## 5 Numerical Modeling of the Vertical Section of the Cava Madre Cavern
The results that can be obtained from the calculation are useful for verifying the behavior of the containment structures of the side walls that are already present and also the ones foreseen in the future in the entrance area. The evaluation of the internal stress induced in these structures by the foreseen mining activities is, in fact, important in order to understand the adequacy of the existing ones to withstand the effects of further excavations and to be able to correctly design the future support and containment structures of the walls. Figures 9-15 show the horizontal displacements, horizontal stresses, and plastic zones detected in the numerical model corresponding to Phase 6 (current situation) and Phase 9 (at the end of the activities envisaged in the exploitation plan for the future), respectively. Figure 9: Horizontal displacements obtained by the numerical modeling of the Cava Madre cavern at Phase 6 (current situation). Numerical terms provided as “4.00E-03” mean “4 \(\times\) 10\({}^{-3}\)”. Figure 11: Plastic zones obtained by the numerical modeling of the Cava Madre cavern at Phase 6 (current situation). Numerical terms provided as \"4.00E-03\" mean \"4 \(\times\) 10\({}^{-3}\)\(\sigma\). Figure 10: Horizontal stresses obtained by the numerical modeling of the Cava Madre cavern at Phase 6 (current situation). Numerical terms provided as \"4.00E-03\" mean \"4 \(\times\) 10\({}^{-3}\)\(\sigma\). Figure 12: Horizontal displacements obtained by the numerical modeling of the Cava Madre cavern at Phase 9 (at the end of the activities envisaged in the exploitation plan for the future). Figure 13: Horizontal stresses obtained by the numerical modeling of the Cava Madre cavern at Phase 9 (at the end of the activities envisaged in the exploitation plan for the future). Figure 14: Plastic zones obtained by the numerical modeling of the Cava Madre cavern at Phase 9 (at the end of the activities envisaged in the exploitation plan for the future). Figure 15: Horizontal stresses in the concrete strut-beams obtained by the numerical modeling of the Cava Madre cavern at Phase 9 (at the end of the activities envisaged in the exploitation plan for the future). Numerical terms provided as “4.00E-03” mean “4\(\times\) 10\({}^{-3\prime}\). At the current stage of mining activities (Figures 9 and 10, modeling Phase 6), the horizontal movements are contained within a few millimeters (maximum 6 mm on the left side and maximum 4 mm on the right side) (Figure 9), thanks to the presence of the new strut beams built at the beginning of the century. The horizontal stresses indicate values lower than 4 MPa in the area above the cap and values slightly higher than 4 MPa on the foot of the cavern (Figure 10). In the current condition, a certain destressing of the right wall of the cavern can be detected. Moreover, a regular localized concentration of stresses at the edges can be seen. The presence of limited plastic areas is noted on both the left and right walls of the cavern (Figure 11). Most of the rock surrounding the cavern in the entrance area exhibits an elastic behavior under current conditions. From Figure 11, it is possible to notice an intense plasticization of the band of fractured material with low mechanical characteristics on the left side of the cave (material No. 2 in Figure 3 and Table 1). This presence, however, does not significantly disturb the stress conditions of the rock in the area close to the left wall. Even at the end of Phase 9 the plastic zones do not increase around the contour of the cavern. The horizontal displacements rise to a maximum of 10 mm on the left wall and 5 mm on the right wall, remaining, however, at low values (Figure 12). The horizontal stresses reach 5 MPa both in the cap and below the foot of the cavern, but still remain contained and below the rock mass strength (Figure 13). Even at the end of Phase 9, the plastic zones are limited to very small portions of rock on the contour of the cavern profile, where some high levels of stress are concentrated (Figure 14).