Numerische Modellierung von Kompensationsinjektionen im Tunnelbau

The subject of this thesis is the numerical modelling of compensation grouting in shallow tunnelling operations. Part of the non-linear constitutive behaviour of soils is the result of stiffness changes due to compaction. For this reason special constitutive models such as Double-Yield and modified Cam-Clay, which incorporate compaction and stiffness changes, are examined for their applicability. For numerical modelling the Finite Difference Programs FLAC and FLAC3D are used. One possibility for modelling displacement grouting is to apply incremental isotropic pressure to injection zones. Soil behaviour in the vicinity of injection points is examined for failure state, the resulting stress states and stiffness. The principles of tunnelling near the surface are examined, special consideration is given to surface settlements and the material properties of the shotcrete liner. An injection geometry, in which the injection holes are drilled radially, originating in the tunnel, is examined. As an alternative to the high stiffnesses of shotcrete liners, required in shallow tunnelling today, the examined measures could allow a reduction of necessary shotcrete stiffness, resulting in thinner liners or greater advance rates of the tunnel.