大于300的板开方洞,洞边周围如何增设补强钢筋?
参考答案:每边不少于2根直径不小于12mm且不小于同向被切断纵向钢筋总面积的50%。
The new technology has opened up a very wide _______ of possibilities.
A.extent
B.number
C.collection
D.range
倾斜长壁采煤法有哪些优缺点?适用于什么条件?