## 5 Conclusions  
This contribution is focused on the influence of direction-dependent and nonlinear material behavior of stratified or foliated rock mass on the mechanical response in deep tunneling. For this purpose, the transversely isotropic rock damage plasticity (TI-RDP) model, recently proposed by [PERSON] et al. [32], was used for modeling the combined effects of nonlinear and direction-dependent rock mass behavior in finite element simulations of tunnel advance of a well-monitored stretch of the Brenner Base Tunnel. The TI-RDP model was formulated by a combination of (i) the isotropic RDP model proposed by [PERSON] et al. [9], considering strain hardening, strain softening and the degradation of the material stiffness due to damaging processes and (ii) the approach by [PERSON] [25] for considering the transversely isotropic material behavior of stratified or foliated rock. For obtaining mesh-insensitive results for the softening behavior, the TI-RDP is regularized by an implicit over-nonlocal gradient-enhancement according to [PERSON] et al. [12]. For considering discontinuities such as joints or faults, which are typical for rock mass, an extension of the TI-RDP model from stratified or foliated intact rock to rock mass, following the approach by [PERSON] et al. [6], was presented in this paper. The material parameters of the TI-RDP model for _Innsbruck quartz-phyllite_ were calibrated by means of triaxial compression tests. To this end, 3D finite element simulations of intact rock specimens were conducted for different angles of the foliation planes with respect to the loading direction and different confining pressures. The parameters were identified by means of the experimentally determined load-displacement curves by [PERSON] [51]. It was shown that in spite of the varying loading angles and confining pressures, good agreement of both the load-displacement curves and the failure modes was obtained. Next, a 2D finite element model considering tunnel excavation in _Innsbruck quartz-phyllite_ was set up for a stretch of the Brenner Base Tunnel. Studies on the influence of the anisotropy parameters of the TI-RDP model in a horizontally layered rock mass and the influence of the orientation of the foliation planes on the mechanical response of the rock mass were presented. The results of the latter were compared to the results predicted by the isotropic RDP model. It was demonstrated that the ratio between the uniaxial compressive strength perpendicular and parallel to the foliation planes significantly influences the location of the highly damaged zones. However, it has only a little effect on the maximum displacement magnitude for a horizontally layered rock mass. In the 2D simulations, the ratio between the shear strength in the plane of isotropy and the shear strength in planes perpendicular to the latter had no impact on the location of the highly damaged zones and thus did not influence the direction-dependent behavior. However, it significantly influenced the predicted displacement magnitude along the tunnel perimeter. For determining the influence of the orientation of the foliation planes on the mechanical response of the rock mass, 2D finite element simulations of tunnel excavation were performed for different angles of the foliation planes \(\beta=0^{\circ},30^{\circ},60^{\circ}\) and \(90^{\circ}\). As the formation pattern of shear bands depends on the orientation of the foliation planes, a strongly direction-dependent deformation pattern of the tunnel cross section was obtained. Thus, consideration of the direction-dependent material behavior, particularly with nonlinear stress-strain relations, including strain hardening and softening, is indispensable for predicting the mechanical response of stratified or foliated rock mass in numerical simulations of tunnel excavation.