Key technology and equipment of hole-forming for surface large diameter borehole in coal mine area

According to the layout of underground roadways, two design methods are proposed for borehole structure based on the different connection modes between large diameter boreholes and underground roadways in mine area. On this basis, in order to improve hole-forming efficiency, combined with the main hole formation process of large-diameter surface drilling in coal mining areas, the theory and engineering summary analysis methods are used to conduct pilot hole drilling, reaming drilling, casing running, and cementing. The key technologies of drilling wells are discussed, typical construction cases were introduced, the status quo of supporting equipment technology was summarized, and the cluster-type pneumatic down-the-hole hammer reverse circulation drilling technology and supporting equipment were analyzed, and the development trend of large-diameter drilling technology and equipment was proposed. The results show that the down-the-hole hammer drilling technology and guide-pipe drilling technology can improve the drilling efficiency of pilot hole, and the air-lift reverse circulation drilling technology and the cluster-type pneumatic down-the-hole hammer reverse circulation drilling technology can increase reaming rate. Casing running by lifting buoyancy method and cementing by interpolation method can meet the requirements for safe casing and cementing quality, the complete set of key technologies and the matching equipment could provide technical support for the rapid hole forming of large-diameter ground drilling in coal mining areas. With the continuous improvement of the technologies and equipment, and the support from National Key Research and Development Program, the air reverse circulation drilling with cluster down-the-hole hammer is expected to become the key drilling technology for surface large diameter borehole in the mine area, and it will ultimately[LM]become the reliable technical system for emergency rescue in mine.