The scheduled work to be carried out for the rest of the year. Map courtesy Department of Transport and Main Roads.
The scheduled work to be carried out for the rest of the year. Map courtesy Department of Transport and Main Roads.

Cunningham's gape

AS MOTORISTS wind their way down Cunningham’s Gap, a lone worker hangs from a rope more than 50m above.

With a large drill in his hands, the contractor plies away at the cliff face to prevent more rocks from slipping on to the highway.

Huge shipping containers filled with gravel have been placed underneath as a safeguard to motorists, should any large boulders cascade down.

This is just a fraction of the repair works to Cunningham’s Gap, a large project expected to cost about $40 million.

The Department of Main Roads is rebuilding sections of highway that have been cut in half due to landslip worries.

Of the 11 identified problem sites, eight of them have been earmarked for excavation and re-filling with rock structures.

Two of them – sites 10 and 7 – were completed in January.

The method of excavation and re-filling is an engineering feat.

After the section of road is dug away, hundreds of 12-metre-long “nails” are drilled in at a precise angle to stabilise the ground beneath the remaining road.

Main Roads South Coast regional director Paul Noonan said this was a well recognised geo-technical method.

“It forms almost a grid underneath the road and really strengthens it,” he said.

“Then we’ll put 18m nails underneath the lower half (of excavated road) before filling that with rock deposits to bring it up to the same height again.”

All this happens while contractors measure the pressure of the soil to ensure the road can cope with heavy vehicles continuously driving over it.

Back to above-road maintenance, keen-eyed motorists may have noticed the installation of a series of cords along one cliff face near the top of Cunningham’s Gap.

Mr Noonan said the machine was an extremely sensitive monitor, which kept movement readings in rock crevices.

He said an alarm would be triggered at the first sign of any rock movement and, immediately, all vehicles would be cleared from the road in expectation of a landslip.



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