The failure of anchors used on a rock cutting made for a 10-year-old North Wales trunk road was ‘very rare,’ Transport Wales told Surveyor this week.
Five anchorages holding back the sides of the 31m deep A5 cutting near Corwen in North Wales have failed, a further 18 are overloaded, and there are ‘concerns for the integrity’ of the remaining 475. The failure of many of the bolts anchoring the sides of a deep cutting for the A5 – opened in 1996 to replace a 200-year-old alignment – meant there was a one-in-64 chance of a catastrophic collapse, forcing the closure of a one-kilometre stretch (Surveyor, 1 June).
While theWelsh Assembly attempts to buy back from local farmers the old A5 road, built by Thomas Telford in order to provide easier access for vehicles to the port of Holyhead, attention has now switched to the causes of the failure. Assembly engineers believe major re-profiling of the cutting will be necessary, and closure lasting 12 months has been mentioned.
Robin Shaw director of Transport Wales, said the use of anchors was widespread, very effective, and nothing similar had happened before in Wales. Failure to such an extent was ‘very rare’. The cutting faces slope typically at 70 degrees. Shaw said the current intention was to reduce this to 35 degrees on the north, and re-anchor the south face. As Surveyor went to press, it appeared likely that the assembly would have to use compulsory purchase powers to buy back the Telford road through Dinmael Bends, after one of the four farmers that now own it had demanded too much money.
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