Dynamic crack propagation of granite subjected to biaxial confining pressure and blast loading

Abstract

To great understanding the dynamic crack propagation of rock under in-situ stress and blasting, the static-dynamic loading experimental platform was built. With different confining pressure 0MPa, 2MPa, 4MPa, 6MPa, 8MPa and different ratios K of horizontal-to-vertical pressure 0, 0.25, 0.5, 0.75, 1 , nine texts have been carried out in quadrate granite samples. The dynamic strain gauges and high-speed HS camera were used to measure strain field and observe crack growth. According to experimental results, the centrosymmetric damage zone is generated around borehole when K 1, the circumference compressive stress is formed by confining pressure, and it reduces the circumference tensile failure by blast loading. The number and size of the broken radius significantly reduce with confining pressure increases. As K decrease from 1 to 0, the tensile stress concentration is obviously around borehole in the vertical direction, and radial cracks grow from the stress concentration zone and develop into boundary under tensile stress wave from blast loading. From the numerical analysis based on Johnson-Holmquist in AUTODYN, crack branching appear near free boundary obviously, meanwhile the radial cracks grow and run through sample by reflected wave at last. Compared to the experimental results, the evolution and final shape of cracks are agree with the experimental results, the central damage area is less than latter because JWL equation neglect the gas loading in numerical calculation.

Johnson–Holmquist-II(JH-2) Constitutive Model for Rock Materials: Parameter Determination and Application in Tunnel Smooth Blasting

“…Ai and Ahrens [26] simulated shock-induced damage in granite targets impacted by projectiles at different velocities using the JH-2 model. Additionally, Ma and An [27], Wei et al [28], Banadaki and Mohanty [29,30], and He and Yang [31] simulated stress-wave-induced fracture in granite due to explosive action using the JH-2 model, and then compared the crack patterns and pressures with lab-scale blast experiments and empirical formulae. However, the simulation methodologies above still remained in two dimensions, which may limit the total presentation for the transmission of stress waves and affect the final blasting results.…”