## 6 Conclusions  
Based on the conducted study, the conclusions can be inferred as follows:  
* The top-to-bottom deepening method was chosen for Shaft II at the Borynia Mine due to its advantages in maintaining operational continuity and excavation stability. This approach allowed for controlled shaft sinking from a sub-level, ensuring safe working conditions despite the challenging geological environment. The method was selected  
Figure 9: Actual view of the hoisting machine chamber supported with primary support (in the foreground) and secondary support (in the background). based on past experiences in Polish mining, where bottom-to-top techniques have seen limited application due to unfavorable rock mass conditions and logistical constraints. * The mechanical properties of the rock mass were determined using borehole data, geological profiles, and in situ observations. The classification of surrounding formations was carried out using the Rock Mass Rating (RMR) and Geological Strength Index (GSI), providing estimates for key parameters such as rock mass cohesion, internal friction angle, and deformation modulus. These values formed the basis for subsequent analytical and numerical analyses. * The support pressure was initially estimated using a closed-form method, based on elasto-plastic strain-softening model. The Mohr-Coulomb failure criterion was applied to estimate the transition between elastic and plastic zones, allowing for an assessment of rock mass response to excavation. The analytical approach provided a first estimate of the expected load on the support system, used subsequently in further calculations. * The primary support system, consisting of yielding steel arches equipped with sliding joints, was designed based on numerical calculations of bending moments and axial forces in frame models. The optimal steel set spacing was determined to ensure required load-bearing capacity while maintaining cost-effectiveness. Additionally, the secondary support system, comprising aforementioned steel sets embedded in fiber-reinforced shotcrete, was designed based on its compressive and shear strength, ensuring long-term excavation stability. * Two-dimensional finite element models (FEM) were developed to analyze stress distribution and state of deformation around analyzed excavations. The model incorporated pre-mining stress conditions, excavation sequence effects, and rock mass properties derived from empirical classification systems. To simulate the gradual formation of the plastic zone, a longitudinal displacement profile (LDP) was applied, allowing for a more realistic assessment of ground-support interaction. * The primary and secondary support systems were evaluated through numerical simulations. The analysis confirmed that the selected steel arches with sliding joints maintained stability under expected loads, while the composite support system of shotcrete and steel reinforcements provided long-term structural integrity. The numerical results validated the analytical calculations, ensuring that the adopted design met safety requirements. * The proposed excavation and support designs were successfully implemented during the excavation of auxiliary workings for the deepening of Shaft II. The pilot drift expansion method was applied to ensure controlled stress redistribution and maximize operational safety. In situ observations confirmed that the implemented support system performed as expected, preventing excessive deformation or rock mass failure. The results demonstrate the effectiveness of the combined analytical and numerical design approach for the design of deep mining excavations. Conceptualization, A.D. and D.P., methodology, A.O. and P.D., formal analysis, A.D., project administration, P.K., supervision, P.K. and D.P., validation, P.K. and D.P., writing--original draft, A.O. and P.D., writing--review and editing, P.K. and A.O. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable.