Study on the blasting damage of prestressed rock-like specimens with different coupling mediums

•Damage of specimens are investigated by blasting tests with different coupling mediums.•The potential ability of STFs to adjust rock fracture is tested.•The effect of pre-stress on crack extension is studied using fractal theory. The performance of rock blasting is significantly influenced by the coupling medium between the explosive and borehole wall. In this study, two shear-thickening fluids (corn starch suspension (CSS) and silica dioxide suspension (SDS)) and water, were used as coupling mediums. The blasting tests were conducted on cement mortar specimens under coupled blasting load and uniaxial static stresses ranging from 0 to 7.5 MPa at intervals of 2.5 MPa. Fractal theory was employed to analyze the extent of damage, crack extension and fractal characteristics of the 3D reconstructed specimens after blasting. The experimental findings revealed that specimens using SDS showed a decrease in damage followed by an increase with increasing static stress, presenting an opposite trend compared to specimens using CSS. The specimens using water exhibited intermediate results. Furthermore, numerical simulations were performed to understand the stress transmission from explosive transferring coupling medium to rock under blasting loads. The variable viscous characteristics of the coupling medium led to divergence in blast load propagation and decay, directly influencing the damage to the specimen. Under blasting load, CSS with a stronger shear-thickening effect played a beneficial buffering role, reducing the strength of the blasting load and minimizing specimen damage. On the other hand, SDS with a weaker shear-thickening effect demonstrated better stress wave propagation ability compared to water. This was reflected in the higher maximum pressure exerted by SDS, as well as the more uniform distribution of pressure, maximum shear stress, and resultant velocity along the borehole wall. The study also highlighted the potential for adjusting blast stress wave distribution by changing the detonation point's location and emphasized the advantages of CSS and SDS as stemming materials in boreholes.