Presently,Many long-wall fully-mechanized faces in shallow depth coal seams are below room and pillar goaf in Shendong mining area. When the working face is advanced out of concentrated coal pillar in upper room and pillar goaf, strong strata behaviors often cause support crushing accident. Aiming at a support crushing accident which happened in Shigetai coal mine of Shenhua group in Shendong mining area, this paper analyses the stress transfer process while mining out of concentrated coal pillar by numerical simulation software FLAC3D. According to the feature, simplifying the roof of upper room and pillar goaf as supporting-beam structure explains mechanism of large area collapse in room and pillar goaf roof. Based on the feature of supporting-beam structure, deep-hole blasting concentrated coal pillar technology is proposed to control the strong strata behaviors in Shigetai coal mine. The blasting control effect is confirmed through characteristics of strata behaviors, growth circumstance of ground crack and multi-point extensometer monitoring results. By using control technology, Shigetai coal mine has been successfully avoided support crushing accident.
Room-and-pillar mining was applied in Shendong mining area before large-scale exploitation, which controlled roof and surface subsidence by remaining coal pillars to support mining. So the roomand- pillar mining is a low mining rate method, and it not only wastes lots of resources but also forms a large area of room and pillar goaf and residual coal pillar. The residual coal pillar would form local stress concentration areas and make below contiguous seam mining much more difficult.
With the increasing exploitation, first primary mineable coal bed in Shendong mining area has been mined-out mainly by room-and-pillar mining. Currently, longwall fully-mechanized mining method is applied in second primary mineable coal bed. Due to close coal seam interval, strong strata behaviors would happen in mining face and even cause support crushing accident; such as accident in Shigetai coal mine of Wulan group (Fangtian Wang et al., 2013; BAI Qingsheng et al., 2012; TU Shi-hao et al., 2011), accident in Daliuta coal mine of Shenhua group (JU Jin-feng & XU Jia-lin, 2010; JU Jin-feng & XU Jia-lin, 2012), accident in Bulianta coal mine of Shenhua group (JU Jin-feng & XU Jia-lin, 2013; JU Jin-feng et al., 2013) and et al.
