Study of the Mechanical Properties and Failure Mechanism of Annular Coal Rock Based on Acoustic–Optic Combined Monitoring and GDEM Numerical Simulation - Fubin Hou; Hanpeng Wang; Yuguo Zhou; Dekang Sun; Bing Zhang; Junpeng Ma; Jianguo Fan; Yongqing Li; Jinhou Zhang (Rock Mechanics and Rock Engineering, 2026)