double benefit短语¹⁴⁴⁹⁷²⁺² 基本例句 🌏二重效益 A coal mining method with a combination of a slicing and caving, a double benefit in control of water conducted crack zone development and in reduction of coal production cost can be obtained. 对厚煤层采用分层与放顶煤相结合的采煤方法，既可控制导水裂缝带的发育高度，又可降低生产成本。 cnki