Fig. 11From: Impact of operational temperature changes and freeze–thaw cycles on the hydraulic conductivity of borehole heat exchangersPlain view on the dismantled specimen of BHE body (A) and surrounding soil (B) at day light (1) and with black light (2) to visualize flow paths in the skin zone (C). The BHE body is drawn in red color in a schematic way to increase the visibility of the BHE groutBack to article page