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Charge structure has an important impact on deep hole blasting effect with a large diameter in thick and large ore bodies. The current charge structure (24.2% air deck length) used in Bangzhong mine of Zhongkai Mining has a serious problem of post-blast impact damage, resulting in blockage, collapse or even scrapping of the latter row of holes, which seriously affects productivity. However, blindly increasing the air deck length ratio has the risk of increasing the boulder yield. Based on the actual explosives and rock parameters of the mine, a study on charging structure optimization was carried out by using the numerical simulation software LSDYNA. The commonly used air spacers were selected as the deck materials. Then, 12 charging structure solutions were designed for numerical simulation with respect to the air deck length ratio, and the relationships between the charging structure and the evaluation indexes (such as the back impact effect, boulder yield, peak particle velocity of free surface and peak effective stress) were obtained. The results show that the peak particle velocity of the free surface and the peak effective stress gradually decrease with the increase of the air deck length ratio. The back impact effect is obvious and the back row of holes may collapse when the air deck length ratio is less than or equal to 30.5%. There is a risk that the boulder yield increases when the air deck length ratio is greater than or equal to 45.3%. The optimal air deck length ratio is 44.2%. The deep hole blasting tests show that the boulder yield of the optimized charge structure is 7.1%, and the back impact effect has been effectively controlled.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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