Advanced method for integrating weak shear layer disruption into slope stability assessment

In Australian open cut coal mines, floor disruption blasting is emerging as a promising technique for mitigating low wall failures by disturbing the continuity of shear planes within weak geological layers. However, the mechanisms governing its effectiveness remain poorly understood, and methodologies for optimising its design are not yet established. In this study, we present a mechanistic framework for integrating disruption effects into slope stability assessment. First, a blast modelling tool is calibrated using full-scale, mine-specific data. Then, the tool is applied to simulate a range of geological configurations and charging conditions, enabling quantification of blasting-induced disruption. To characterise the disruption, the concept of shear layer roughness is introduced, and dimensional analysis is conducted to establish a predictive model for roughness development. Finally, slope stability analyses are performed by incorporating post-blasting shear layers with varying roughness to evaluate their influence on the Factor of Safety (FoS). Results indicate that surface heave alone is not a reliable indicator of subsurface disruption. Disruption intensity increases when explosive charges are placed below the weak layer, but the effect diminishes as the distance between the layer and the charge increases. Quantitatively, FoS improves systematically with increasing shear layer roughness, weak layers with predicted roughness of 0.75 m achieved up to 13.2% greater FoS compared to undisrupted weak layers. This work provides a novel methodology that integrates blast-induced shear layer disruption with slope stability assessment, offering a scientific basis for the evaluation and optimisation of floor disruption blasting in coal mining operations.