Doctor's Theses (authored and supervised):

Ch. Hellmich:
"Shotcrete as Part of the New Austrian Tunneling Method: From Thermochemomechanical Material Modeling to Structural Analysis and Safety Assessment of Tunnels";
Supervisor, Reviewer: H.A. Mang, F.-J Ulm; Institute for Strength of Materials, Vienna University of Technology , Vienna, Austria, 1999.

English abstract:
According to the pertinent literature on the New Austrian Tunneling Method (NATM), the success of this method is strongly based on the rapid hardening characteristics as well as the pronounced creep properties of shotcrete. Because of these properties, the erection of an integrated soil-shotcrete compound structure is possible. Remarkably, the shotcrete is loaded during hydration, i.e., during its chemical `genesis'. This is accounted for in this work by choosing a thermodynamic approach, enabling a physically consistent synthesis of continuum mechanics and physical chemistry, leading, in the end, to a thermochemoplastic material law. Within this approach, the exploration of the intrinsic material behavior, i.e., the behavior independent of field or boundary conditions, is a central issue. This results in a minimization of the involved material parameters, which, moreover, are all linked clearly to distinct chemo-physical properties, resulting from phenomena occurring at the microlevel of the material. Nevertheless, the chosen approach is macroscopic. Hence, all relevant material properties (strength growth, aging elasticity, chemical shrinkage, hydration heat, creep) are determined from standard (macroscopic) experiments or relations given in pertinent standardizations for shotcrete/concrete.

Based on an efficient algorithmic treatment, the material law is implemented into a non-linear Finite Element code, making the law applicable for the solution of real-life engineering problems.

Before tackling such problems, comprehensive numerical studies on the soil-shotcrete interaction governing the NATM are performed. The aim of these studies is to clarify the influence of the governing material properties of shotcrete and soil (e.g., dilatation behavior, creep, shrinkage) on the overall structural behavior of tunnels driven according to the NATM.

Finally, a hybrid method, combining 3D displacement measurements with thermochemomechanical material modelling of shotcrete, is presented, enabling to quantify the stresses in the shotcrete tunnel shell and, thus, allowing to assess the safety of the shell. This is demonstrated by means of 2D and 3D thermochemomechanical Finite Element analyses of the Sieberg tunnel, being part of the high-capacity railway line Vienna-Salzburg.

Keywords: shotcrete, viscoplasticity, @dissertation, chemoplasticity, soil-shotcrete interaction, 3D displacement measurements, New Austrian Tunneling Method, hybrid method, safety assessment of tunnel shel, thermochemomechanical material m

Created from the Publication Database of the Vienna University of Technology.