MAINTENANCE ASPECTS - The Westerschelde Tunnel: Approaching Limits - page 274

Fig. 18.2
Repair work

- possible shifts of the tunnel rings and segments due to changes in pressure;
- deterioration of the sealing between segments and rings;
- changes in the quality of the heat-resistant cladding.

Macro-cell corrosion One of the problems which could occur due to the
relatively thin lining of the Westerschelde Tunnel in respect of other tunnel
types, is macro-cell corrosion. This factor could occur when the reinforcement
of a concrete cross section which has been saturated with water on one side,
continues from the saturated section through to the non-saturated sections.

Fig. 18.3
The principle of macro-
cell corrosion

Water containing
chloride

Air (inside)

Adequate electrical
conductivity?

O 2

?

2H 2 O

Cl 2Fe 2

2Fe(OH) 2

Cathode

Anode

4 e

Moisture front