Theoretical analysis of rockburst prevention in continuous mining and continuous backfilling under complex geological conditions

In order to explore the differential mechanical response mechanism of fully mechanized coal mining and continuous mining and continuous backfilling processes under thick coal seams and fault structures, and to clarify the anti-scouring mechanism of continuous mining and continuous backfilling coal mining under the disturbance effect, the stability and fault slip characteristics of the thick-bottomed coal of the two processes under the disturbance effect were studied by means of theoretical analysis and on-site monitoring. The bottom coal mechanical model and fault mechanics model were established and their disaster mechanism was revealed, the bottom coal impact risk coefficient ηd and the fault instability evaluation index Ic were proposed, and the anti-scouring mechanism of the continuous mining and backfilling process was analyzed by comparing the change characteristics of the two under different coal mining processes, and finally verified by the microseismic measurement results. The results show that the basic conditions for the instability failure of bottom coal are that the horizontal stress is greater than the critical horizontal stress it bears, ηd is negatively correlated with the thickness of the bottom coal z, and the critical mining failure length is 50 m under the continuous mining and continuous backfilling process, which is 69% higher than that of the fully mechanized coal mining process. The basic condition of fault instability and slip is that the cohesion of the rock layer on the fault plane is greater than the actual cohesion when the rock layer is in the ultimate failure state, the Ic increases with the increase of the fault dip angle θ and its growth rate shows a nonlinear increasing trend, and the head-on failure distance from the boundary of the fault under the continuous mining and continuous backfilling process is 30 m, which is 100% lower than that of the fully mechanized coal mining process. During the mining of the working face, there was no large-energy event of more than 1×104 J, and the average energy of a single microseismic in each branch roadway showed a gradual increase and a small increase in the initial stage of mining, and the microseismic frequency increased by 270% compared with the far-field stable stage in the near-field active stage of the fault but did not show a step-like increase in high-energy level events. The continuous mining and continuous backfilling; process significantly improves the anti-scouring effect of the working face.