**4.3 Feasibility of excavation**

The results obtained show that:


**Figure 19.**  *SF versus wall thickness (m) for A, B, and C hypotheses of mechanical properties.* 

*Application of Seismic Tomography and Geotechnical Modeling for the Solution of Two Complex… DOI: http://dx.doi.org/10.5772/intechopen.81876* 

 be considered constant (see **Figure 18**) for any wall thickness. The subsequent excavation n.2, corresponding to the removal of a rock portion, determines reductions in the SF (see diagrams in **Figures 18** and **19**) between 30% and 55%. As less thick is the wall as smaller is the SF (see **Figure 20**).

 • The possibility and the ways of carrying out the excavation in front of the wall are linked to the verification of its thickness.

 In summary, in all the cases examined, the execution of the excavation must always be preceded by retaining structures; these must concern only the base of the wall, if only the first excavation will be carried out, or even the rock wall, if the second excavation will be carried out. The retaining structures design will have to consider the effective thickness of the wall and will have most important and binding extension, the lower the measured thickness will be (**Figure 20**).

**Figure 20.**  *SF reduction for the second excavation versus wall thickness (meters).* 
