Performance analysis of parallel hole-cuts based on dimensionless ratios

For over 150 years, a wide array of parallel hole-cut patterns for tunnel driving has been designed, tested, and (successfully) used. The geometrical aspect of the parallel cut problem is crucial, and the paper, in its first part, meticulously analyses the correlations linking dimensionless ratios (characterising the patterns) to performance indicators. This rigorous and comprehensive procedure is the most logical way to derive practical general-purpose design rules from the vast array of successfully used patterns. The statistical basis for this analysis is derived from literature and directly observed cases, further enhancing the reliability of the proposed rules. The second part of the paper delves into the sensitivity of pattern performance to drilling precision, a critical factor in pattern selection. Drawing from literature and observed cases, the paper proposes tolerance standards for drilling machinery related to drilling pattern features and highlights their immediate practical relevance. These standards, when implemented, can significantly improve the efficiency and effectiveness of tunnel excavation, demonstrating the practical relevance of this research. The paper succinctly summarizes the investigation’s key findings in the concluding remarks. It highlights the general guidelines and correlations that have emerged from the analysis. These insights guide future tunnel excavation projects, providing a direction for further research and practical application.