Optimal Design of Presplit Blasting Network of Deep Concave Open-Pit Mine Slope with Heterogeneous Complex Rock Mass

Abstract

To ensure that the mining steps of deep concave open-pit coal mines with heterogeneous complex rock masses in arid areas are safely bounded by the design requirements and form a fixed side wall, to avoid the occurrence of instability and disaster caused by blasting vibration, based on non-homogeneous rock mass structure, lithology characteristics, fracture surface composition, morphology and joints, analysis of fissure development trend, and case studies of wedge-shaped landslide accident caused by blasting vibration, we proposed: (1) The pre-split instantaneous denotation charge is the dosage used for the segment unit charge of the primary blast hole and buffer hole, and it’s used for calculating . Based on this, the time intervals of segmented detonating cord and fuse are calculated and the actual detonating unit charge is decided. (2) Leave lateral free surface on the fixed side boundary and drill inclined blast holes along the slope of the steps, connect detonating cords to the blasting network, multi-point instantaneous detonate uncoupled segmented charge holes, use the pre-crack and fracture surface to reduce the damage caused by the explosion shock wave of the primary and buffer blasting holes. (3) The main blast hole and buffer hole are connected by non-conductive detonating cord and “four-way” blasting network, couple continuous concentrated charge using non-conductive detonating cord and fuse plus or detonator plus segmented ammonium dynamite initiator and expanded ammonium oil charge for millisecond interval detonation. Control the number of blasting holes and unit detonating charge over equal segments of fuse and detonating cord, reduce the impact of close-range blasting vibration of vertical deep holes on fixed side wall and step slope. Results of the blasting experiment show that using the technology of detonating cord in combination with non-conductive detonator’s pre-split hole millisecond differential blasting network plus reserved free face and segmented unit charge detonation, provide 1-2 blasting lateral free face or positive free face, making the blasting effect dispersed around the blasting hole. It has better solved the major safety problem of instability and disaster caused by the blasting effect on the fixed border-to-boundary steps of deep concave open-pit mine in arid region.