High-Stakes Headrace

Quelle/credit: Robbins

The 6.2 m diameter Crossover (XRE) TBM is the first Crossover machine to be used in Europe

Quelle/credit: Robbins

The Robbins machine is ramping up production: From late November 2016 until March 2017 it had bored 230 m of tunnel in primarily siltstone flysch

Quelle/credit: Robbins

The machine can be sealed against water inflows up to 20 bar (in blue) using a large sealing gate in the bulkhead just above the TBM belt conveyor

Quelle/credit: Robbins

The Devoll machine utilizes two-speed gearboxes that allow the machine to operate in an EPB-like mode. High rpm/low torque can be used for hard rock and low rpm/high torque can be used for soft and/or blocky ground

Quelle/credit: Robbins

Due to the remoteness of the area and unpaved roads, the machine was assembled at the jobsite using Onsite First Time Assembly

Quelle/credit: Robbins

A heavy lift crane was not available locally for the onsite assembly, so a crane was sourced from the Balkans to lift the cutterhead, shields, and other large components

Quelle/credit: Robbins

Moglicë, Albania is a small town on the upturn due to construction of the Moglicë Hydropower Station – part of a new project known as Devoll Hydropower that will increase the country’s electricity production by 17 %. The new station, together with the nearby Banja Hydropower Station, will have an annual generating capacity of 242 MW. Once a dying community, residents are returning to Moglicë and finding work at the hydropower construction. At least 200 people have returned to the community after emigrating to Greece. But the project has not been without challenges: the remoteness of the jobsite, the mountainous terrain, and the complex geology make the excavation of the power station and its 6.7 km long headrace tunnel anything but simple.

The JV contractor responsible for the headrace tunnel, Limak/AGE, opted for a unique type of TBM to bore in ophiolite, flysch, mélange and breccia with suspected water inflows up to 20 bar. The 6.2 m diameter Robbins Crossover XRE TBM is the first such machine to be used in Europe (Fig. 1), and has been designed with features of both hard rock Double Shield and EPB TBMs.

Power to the People

Currently, nearly all of Albania’s electricity is provided by aging hydroelectric power plants, which are becoming ineffective due to increasing droughts. In answer, Devoll Hydropower Sh.A., an Albanian...