Experimental investigation of blasting stress wave attenuation in sandstone with columnar charging using high-speed...

The propagation and attenuation characteristics of blast stress waves in geotechnical media directly influence the fracture behavior of the medium and serve as a crucial basis for optimizing blasting parameter design. To examine the attenuation characteristics of cylindrical blast waves in rocks, the indoor blasting experiments were conducted using sandstone with cylindrical charges. Digital image correlation technology was employed to successfully capture the full-field strain evolution around the borehole during blasting, and the strain-time curves of the rock surrounding the borehole were obtained. To account for the influence of blasting stress wave loading rates on dynamic elastic modulus, Split Hopkinson Pressure Bar tests were performed to establish a precise relationship between dynamic elastic modulus and strain rate. By analyzing the attenuation of the peak strain, a stress wave attenuation equation within the fractured zone was developed, and the stress wave attenuation index was examined. The results indicated that the experimental method effectively simulated the blasting process of cylindrical charges. The strain wave propagation was accompanied by energy transformation, where the descending phase of the strain-time curve represented the rapid energy input to the rock near the borehole due to blast loading, whereas the ascending phase reflected the radial release of elastic energy, further promoting the development of circumferential cracks, albeit at a lower energy release rate than the descending phase. As the distance from the blast center increased, both the dynamic elastic modulus and strain rate of the rock under blast loading decreased, leading to differences between the attenuation characteristics of stress waves and strain waves, with the former following a power function decay. The complex nature of stress wave attenuation in rocks was primarily governed by physical attenuation properties, with the physical attenuation index exceeding the geometric attenuation index in crushed and cracked zones. Finally, the accuracy of the stress wave attenuation equation and the reliability of the experimental method were validated by analyzing the fracture morphology of the blasted specimens and the extent of the cracked zone.