Design and field application of air DTH hammer casing-following drilling for dredging of mine orepasses

Abstract:

The air DTH hammer casing-following drilling technology presents prominent advantages in complex formations drilling. Aiming at the frequent blockage of orepasses that seriously endangers mine safety production， this study takes the severe ore blockage occurring in No.1 orepass of a limestone mine for cement production in Dujiangyan as the research object， combined with the requirements for drilling blasting holes to clear orepass blockages， multiple types multi-dimensional drilling schemes for blasting holes are proposed， including long-distance inclined holes， near-end vertical holes and near-end inclined holes based on the rapid drilling technology of air DTH hammers. Field application results show that the near-end inclined holes were successfully drilled through the blockage sections using concentric DTH hammer casing-following with directional and straight-hole maintaining performance， and the rapid construction of high-precision blasting holes realized effective orepass clearing. For the ZK5 blasting hole， the average drilling rate reached 8 m/h at the interval of 0~68 m and 15 m/h at 68~143 m. The overall drilling efficiency was greatly improved compared with conventional drilling methods. Although open-hole drilling with air DTH hammer achieves fast hole-making， however， swing of the bottom hammer tends to induce significant hole deviation. Drilling trajectories are especially prone to deflection in inclined holes under the effect of gravity and weight-on-bit. Accordingly， an in-hole data acquisition and analysis system is recommended in follow-up research to realize real-time downhole-surface interaction and borehole trajectory control. This study verifies that the concentric air DTH hammer casing-following drilling technology can achieve efficient and precise orepass clearing， providing a solid technical reference for the treatment of orepass blockage in mines.