MAINTENANCE ASPECTS - The Westerschelde Tunnel: Approaching Limits - page 273

phase. However, during the implementation there was damage to the con-
crete segments as well as to the rubber sealing sections which take care of
the waterproofing. In the first phase of the boring process the number of
cases of damage were quite high, but were soon substantially reduced due
to the taking of a number of implementation measures. The damage spots
were repaired as much as possible, but it remained unclear whether the
result in respect of the quality, was comparable to the original materials.
Also, damage on the outside of the segments could not be detected and so
could not be repaired.
Fig. 18.1
Damage to the lining
Although the repair spots are no longer visible, it is known where they are
situated: every segment is provided with a sequence number with which all
the details concerning the relevant segment are accessible.This information
not only concerns the manufacture of the segment, but also the location
where the segment has been built in. Besides, in the cases of damage a
record was made as to what repairs have been undertaken.
In view of the desired life span, it is most desirable to have instruments
available with which one can establish how the repair spots behave. These
instruments (inspection and monitoring technology) must provide an
insight into:
- leakages; leakages can act most destructively on concrete, but also on
heat-resistant cladding;
- stresses at the spots of repair and of cracks caused as a result thereof;
- the degree of ageing and deterioration of the repair materials;
- the loosening or loose repair spots;
- the risk of corrosion of the reinforcement steel due to the penetration of
chloride;
- the location where macro-cell corrosion occurs or can occur due to the
penetration of chlorides;
- the location of major damages to the outside of the tunnel wall which
occurred during the construction phase;