Asymmetric Damage Mechanism of Floor Roadway based on Stope Floor Zonal Damage Characteristics: A Case Study

By means of field observation, theoretical analysis, numerical simulation etc., the zonal failure characteristics of stope floor and the asymmetric failure mechanism of floor roadway were studied. The study results showed that the floor roadway rib near the residual coal pillar has lower ultrasonic wave velocity than the other rib, with more developed fissures. The deflection is larger in the middle of the roadway roof and the tensile failure is the dominant one, and as a result, the ultrasonic wave velocity in the middle of the roadway roof is lower than that on both sides; under the advance abutment pressure, there was no large-scale failure in stope floor, while in the compaction stability stage, a large range of compressive shear failure was found in the residual pillar floor. The mining-induced unloading causes a large tensile stress at the internal defects of the floor rock in the goaf, which leads to the goaf floor dominated by tensile failure; the numerical simulation results revealed that there is a spherical stress concentrated shell and spherical stress relief body in the goaf floor. The shape and range of tensile plastic zone of the goaf floor correspond to the spherical stress relief body, and the shape and range of shear failure zone of the floor correspond to the spherical stress concentrated shell; One side of the floor roadway is close to the rock mass with compressive shear damage and the other side close to the rock mass with unloading-induced tensile damage, which is the main reason for the asymmetric failure of the roadway. According to the asymmetric failure mechanism of the floor roadway, asymmetric support measures are proposed for the roof and floor respectively.