Research on Application of Compound Wedge Cut in Large Section Tunnel Excavation

The blasting effect of cut holes has a significant impact on the overall quality of blasting in large section tunnels. To address the challenges associated with difficult excavation and low utilization rate of blast holes, this study employs a fluid structure coupling algorithm based on ANSYS/LS-DYNA to compare and analyze the internal effective force and damage range between single wedge cut blasting and compound wedge cut blasting. The research findings confirm that compound wedge cut blasting yields better results compared to single wedge cut blasting, providing an explanation for this improved performance. The results indicate that in single wedge cutting, peak stress occurs at the bottom of the hole, gradually decreasing from the bottom to the stemming section before dropping sharply from the stemming section to the palm surface. In contrast, double wedge cutting exhibits higher peak stress values at the bottom of the first level cutting hole compared to single wedge cutting. The damage area cross-sections are found to be similar for both types of cutting models. However, in single wedge cutting models, rock from the blockage section to the palm face area remains unbroken and disconnected. Conversely, in compound wedge cutting models, there is complete connectivity throughout the entire groove cavity. Based on these numerical simulation results, an improved blasting scheme was implemented for a specific highway tunnel project. On-site experiments were conducted accordingly. Compound wedge cuts proved more effective in addressing issues such as low utilization rate of blast holes in large section tunnels and multiple large blocks after blasting.