Roadheader Drive

Sonnenburg Tunnel: Roadheader Drive under tricky geological Conditions

Side view of a WIRTH T2.20 heavy roadheader as applied for the Sonnenburg project

Aerial view of the route with the cut-and-cover and trenchless part-sections [1].

Cutting rate diagram for the roadheader with the characteristic values for the various types of rock applied in the feasibility study [2]

(Foto: Plinninger)

Roadheader excavation in quartz phyllite. The cutting lines of each bit are clearly discernible at the face on account of the low segmentation of the rock

(Foto: Plinninger)

Graphs of the specific tool wear and the net cutting rate

Pie chart of the tool wear forms encountered (classification according to [4])

Roadheader breakthrough at the Amtmannbühel Tunnel

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).

Construction was executed accompanied by what must be a unique engineering geology investigation programme – for a project of this magnitude. It comprised rock mechanical lab tests as well as performance and wear documentations. This report examines the problems, which led to switching from drill+blast to excavating via roadheader. It presents the models applied in the course of the feasibility study and the findings obtained on the interactions of rock and rock mass characteristics as well as extraction rate and tool wear. In this particular project these models proved their worth as basic...