Study on borehole stabilization technology in directional drilling of raise boring machine

In unfavorable geology,pilot hole drilling of raise boring machines is often susceptible to sticking and hole collapse due to the instability of the surrounding rock. This study presents a coupled mechanical model of a steerable rib and borehole to investigate the influencing factors and rules of contact stress and the deformation characteristics of surrounding rock during directional deviation correction. The study also proposes a stability control technology for surrounding rock in rotary directional drilling of raise boring machines. Theoretical calculations and ANSYS Workbench numerical simulations were performed to evaluate the effectiveness of 15°+30° chamfers,which are found to be better than normal chamfers in reducing contact stress and deformation of surrounding rock. The surrounding rock stability technology,including dynamic drilling parameters,reasonable distribution of guiding force,and optimized rib structures,can effectively reduce the risk of sticking and hole collapse caused by steerable ribs falling into the borehole in unfavorable geology. This research provides valuable insights for raise boring projects in soft strata.