• A semi-theoretical method for deriving roof characteristic curves in room-and-pillar mining was proposed and validated against laboratory similar tests, showing good agreement.
• Pre-stressed expandable props outperform natural pillars and concrete props as yielding supports, effectively controlling roof deformation and preventing collapse.
• The weakening factor for the plastic zone in the roof characteristic curve was estimated at 0.75, providing a quantitative basis for support design.
• The study offers practical insights for optimizing support strategies, enhancing safety and efficiency in room-and-pillar mining operations.