## 3 Results and Discussion
For the mining conditions as of Year 3 (Figures 6 and 7): on the left-hand side of the advancing face, near the old workings, between the descending galleries J-13/14 and J-15/16 (zone 1) and in the vicinity of development openings in between the descending galleries J-15/16 and J-17/18 (zone 2);
* For the mining conditions as of Year 6 (Figures 8 and 9): on both sides of the advancing face alongside the development openings separated by a cluster of galleries T,W-243, between the panelling line and the descending galleries J-13/14 and J-15/16 (zone 1, zone 2). The fact that the extreme values of elastic strain energy density and of the effort factor are registered over the undisturbed orebody seems unchallenged, chiefly on account of the tensile nature of horizontal stresses. On the other hand, there may be some discrepancies in interpretations of seismicity assessments and analyses (especially in regard to high-energy events). The graphical representation of the maximum-value zones (zone 1, zone 2) will only roughly correspond with graphed foci locations of tremors registered in December in Year 3 (Figures 6 and 7) and in December in Year 6 (Figures 8 and 9). Simulation results covering the moment when the first rockburst occurred reveal the presence of the  
Figure 8: Shear strain energy density (end of Year 6). Figure 9: Effort factor (end of Year 6). maximum-value zones in between the descending galleries J-13/14 and J-15/16 (zone 1) whilst the epicentre of the tremor of 5.1 \(\times\) 10\({}^{7}\) J (followed by an aftershock of 1.3 \(\times\) 10\({}^{6}\) J) was registered in between the galleries J-15/16 and J-17/18 (zone 2 in Figure 6). This state of affairs can possibly be explained in the light of the underlying assumptions whereby seismic activity prior to the rockbursts and its effects on the structure and elastic properties of roof strata should be neglected in numerical simulations. One has to bear in mind that prior to the impact-exerting rockburst, some seismic activity would be already registered in the area, revealed by a number of seismic events in a full range of energies, including the events in the energy class \(\geq\) 10\({}^{7}\) J (Table 2). The effects that high-energy tremors have on rock formations lead to microcracking and rock fracturing, and, consequently, to the weakening of burst-prone strata causing the change of their geomechanical parameters. Recalling the mechanics of deformable bodies, it can be demonstrated that the amount of elastic strain energy accumulated in a fractured medium (a part of which will be released during the fracturing process) should be less than energy accumulated in a fracture-free rock. That is why the elastic strain energy density and the effort values derived for zones overlying the undisturbed rock body might be overestimated. In consequence, in terms of energy release, the main roof at numerically modelled zones might not be able to handle a high-energy tremor. What is more, neglecting the effects of faults with small downthrow might produce reverse effects (i.e., locally underestimated values of respective indices). In the case of tectonic disturbances adjoining the burst-prone layer, there are still unrelieved stresses (and energy changes) due to primary rock deformation. Notwithstanding, the forecasts being developed allow us to draw conclusions at least in qualitative terms, considering that the available set of data on geomechanical parameters of the rock strata is yet limited. Results of the analytical assessment carried out for two considered cases (i.e., mining conditions at the end of Year 3 and Year 6) have revealed the local zones in roof formations above the orebody horizon which are subject to the complex and most unfavourable state of stress. These analyses suggest that high-energy tremors in the energy class 5.1 \(\times\) 10\({}^{7}\) J (end of Year 3) and 1.5 \(\times\) 10\({}^{8}\) J (end of Year 6) might have been caused by failure of strongly deformed main roof layers.