Effect of borehole deviation on raise formation via long-hole raise blasting

Abstract

During Long-hole raises blasting (LHRB) in underground mines, borehole deviation seriously affects the blasting effect, greatly increases the difficulty of raise formation, and reduces the quality of formed raises. To study the effect of borehole deviation on raise formation via burn cuts blasting mode (BCBM), this study theoretically analysed the effect of borehole deviation on raise formation via blasting, constructed and validated a mechanism model of underground deep hole deviation, revealed the effect pattern of borehole deviation on the formation of Long-hole raises via BCBM under different cut modes, and guided the practice of raise formation via deep hole blasting in mines. The results showed that (1) deviation-inducing rock strata with alternating soft and hard rocks are important causes of borehole deviation in deep holes; (2) under the same geological conditions, the borehole deviation is usually negatively correlated with the borehole diameter; (3) the resistance to borehole deviation of the four-empty-hole barrel cut mode (FECM) is better than that of the single-empty-hole spiral cut mode (SECM),and (4) optimizing the firing order of blasting based on the actual measurement of borehole deviation can significantly improve the quality of raise formation. The results of this study provide a basis for assessing the mechanism of Long-hole deviation and theoretical and practical references for the design of LHRB under the condition of borehole deviation.