. The binders used were cement, lime, slag, and fly ash in different combinations. Comparisons have also been made with results from previous tests on two organic soils stabilized with much the same types of binder. The results show that both the cementation processes involved and the stresses applied during curing affect the quasi-preconsolidation pressure. This pressure is strongly linked to the strength of the stabilized soil and has a considerable influence on its deformation behaviour. A model is proposed which describes the strength behaviour in the same effective stress plane that is commonly used for natural clays.