the underground of coal mine 基本例句 煤矿井下 In the mine drainage system many drainage pumps must work correspondly.摘要在煤矿井下的排水系统中，需要多台排水泵协调地工作。 The State shall take special protective measures for miners working in underground coal mines.国家对煤矿井下作业的职工采取特殊保护措施。