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Author(s):	Walter, H.
Title:
Abstract:	State-of-the-art material laws in numerical models make it possible to integrate the structural design and the ultimate limit state analysis into the numerical model (“Implicit design”). The material laws limit the stresses to values, which the material can bear. Partial factors of safety on the load and resistance sides can also be taken into account. Using the example of a time-independent, 3D mathematical model for an underground railway station with tunnel junctions, which is being constructed by mining in soft soil, this paper investigates to what extent the material laws and the mathematical model fulfill the requirements laid down in the Eurocode for ultimate limit state analysis and how near these results are to the real situation. Some simplifications and weaknesses of the mathematical model are explained, their effect on the results investigated and evaluated in relation to the uncertainties in the characteristics available for materials. Suggestions are made as to how the effects of defects in the model in an unsafe direction can be avoided. Further aspects, which can affect the reliability of calculations, are also pointed out. Hochwertige Stoffgesetze in Berechnungsmodellen erlauben es, die Bemessung und den Tragsicherheitsnachweis in das numerische Modell zu integrieren (“Implizite Bemessung”): Die Stoffgesetze begrenzen die Spannungen auf Werte, die das Material ertragen kann. Auch Teilsicherheitsbeiwerte auf Last- und Widerstandsseite können erfasst werden. Am Beispiel des zeitabhängigen, räumlichen Rechenmodells für eine U-Bahnstation mit Tunnelverschneidungen, die in bergmännischer Bauweise im Lockergestein hergestellt wird, wird untersucht, wie weit die Stoffgesetze und das Rechenmodell die in den Eurocodes festgelegten Anforderungen zum Nachweis der Tragsicherheit erfüllen und wie realitätsnah die Berechnungsergebnisse sind. Es werden einige Vereinfachungen und Schwächen des Rechenmodells beleuchtet, ihre Auswirkungen auf das Ergebnis untersucht und in Relation zu den Unsicherheiten bei den zur Verfügung stehenden Materialkennwerten bewertet. Vorschläge werden unterbreitet, wie Auswirkungen von Modellfehlern auf der unsicheren Seite vermieden werden können. Auf weitere Aspekte, die die Zuverlässigkeit von Berechnungen beeinträchtigen können, wird ebenfalls hingewiesen.
Source:	Geomechanics and Tunnelling 2 (2009), No. 4
Page/s:	319-332
Language of Publication:	English/German

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