Analysis of the impact of vertical deep hole blasting at the bottom of the hole on the lower ore body based on LS-dyna numerical simulation.

Abstract

With the depletion of shallow resources, the transition from open-pit to underground mining has become an inevitable trend in the mining industry. Although the vertical longhole stage fill mining method is efficient and safe, its second-step stoping blasting is prone to damaging the underlying strategic rare orebody. To quantify the protective effect of the protective layer, this study established a three-dimensional fluid-structure interaction (FSI) numerical model for explosives-rock-backfill interactions using the ANSYS/LS-DYNA platform, based on the case of a large polymetallic mine. Systematic simulations were performed for six protective layer thicknesses ranging from 0.5 to 3.0 m, analyzing the cross-media propagation and attenuation characteristics of blasting stress waves and their dynamic damage mechanism to the underlying orebody.The results indicate that the protective layer thickness is a core parameter controlling damage, showing a significant negative correlation with the peak stress and displacement of the orebody. When the thickness is less than 1.5 m, the orebody response exceeds its damage threshold, leading to irreversible failure. When the thickness is ≥ 1.5 m, the peak stress can be reduced below the orebody's ultimate compressive strength (74.871 MPa), and the displacement response is confined within the slight influence range (0.1-0.3 mm), achieving effective protection. The study innovatively applied the "Post Line Contour Mode" post-processing technique in LS-PrePost to achieve precise quantification of stress gradients and accurate localization of damage boundaries, validating the critical protective thickness of 1.5 m. This research clarifies the buffering mechanism and protection standards of the protective layer, providing a theoretical basis and design reference for safe and efficient coordinated mining of mineral resources under similar conditions.