Effect of closed and open system freeze–thaw cycles on GMB–GCL interface transmissivity

Abstract

An experimental study of the effect of closed system and a limited study of open system freeze-thaw cycles on the interface transmissivity at applied stresses between 10 and 150 kPa is described. The effect of closed system freeze-thaw is most apparent after 100 freeze-thaw cycles and permeation at a stress ≤25 kPa. The effect of permeating fluid chemistry is also evident but decreased with increasing stress. One notable effect of permeant is the potential for internal erosion along weaknesses in the bentonite created by freeze-thaw cycles when permeated by distilled or reverse osmosis water. This is not observed when permeated with simulated porewater containing cations. In terms of practical application, closed system freeze-thaw cycles appear to have little effect on interface transmissivity, and to the extent that there is an effect, it is beneficial. In contrast, cryogenic suction arising with open system freeze-thaw cycles is shown to result in the formation of ice lenses both within the GCL and at the GCL geomembrane interface. Although limited, the data suggest that the effect of ice lens formation on interface transmissivity after open system freeze-thaw cycles is largely eliminated at applied stress above 20-25 kPa, although more research is warranted.