төмрийн хүдэр ба нүүрсний олборлолтын ялгаа
English for Mining Engineers March 2012. Mar 26 2012 The term drilling is used for smaller diameter holes with a few exceptions such as shaft drilling and raise drilling where larger excavations are created by special machines including cluster drilling The majority of blasthole drilling is performed by two primary methods Percussive drilling and Rotary drilling Өрөмдлөг