坚硬难冒顶板条件下采煤,顶板悬而不冒,可产生大面积来压或冲击地压,造成极大灾害。 因此,坚硬难冒顶板的管理,已引起国内外的极大重视。 一、坚硬难冒顶板特征 坚硬难冒顶板多为砂岩、砂页岩、石灰岩,少数情况为砾岩,抗压强度一般为700～1800公斤/厘米~2。加拿大学者D.F.科茨认为单向抗压强度大于700公斤/厘米~2为坚硬岩石;1800公斤/厘米~2以上为极坚硬岩石。国外坚硬顶板岩石试件抗压强度一般为700～1400公斤/厘米~2。大同矿区顶板岩石的抗压强度为600～1800公斤/厘米~2,北 Hard to take the roof under the conditions of coal mining, roof without hanging, can produce a large area to pressure or impact pressure, causing great disaster. Therefore, the hard-to-roof management has drawn great attention at home and abroad. First, hard hard to take the roof characteristics Hard hard to take roof mostly sandstone, sand shale, limestone, a few cases of conglomerate, compressive strength is generally 700 ~ 1800 kg / cm ~ 2. Canadian scholar D.F. Coates that the unidirectional compressive strength of more than 700 kg / cm ~ 2 as hard rock; 1800 kg / cm ~ 2 for very hard rock. Compressive strength of foreign hard roof rock specimen is generally 700 ~ 1400 kg / cm ~ 2. Datong mine roof rock compressive strength of 600 ~ 1800 kg / cm ~ 2, north