Coal Engineering ›› 2025, Vol. 57 ›› Issue (9): 146-155.doi: 10. 11799/ ce202509020

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Combination optimization and verification of cylindrical charge delay time driven by coal-rock crushing efficiency

  

  • Received:2025-04-07 Revised:2025-07-05 Online:2025-09-10 Published:2025-10-13

Abstract:

Based on the cylindrical charge blasting crater theory and similarity criteria, a series of single-hole blasting crater experiments with variable borehole depths and spacings were designed and conducted on coal bench slopes. Key blasting parameters under experimental conditions were obtained, including the elastic deformation energy coefficient, critical depth ratio, optimal burial depth ratio, and rational borehole spacing of the coal-rock mass. According to the square root similarity law for cylindrical charges, the optimal row spacing for 200 mm borehole diameter was derived as 7.60 m (preferred range: 7.26–7.60 m), with an optimal borehole spacing of 8.38–10.44 m. Combining similar engineering experience and field conditions, the optimized borehole × row spacing was determined as 9 m × 8 m. A 2D numerical model using ANSYS/LS-DYNA was established to quantitatively characterize coal-rock damage evolution and stress wave propagation under two delay time sequences (42 ms × 65 ms and 42 ms × 100 ms), revealing the control mechanism of delay time on fragmentation uniformity. The 42 ms × 100 ms sequence enhanced stress wave superposition, significantly expanded the fracture network, increased the effective fragmentation area, and improved coal-rock fragmentation uniformity. Field trials demonstrated that the optimized timing produced a gentle-sloped muck pile with moderate height, visible through-cracks on free surfaces, appropriate looseness, and reduced boulder rates. Compared to the 42 ms × 65 ms sequence, electric shovel operational efficiency increased by approximately 10%, consistent with numerical simulation results. This research advances cylindrical charge blasting parameter design theory from the perspectives of energy matching and wave interference, providing a scientifically robust and economically viable engineering solution for efficient open-pit coal mining. Keywords:Digital Electronic Detonator; Cylindrical Charge; Blasting Crater Experiment; Delay Time Combination; Coal-Rock Fragmentation Efficiency

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