In open-pit mining, highwall failure refers to the instability and collapse of a steep and excavated rock face. To avoid dangerous accidents, mines have emergency evacuation plans, which refer to procedures used to evacuate personnel and equipment from hazardous areas quickly. Knowledge of the exact parameters of mining operation that cause the initiation of these life-saving plans is very important in geotechnical risk management.
Highwall instability involves many different geological and environmental conditions. The process of mining affects in-situ stress, which takes some time for the rest of rock mass to attain an equilibrium (Sharon, 2020). The failure mechanisms depend greatly on structural discontinuities, higher pore pressures, and constant weathering processes (Kolapo et al., 2022). For instance, extremely dangerous plane failures are likely to happen in cases when the angle of a discontinuity is smaller than the slope angle but larger than the surface friction angle (Kolapo et al., 2022).
Highwall failure probability is based on ongoing real-time monitoring of the deformation process by the use of sophisticated technology known as Slope Stability Radar (SSR). The first condition in operation is that there must be an increasing displacement rate in the rock face. In geotechnical engineering, an inverse velocity versus time graph is used, and when this curve shows a linear relationship that intersects with the time axis, it indicates impending collapse and determines the predicted failure timeline (Cabrejo, 2013).
The time windows used determine how prediction warnings are set up. When using large time windows such as 24 hours, the deformation process can be detected earlier, giving an alarm in the process (Cabrejo, 2013). However, using smaller time windows such as one hour provides the most recent state of deformation and provides highly accurate predictions of the timing of failure and confirmation of clearing the pit (Cabrejo, 2013).
If the pre-existing thresholds of inverse velocity are exceeded, the emergency evacuation process is set into motion. The forecasted time when the structure would collapse provides a time limit for all the evacuations (Cabrejo, 2013). The immediate steps would involve sounding automatic sirens, stopping the blasting and loading process and leading the staff to safe areas till the risky sector of the pit is cleared off.
To sum up, the effective handling of slope risks requires an integration of both geotechnical monitoring and operational preparedness. Even though some rockfall events may occur with little or no warnings at all, the well-disciplined monitoring system gives enough information for predicting the occurrence of big disasters (Sharon, 2020).
References
Cabrejo, A. (2013). Analysis of failures in open pit mines and consideration of the uncertainty when predicting collapses. Proceedings of the 2013 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, 483–497. https://doi.org/10.36487/acg_rep/1308_31_cabrejo
Kolapo, P., Oniyide, G. O., Said, K. O., Lawal, A. I., Onifade, M., & Munemo, P. (2022). An overview of slope failure in mining operations. Mining, 2(2), 350–384. https://doi.org/10.3390/mining2020019
Sharon, R. (2020). Slope performance monitoring: system design, implementation and quality assurance. Proceedings of the 2020 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, 17–38. https://doi.org/10.36487/acg_repo/2025_0.02
