ABSTRACT
A self-sealing salt backfill (SVV) based on anhydrous magnesium sulphate has been developed. Fine grained dry initial material (SVV) can be emplaced pneumatically. Artificial flooding of the pore space with brine initiates a reaction that leads to the formation of a brine tight seal. The reaction consumes the brine completely and forms an impermeable plug with a new mineralogy and greater volume of solids. The initial high porosity is reduced to 2–5 vol.-% of isolated pores. Mineralogical assemblages obtained in the experiments and measured by X-ray diffraction agree well with results of geochemical modelling with EQ3/6. The geochemical modelling allows the quantification of the short- and long-term volume changes in the system and demonstrates that in the long run stable mineral assemblages will be obtained. The volume increase leads to a considerable crystallization pressure. The porosity/permeability relationship resembles that of highly compacted crushed rock salt backfill. The mechanical properties are comparable with the values of undisturbed rock salt. These results indicate that SVV is a self-sealing long-term stable and to wide extend predictable predictable material.
