2142 Figure 5 – CumHits–σ curve showing the identified Kaiser point (σK). Figures 6 and 7 present the estimated in-situ stress levels derived from acoustic emission measurements and Kaiser effect analysis for core samples obtained from boreholes drilled in the roof and sidewalls. Figure 6 – Kaiser stress (σK) versus depth in the borehole for Boreholes drilled in the roof Figure 7– Kaiser stress (σK) versus depth in the borehole for Boreholes drilled in the sidewalls Based on the Kaiser-effect AE tests (loading along the core axis), the estimated stress shows a clear split between roof and sidewall cores. Roof samples (treated here as σv) give mostly moderate-to-high values in BH1, and the highest σK appears in the deeper intervals, which fits a transition from the disturbed zone near the excavation to more representative in-situ conditions. BH2 and BH3 roof dolomite are much lower 0 10000 20000 30000 40000 50000 0.000 5.000 10.000 15.000 20.000 25.000 30.000 35.000 40.000 CumHits σ [MPa] R² = 0.3395 R² = 0.672 R² = 0.7569 R² = 0.7691 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 14 16 18 σK [MPa] Depth in hole [m] BH1 - dolomite BH1-anhydrite BH2-dolomite BH3-dolomite R² = 0.8588 R² = 0.3206 R² = 0.6515 R² = 0.9108 0 5 10 15 20 25 30 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 σK [MPa] Depth in hole [m] BH1- sidewall (anhydrite) BH2- sidewall (anhydrite) BH3- sidewall (sandstone) BH4- sidewall (sandstone)
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