Characterization of Damage to Adjacent Backfill by Blasting of Slit Packets

In order to accurately regulate the damage effect of slit pack blasting on the backfill of the quarry in deep mines, this study focuses on the damage control mechanism of the peripheral hole spacing (500, 600, 700, 800 mm). Based on the theory of elastic fluctuation and the dynamic propagation characteristics of shock waves in rocky media, the diffusion mechanism of the stress wave under the action of multi-media in the constrained orientation during slit packet blasting is established. Combined with the strong correlation between brittle concrete materials and the damage evolution of the backfill, the cross-media equivalence calibration framework of the Riedel-Hiermaier-Thoma (RHT) intrinsic model is established. Based on the numerical simulation software ANSYS/LS-DYNA, we constructed a multi-media dynamic coupling numerical model of “filling body-mineral body-cutting slit package”, arranged observation points at the junction of filling body-mineral body, and conducted a combined analysis of the peak stress change, the change of the blast vibration velocity, and the damage evolution of the filling body at the observation points. Then, based on the blasting test of the approach and return stage of the neighboring filling body in Jinchuan Three Mining Area, the blasting test of conventional packs, slit packs and different peripheral hole spacing was conducted. The test shows that: slit pack blasting triggers gas-phase jet and strain-energy convergence effects in the unconfined direction, synchronously suppresses the stress and vibration peaks in the confined direction, and achieves directional attenuation of the blasting load on the neighboring filling body; the field test shows that, compared with the conventional charge, the slit pack significantly reduces the degree of damage of the backfill by more than 36%; the degree of blasting damage and the peripheral hole spacing show a negative correlation, and the damage suppression efficiency is improved with the increase of the spacing. The damage suppression efficiency is improved when the spacing increases.