Abstract
To thoroughly investigate the degree of surrounding rock damage during the bench blasting process in tunnel engineering, this study takes a certain Grade II surrounding rock as an example, starting from the mechanism of crack generation in a single blasthole, exploring the interaction mechanism between adjacent blastholes and the cutting mechanism of multiple blastholes, thereby forming an analytical system for surrounding rock damage mechanisms. Using ANSYS/LS-DYNA, numerical simulation was conducted for the bench blasting process of this Grade II surrounding rock, investigating the surrounding rock damage under the combined action of stress waves and explosion gases from cutting holes, as well as the surrounding rock damage across the entire bench face. The study found that: the degree of surrounding rock damage exhibits a significant correlation with crack propagation; the strain rate induced by cutting holes in the surrounding rock is lower than that in other sections, but causes damage to develop first at the initial cracks, which is beneficial for improving rock fragmentation efficiency; under reverse initiation conditions, the surrounding rock damage around the bench face is well controlled, and the cutting contour formation effect meets expectations; blasthole spacing directly influences crack development during blasting, where initial cracks form first between blastholes with smaller spacing, but rock fragmentation between blastholes with excessive spacing is non-uniform, resulting in a certain "spatial effect".
Full Text
Preamble
Theoretical Analysis and Numerical Simulation of Surrounding Rock Damage in Stepped Section Blasting for Tunnel Engineering
ZHANG Lei
China Railway 16th Bureau Group Fourth Engineering Co., Ltd., Beijing 101400, China
Abstract
To thoroughly investigate the extent of surrounding rock damage during stepped section blasting in tunnel engineering, this study examines a case of Grade II surrounding rock. Beginning with the mechanism of single-blasthole crack generation, it explores the interaction mechanisms between adjacent blastholes and the cutting action mechanism of multiple blastholes, thereby establishing a comprehensive analytical framework for surrounding rock damage mechanisms. Using ANSYS/LS-DYNA, numerical simulations were conducted on the stepped section blasting process for this Grade II surrounding rock to investigate the damage conditions under the combined action of stress waves and explosion gases from cutting holes, as well as the overall damage distribution across the entire upper bench section.
The research findings reveal a clear correlation between the degree of surrounding rock damage and crack propagation. Although cutting holes generate lower strain rates in the surrounding rock compared to other sections, they initiate damage development at initial crack locations, which proves beneficial for improving rock fragmentation efficiency. Under reverse initiation conditions, the surrounding rock damage around the upper bench section is well controlled, and the cutting contour formation achieves the desired outcome. Blasthole spacing directly influences crack development during blasting: smaller spacings facilitate initial crack formation between blastholes, while excessively large spacings result in non-uniform rock fragmentation, introducing a certain "spatial effect."
Keywords: stepped blasting, surrounding rock damage, initial crack, numerical simulation, "spatial effect"