Figure 4: The distribution of the intraporous moisture volumes in the exterior layer W1, by the wide mouth of the funnel W2 and by the narrow mouth

The concrete inside the volume of the tunnel has a diminishing pore character in relation to the exterior wall layer, and the intraporous moisture is distributed in a similar manner. As is known, the level of osmotic pressure and that of the moisture volume are inversely related, and therefore the pressure of the migrational flux will increase from the exterior layer to deep into the wall. In conditions of low temperature this process is accelerated and it is possible to move the moisture from the exterior layer into the warm zone of the wall, ie towards the narrow end of the funnels.