Burden Effects on Rock Fragmentation and Damage, and Stress Wave Attenuation in Cut Blasting of Large-Diameter Long-Hole Stopes

Cut blasting with single free surface is the first step of the large-diameter long-hole (LDL) mining method, which creates more relief space for subsequent blasting procedures. The minimum burden (W) is a critical factor affecting the cut blasting effect, but its influence on rock fragmentation and damage, and stress wave attenuation is not completely clear. In this study, nine groups of small-scale model tests were designed to explore the effect of W on rock fragmentation and damage, and stress wave attenuation in cut blasting. First, the strain caused by blasting in each model test was measured. Then the degrees of rock fragmentation and rock damage range were calculated. The results show that when the stemming length is the same, with the increase of W, the total mass of the fragments, the maximum fragment size, the mean radius and area of the crater, and the fragmentation energy consumption all first rise and then decrease. As W increases, the fragmentation energy density and fractal dimension both decrease, implying that the rock fragmentation effect becomes worse. The damage factor shows a power function attenuation with the increase of the distance from the explosion source, and the damage radius decreases with the increase of W. When the W is the same, 4 cm stemming improves the utilization rate of fragmentation energy consumption by 2.79–3.58 times compared with no stemming. The tensile strain has a more severe attenuation than the compressive strain, and the reflected tensile wave plays a significant role in the formation of blasting crater. This study is helpful to understand the rock fragmentation and stress wave attenuation in cut blasting of LDL stopes.