Research on technology of negative pressure dust removal in leading two-endedlarge-diameter directional drilling and its application

In order to solve the problems such as heavy dust pollution and excessive gas flow during underground roadway excavation in coal mine, we used underground directional drilling technology to drill leading large-diameter two-ended borehole in the space of pre-driven roadway. By putting large-diameter PVC sieve tube into the borehole, with access to negative-pressure drainage pipelines, dust and gas were drained out through the negative pressure during the roadway excavation. Using waterjets and spraying measures jointly during the rock roadway excavation in Xianzhuang Mine in Huaibei, the maximum efficiency of dust suppression is up to 97.2%, which is 3.33 times that by the conventional measures of dust control. In addition, the total pure gas drainage volume during the roadway excavation in Luling Coal Mine is 221 000 m3.The applications show that leading large-diameter two-ended drilling is effective in reducing dust and draining gas, and thus is of great significance to coal mine safety production, improving working environment and increasing construction efficiency.