Integrated rotary drilling and hole forming technology and application for deep and large anti-slide piles with hard rock

Abstract:

The efficiency of pile hole formation for deep and large anti-slide piles in hard rock has always been a highly concerning issue in the industry. This study selected the formation of anti-slide pile holes in typical complex mountainous areas with hard rock landslides in southwestern Sichuan as the research subject. It systematically analyzed the traditional drilling pain points in deep hard basalt formations with weakly developed fractures， and designed nine combined rotary drilling hole formation process schemes for on-site pile testing. An analysis and demonstration were conducted from the aspects of drilling efficiency， technical and economic feasibility. The on-site testing and analysis results showed that the integrated hole formation technology of “large torque cutting tooth barrel drilling rotary drilling and stepwise borehole expansion with optimal cutting diameter difference of 0.4m” has the highest drilling efficiency， lowest tool wear， and lowest cost in hard rock formations. It verified the feasibility and efficiency of the high-efficiency rotary drilling stepwise borehole expansion technology for anti-slide piles in hard rock formations. Compared with existing manual hole formation， impact drilling， and one-time rotary drilling， this technology has greatly improved safety， efficiency， and cost. The technology has been successfully applied to the construction of pile foundations for landslides at the rear edge of the relocated Baihetan Town， with an average time consumption of 1.6 hours per meter， which is three times more efficient and 60% percent less costly than the previous improved one-time rotary drilling efficiency. This technology provides an efficient and feasible construction technical solution for the rapid hole formation of water-sensitive and earthquake-sensitive hard rock landslide anti-slide piles under complex geological conditions.

Key words:anti-slide piles;hard rock;rotary drilling;stepwise borehole expansion;integrated drilling;landslide prevention and control