Combination optimization and verification of delay timing for column charges driven by coal-rock fragmentation efficiency

WANG Hao; LI Xianglong; HU Tao; LI Haoming; ZHOU Yu; WANG Xiaoping

doi:10.11799/ce202509020

Abstract：Based on the blasting crater theory of cylindrical charges and similarity criteria,a series of single-hole blasting crater tests with variable depths and spacings were designed and carried out on coal bench slopes.Key blasting parameters of the coal-rock mass under experimental conditions were obtained,including the elastic deformation energy coefficient,critical depth ratio,optimal burial depth ratio,and reasonable borehole spacing.According to the square root similarity law of cylindrical charges,it was deduced that for a borehole diameter of 200 mm,the optimal row spacing is 7.60 m and the optimal borehole spacing ranges from 8.38 m to 10.44 m.Combining empirical data from similar projects and actual field conditions,the borehole and row spacing were optimized and finally determined as 9 m and 8 m,respectively.A two-dimensional numerical model was established using ANSYS/LS-DYNA to quantitatively characterize the damage evolution and stress wave propagation in coal-rock under two delay time combinations:42 ms×65 ms and 42 ms×100 ms.On this basis,the control mechanism of delay time on fragmentation uniformity was revealed:the 42 ms×100 ms combination enhances stress wave superposition,significantly expands the fracture network,increases the effective fragmentation area,and thereby improves the uniformity of coal-rock fragmentation.Field industrial trials showed that under the optimized delay timing,the muck pile exhibited a gentle slope morphology with moderate height,visible through cracks on the free surface,suitable looseness,and reduced boulder fraction.Compared with the 42 ms×65 ms combination,the efficiency of electric shovel operations increased by approximately 10%,which is consistent with the numerical simulation results.From the perspectives of energy matching and wave interference,this study enhances the theory of blasting parameter design for cylindrical charges and provides a scientific and economical engineering solution for efficient open-pit coal mining.