Floor heave and control technology of mining roadway in ultra-thick coal seam of Huayang No. 1 Mine

To meet the requirements of surrounding rock control in roadways under the background of increasing deep mining intensity, and to address the prominent problem of floor heave in extra-thick coal seams under high stress and weak floor conditions, thereby improving roadway stability and safety production capacity, it is of great significance to systematically study the mechanisms of floor softening and pressure relief. Taking the 15403 working face of Huayang No.1 Mine as the engineering background, a technical route combining theoretical analysis, numerical simulation, and field tests was adopted. Firstly, a mechanical model of the arc triangular block structure above the coal pillar on the gob side was established to explain the rock stability and floor heave formation mechanism. Based on the slip line field theory, a failure criterion for the soft rock floor was developed. Subsequently, FLAC^3D was used to compare the surrounding rock stress evolution, plastic zone expansion, and floor heave deformation characteristics under the original support scheme and the floor grooving pressure relief scheme. The simulation showed that after grooving, the depth of the floor plastic zone decreased from 1.3 m to 0.35 m, the vertical stress on the coal pillar was reduced from 20.9 MPa to 17.22 MPa, and the floor heave amount decreased from 504 mm to 203 mm. Industrial field tests further verified that the maximum floor heave was reduced to 39 cm, with an average value of 31.05 cm, a decrease of 15.1% compared to the original support conditions. The floor grooving pressure relief technology can significantly optimize the stress structure of the roadway floor and coal pillar, inhibit the expansion of the plastic zone and floor heave deformation, ensure the stability of the roadway in the extra-thick coal seam working face.