基于超欠挖控制的隧道爆破参数优化研究OA

To address the difficulties in controlling overbreak and underbreak and the insufficient stability of initial support caused by improper blasting parameters of drill-and-blast tunnelling in weak surrounding rock,the Ranjiapo Tunnel of the Xi'an-Chongqing High-speed Railway was taken as the engineering background.A combined approach of numerical simulation and field testing was adopted to systematically study the effects of peripheral blasthole spacing and radial decoupling coefficient on overbreak/underbreak and the vibration characteristics of the initial support.The results indicate that when the peripheral blasthole spacing is fixed,the excavation profile control gradually shifts from overbreak to underbreak with the radial decoupling coefficient K increases,and the reasonable range of K is 1.25～1.5;When the radial uncoupling coefficient K=1.25 and the blasthole spacing is 45 cm,the disturbance to the surrounding rock and initial support structure is minimized,achieving the best comprehensive benefits;Field tests further verify the reliability of the optimized scheme,showing that the excavation profile after blasting is well formed,the fragmentation is uniform,and both the maximum overbreak/underbreak and the relative deformation of the initial support meet the specification limits.