Optimization of Hole Distribution and Delay Time in Blasting Excavation of Mine Roadway

In order to improve the effectiveness of mining roadway blasting excavation and reduce the damage of blasting vibration, the method combined field blasting tests, blasting vibration monitoring tests, and numerical simulation analysis was adopted. The allocation of actual holes and vacant holes was determined according to the utilization rate of the blasting hole. The reasonable delay time was determined based on the peak of particle vibration velocity. At the same time, a numerical model was established based on the size of the roadway and the physical and mechanical properties of both the roadway and the surrounding rock. Based on the material parameters, the impact of roadway blasting excavation on the surrounding rock structure was analyzed using ANSYS/LS-DYNA numerical simulation software. The research findings demonstrate that employing the layout method of central real holes coupled with surrounding empty holes for roadway blasting excavation results in a utilization rate of cut holes exceeding 96%, with the highest utilization rate reaching 97.9%. This indicates that the strategic arrangement of real and empty holes can significantly enhance the efficiency of blasting excavation. Besides, when the delay time increased from 50 ms to 75 ms, the attenuation rate of the peak of particle vibration velocity exceeded 20% at the same position. When the delay time was 100 ms, the peak particle vibration velocity decreased to 2.97 cm/s at 25 m, indicating that the delay time can significantly reduce the damage caused by blasting vibration. Meanwhile, when the layout of central real holes and surrounding empty holes with a delay time of 100 ms was employed to analyze the surrounding rock structure during roadway blasting excavation through numerical simulation, it was observed that a tensile stress of 9.1 MPa was generated at the arch crown position within a 1-meter range from the roadway section. Tensile stress greater than 5 MPa was present at the arch waist position within a range of 1 to 4 m. Therefore, it is recommended to add steel frame support to the arch crown position and spray concrete on the arch waist position.