Timber-Support Risk Mitigation Framework (TRF) in underground mining: A mechanistic, cost-benefit and risk assessment approach for artisanal and small-scale mining of critical minerals

Artisanal and small-scale mining (ASM) plays a critical role in supplying critical minerals essential for clean energy, yet underground rock collapse remains a major safety and sustainability challenge. This study proposes the Timber- Support Risk Mitigation Framework ( TRF ), a cost–benefit and risk assessment approach integrating rock mechanistic principles and eco-friendly materials to enhance excavation stability under resource constraints in ASM. Using compression tests and probabilistic analysis, eight timber-based support configurations were evaluated for rock strength improvement, probability of failure ( P _failure ), and installation costs. Additionally, the standard deviation ( SD ) and variance (σ²) were incorporated to quantify the uncertainty of rock strength improvement and utilized to calculate the probability of failure. Results show that a staggered support pattern (SSP) with small-sized soft timber delivers the highest rock mass stability, improving rock strength ( UCS ) by +82 % and reducing P _failure to 0.2, at the lowest cost range of $100–$150 per 1.2 m advance. Conversely, large-sized soft timber in SSP yields minimal strength enhancement (+34 %) and incurs the highest costs ($700–$750) with the highest P _failure of 0.7. Uncertainty analysis also highlights the importance of consistent UCS performance by prioritizing ground support systems for reliable tunnel stability predictions. Practical implementation pathways were also provided, which include local cooperative-led training, micro-grants, standardized permits and timber specifications, and policy integration to institutionalize ground-control practices in ASM. The proposed innovative rock mechanics-based cost-benefit framework, TRF, offers a simple, low-cost decision-making tool for ASM operators, enabling safer, more sustainable extraction of critical minerals.