Expert: A long-term fix for landslides will not be cheap or simple

A solution to permanently fix the notorious A83 Rest and Be Thankful road will not be easy or cheap, according to one of the world’s leading civil engineers.

Professor emeritus Jean Benoît is an expert in geotechnical engineering including landslides and issues related to roads, foundations and tunnels.

The University of New Hampshire expert has been involved in drilling, sampling and field testing on major civil engineering projects for more than 30 years starting on hydroelectric projects in Canada.

He said: “Finding a solution to this stability problem along the A83 is very complex. To provide solutions, one has to understand the geology of the area, the history of landslides, the geotechnical properties and thicknesses of the overburden layers, location of current and past slip surfaces, volumes of slides and water infiltration into the slide areas.

“Without this information it is difficult to come up with safe, economical solutions. During maintenance or repair of the roadway, the slide masses on the road have to be removed which often leads to more instability as the volume of earth at the toe of the slope provides buttress support.”

Benoît has carried out research and consulting work throughout the US, Canada, France, Italy, Egypt, Iran and Algeria.

Some of his significant projects include the Central Artery in Boston, Massachusetts, the Olmsted Locks and Dam in Illinois, the Loire River in France and the Leaning Tower of Pisa in Italy.

Certain measures will help the A83 including soil nailing

– a technique using grouted steel nails to reinforce soils and create a gravity retaining wall for permanent or temporary support, according to Benoît.

He said: “Building retaining walls is costly and sometimes they cannot be made large enough to retain the sliding material.

“The best approach is to determine what causes the instabilities and address those. That could include rerouting the incoming infiltration, creating drainage paths, soil nailing and benching of the slopes.”