A9 Pyhrn highway, completion of Tunnelkette Klaus, Austria

As part of a construction project completing improvements to the A9 Pyhrn highway, the construction of four bridge structures with lengths from 83m to 278m and heights from ca. 25m to 50m is foreseen. The bridges are located in an 8-km-long section of the highway known as “Tunnelkette Klaus”, which connects Klaus and St. Pankraz-Hinterstoder in Upper Austria. Two of the bridges, one crossing the Steyr valley and the other crossing the Pertlgraben valley, will be constructed using a free cantilever method, while the other two bridges crossing Rettenbach and Teichl are planned as arch bridge structures.

The geotechnical conditions at the project locations are characterized topographically by deeply-cut river valleys, with the valley flanks almost vertically inclined. The subsoil conditions vary locally and are characterized by carbonate material, conglomerates, terrace gravels and loosely bedded fluvial sediments.

INSITU Geotechnics was tasked by the ASFINAG (Austrian highway authority) with providing geotechnical consultation and construction supervision services related to the construction of the bridge structures.


  • Geotechnical consulting services during construction of the bridge structures as well as for necessary earth retaining structures and slope stabilization measures
  • Analysis, evaluation, and documentation of the existing subsoil conditions
  • Adjustments to geotechnical measures based on the observed subsoil conditions on-site; conceptualization of additionally necessary and special geotechnical measures
  • Design of excavation and slope stabilization measures
  • Consulting services for the client and site supervision personnel related to geotechnical problems


ASFINAG, Wien / ASFINAG Bau Management GmbH, Bruck/Mur


since 2013

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