Figure 8 : Exposure of tendons at crown of tunnel
The external surfaces of all the exposed ducts were found to be in very good condition . It was found that the ducts were well protected by the tunnel concrete and the anchorages were not allowing the ingress of water .
When the first ducts were cut open , the grout was found to be in remarkably good condition . The wires in the strands were without any visible signs of corrosion . No evidence of a change in diameter was found suggesting no internal corrosion had occurred .
All the strands within the 18 ducts were exposed and all were found to be in a similarly good condition . No significant negative changes were found .
After careful consideration it was decided that enough evidence had been gathered to enable the conclusion that the anchorages on the southern bridgehead were in satisfactory condition and that the risk of having to replace the anchorages during the remaining service life of the bridge was relatively low .
The ducts and grout were reinstated followed by sequenced mass infill concrete casting .
Figure 9 : All ducts exposed in south west tunnel
Figure 10 : Strands exposed and wedged to enable visual inspection around the circumference
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