Engineers have secured the first of three large boulders which were exposed in landslips above the A83 at the Rest and Be Thankful in Argyll.
The safety work involves using hydraulic gear to drill into the rocks and break them into smaller pieces.
The largest boulder, which is 300m above the roadside, was estimated to weigh about 75 tonnes.
A 60-mile diversion has been in place since Tuesday and the A83 and Old Military remain closed.
Bear Scotland said more than 2,500 tonnes of landslide debris reached the catch-fences above the carriageway during severe weather in the area.
Aerial assessments using helicopters have allowed geotechnical engineers to fully investigate the hillside and the scale of the landslips.
Tommy Deans, Bear Scotland’s north west network manager, confirmed work on securing the second boulder was set to get under way.
Removing the debris
He said: “Until this work on the boulders is complete, we cannot open either the A83 or the Old Military Road local diversion.
“The local diversion route is ready to go and once we have the go-ahead from the geotechnical assessments we’ll look to open this.
“After that we’ll begin repairing and removing the debris from the catch-fences above the A83 carriageway.
“Yesterday allowed teams to fully assess the scale of Tuesday’s slips, which are some of the largest in recent years.”
Local SNP MP Brendan O’Hara has called on the Scottish government to provide more investment to tackle the transport and economic problems surrounding the A83.
Mr O’Hara said: “Closures of the A83 leads to untenable diversions and rerouting of traffic onto other roads which are simply not designed to withstand these volumes of traffic.
“A solution to infrastructure investment to stem the flow of people and investment from the west coast must be found as a matter of urgency.
“The rural west of Scotland had suffered decades of underinvestment and depopulation and while I’m extremely grateful for the work the Scottish government have done thus far at the Rest and Be Thankful, we need a permanent solution and that means investment.”