Tunneling characteristics of high-strength bedrock stratum pretreated by blasting

The shield cutter cannot effectively break the rock with the slurry shield tunneling in the high-strength granites, while pretreatment of the bedrock by controlled blasting can strictly control the broken block size to enhance stronger rock breaking capacity, but the relationship between tunneling parameters and rock is very complicated during shield construction. Based on the intake tunnel of Taishan Nuclear Power Station, the field parameters are studied to analyze selection features of thrust force and torque of cutter head and tunneling rate. On this basis, the parameter conversion indices FPI, TPI and specific energy are introduced for analysis. The results show that the rock is too hard in the high-strength granites, the thrust force is close to its peak value, however the penetration is lower, it is too difficult to give full play of the torque capacity of the cutter head. The bedrock is destroyed by blasting to a certain extent, thus the slurry shield can take full advantage of its torque force as well as the thrust. In this situation, the tunneling performance is improved. Therefore the thrust and torque are adjusted to better adapt to the strata within the workload scope of the shield machine according to the fragmentation effect of blasting so as to achieve efficient and safe excavation.