An integrated geophysical and geotechnical solutions for assessing slope instability challenges in open-pit mining: safeguarding mining operations

Abstract

Pakistan, a country blessed with diverse mineral wealth, has witnessed a rapid expansion of open pit mining operations in recent decades. Open pit mining has long been a cornerstone of the mineral extraction industry of Pakistan, allowing for the extraction of abundant natural resources critical for economic growth of the country. However, the pursuit of these valuable minerals often comes at a steep price, with slope stability issues posing significant challenges to mining operations across the country. This research paper investigates the challenges of slope instability in open-pit mining operations in Pakistan, focusing on the Muhammad Khel Copper Mining Project (MKCMP), using an integrated approach of geophysical and geotechnical investigations. The study first utilizes electrical resistivity tomography (ERT) technique, to comprehend subsurface dynamics critical for mining safety and efficiency. Through strategic ERT profile deployment, the research delineates strata types, traces water seepage patterns, and identifies potential causes of mass sliding. Analysis of four sets of ERT profiles reveals the complex interplay of geological, hydrological, and anthropogenic factors influencing subsurface dynamics. Findings underline the significance of moisture-induced destabilization, directional seepage flow, weak matrices, and cultural changes in driving slope instability within the study area. In addition to geophysical analysis, the paper also incorporates geotechnical investigations to enhance the understanding of slope behavior. The stability of the open-pit mine slopes was assessed using Limit Equilibrium Methods and Generalized Hoek & Brown (GHB) failure criteria in Slide 2D software. The western slope (Unit-I) was found to be more prone to circular failure due to weak rock mass properties and water infiltration, while the southern slope (Unit-II) exhibited lesser instability, with tension cracks and weak upper layers behaving like soil. Two stabilization methods — slope geometry modifications and soil nailing systems — were evaluated for both units. This comprehensive approach, combining geophysical and geotechnical techniques, provides valuable insights into slope instability mechanisms and effective stabilization strategies. The findings emphasize the importance of integrating subsurface analysis with engineering solutions to ensure long-term stability in open-pit mining operations, offering practical recommendations for improving safety and sustainability in Pakistan’s mining industry.