Large deformation mechanism and “stress relief-support reinforcement” synergetic control method of soft rock roadway in footwall of deep normal fault

• Numerical simulation revealed the deformation and failure law of roadway surrounding rock under different fault protection pillar widths in a deep normal fault footwall. • A mechanical model incorporating hanging wall overburden migration and fault slip was established, uncovering the energy-driven mechanism of large deformation. • An energy ratio T (applied to resistant energy of anchored surrounding rock) was defined as a criterion for roadway deformation risk. • The “stress relief-support reinforcement” synergetic control method was implemented, with on-site monitoring confirming its effectiveness.