Instability Assessment and Control of Floor Abandoned Roadways During Longwall Mining: Coupling of Floor Failure Depth and Plastic Zone Evolution

Floor abandoned roadways (FARs) act as mechanically weak discontinuities in floor strata and may induce severe instability during upper longwall panel face (ULPF) mining, yet the interaction between mining-induced floor failure and FAR plastic zone evolution remains insufficiently quantified. This study develops an analytical framework that combines semi-plane elastic theory, the Mohr–Coulomb criterion, and an equivalent-circular roadway model to link the maximum floor failure depth with the directional plastic-zone boundary of the FAR. Based on their relative geometric relationship, strong-, moderate-, and weak-coupling states are defined for preliminary instability-risk classification and targeted control. For panel #2218, the model predicts a maximum floor failure depth of 6.32 m, while borehole observations and monitored roadway convergence provide field evidence consistent with the predicted damage magnitude and strong-coupling response. The proposed framework provides an explicit and computationally efficient basis for preliminary risk screening and differentiated control of FARs under longwall mining conditions.