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R. Lackner, H.A. Mang:
"Cracking in Shotcrete Tunnel Shells";
in: "Proceeding of the 4th International Conference on Fracture Mechanics of Concrete and Concrete Structures (FraMCoS-4)", R. de Borst, J. Mazars, G. Pijaudier-Cabot, J.G.M. van Mier (ed.); Balkema, Rotterdam, 2001, 857 - 870.

In this paper, a material model for the numerical simulation of cracking of shotcrete is presented. Cracking is described by means of a multi-surface chemoplasticity model formulated in the framework of thermodynamics of chemical reactive porous media. The material model is calibrated by means of the fracture energy concept. This concept is extended towards chemoplasticity accounting for early-age cracking of shotcrete and towards consideration of interaction between shotcrete and the reinforcement. The applicability of the material model is demonstrated by means of a numerical analysis of a shotcrete tunnel shell of the Sieberg tunnel, Lower Austria. For this purpose, a hybrid method proposed by Rokahr and Zachow (1997) is reformulated. The term "hybrid" refers to the combination of in situ displacement measurements and a material model for shotcrete. The amount of cracking in the shotcrete shell is investigated. From the obtained stress state, a "level of loading" is computed serving as safety measure of the shell.

Keywords: cracking, shotcrete, fictitious crack concept, tunneling