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Eine wichtige Aufgabe beim Tunnelbau in Lockergestein ist die Bestimmung des erforderlichen Stützdrucks der Ortsbrust. Dazu wurden diverse Berechnungsmodelle entwickelt, einige davon erst im Laufe der letzten Jahre. In diesem Beitrag wird zunächst ein mechanischer Ansatz analytisch hergeleitet und dann auf Unterschiede zu bestehenden Modellen untersucht. Anhand eines Rechenbeispiels wird aufgezeigt, wie sich diese Unterschiede auf die Berechnungsergebnisse einer fiktiven Problemstellung auswirken. Die große Schwankungsbreite der Resultate verdeutlicht, daß auf diesem Gebiet immer noch ein Forschungsbedarf besteht.

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Digitale Lehr-und Lernszenarien sind bereits seit mehreren Jahren wichtige Bausteine moderner Hochschullehre. Aber gerade durch die Corona-Pandemie haben die digitale Lehre in der Geotechnik und die damit verbundenen Innovationsansätze einen besonderen Schub erfahren: Durch die erzwungene Umstellung von Präsenz-auf Online-Lehre sind vielerorts neue Möglichkeiten entstanden, Lehrinhalte digital gestützt zu vermitteln. Studieninhalte lassen sich abwechslungsreich präsentieren (z. B. durch Lehrfilme und Animationen), individuell abfragen (z. B. durch elektronische Übungsaufgaben), gemeinsam erarbeiten (z. B. durch kollaborativ erstellte Dokumente) oder auch spielerisch vertiefen (z. B. durch interaktive Elemente). Darüber hinaus kommen digitale Angebote der Diversität der Studierenden entgegen, indem ein orts-und zeitunabhängiges Erarbeiten des Lernstoffs ermöglicht wird, wie u. a. der Wissenschaftsrat in seinen aktuellen Empfehlungen zur Digitalisierung in Lehre und Studium formuliert [1].

SUMMARYFoliated rocks such as micaceous schists are particularly prone to anisotropic creep. This fact may cause severe problems of squeezing when driving deep tunnels, especially when the tunnel axis is not perpendicular to the foliation planes. A rational approach to the prediction and assessment of squeezing as a process in time and, therefore, also pertinent experimental results are still missing.Starting from a simple approach to anisotropic creep/relaxation we show its implications for tunnelling by means of numerical simulations.

Bored pile walls can be constructed between buildings and tunnel alignments to protect sensitive buildings from settlement resulting from tunnelling. The aim of the research work presented here was to evaluate the effectiveness of such a bored pile wall with FE calculations and identify influential parameters. Two methods of predicting settlement were investigated with the programme ABAQUS: The GAP method, where the deformations of the tunnel contour are prescribed, and the stress reduction method, with which the support pressure at the tunnel contour is reduced. The ground is modelled as linear-elastic, ideal-plastic with a Mohr-Coulomb failure criterion as well as with a hypoplastic constitutive law. The contact surface between wall and ground was modelled with complete bonding as well as with a contact law with friction.The simulation results with the stress reduction method and the hypoplastic material model show the best results qualitatively. The predict settlements agree well with empirical methods and centrifuge tests from the literature. The simulations show that the effectiveness of the wall is significantly influenced by the contact properties in the boundary surface. It achieves the best protection effect when frictionless. IntroductionBored pile walls between buildings and tunnel alignments serve to protect sensitive buildings from settlements resulting from tunnelling. For example, on contract H8 on the Lower Inn Valley line of the European railway axis from Munich to Verona, a contiguous bored pile wall approx. 150 m long was used to fulfil the stringent requirements for permissible settlement resulting from the work to build the Jenbach/Wiesing tunnel.A numerical parameter study served to quantify the influence of such a bored pile wall on the settlements on the far side of the wall. This was done by investigating in detail two possibilities for 2D modelling of a tunnel excavation, the GAP method and the stress reduction method, as well as the influence of friction between ground and bored pile wall. A. Kirsch/L. Piazzi · Numerical investigation of the effectiveness of a bored pile wall for the minimisation of settlement resulting from tunnel driving Methods for predicting settlement with 2D FE calculationsA tunnel drive is a spatial problem. Because stress transfers and ground movements cannot be taken into consideration in a 2D model, a simplified calculation with planar elements is always prone to error. In order nonetheless to make a qualitative statement about the effectiveness of the bored pile wall and keep the computing time short enough for a parameter study, these errors were tolerated.The literature, e.g.[6], describes two methods for the numerical calculation of settlement for mechanical tunnelling, the GAP method and the stress reduction method (also described as β or λ method [13]). GAP methodThe GAP method [17] GAP-Methode

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