Abstract: Rib spalling in “three-soft” thick seam with fully-mechanized and large height mining is difficult to control, especially under closed mined gob, and is still a main safety hazard. Based on geological conditions of No.12124 longwall panel in Panbei coal mine and its strata behaviors during initially extracting process, characteristics and factors of coal spalling have been investigated through lab experimental analyzing, theoretical calculating, and computer simulating with FLAC^3D. Strata behaviors, such as modes of coal wall spalling, mining-induced stress evolution characteristics, deformation and breakage area, have been systematically analyzed and obtained during the mining advancement in No.12124 longwall panel and after No.12125 longwall panel was mined. Coal properties, abutment pressure superposition of multiple-seam mining and performance of hydraulic support are the key factors to result in rib spalling. And the rib spalling mechanism with multiple mining-induce stress superposition in closed distance seams under complex geological conditions has been revealed. Technical measures have been proposed and put into practice, such as to increase support resistance, infuse water into coal, and pave double mesh networks. Engineering practice have shown that three technological applications have achieved safety effectiveness and provided references for longwall panel layout, spalling control, and hydraulic support design in similar geological conditions.

Key words: closed-distance coal seams, rib spalling mechanism, mining-induced stress superimposition, rock stability control, double mesh network