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Abstract: The underground nearly-horizontal directional drilling technology and equipments, which are firstly developed by Xi’an Research Institute of China Coal Technology & Engineering Group from 2005, are the most advanced in the industry of mining. The directional drilling equipment came into use in 2008, and up to now has obtained the good effect in China''s coalmine. Three hole-depth records of 1046m, 1059m and 1111.6m have been made continuously in underground in-seam directional drilling. In this paper, the technical contents, features and application of the directional drilling technology and equipments are introduced, the future work and trends are subsequently presented. [Copyright &y& Elsevier]

Abstract: The auger drilling technology and moderate pressure air drilling technology for soft coal seam in underground coal mine are introduced with their corresponding applications. According to the requirements of gas extraction borehole construction and the present status of drilling technology, the drilling problems and the developing trend of new drilling technology in soft coal seam are also discussed. Finally, some suggestions on borehole protection, pulverization dust control in borehole and directional drilling technology by air drilling motor are proposed. [Copyright &y& Elsevier]