Rock slopes are affected by landslides more frequently than generally believed. The design of tunnels passing through such slopes has to take into account the special kinematics imposed by the moving rock mass. Support measures of tunnels running parallel to moving slopes (sagging) show characteristic stresses and stress developments. As a consequence of rock creep, bending tensile stresses increase in the concrete lining of conventional tunnel profiles, rock bolts installed in particular positions are subjected to compression and therefore pushed into the tunnel. Alternatives preventing such stresses are given.


Les glissements de terrain sont plus frequents qu'on ne le suppose. Lors de la conception et de I'avancement de tunnels dans les zones de glissements, il est indispensable de tenir compte de la cinematique du massif rocheux en mouvement. Les moyens d'appui des tunnels parallèles aux glissements de terrain (affaissements) presentent les effets des contraintes caracteristiques qui se developpent avec Ie temps. Suite au fluage dans les versants instables, les contraintes de traction en flexion croissantes agissent sur Ie revêtement en beton des tunnels habituels, et les têtes d'ancrage dans des parties particulières des sections s'enfoncent dans Ie tunnel. Des alternatives destinees à evirer ces contraintes sont donnees.


Massenbewegungen treten wesentlich haufiger auf als allgemein angenommen wird. Entwurf und Ausfuehrung von Tunneln durch Massenbewegungen sind der Kinematik des sich bewegenden Gebirges anzupassen. Die Stuetzmittel von Lehnentunneln, die durch Massenbewegungen (Sackungen) verlaufen, weisen charakteristische Beanspruchungen sewie Beanspruchungsverlaufe ueber die Zeit auf. Durch die Kriechbewegungen in instabilen Hangen treten im Auskleidungsbeton herkömmlicher Tunnelprofile mit der Zeit anwachsende Biegezugspannungen auf, Ankerköpfe in bestimmten Querschnitsbereichen werden in den Tunnel gedrueckt. Alternativen, die solche Beanspruchungen vermeiden, werden aufgezeigt.


Rock slopes arc affected by landslides more frequently than generally believed, since nature cannot afford high safety factors. Thus every rock slope is in motion, at lower or higher velocities. Unless the geologist points out the dangers of mass movements regarding construction and maintenance of a tunnel at an early design stage, and unless this advice is heeded, there is little chance of a search for alternatives - except maybe after the damage has been done. If landslides are not taken into account when choosing and designing alignment, tunnel cross section, tunnel lining or slope stabilisation measures, the consequences will have to be accepted sooner or later, usually in the form of enormous maintenance cost. This paper concentrates on landslides where displacement velocity decreases with depth and where no clear continuous slip planes exist over the full extent of the slope. In slopes in ductile rocks (e.g. clayey shale, phyllite, mica schist), such mechanisms take the form of slope sagging, in hard but jointed rock, toppling failures occur (Fig. 1). In nature, the mechanism is often a combination of toppling in the upper part of the slope (even in phyllites !) and sagging due to rock overstressing in the lower part of the slope. Landslides in ductile rocks can be modelled very well numerically by assuming visco-plastic material behaviour (Zienkiewicz & Humpheson, 1977). Plastic deformations are delayed by this material law. This results in a displacement velocity distribution in the slope well known from inclinometer readings in moving slopes: the creep movements of the ductiIe rock mass decrease continuously with increasing depth below surface (Fig. 2).

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