Asymmetric damage mechanism of floor roadway based on zonal damage characteristics of longwall panel floor: a case study

By means of field observation, theoretical analysis, numerical simulation, etc., the zonal failure characteristics of longwall panel 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 ultrasonic wave velocity in the middle of the roadway roof is lower than that on both sides. Under the abutment pressure, there was no large-scale failure in longwall panel floor, while in the compaction stability stage, a large range of compressive shear failure was found in the residual pillar floor. The goaf floor is dominated by tensile failure under the action of unloading. 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; the main reason for the asymmetric failure of the floor roadway is the different failure modes of the rock mass on both sides of the roadway. According to the failure mechanism of floor roadway, the asymmetric support measure is proposed.