Cracking worsens at Gap
CUNNINGHAM'S Gap could stay closed until New Year's Eve on Friday as Main Roads tries frantically to assemble crews to repair a road slip which has worsened this week.
The highway was closed early yesterday after new cracks appeared in the road surface at Claytons Gully on the Brisbane side of the Gap, where two lanes have been closed since last Monday due to slippage from the nearby waterfall.
Torrential rain on Monday this week caused more erosion below the road, with new cracks appearing in the inside lane which was open to traffic.
The closure follows recent delays at the Gap caused by blasting further up in the landslide zone on unstable sections of the cliff face.
A Main Roads spokesman said yesterday keeping the inside lane open over Christmas had taken its toll on the road at Claytons Gully, particularly heavy vehicle movements.
The road surface at Claytons Gully has been monitored with a high-tech measuring device – an inclinometer – for several years, with only minor movement detected until the first week of December.
The Main Roads spokesman said concerns increased Monday last week after heavy rain fell the previous weekend.
“It was then that we put barriers in place and kept the inside lane open under stop-go conditions while we placed around 6000 cubic metres of rock to buttress the road,” the spokesman said.
“We then resurfaced the closed-off lanes last Thursday and were hoping that would provide a temporary repair.
“But due to the rain of the last 48 hours that new surface has cracked and has worsened (overnight on Monday this week), also affecting the lane which had been open.
“We are hopeful we will get traffic moving before the end of the week, but we do need to mobilise a fairly large team and it's a time of year when people are away and resource suppliers are shut down.
“Re-opening the lane by Friday is a challenge but it's by no means impossible.”
The spokesman said an area measuring 20 by four metres would need to be excavated “to a considerable depth” to fix the new cracks on the inside lane, which, when re-opened, would continue under stop-go.
He said it could be several more weeks before all four lanes in the Claytons Gully section were re-opened, with thousands more cubic metres of rock fill needed for stability.
He also defended the decision by Main Roads to keep all four lanes at Claytons Gully open after cracking was first detected in the first week of December, saying it was “very, very minor at that stage”.
Meanwhile, blasting of unstable boulders in the landslide zone closer to the top of the Gap has been completed, but more “clean-up” work will be needed in early January.
The spokesman said the waterfall near the blasting area – now dominated by red shipping containers which buffered the road from the tumbling rocks – had caused further erosion but would not require blasting.
He also said huge “rock bolts” inserted into other nearby sections could remain in place for up to a decade.
“We can't blast these out as they are what might be called keystones – if you remove them you don't know what else might come down,” he said.
“The bolts go about six metres deep into the rocks and they will be totally stable.”