A.斜眼掏槽 B.直眼掏槽 C.楔形掏槽 D.混合掏槽
A.1 B.2 C.2.5 D.3
A.圍巖破碎不嚴(yán)重 B.地應(yīng)力相對(duì)集電 C.煤層酥松 D.煤質(zhì)堅(jiān)硬