Sonnenburg Tunnel: Roadheader Drive under tricky geological Conditions
The Sonnenburg Tunnel is part of the upgrade for the existing Pustertal valley national highway SS 49 through the autonomous Province of Bolzano, South Tyrol at St. Lorenzen. The total construction section is some 1.7 km long. The roughly 310 m long tunnel under the listed Sonnenburg Castle, the core of the project, was built by trenchless means. Although initially the geological general conditions appeared unsuitable for using a TBM, the driving activities beneath the Sonnenburg were tackled by a heavy roadheader (TSM) owing to prior problems with vibrations deriving from blasting (Fig. 1).
