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In order to study the optimal scheme of staggered distance mining in double coal seam and its influence on the key strata of overburden structure, take the geological conditions of Yushen Mine Area as the background, the optimal scheme was selected from the five simulation schemes of staggered distance mining by the FLAC3D numerical simulation method. Based on the Mohr-Coulomb strength criterion and numerical simulation results, the influence of different staggered distance on the key strata of overburden structure was discussed. The results show that the tensile stress of overburden strata on the working face shows a “valley-peak-valley” distribution with double coal seam staggered distance mining, the maximum principal stress in the influence range of staggered distance coal pillar shows a “flat peak” distribution, and the subsidence value shows a “peak” distribution. The optimal staggered distance is 40 m and the most unfavorable staggered distance is 0 m. Through the optimization of the staggered distance scheme of double coal seam mining, the integrity of the key strata of overburden structure can be effectively protected and the failure range of overburden structure can be reduced.

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. [ABSTRACT FROM AUTHOR]