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Aiming at the problem of reasonable spacing-burden ratio in wide hole spacing blasting technology, laboratory blasting experiments of PMMA plates with the spacing-burden ratios of 1.7, 2.5, 3.5 and 4.5 were carried out based on related rock fragmentation mechanism at home and abroad. Meanwhile, a blasting calculation module was developed to study the crack propagation process and the response law of displacement based on the principle of near-field dynamics of conventional modes. The results show that the radial cracks present the character of branching to the corner of the free face and finally form the main cracks of a funnel shape, affected by the reflected tensile stress wave. Under the condition of fixed minimum resistance line, the stress reduction area gradually increases with the increase of the spacing-burden ratio, and the radial cutthrough cracks between the blastholes in the same row disappeared. An excessive spacing-burden ratio will further cause the disappearance of the cutthrough cracks between two rows of holes, and finally lead to the occurrence of individual hole blasting. The displacement results further confirm the above rule, and the rock ridge left by the front row of holes is just broken by the rear row of holes when the spacing-burden ratio is small. This breaking effect gradually decreases with the increase of the spacing-burden ratio. It is suggested that the spacing-burden ratio should be appropriately adjusted according to the mechanical properties of rock mass, geological conditions and blasting purposes to reduce explosive consumption and boulder yield in practical projects.
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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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