Structure evolution and rockbursts prevention in multi-face mining in geological anomaly area

Aimed at the phenomenon of variable overburden spatial structures and complex disaster factors in multi-face mining in a geological anomaly area of a mine, taking the actual geological occurrence conditions and mining technology conditions as the engineering background, this paper studied the changes rule of overburden spatial migration structures and the distribution characteristics of abutment pressure in the geological anomaly area by theoretical analysis and numerical simulation. Taking single-layer bending thin plate as an example, mechanical models of plates at different mining stages were established, and the characteristics of bending energy release of plates at different mining stages were revealed. Based on the structural regulation theory, the prevention measures of rock burst at the beginning and end of mining were proposed to reduce the collapse span of thick and hard rock strata. The main conclusions were as follows: ①With the successive mining of multiple faces working, the overburden spatial structure evolution of “一” → “S”→ short “Ω”→ irregular “Ω”→ long “Ω” →“O”→shaped overburden spatial structures has been experienced in the area of geological anomalies successively, enriching the types of overburden spatial structure; ②Due to the influence of geological anomalies, more initial pressure and “square” pressure are borne in the mining process of multiple faces working. The dynamic load disturbance and abutment pressure distribution of roof collapse in this area were more complex and changeable, which were easy to cause the risk of overall instability rock bursts of wide coal pillar; ③Based on the mechanical model of single-layer bending thin plate, it was concluded that the bending energy of different plate structures increased exponentially or linearly with the length of the side, and the free edge had a greater influence on the bending energy than the fixed edge; ④The effect test of the pre-pressure relief and danger relief measures showed that there were no big micro-seismic energy events in the working face mining process and the coal body stress remained stable. The structural control measures basically guaranteed the prevention effect of rock burst at the beginning and end of the multi-working face mining in the geological abnormal area.