Abstract：The lowering of large diameter gas drainage hole casing in coal mine has become the most critical process in the construction process. In order to use the small drilling tower to replace the heavy crane pipe laying process, a set of safe, economic and efficient heavy casing laying process for large-diameter gas drainage holes in coal mines is summarized. Taking the construction of gas direct drainage well in Liangbei Mine of Xuchang Xinlong Mining Industry in Henan Province as an example, based on the principle of ' tunneling buoyancy method ', the various links and data analysis in the process of pipe down are studied. The results show that the use of ' tunneling buoyancy method ' is feasible in the process of placing 246 t casing under 90 t drilling tower, and the safety factor can reach 2.0. Saving crane rental cost 4.25 million yuan, construction period 7 d, whether from the safety, construction period, cost are better than heavy crane pipe process.
