## 4 Summary and Conclusions
* The findings of the deterministic evaluation and probability analysis enabled a quantification of overbreaks using statistical analysis considering the large amount of data obtained for each mapped face: (a) rock mass quality (RMR value), (b) spatial discontinuity orientation, and (c) number of joint sets. * The interpretation of significant trends of the statistical analysis led to the conclusion that any overbreak larger than 2.5 m\({}^{2}\) can be treated as geological, whereas overbreaks smaller than 2.5 m\({}^{2}\) had to be analysed in more detail to determine the interplay between technological and geological overbreaks. * The threshold value of 1.6 m\({}^{2}\) for technological overbreaks was statistically determined if the favourable orientation of the discontinuity coincided with the high quality of the rock mass (e.g., high RMR greater than 60). * In sections in which measured overbreaks were greater than 1.60 m\({}^{2}\) and less than 2.5 m\({}^{2}\), a detailed inspection of geodetic measurements on adjacent profiles showed that overbreaks that were always greater than 1.60 m\({}^{2}\) implied the geological type in most cases. * The volume of technological overbreaks was obtained by combining the volumes attributed to technological causes along the tunnel layout, whereas the volume of geological overbreaks was derived by subtracting the volume of technological overbreaks from the total volume. One of the aims of the deterministic and probabilistic analyses developed as part of the methodology was to check the reliability of the input data that had been gathered during the excavation of the tunnel. It was demonstrated on key examples that the input data gave reliable indications of the types and forms of wedge failure. This was a necessary pre-condition to extrapolate these findings and statistically evaluate the volume quantities for the whole tunnel. In that sense, the reliability of the method was confirmed for the presented case example. In cases in which the input data are poor and/or unreliable, the proposed methodology would establish a poor relationship between calculated and observed behaviour, and the inevitable conclusion would be that the statistical evaluation would not give reliable results and would not be conducted. It can be concluded that the developed methodology was successfully utilised for the given case example of tunnel construction in hard rock. Both deterministic and probabilistic analyses required high-quality site investigation data, including direct shear tests along the representative discontinuity planes. The case for extrapolating the results was based on the relative homogeneity of the rock mass, whereas the accuracy of the methodology was supported by the good agreement between deterministic and probabilistic analyses. Finally, the good compliance of the application enabled quantification by statistical analyses, which considered large amounts of data to calculate overbreak volume by determining the threshold between geological and technological overbreaks. Conceptualisation, Z.B. and V.J. ; methodology, Z.B. and D.B. ; software, Z.B. ; validation, Z.B. and D.B. ; formal analysis, Z.B. ; investigation, Z.B. and D.B. ; resources, D.B. ; data curation, Z.B., D.B. and V.J. ; writing--original draft preparation, Z.B. ; writing--review and editing. V.J. ; visualisation, Z.B. and D.B. ; supervision, V.J. All authors have read and agreed to the published version of the manuscript. This research received no external funding. **Acknowledgments:** The authors express their gratitude to the Ministry of Education, Science and Technological Development of the Republic of Serbia for supporting scientific research, which is essential for the advancement of a knowledge-based society. The authors are thankful to [PERSON] and [PERSON] at the University of Skopje for providing the results of direct shear tests presented in [28]. **Conflicts of Interest:** The authors declare no conflict of interest.