Burying utilities and roads is a strategic need in Monaco to keep land available for exotic real estate development, but getting them underground presents challenges, such as minimising the disturbance, especially vibration, that could perturb residents.
So, when drill and blast was ruled out for a project to divert a road into a 145m long cliff tunnel (7m wide by 8m high), Bachy Soletanche needed a low disturbance solution for the portal ends. The rock, a compact, dolomitic limestone, felt more like a UCS 60-100MPa barrier than the 50-70MPa from lab tests and which would be fine for roadheaders.
The eventual solution was to grind the ends with a rotary drum cutter. The low speed, high torque milling was done by an Erkat ER 3000-2 unit, supplied by Eurofor and fitted on a Liebherr 954 excavator. Progress was approx. 3.5m/day/5 day week. Profiling was aided by 64mm bores. The full tunnel dig finishes this month.
For obvious reasons drill and blast was ruled out The portal site of the Monaco tunnel Rotary drum cutter in use The drum cutter mounted on a Liebherr 954
