Study on the symmetric bilinear initiating technique of deep-hole boulder blasting in the TBM tunnel excavation

摘要

The excavation of the deep-buried tunnel with tunnel boring machines (TBM) is often affected by boulder, which harm the cutter disc of the TBM. It is sometimes difficult to achieve the ideal blasting effect by the conventional blasting technology. In this study, a novel symmetric bilinear initiating (SBI) technique based on detonation wave collision was proposed to reduce the oversize boulders and improve the construction efficiency. The blasting parameters design and unit consumption of explosive were analyzed by using the empirical formula based on field tests in the Hongyan River Nuclear Power Plant (HRNPP) intake tunnel boulder blasting project. Numerical simulation models of the actual engineering parameters were also developed to reduce the risk of engineering test, and to analyze the detonation wave pressure, shock wave propagation, and crack state distri-bution. The results showed that the SBI technique obviously affects the detonation pressure distribution and crack state compared to the central point initiating (CPI) technique. Furthermore, different treatment methods of boulder were carried out in the field test. The results of rock sample size of the core-drill and TBM advance rate showed that it is possible to form better blasting effect when using SBI technique, and the results of blasting particle velocity also proved that SBI can improve the energy utilization rate of explosive. This study provides a novel method based on SBI system for the boulder blasting to ensure a safe and efficient TBM excavation.