Water-Pathway Sealing by Crystallization under Advective Supersaturated Solution Conditions

Abstract

The objective of this study is to promote understanding of the structural evolution of fractures that affect the transport of contaminants in geological media. Highly soluble potassium alum was used as an analogue material, and was grown in an open fracture from a solvent transported by advection along the fracture, in order to observe decreases in the aperture of the fracture. In addition, the growth rate law of K-alum was experimentally determined based on the relationship between relative supersaturation and linear flow velocity. The sealing result was compared with simulations based on a simplified numerical model using the experimentally determined growth rate law, and it was found that the time necessary for sealing was longer for the simulation than for the experimental sealing. This discrepancy was explained by the additive growth rate of the original seed crystal and secondary crystals nucleated near the fixed seed crystal. Thus, it was shown that primary and/or secondary nucleation is an additional factor for prediction of the structural evolution of fractures in geological media.