| dc.description.abstract | It is widely accepted that inter granular pressure solution is a dominant deformation mechanism in solid/liquid systems. However, several authors suggest that this stress driven mechanism slows down, where opposing interfacial energy driving forces become important, and will stop until a certain ’yield stress’ for pressure solution is reached, below which the process is prevented by surface energy grain boundary healing. This yield stress for rock salt and dominant mechanism(s) operating when pressure solution creep slows down and even stops has received little attention.
In this research, short term uniaxial compaction experiments were conducted under chemically closed system conditions on brine- and n-decane saturated granular salt to allow identification of the compaction mechanism(s) and to test the applicability of the predictions made by accepted analytical pressure solution models. In combination with long term compaction experiments and microstructural observations, the mech- anisms operating and associated interfacial surface energies in low and high strain fields were defined. It is found that the experimental data on brine-saturated granular salt follows the analytical models of diffusion controlled pressure solution until volumetric strains up to 20%, whereas the addition of n-decane counteracts on dissolution and precipitation processes can not operate. Microsctructural observations confirm that pres- sure solution creep was the dominant deformation mechanism at low volumetric strains (<15%) (i.e. high porosities) and neck growth and grain boundary migration were deformation mechanisms operating at high volumetric strains (>20%) (i.e. low porosities). A yield stress of 55 MPa was found, indicating that grain boundary healing occurred and pressure solution slows down and eventually stops at high volumetric strains (32%). The grain contact area turned out to be larger than pore wall area at low porosities, whereas the grain contact area < pore wall area when pressure solution creep operates. | |
