Blasting Damage Depth in Layered Jointed Basalt before and after Grouting

This paper compares blasting damage depth in layered jointed basalt before and after grouting. First, a method of determining blasting damage depth in layered jointed basalt is proposed, with a thorough theoretical analysis, and the improvement effect of grouting on damage control in the layered jointed basalt is evaluated quantitatively. The results demonstrate that the reflected tensile stress transmitted back to the previous joint is the key factor for the occurrence of damage. Consolidation grouting could reduce damage depth by 15-35%. The spatial distribution of blasting damage in the layered jointed basalt is then predicted with numerical simulation using the commercial software LS-DYNA. Results reveal that the damage depth estimated based on numerical simulation matches well with that estimated based on the theoretical analysis. Two types of damage zones exist in the layered jointed basalt. Last, a field experiment was implemented to investigate blasting damage depth in layered jointed basalt before and after grouting based on an excavation of the Baihetan high rock slope. Results demonstrate that the depth and degree of damage of the layered jointed basalt were both larger than that of conventional basalt and that grouting could significantly reduce damage depth. The error between the experiment, theoretical calculations, and numerical simulation was within 10%.