Study on the floor heave mechanism and control technology for the gob-side roadway in the stopping mining area of thick coal seam

Due to the influence of the lateral abutment pressure and the protective coal pillar of the main roadway, the surrounding rock stress environment of the gob-side roadway in the stopping mining area of a thick coal seam is highly complex, making the roadway extremely prone to strata pressure manifestations such as floor heave, with significant differences in floor heave characteristics at different locations. This study focuses on the floor heave of the gob-side roadway in the stopping mining area of a thick coal seam. By adopting a combined research methodology of theoretical analysis, physical similar simulation experiments, numerical simulation, and field tests, a structural mechanical model of the roadway floor in the stopping mining area was established. The differential failure mechanism of floor heave between the gob-adjacent and roadway-adjacent sides of the gob-side roadway was revealed. Quantitative differences in floor heave failure patterns, stress concentration degrees, and plastic zone ranges were comparatively analyzed, and the asymmetric floor heave law of the gob-side roadway in the stopping mining area was clarified. Furthermore, a “pressure relief-reinforcement” control technology was proposed. The research results indicate that: at the gob-adjacent location of the gob-side roadway in the stopping mining area, the extrusion pressure on the solid coal side of the floor is greater than that on the coal pillar side, and the floor on the coal pillar side is squeezed upward, forming asymmetric floor heave biased towards the coal pillar side. Due to the different stress environment, the roadway-adjacent location exhibits the same floor heave pattern but a different magnitude. Through similar simulation experiments and numerical simulations, it was obtained that the floor heave of the gob-side roadway in the stopping mining area is biased towards the coal pillar side, with the degree of floor heave at the gob-adjacent location being more severe than that at the roadway-adjacent location. Stress concentration is located on the solid coal side, with a maximum stress concentration factor of 3.8, which verifies the accuracy of the floor heave mechanism. The study concludes that the high-stress environment is the main driving factor for floor heave. A control technology primarily based on slotting for pressure relief and grouting reinforcement was proposed. Field tests show that the maximum floor heave of the roadway is 45 mm, indicating a good control effect.