Geomechanical knowledge gained from the Paierdorf investigation tunnel in the section through the Lavanttal main fault zone /

Abstract

One of the main goals of the ground investigation for the Koralm Tunnel project was the detailed investigation of the Lavanttal fault systemwhich lies in the contact between the Koralm crystalline and the neogenic formations of the Lavanttal. The above-ground investigation programme (mapping, core drilling, geophysics) was able to deliver the first estimation of the geological, hydrogeological and geotechnical rock conditions of the fault zone many hundreds of metres thick ( fig. 1). The Paierdorf investigation tunnel, which has now been constructed, clarified the thickness and the internal structure of the fault zone as well as the hydraulic and mechanical rock properties along the tunnel. Equally important was the practical experience gained by tunnelling through the fault zone. The knowledge gained from the Paierdorf investigation tunnel will be used in further design work for the mechanical driving of this very heterogeneous region of rock.1 Knowledge of engineering geology gained from the investigation tunnel Main fault zoneThe prognosis Immediately to the East of the neogenic-crystalline boundary, a main fault zone of the Lavanttal fault system was forecast, with a thickness of several hundreds of metres. In this region, a sequence of softly plastic, finegrained and coarse-grained cataclasites was expected, alternating with less faulted, competent blocks of rock. The thickness of the cataclasites was supposed to be a few metres to many tens of metres. Steeply dipping faults were expected to be dominant, dipping towards and also against the advance direction.The groundwater table in this area is up to 270 m above the crown of the tunnel. In the main fault zone dry to damp conditions for tunnelling were expected with locally trapped water pockets. In the jointed competent rock and in the boundaries of steep faults trickling water ingress was expected. Isolated water or mud inflows with up to some tens of l/s were also considered possible. The conditions encountered

Novel method for ductile lining pre‐design / Neues Verfahren zur Vorbemessung eines duktilen Ausbaus

“…Schubert et al ( [9]) have conducted a back analysis of the rock mass properties in this area (both by using convergence confinement method and by numerical analysis). The thus obtained rock mass properties have been largely confirmed by the results of the test adit [19], allowing both the verification and the practical application of the method presented above: after the back-analysed rock mass properties and the assumed primary stress state are used as input data, the calculated displacements should equal the measured ones.…”

“…P. Schubert et al [9] führten eine Rückrechnung der Gebirgseigenschaften (sowohl mittels Kennlinienverfahren als auch mit numerischen Methoden) durch. Die rückgerechneten Gebirgseigenschaften wurden durch die Ergebnisse eines innerhalb der Störungszone quer zur Achse des EKT errichteten und mit Messinstrumenten ausgestatteten Versuchsstollens [19] größtenteils bestätigt.…”

Checking the system behaviour using a numerical model

“…Auf Basis der gemessenen Verschiebungen wurde zum Abgleich mit den statischen Berechnungen aus der Planungsphase eine Rückrechnung der Gebirgsfestigkeit und des EModuls durchgeführt. Diese Rückrechnung ba siert auf analytischen Berechnungen (Gebirgskennlinien) und folgt dem in [7] präsentierten Konzept. Als Eingangs parameter dienen hierbei die zeitliche Verschiebungsent wicklung (einschließlich der Vorverschiebungen) sowie der mobilisierte Ausbauwiderstand.…”

Yielding elements – requirements, overview and comparison / Stauchelemente – Anforderungen, Überblick und Vergleich

“…16). The deformability of the rock mass was initially decided from the test results from the EKT Paierdorf investigation tunnel [15] and already published back-calculations [16]. Then the separate mobilisation of friction and cohesion was determined using direct shear tests on intact rock samples from the EKT Paierdorf.…”

“…Zuerst wurde die Gebirgsverformbarkeit anhand der Versuchsergebnisse aus dem Versuchsstollen im EKT Paierdorf [15] und bereits publizierten Rückrechnungen [16] festgelegt. Danach wurde die getrennte Mobilisierung von Reibung und Kohäsion mittels Direktscherversuchen an intakten Gesteinsproben aus dem EKT Paierdorf ermittelt.…”