Advanced modeling of seepage dynamics and control strategies in thick coal seams under high-confined aquifer conditions: A case study

The hydraulic behavior of the connection between the floor failure area and the aquifer water-conductive zone is considered to be the root cause of mine water inrush disasters. Therefore, unraveling the floor failure mechanism is particularly important for safe coal mining above the high-confined aquifer. This paper estimates the depth of the baseplate failure to be 18.4–27.3 m by combining network parallel electrical methods with drilling visualization technology. The FLAC3D-based numerical model considering the strain hardening of caved rock was established with rigorous calibration and verification. The results showed that the depth of damage to the floor is 23.1 m, and the dominating floor failure mechanism is shear failure caused by the vertical stress exceeding the rock bearing capacity. Moreover, the stress recovery process of the baseplate does not alter the failure morphology of the baseplate. Based on the above research findings, the in-situ floor control technique of the working face No. 4305 is proposed and practiced in the field. Field measurements show that floor control performance is satisfactory with water inflow in the goaf being roughly stable at 50 m 3 /h. Our results can provide useful reference for safe mining above confined aquifer and prevention and mitigation of water-related hazards. ● A quantitative characterization method of floor fractures using MATLAB on the basis of borehole visualization technique was proposed, and it is clear that the development of floor fractures exhibit a negative logarithmic decrease as the drilling depth increase. ● The overburden load is transferred to the floor over the compaction of the caved rock in the goaf, recovering the floor stress environment without altering its failure characteristic. ● The main factors controlling the floor failure are burial depth and working face length, and the floor failure depth increases linearly with the increase of burial depth and working face length. ● The resistance-adding repair technology of the floor water-blocking zone and the resistance-adding modification technology of the aquifer water-conductive zone were proposed. Field practice show that floor control performance is satisfactory with water inflow in the goaf being roughly stable at 50 m 3 /h.