Environmental aspects have become an important issue in the realisation of major civil engineering projects. This is especially true if areas of distinct natural features are under threat. In this paper the changes of the groundwater level due to the planned construction of a road tunnel are investigated by means of numerical methods. The effect of grouting in advance of the tunnel face has also been evaluated. Although the problem discussed in the paper is essentially threedimensional, reasonable results could be achieved by combining a 2-D and an axisymmetric system with a horizontal groundwater model. The analyses were performed time dependent and thus the lowering of the groundwater could be determined in time and space according to the advance rate of the tunnel excavation. It could be shown that advance grouting minimizes the influence of tunnelling on the groundwater table and that the nearby located national reserve will not be affected by the tunnel construction.
Die Realisation groβer Bauvorhaben hangt heute sehr wesentlich von den möglichen Auswirkungen auf die Umwelt ab, besonders dann, wenn Landschaftsschutzgebiete betroffen sind. In diesem Beitrag wird der Einfluβ eines Tunnelvortriebes auf das Grundwasser mit Hilfe numerischer Methoden untersucht. Obwohl die Problemstellung eine dreidimensionale Betrachtungsweise erfordert, konnten gute Ergebnisse durch eine Kombination von vertikalen und axisymmetrischen Berechnungen mit einem horizontalen Grundwassermodell erzielt werden. Die Berechnungen erfolgten zeitabhangig und somit wurde der zeitliche und örtliche Verlauf der Grundwasserabsenkung gemaβ dem Tunnelvortrieb bestimmt. Es konnte gezeigt werden, daβ durch einen vorauseilenden Injektionsschirm der Einfluβ auf das Grundwasser minimiert wird und daβ keine Beeintrachtigung des in der Nahe liegenden Landschaftsschutzgebietes zu erwarten ist.
la realisation de grande projets de construction est fortement dependante de I'environnement, en particulier lorsque des zones protegees sont en cause. Cet article etudie à l'aide de methodes numeriques l'influence du creusement d'un tunnel sur la nappe phreatique. Sien que le problème traite dans l'article soit essentiellement tridimensional, on a pu obtenir de bons resultats grace à la combinaison de calculs verticaux et axisymetriques avec un modèle de nappe phreatique horizontal. Les calculs ont ete effectues en fonction du temps, et on a pu ainsi determiner le comportement dans le temps et dans l'espace de la baisse de la nappe phreatique correspondant au creusement du tunnel. On a pu montrer qu 'un ecran injecte à I' avant minimisait les repercussions sur la nappe phreatique et que le milieu protege n'etait pas affecte par la construction du tunnel.
Environmental considerations have become an important aspect already in the early design stages of major civil engineering projects. If protected areas of distinct natural features are affected by ambitious projects, the discussion on feasability and technical problems is often in the background in favour of arguments of more political or even fundamental nature. It is already in this part of the project design that numerical methods can play an important role. Very often the geological and hydrological conditions of the area under discussion are not investigated at a scale to allow for a comprehensive judgment of the influence of e.g. a tunnel construction on the in-situ conditions. A realistic assessment of the groundwater situation and the hydrological parameters in-situ is usually very difficult. This is not only important because water pressures and seepage forces are a dominant factor in the lining design (Schweiger, Pottier & Steiner, 1991) but from an environmental point of view this is one of the major issues to be discussed. In many cases arguments in favour or against a project are more intuitively rather than rational. At this stage computational models can be of considerable help.