Blasting Failure Characteristics of Rock Specimens under In-Hole Layered Column Charge

• • Layered in-hole charge increased rock fragment horizontal velocity from 2.0 m·s⁻¹ (continuous) to 7.0 m·s⁻¹, indicating more efficient energy transfer to the upper bench section, which is critical for reducing oversized boulders in production blasting. • • Maximum block size in the top specimen section dropped from 9.0 cm (continuous) to below 5.0 cm (layered), directly addressing the common problem of oversized rocks in the upper part of bench blasts, thereby reducing downstream crushing costs. • • DEM-PBM simulations closely matched experiments, predicting a maximum block size of 8.8 cm for continuous and <5.0 cm for layered charge, with velocity of 6.8 m·s⁻¹, validating the numerical model as a reliable tool for blast design optimization. • • Field-scale application in open-pit coal mine overburden reduced boulder yield from 48.1% to 5.6%, demonstrating that layered charge can dramatically improve fragmentation efficiency and operational productivity in real-world deep-hole blasting.