a b s t r a c tWhen analysing the measured displacements at the Trojane tunnel (Slovenia), excavated in soft foliated rock mass, some interesting deformation patterns were observed, especially large surface settlements that appeared despite quick ring closure, stiff lining and consequently small tunnel lining displacement. It soon became clear that most of these phenomena are the consequences of highly anisotropic nature of the soft foliated rock mass. A vast number of numerical analyses were performed, varying dip direction and dip angle of the anisotropy planes as well as strength and stiffness parameters of the rock mass (degree of rock mass anisotropy). The share of displacements that occur ahead of the tunnel face and the extent of influential zone ahead of the tunnel face are presented as primary results. Further on, the effect of tunnelling with and against the anisotropy planes in the same material is presented. The effect of overburden above the tunnel and the influence of the orientation of anisotropy plane on the surface settlements were investigated. To verify the obtained numerical results, comparisons to the measurements inside and above the Trojane tunnel were made.

During construction of the Šentvid tunnel a unique opportunity arose to measure the 3D displacements ahead of the motorway tunnel excavation face, since the exploratory tunnel was already constructed in the axis of the main tunnel. According to reviewed literature such measurements had not been performed yet and several problems regarding equipment and complete scheme of the experiment needed to be overcome. The paper gives a brief description of the Šentvid tunnel project, presents significant factors that affected the choice of the geodetic equipment and describes the scheme of the experiment. A special attention is focused on the problems relating to the operation of the instrument in demanding environmental conditions (water, dust).

The Šentvid tunnel had first been designed as twin tube double‐lane tunnel. Later on, the design included the third traffic lanes and connecting ramp tunnels. The underground junctions required the construction of large caverns. A small diameter exploration gallery was excavated in order to find the optimum locations for both caverns in foliated Perm‐Carboniferous soft rock conditions and to provide geotechnical model and material parameters for the design. The exploration gallery furthermore enabled displacement measurements ahead of the excavation face of the main tunnel during its construction. This paper presents some details of the exploration gallery and the results obtained from it, showing the results of displacement measurements ahead of the tunnel face and comparisons of the observed displacements ahead of the tunnel face with geological conditions.The tunnel construction won international attention due to its complexity and as an example of best practice in the construction of very large excavations in diverse geotechnical conditions. During the decision making process, an international panel of recognized experts from consulting companies and universities was involved. Later on, the panel regularly monitored the progress of tunnelling works and contributed to the decisions during critical steps of the project. The decision to involve international experts with different experiences and approaches permitted the client to keep the construction risks within acceptable limits.Der Sentvid‐Tunnel war zunächst mit zwei Röhren mit jeweils zwei Fahrstreifen geplant worden. Später wurde der Entwurf um einen dritten Fahrstreifen und Verbindungstunnel erweitert. Die unterirdischen Verzweigungen erforderten die Errichtung von großen Kavernen. Ein Erkundungsstollen mit kleinerem Durchmesser wurde ausgebrochen, um die optimalen Standorte für die beiden Kavernen im weichen, geschieferten Fels aus dem Perm bis Karbon zu finden und um geotechnische Modell‐ und Materialparameter für den Entwurf zu erhalten. Der Erkundungsstollen hat weiterhin ermöglicht, Setzungsmessungen im Bereich vor der Ortsbrust des Haupttunnels während dessen Errichtung durchzuführen. In diesem Artikel werden einige Details des Erkundungsstollens und der mit seiner Hilfe gewonnenen Ergebnisse dargestellt. So werden die Ergebnisse der Messungen der der Ortsbrust vorauslaufenden Setzungen gezeigt und ein Vergleich der beobachteten Setzungen mit den geologischen Verhältnissen angestellt.Der Tunnelvortrieb hat international Aufmerksamkeit auf sich gezogen aufgrund seiner Komplexität und als vorbildliches Praxisbeispiel für die Errichtung von sehr großen Hohlräumen in den unterschiedlichsten geologischen Verhältnissen. In den Entscheidungsprozess war ein internationaler Ausschuss von anerkannten Experten aus Beratungsfirmen und Universitäten eingebunden. Im weiteren Verlauf hat dieser Ausschuss regelmäßig den Fortschritt der Arbeiten an dem Tunnel verfolgt und in kritischen Phasen des Projektes bei wichtigen Entscheidungen unterstützt. Die Entscheidung, internationale Experten mit verschiedensten Erfahrungen und Herangehensweisen einzubinden erlaubte dem Kunden, das Risiko der Baumaßnahme in einem akzeptablen Rahmen zu halten.