Abstract:During the construction of large diameter pumping well crossing multi-layer goaf, the leakage problem of conventional mud rotary drilling and the aperture limited problem of DTH hammer drilling were solved by introducing the DTH hammer and air-cooled roller bit combined drilling technology. The application of this technology in 2 φ550mm pumping wells crossing four-layer goaf indicates that the average drilling speeds of φ350mm DTH percussive drilling and φ550mm air-cooled roller bit reaming are 3.31m/h and 2.27m/h respectively. High drilling efficiency was kept in complex formation with obvious application effects. The paper introduces the application cases of φ550mm large diameter pumping well project in Datong mining area, the practice proves the feasibility of this technology, which can be provided for similar drilling construction.