Control technology for hard roof in coal face under magmatic rocks intrusion

The immediate roof is magmatic rocks or some parts of immediate roof have magmatic rocks about two to four meters high above the coal seam about four and thirty meters in wo long hu mine, The length of hanging roof can reach eleven meters. According to analysis on the strata behavior and control method of hard roof under this geological conditions, a method of strengthening the support of cutter roof and artificial caving compulsorily is put forward, the formula of setting load and line density of concentrated props is established, the parameters of strengthen supporting of first roof caving stage and first weighting stage is gave, and the parameters of forced roof caving is determined. Actual measurement shows, the immediate roof can falls after mining and the roof which is affected by magmatic has no hanging or the length of hanging roof is two meter.