Stage-dependent failure–motion response of layered hard roofs around a gob-side roadway under sequential longwall mining

Sequential longwall extraction subjects gob-side roadways to inherited loading and renewed disturbance, while layered hard roofs respond through movement and discontinuity failure. Stage-aligned FLAC3D and 3DEC models represent a roadway beside a 20-m coal pillar. Adjacent-gob extraction raises peak pillar stress from 10.78 to 22.03 MPa, then adjusts before face passage. Between M20 and P20, stress rises from 23.82 to 26.71 MPa, roof–floor closure from 74.8 to 127.3 mm, and yielding from 3.43% to 10.41%. Lower-roof failed area reaches 766 m2 across 220 subcontacts; 212 lie on the primary gob-edge plane, accounting for 97.64% of failed area. Maximum lower-roof shear displacement increases from 0.9 to 3.9 mm. Within-model ratios are 1.12 (stress), 1.70 (closure), 3.04 (yielding), and 4.40 (maximum shear); area-weighted median and 95th-percentile shear ratios are 1.24 and 3.95. All 20 upper-roof partitions subside further, with matched-point median increments of 98.5–119.3 mm, but no failure is recorded on upper-roof discontinuities under joint network and parameters. These identify a stage-dependent failure–motion contrast over the sampled 40-m face-passage interval, not a resolved temporal onset sequence. Fourteen support-resistance reports provide engineering context rather than validation. The contrast motivates separate observation of roadway convergence, localised lower-roof activation, and higher-roof movement.