between 1930 and 1948 the portion of underground coal that was loaded by machine rose from less than onetenth to nearly two mining allowed for increased supervision, because "it was possible to obtain the desired production with a smaller number of miners and fewer working places than hand mining."14in addition, timbering .
Complex Surface Mining Equipment. Complex surface mining equipment is used directly or as support in the mineral extraction process: Draglines. Shovels. Loaders. Haul Trucks. Highwall Miner. Blasthole Drills. Dozers.