This unit group includes excavating, grading, paving, drilling and blasting contractors who own and operate their own business.
本单元组包括拥有和经营自己生意的挖掘，分级，铺路，钻井和爆破承建商。
2
A new type of close blasting network system of Nonel tube with four-path reflecting unit as a connector has been developed and its application in mining is realized.
文中对一种矿山新型的导爆管反射四通闭合起爆网路系统进行了可靠性试验、分析和现场应用，效果良好。
3
The empirical unit consumption of explosive under special conditions is considered as a proper blasting strength, from which the calculation formula for the blasting of cylindrical charge is derived.