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Figure 5: Corestone intercepted in the temporary northern cut face with residual granitic soil below the corestone.
Current excavation level
Hypothetical failure plane
Figure 4d: Corestone partially intercepting the failure surface, with soil present behind.
Figure 4b: Corestone located within the failure wedge.
Figure 4c: Excavation below an inadequately stabilised corestone, potentially resulting in instability or rock fallout or the requirement for additional/increased density of geonails or grouted anchors below its base.
Figure 4e: Large corestone extending to bulk excavation level but not fully intercepting the failure plane.
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