Analysis of the impact of rock joint cracks on blastability of burnt rock in Xinjiang open pit coal mines

In response to the problems of developed rock fractures and unsatisfactory bench blasting effects in open-pit coal mines in Xinjiang, China, By using on-site research, theoretical analysis, numerical simulation and other methods, the main influencing factors of burnt rock blasting are analyzed, and the impact of joint cracks in burnt rock on its blastability is quantitatively evaluated and graded. Research shows: the main influencing factors on the blastability of burnt rock are the density of original rock joint fractures, the length of original rock joint fractures, the radius of crack propagation after blasting, and the peak blasting stress. We have established quantitative mathematical models for various influencing factors, established a classification evaluation model and evaluation standards for the blastability of burnt rocks in Xinjiang region. The comprehensive evaluation index G of blastability is divided into five levels: Level I (G > 20.7) extremely easy to blast, Level II (G = 16.7-20.7) easy to blast, Level III (G = 12.7-16.6) difficult to blast, Level IV (G = 8.7-12.6) difficult to blast, and Level V (G < 8.7) extremely difficult to blast. And a study was conducted on the blastability evaluation and classification of burnt rocks in six open-pit coal mines in Xinjiang region, and the results of blastability classification were obtained: open-pit mine 1: G = 13.3 is level III difficult to blast, open-pit mine 2: G = 13.0 is level III difficult to blast, open-pit mine 3: G = 13.3 is level III difficult to blast, open-pit mine 4: G = 13.1 is level III difficult to blast, open-pit mine 5: G = 12.8 is level III difficult to blast, and open-pit mine 6: G = 12.5 is level IV difficult to blast.