Investigating Blast-Induced Damage: A Comprehensive Study of Crack Development Profiles Under Decoupled Charges

Abstract In mining, tunneling, and other blasting applications, excessive rock fracturing can compromise stability and deteriorate environmental and economic outcomes. Predicting the extent of blast-induced cracks is critical to accurately assess structural damage and optimize blast design. Seven blast tests were performed on 150 × 300 mm cylinders with a central blasthole of 280 mm length. PETN cord (5 g/m) was used, and the decoupling ratios ( f ) of 2.5, 4.2, and 5.0 were achieved by varying the blasthole diameters. In this study, qualitative and quantitative aspects of the induced cracks (number, type, velocities, propagation patterns, etc.) were examined using ultra-high-speed (UHS) photography and 2D Digital Image Correlation (DIC) method. Numerical modeling with LS-DYNA was conducted to simulate the experiments, to expand the analysis from 2D to 3D. The experimental results showed that crack initiation, gas ejection, and damage level decreased when increasing the decoupling ratio; notably, no damage occurred when f = 5. Crack propagation velocity using the DIC results showed $$\overline{{V }_{c}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:msub> <mml:mi>V</mml:mi> <mml:mi>c</mml:mi> </mml:msub> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> = (839.40 ± 46.57) m/s. A model for $${V}_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>V</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> from the experimental results was established through curve fitting with a $${R}^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> </mml:math> &gt; 97%. The DIC analysis enabled the distinction of the fracture process zone and the crack tip location. The numerical modeling results provided a realistic estimation of the cracks and damage compared to the experiments. The experimental and numerical results show that increasing the decoupling ratio reduces qualitative and quantitatively the blast-induced cracks, demonstrating how blast-induced damage could be limited.