The researchers studied how to safely mine coal seams close together by filling the empty spaces with compacted material. They found that using a specific ratio of compacted material helped control the movement of the ground above the mined area. By analyzing the height of cracks in the ground, they determined that the key factors affecting safety were the compaction ratio and the height of mining. They established a model to predict the safe compaction ratio for mining close-distance coal seams, and successfully implemented it in the Dafosi Coal Mine.