The knowledge of the geological sequence and hydrological conditions in the area of portals was the basis for the design of the entry of the highway into tunnel Trojane. Mudstone, claystone and sandstone dominate the rock layering, which is tectonically reworked and contains structural anomalies. The complexity of the sequence makes it impossible to survey all the relevant features along the full 3km length of the tunnel. Sudden and frequent transitions between litological sequences impose potential instabilities and make the excavation of the tunnel particularly difficult. The initial survey established the zones of potential failures. These were monitored using topographic survey and inclinometers with an aim to make further geotechnical analyses more reliable and adjusted to the ground conditions. The analyses of the wall construction and the results of the monitoring showed that the design of the retaining wall was adequate.

La connaissance de la sequence geologique et des conditions hydrologiques dans l'aire des portails a ete la base pour la planification de l'entree de l'autoroute dans le tunnel Trojane. Le schiste, l'argilite et le grès dominent la couche rocheuse qui est tectoniquement transformee et contient les anomalies structurales. A cause de la complexite de la sequence, il est impossible de revoir toutes les particularites le long des 3 kilomètres de la toute longueur du tunnel. Les transitions soudaines et frequentes entre les sequences lithologiques imposent l'instabilite potentielle et font l'excavation du tunnel particulièrement difficile. La revue initiale a ete etablie sur les zones où il existe l'eboulement potential. Elles etaient contrôlees à l'aide de la revue topographique et de l'inclinomètre pour que les analyses geotechniques suivantes soient plus sûres et adaptees aux conditions du sol. Les analyses de la construction des murs et des resultats du contrôle ont montre que la planification du mur reteneur etait correspondante.

Der Autobahneingang in den Trojane Tunnel war projektiert auf Basis von der Kenntnis der geologischen und hydrogeologischen Bedingungen in dem Portalgebiet. Das Gebiet besteht aus dem Tonstein und dem Sandstein. Die Schichten sind tektonisch verformt und sind deswegen sehr heterogen. Die anfaenglichen Untersuchungen haben die Zonen von den potentiellen Bruechen definiert. Weitere geotechnische Analysen waren fitted an reale geologische Bedingungen durch das Monitoring der potentiellen Bruchzonen, welches aus den topographyschen Messungen und Inklinometerdaten entstand. Die Analyse des Wandbaues und die Resultate von dem Monitoring haben erwiesen, dass die Wandprojektierung entsprechend war.

Introduction

The initial geological assessment in the area of Trojane west portals indicated the existence of an old landslide that was partly active in recent geological conditions. There was a possibility that any further excavation works can activate the old landslide. Also, the significant amount of groundwater at higher elevations was registered in the wider area of the portals. Taking into account this situation and the potential complexities this may bring during the construction works, the investor had decided back in 1994/95 to establish the monitoring scheme of the area. The aim was to follow the ground movements of the preexisting landslide and the oscillation of the water table so that the detailed information becomes available for the final design. Measurements, carried out in between 1995 and 1999 showed clearly that large movements up to 40mm can be expected in the area of the old landslide, as shown in Figure 1. The measurements in inclinometers showed that, at some positions, the movements were extending up to 15 to 17m depth.

The basis for the design of the retaining structures on both west portals of the tunnel Trojane was based on the protection of the both sides.

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