Improved Design Method for Pre‐stressed Water Tunnels

Abstract

The final design of the pumped-storage project Feldsee features a complex lining and pre-stress grouting concept, rendering the method presented by Seeber insufficient for an accurate determination of the system behaviour in all stages of construction and operation. A calculation procedure based on the matrix stiffness method has been implemented, allowing incorporation of multistage pre-stressing injections at different locations of a lining being composed of several layers with different mechanical properties. Based on the design obtained by applying the above method, another question of maximum allowable non-symmetric displacement of the pre-cast concrete segment arose. A parametric study has been used to determine the boundaries of asymmetric displacements throughout the pre-stressing procedure, allowing establishment of threshold values for the monitoring conducted during the pre-stressing injections. Fortschrittliche Bemessungsverfahren für vorgespannte

First operational experience with a high‐pressure tunnel with innovative lining methods / Erste Betriebserfahrungen bei einem Hochdruckstollen mit innovativen Ausbaumethoden

“…The innovative solution is based on a composite structural system with the distribution of the load-bearing effect between the lining (concrete inner lining + GRP + prestressed concrete backfilling) and the rock mass. The permissible share of pressure on the rock mass has to be determined and the occurrence of tension cracks prevented [7]. Depending on the rock quality (deformation modulus) and the overburden depth (pre-hardening of the rock mass), the permissible internal pressure can be evaluated with regard to the water-tightness of the tunnel and the lack of cracking to the inner lining concrete.…”

“…Der innovative Lösungsansatz baut auf ein Verbundtragsystem mit der Aufteilung der Tragwirkung auf Auskleidung (Betoninnenschale + GFK + vorgespannter Hinterfüllbeton) und Gebirge. So gilt es, den zumutbaren Druckanteil des Gebirges zu erfassen und auftretende Zugrisse im Gebirge in Grenzen zu halten [7]. In Abhän-gigkeit der Gebirgsqualität (Verformungsmodul) und der Überlagerungshöhe (Vorverfestigung des Gebirges) kön-nen die zulässigen Innendrücke im Hinblick auf die Dichtheit des Stollens sowie im Hinblick auf die Rissefreiheit der Innenbetonschale beurteilt werden.…”