Mechanical Response of Floor Roadway Under Remnant Coal Pillar with Multi-parameter Characterization

Aiming at the stability problem of surrounding rock in floor roadways affected by remnant coal pillar, mechanical response characteristics of floor strata and roadway surrounding rock under the action of remnant coal pillar was systematically investigated based on a multi-parameter characterization method. First, the bearing structure of remnant coal pillar was modified in combination with the Mohr-Coulomb yield criterion, and a stress distribution model considering the shallow plastic bearing equilibrium zone was established. On this basis, a superposition model of floor stress under the synergistic effect of multiple adjacent sub-coal pillars was constructed. Multiple parameters including stress concentration coefficient k, stress gradient G and lateral pressure coefficient λ were introduced to realize the quantitative characterization of the floor stress field. Secondly, by combining theoretical analysis with FLAC3D numerical simulation, the evolution law of floor stress at different burial depths and the spatial differentiation characteristics of multi-parameters were revealed. Furthermore, a numerical model of the roadway was established to analyze the influence mechanism of single parameters and coupling effects of k, G and λ on the stress and displacement response of surrounding rock. Finally, the deformation law of roadway surrounding rock was verified with field monitoring data. The research indicates that the floor stress presents an obvious non-uniform distribution under the influence of remnant coal pillar. The shallow part suffers intense stress disturbance which decays rapidly with increasing depth. The coupling effect of multi-parameters significantly amplifies the deformation response of surrounding rock and displacement is more sensitive to parameter variations. Roadways located in areas with low values of k and G as well as λ close to 1.0 possess the optimal surrounding rock stability. The research findings can provide theoretical basis and technical support for roadway layout and surrounding rock control under the influence of remnant coal pillar.