Evaluation of post-blast damage in cut blasting with varying extra-depths: insights from 2D simulations and 3D experiments

TL;DR

This study investigates how varying extra-depth in cut blasting affects post-blast damage and efficiency, using 2D simulations and 3D experiments to optimize blast design for better borehole utilization.

Contribution

It provides a systematic analysis of the nonlinear effects of extra-depth on blast damage, combining simulations and experiments to optimize blasting parameters.

Findings

Damage increases then decreases with extra-depth

Optimal extra-depth improves rock breakage efficiency

Excessive extra-depth reduces efficiency due to confinement

Abstract

In blasting engineering, borehole utilization is a key metric for evaluating blasting performance. While previous studies have examined the effects of expansion space, cutting design, in-situ stress conditions, and rock properties on borehole utilization, research on the intrinsic relationship between extra-depth defined as the portion of the cut hole extending beyond the depth of auxiliary holes and borehole utilization remains insufficient. This gap in understanding has hindered the resolution of issues such as residual boreholes and unbroken rock at the borehole bottom in deep-hole blasting, thereby limiting improvements in borehole utilization. This study employs a simplified double-hole model for extra-depth cut blasting to conduct two-dimensional numerical simulations and three-dimensional cement mortar model experiments. It systematically investigates the blasting damage characteristics, fractal damage, and energy evolution under varying extra-depth as a single variable. Experimental parameters such as borehole utilization, cavity diameter, cavity volume, and fragment size distribution were obtained to comprehensively analyze the nonlinear effects of extra-depth on post-blast rock damage and its mechanisms. Both simulation and experimental results indicate that blasting damage parameters exhibit a nonlinear trend of initially increasing and then decreasing with increasing extra-depth. Appropriately increasing the extra-depth improves rock breakage efficiency, while excessive extra-depth reduces efficiency due to confinement effects at the borehole bottom. Adjusting the extra-depth can optimize the distribution of explosive energy between rock fragmentation and rock ejection.