Searching for the Optimal Parameters of the Thick Steep Seams‘ Under-Level Development Svetlana Kostyuk, Nikolay Bedarev, Oleg Lyubimov and Nikolay Kovalyov E3S Web Conf., 41 (2018) 01002 Published online: 26 June 2018 DOI: 10.1051/e3sconf/20184101002