Small strain stiffness evolution of reconstituted medium density chalk

The mechanical behaviour of reconstituted chalk deposited has been investigated in a comprehensive experimental campaign using measurement and dynamic testing in the form of bender elements. Characterisation of the small strain shear stiffness (G₀) of this material has been performed over a range of the isotropic stress levels and over-consolidation ratios. A variation of (G₀) with current stress and overconsolidation ratio is, for the first time, proposed for this material. Following the widespread idea that the process of remoulding chalk may release calcium carbonate, which provides a cementing agent for grain contact overgrowth, the G₀ evolution at the constant stress state, over time, has been investigated for curing periods up to 23 days. Regardless of the previous stress path history prior to curing, an increase of the small strain shear stiffness with time was observed under a constant effective stress condition. This appeared to be partly associated with creep (or secondary) deformation but further increase was also observed when measurable creep deformations ceased.