Hybrid analysis method for on-line quantification of stress states in tunnel shells

A hybrid method for quantification of the loading of tunnel shells, combining thermochemomechanical material modeling of shotcrete with 3D in situ displacement measurements, is presented. Histories of displacement fields, determined from in situ measurements by suitable interpolation functions, are prescribed on the inner boundary of the tunnel shell. The main goal is determination of the level of loading, amounting to 0% for the unloaded shell and to 100% for the material loaded up (locally) to the compressive strength. For the numerical simulation of the behavior of shotcrete a plane-stress thermochemomechanical material model is employed. Besides aging effects such as chemical shrinkage and increase of strength and stiffness, microcracking and creep are taken into account. The performance of the proposed hybrid method is illustrated by means of applications to the Sieberg tunnel in Lower Austria and the Lainzer tunnel near Vienna, both constituting parts of the high capacity railway line between Vienna and Salzburg.