Abstract: Significant floor heave issues arise during the initial mining and roadway retention periods due to the complex stress environments where roof-cutting roadways are situated and their long service periods for retention. The engineering research background drew upon the specific conditions of roof-cutting roadway retaining of 1462(1) track alignment at Dingji Coal Mine in Huainan. A discrete-element numerical calculation model was established to obtain the asymmetric deformation characteristics of the floor and its force state from the primary excavation to the stable stage of roadway retention. Besides, the work constructed the mechanical model of the doubly-clamped twice statically indeterminate floor beam. An equivalent load was introduced to solve the mathematical expression of the floor deflection under each distributed force. The superposition principle was used to derive the deformation expression of the roof-cutting roadway retaining. Roady retaining conditions were utilized to obtain the average floor heave of the roadway (0.74 m) and maximum floor heave (0.77 m). The maximum heaving position was biased to the side of the goaf, 1.15 m from the middle of the roadway. The results were more consistent with the on-site measurements and numerical calculations. Based on the floor deformation expression, the influencing factors of roadway-retaining heave floor were analyzed. The increase in floor heave and floor stiffness exhibited an exponential decrease. When floor stiffness changed at 5−13 MN•m², floor heave in the roadway was more sensitive to its changes. There was a linearly positive correlation between floor heave and the floor load, support load, coal side load, and stress concentration coefficient, with growth rates of 0.082 6, 0.034 9, 0.027 2 m/MPa and 0.007 m/(λ), respectively. The force deformation of roadway-retaining floor and its influencing factors were analyzed to propose the prevention and control countermeasures of “mutual control of roof and floor as well as side and floor reinforcement.” Engineering practice showed that, compared to the initial stage of roadway retention, floor deformation was effectively controlled, with a significant reduction in floor heave. The retained roadway meets the requirements for reuse.

Key words: floor heave mechanism, gob-side entry retaining, roof-cutting pressure relief, floor heave prevention and control