Optimization of staggered distance of coal pillars in multiseam mining: Theoretical analysis and numerical simulation

• Published in: Energy science & engineering 2021-03, Vol.9 (3), p.357-374
• Main Authors: Sun, Xueyang, Lu, Mingjiao, Li, Cheng
• Format: Article
• Language: English
• Subjects: Coal mines; Coal mining; Loss reduction; Mathematical models; multiseam; numerical simulation; optimal staggered distance; Optimization; Retention; Shear strength; Simulation; slip line field theory; Slip line fields; Stress concentration; Subsidence; subsidence coefficient; Theoretical analysis
• ISSN: 2050-0505; 2050-0505
• DOI: 10.1002/ese3.824

Aimed at solving problems related to water retention and loss reduction in multiseam mining, a mechanical model of staggered distance mining was established. First, elastic and plastic slip line field theories were used to calculate the reasonable staggered distance expressions of multiseam mining. The staggered distance schemes of multiseam mining were optimized using the numerical simulation software FLAC3D. By performing an experiment comparing similar materials, the influence on water retention and loss reduction by optimal and unfavorable staggered distance schemes in multiseam mining was explored. The results showed that the σzz curve was distributed in the shape of a “peak” of the staggering distance coal pillars, the Z displacement curve was a “Л,” and the surface subsidence curve was a “W.” Each of these displayed the rule of “decrease then increase.” In staggered distance multiseam mining, the optimal staggered distance value for coal seam Nos. 2 and 3 was 40 m, while the most unfavorable staggered distance value was 0 m. The corresponding subsidence coefficients of the optimal staggered distance values were 0.29, 0.23, and 0.19, under the condition of keeping the optimal staggered distance value for coal seam Nos. 1 and 2 unchanged. These results could be beneficial in reduction of surface subsidence and may also have specific practical engineering significance. A mechanical model of staggered distance mining was established. First, elastic and plastic slip line field theories were used to calculate the reasonable staggered distance expressions of multiseam mining. The staggered distance schemes of multiseam mining were optimized using the numerical simulation software FLAC3D.