Influence of Geotechnical Factors on Slope Stability in the Western Bielawy Limestone Open-Pit Mine (Poland)

The stability of the slope is closely related to the safety of mining operations, rational excavation planning, and the optimal utilization of the deposit. The stability of an open-pit mine is controlled by both geotechnical and geological factors. Thus, this study aimed to investigate the influence of complex geological conditions like karst, tectonics, and lithology on the stability of the northern slope of the Western Bielawy limestone open-pit mine in central Poland. The site, located within the Barcin-Piechcin-Pakość limestone deposit, exhibits complex lithological variability, karst features, and tectonic disturbances. An integrated approach, combining laboratory testing, detailed rock mass characterization, and numerical modelling, was employed to assess slope stability. A 3D numerical model of the northern slope was used to evaluate stability under the planned excavation geometry. Numerical simulations, conducted with FLAC 3D software, employed the Modified Shear Strength Reduction Method. The results showed that the initially planned slope geometry yielded a safety factor below acceptable thresholds due to weak, fractured claystones and weathered limestones. By modifying bench widths and reducing the slope angle, the safety factor was improved to meet the minimum required value of 1.30. The study demonstrates the necessity of integrating geological, geotechnical, and numerical methods for reliable slope stability assessments. These findings provide valuable insights for optimizing excavation designs in carbonate formations affected by tectonic and weathering processes.