Experimental and numerical studies on rock damage law in straight-hole cut blasting under biaxial confining pressure

Abstract

To study the relationships between rock mass crack propagation and damage and confining pressure under blast impact loading during straight-hole cut blasting, tests were performed under different confining pressures. Then, the characteristics of rock mass crack development were analyzed, and the pressure resistance values of core samples before and after blasting were compared to study the trends of rock mass damage. Moreover, a three-dimensional numerical simulation model was established by LS-DYNA to analyze the stress wave propagation, cavity shape and crack propagation characteristics under different confining pressures. The propagation of rock blasting cracks is negatively correlated with the confining pressure. The greater the confining pressure, the shorter the crack development time. Additionally, the crack width is reduced from 0.4-1.7 to 0.04-1.4 mm, and the length is shortened from 280 to 120 mm. A comparison of the compressive strength revealed that blasting reduces the compressive strength of the rock mass. The greater the distance from the explosion source, the lower the degree of strength attenuation. An increase in the confining pressure can inhibit strength attenuation. Numerical simulations revealed that under the same confining pressure, the stress first peaks at the bottom of the blast hole. The greater the confining pressure, the longer the stress peak duration, the smaller the cavity volume, and the shorter the crack propagation length and depth. Under a confining pressure of 4 MPa, the longest crack was only 154.5 mm in length and 102 mm in depth. The research results provide a scientific basis for controlling rock damage and optimizing design in the excavation of deep rock roadways by blasting.

Keywords

Biaxial confining pressure / Straight-hole cut blasting / Exploded stress wave / Crack growth / Rock damage

Acknowledgment

Funding support: The National Natural Science Foundation of China (No. 51874189), the Shandong Provincial Natural Science Foundation (Nos. ZR2023ME106 and ZR2023ME055), and the Open Fund Project of the Engineering Research Center of the Ministry of Education for Mining Underground Engineering (No. JYBGCZX2021102).

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