Application of Specific Drilling Energy for Rock Mass Characterization During Tunnel Construction

Drilling parameters recorded during drill and blast tunnelling provide continuous and cost-effective information for real-time geotechnical characterization of the ground. By combining thrust, torque, rotation speed, and penetration rate, the specific drilling energy (SE) can be calculated and correlated with intact rock strength and rock mass quality indices. This study evaluates SE as a predictive and decision-support tool through two tunnel case studies excavated in contrasting geological settings, integrating Measure While Drilling (MWD) data with field mapping and laboratory testing to estimate uniaxial compressive strength and rock mass classifications during construction. The results show that SE provides a reliable and continuous indicator of lithological and geomechanical variability, enabling early detection of unfavorable conditions and optimization of excavation and support systems, thereby improving safety, operational efficiency, and construction control in both conventional and mechanized tunnelling.