Down-hole ø550 mm super large diameter coal seam borehole drilling technology and equipment and its engineering application

For the prpose of improving the gas control efficiency and reduce the cost in the goaf of “U” ventilation face, the ø550 mm super-large diameter borehole was used to replace the cross-heading buried pipe for gas drainage in goaf. According to the characteristics of super-large diameter borehole and the technical problems existed in construction, a ZDY15000LP super-large diameter spiral drilling rig with maximum torque 15000 N·m, maximum penetration 700 kN, and maximum stroke 1.3 m has been developed, which adopted the two-body layout of main engine and pump station, and the innovative design of key parts such as main engine, pump station, mechanical arm and power head of the rig is carried out. The super-large diameter drilling technology based on “pilot borehole + secondary reaming” was developed, the ø426 mm large spiral drill pipe and ø550 mm large diameter reaming bit supporting the super large diameter drilling construction were developed, and a complete set of construction technology and equipment for super-large diameter borehole was studied and formed. The engineering application in Wangpo Coal Mine of Shanxi Tiandi Coal Industry Co. Ltd. shows that the drilling rig has large output torque, good overall stability, cross belt and rapid relocation, and the supporting drilling technology is advanced and reliable, which meet the needs of borehole with super-large diameter forming in coal seam. A total of 17 large-diameter gas drainage boreholes were constructed in working face 3307, with a cumulative footage of 583 m. The drilling construction lasted 30 days, and the comprehensive construction efficiency was increased by 20%. The test results show that the drilling rig has high output torque, good overall stability, and can realize the functions of cross-belt construction and rapid displacement, etc. The performance of the supporting drilling tools is reliable, and the drilling process is highly operable, which can meet the demand of forming holes in large diameter coal seams. The research can provide technology and equipment support for super-large diameter in-seam borehole construction, and provide technical experience for mine gas control under similar geological conditions and mining conditions.