1473 Pilot well reverse drilling and forward drilling process A. Direction al pilot hole drilling using screw drill bit B. Enlargin g the pilot hole using a directio nal drilling rig D. Raise the drill pipe G . Raisehole drilling rig enlarge ment drilling pilot well J . Temporar y support during drilling and well completi on ABDGJL DRBFB construction method （Directional Raise Boring and Forward Boring） Pilot well drilling and blasting well completion technology / / C. Raisedrill rig pilot hole drilling I . Simultan eous Temporar y Support for Excavatio n Using Drill and Blasting Method / CGI RBB construction method （Raise Boring and Blasting） Well completion process of pilot shaft tunneling machine / / E. Rotary steerabl e borehol e drilling with a raise boring machin e K . Temporar y support during tunneling by the tunneling machine M . Perman ent well walls are constru cted from top to bottom using slipform excavati on. EGKM RSDSB construction method （Rotary Steering Drilling and Shaft Boring） 4. CONCLUSION (1) The development and utilization of underground space is an inevitable trend in sustainable development strategies. Leveraging existing transportation systems, safe and efficient well construction can be achieved through mechanical rock-breaking and gravity-driven slag removal technology. This approach facilitates the creation of large-volume underground chambers, where a pilot shaft serves as a slag chute, enabling rapid excavation via large-scale mechanical or blasting methods. (2) The primary constraint on gravity-driven slag removal drilling technology for large-diameter wells is geological conditions. It is suitable for stable rock formations. For water-rich, fractured, or karstdeveloped strata, pre-grouting modification is required for sealing and reinforcement. In weak, unstable, or water-bearing formations, ground freezing provides temporary stabilization to meet drilling requirements. (3) The advancement of mechanical rock-breaking drilling technology and equipment for largediameter wells has accelerated underground mineral extraction and subsurface engineering in China. Gravity-driven slag removal offers significant energy-saving and cost advantages. Continued innovation in technology, processes, and equipment is essential to promote safer, greener, mechanized, and intelligent drilling systems, expanding their application in resource development and underground construction.
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