1677 1. INTRODUCTION The transition from open-pit to underground mining has become a strategic challenge for medium and long-term mine planning. While mining remains a pillar of economic development (Jianing et al., 2024), sustained demand growth, driven by urbanization, industrial expansion, and technological change, has intensified sustainability challenges across the sector (Jiskani et al., 2022; Pouresmaieli et al., 2023). In this context, there is a growing need to incorporate sustainability criteria explicitly into strategic decisions, beyond approaches focused solely on techno-economic performance (Sahu et al., 2015). Mining impacts on the environment arise through multiple, interrelated mechanisms. In surface mining, the removal and haulage of large volumes of material typically translate into a substantial land footprint and high waste generation, whereas underground mining tends to concentrate extraction on the ore and leave a significant portion of waste rock in situ, potentially reducing the magnitude of surface intervention (Arboleda, 2017; Sahu et al., 2015). Key impacts include changes in topography and land use, habitat degradation and biodiversity loss, and effects associated with waste management and emissions, such as particulate matter, water contamination from runoff and seepage, and effluents such as acid mine drainage (Azapagic, 2004; Dasgupta et al., 2012; Richards, 2002). In areas with multiple nearby operations, these effects may be amplified through spatial accumulation and the presence of large waste disposal facilities (Richards, 2002). Further, across Latin America, accumulated social experience with mining-related socioenvironmental impacts has strengthened risk perceptions and conflict, particularly in territories where water and land sustain livelihoods and local identities (Bastidas-Orrego et al., 2018). This context is especially significant for copper, given its importance in technologies associated with the energy transition. As extraction shifts toward deeper and larger-scale deposits, technical and socioenvironmental complexity increases, reinforcing interest in operational evolution strategies, including the move from open-pit to underground mining (Badakhshan, 2023; Heydari & Osanloo, 2024). However, the literature on open-pit to underground transition decisions tends to address the problem primarily through techno-economic and operational constraints, while socio-environmental criteria are often treated as secondary considerations or lack explicit weighting (Chung, 2016; Xu et al., 2019). This points to a methodological gap: the need for multi-criteria frameworks that can prioritize socio-environmental variables and assign traceable weights based on expert judgment and consistent procedures. Chile provides a particularly relevant case to address this challenge. The north–central zone concentrates a large share of large-scale operations under conditions of high socio-environmental sensitivity, shaped by structural water constraints, fragile ecosystems, nearby communities within areas of influence, and growing exposure to climate hazards (Del Rio et al., 2023; ICMM, 2019). Moreover, Chile’s role in global copper supply increases the broader relevance of its strategic decisions. Sector projections indicate national refined copper production of approximately 5.41 Mt in 2025, peaking around 2027 and stabilizing near 6.0 Mt toward the end of the 2025–2034 period (Cochilco, 2025), reinforcing the need for tools that support robust decisions under multiple pressures. In line with the above, this study proposes the use of the Analytic Hierarchy Process (AHP) to structure, prioritize, and weight socio-environmental variables relevant to transition decisions, based on expert-driven pairwise comparisons with consistency verification. As a core contribution, the study provides a transparent and replicable methodological basis to derive relative weights and a final ranking of socioenvironmental criteria, supporting the construction of an integrated socio-environmental risk indicator as an input for strategic assessments in mine planning. 2. STATE-OF-THE-ART TRANSITION MODELS AND KEY DECISION VARIABLES The decision to transition from open-pit mining to underground mining has historically been addressed through models aimed at determining the optimal switching point under profitability and technical
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