Study of rock drillability evaluation based on drilling parameters of cutting rig

Accurate assessment of mechanical properties and interface information in layered rock formations is crucial for informed decision-making in geotechnical engineering. In this study, we investigated the rock drillability distribution to determine interface information in layered rock masses. Using a self-developed digital rotary drilling system, we conducted indoor experiments on layered rock masses with varying strength grades. We proposed a rock drillability index (Ld) based on the correlation between drilling specific energy and penetration rate, and analysed its variation within the rock mass. Our results demonstrate significant fluctuations in Ld across rock strata, particularly at interfaces, indicating high sensitivity to interface recognition. Additionally, we found that Ld has a positive relationship with penetration rate and a negative correlation with rock strength, reflecting both the rock's resistance to drilling damage and the interaction between the rock formation and drilling rig. In conclusion, Ld accurately identifies layered rock mass interfaces and establishes the relationship between drillability and rock strength. This study provides a theoretical framework and methodology for the application of digital drilling technology in engineering rock masses. [Received: March 20, 2023; Accepted: January 10, 2024]