Multi layered shotcrete design for tunnel construction

Shotcrete linings have been applied successfully for a large number of tunnel constructions within the last couple of decades all around the world. While up to the 1980’s the structural design of the shotcrete linings mainly was based on experience gathered throughout the construction and some simplified analyses in the following years the application of the Finite Element Method lead to much more sophisticated design and more accurate estimation of deformations and stress state in the shotcrete lining. This was amongst others achieved by considering the time and construction sequence - dependent development of the deformations as well as by applying simplified time dependent material laws for shotcrete. The design verification as such is commonly done by using the methods as stated in Eurocode 2 for ULS and SLS. The design becomes even more complex for cases in which during a first construction stage one shotcrete layer is applied and stressed and only later additional, stress free layers are applied in order to carry additional loads caused by further construction stages. With such situations tunnel designers have to deal frequently in cases when cross sections between two main tunnels need to be installed or a second, parallel tunnel is driven while the first tunnel is already in place. Within this paper the special case of such multi – layer shotcrete linings is discussed and proposals for the calculation of the stress state in the lining and the design verification are made

Untersammelsdorf Tunnel – Challenges, Special Measures and use of Special Shotcrete for Tunneling in Lacustrine Clay

The 665 m long, twin-track Untersammelsdorf Tunnel is being built in the course of the construction of the Koralmbahn line between Graz and Klagenfurt. The tunnel is located in extremely challenging subsoil conditions consisting of silty to fine sandy lacustrine deposits. The developed tunneling concept provided wide-ranging special underground engineering measures as piling, jet grouting and temporary struts and represents a unique construction method to date. Accordingly, numerous challenges arose in the design phase, which could be verified by carrying out extensive trials and investigations in the preparatory period or for which fallback levels had to be provided for the support system. Please click Additional Files below to see the full abstract

Modelling of input data uncertainty based on random set theory for evaluation of the financial feasibility for hydropower projects

The design of hydropower projects requires a comprehensive planning process in order to achieve the objective to maximise exploitation of the existing hydropower potential as well as future revenues of the plant. For this purpose and to satisfy approval requirements for a complex hydropower development, it is imperative at planning stage, that the conceptual development contemplates a wide range of influencing design factors and ensures appropriate consideration of all related aspects. Since the majority of technical and economical parameters that are required for detailed and final design cannot be precisely determined at early planning stages, crucial design parameters such as design discharge and hydraulic head have to be examined through an extensive optimisation process. One disadvantage inherent to commonly used deterministic analysis is the lack of objectivity for the selection of input parameters. Moreover, it cannot be ensured that the entire existing parameter ranges and all possible parameter combinations are covered. Probabilistic methods utilise discrete probability distributions or parameter input ranges to cover the entire range of uncertainties resulting from an information deficit during the planning phase and integrate them into the optimisation by means of an alternative calculation method. The investigated method assists with the mathematical assessment and integration of uncertainties into the rational economic appraisal of complex infrastructure projects. The assessment includes an exemplary verification to what extent the Random Set Theory can be utilised for the determination of input parameters that are relevant for the optimisation of hydropower projects and evaluates possible improvements with respect to accuracy and suitability of the calculated results.Die Auslegung von Wasserkraftanlagen stellt einen komplexen Planungsablauf dar, mit dem Ziel das vorhandene Wasserkraftpotential möglichst vollständig zu nutzen und künftige, wirtschaftliche Erträge der Kraftanlage zu maximieren. Um dies zu erreichen und gleichzeitig die Genehmigungsfähigkeit eines komplexen Wasserkraftprojektes zu gewährleisten, besteht hierbei die zwingende Notwendigkeit eine Vielzahl für die Konzepterstellung relevanter Einflussfaktoren zu erfassen und in der Projektplanungsphase hinreichend zu berücksichtigen. In frühen Planungsstadien kann ein Großteil der für die Detailplanung entscheidenden, technischen und wirtschaftlichen Parameter meist nicht exakt bestimmt werden, wodurch maßgebende Designparameter der Wasserkraftanlage, wie Durchfluss und Fallhöhe, einen umfangreichen Optimierungsprozess durchlaufen müssen. Ein Nachteil gebräuchlicher, deterministischer Berechnungsansätze besteht in der zumeist unzureichenden Objektivität bei der Bestimmung der Eingangsparameter, sowie der Tatsache, dass die Erfassung der Parameter in ihrer gesamten Streubreite und sämtlichen, maßgeblichen Parameterkombinationen nicht sichergestellt werden kann. Probabilistische Verfahren verwenden Eingangsparameter in ihrer statistischen Verteilung bzw. in Form von Bandbreiten, mit dem Ziel, Unsicherheiten, die sich aus dem in der Planungsphase unausweichlichen Informationsdefizit ergeben, durch Anwendung einer alternativen Berechnungsmethode mathematisch zu erfassen und in die Berechnung einzubeziehen. Die untersuchte Vorgehensweise trägt dazu bei, aus einem Informationsdefizit resultierende Unschärfen bei der wirtschaftlichen Beurteilung komplexer Infrastrukturprojekte objektiv bzw. mathematisch zu erfassen und in den Planungsprozess einzubeziehen. Es erfolgt eine Beurteilung und beispielhafte Überprüfung, inwiefern die Random Set Methode bei Bestimmung der für den Optimierungsprozess von Wasserkraftanlagen relevanten Eingangsgrößen Anwendung finden kann und in wieweit sich hieraus Verbesserungen hinsichtlich Genauigkeit und Aussagekraft der Berechnungsergebnisse ergeben