Full
Outline
To achieve the mining production capacity of 15 million tons per annum for the transition of open-pit to underground mining project of Sijiaying Iron Mine, the vertical zonal mining method was adopted, and a horizontal isolated pillar was required between the upper and lower mining areas. For improving the overall stability of the mining area, FLAC3D numerical simulation method was used to investigate the evolution characteristics of the stress field, the development law of deformation and failure, and the influence of the horizontal isolation pillar thickness on the surface settlement deformation of the open pit under five different thicknesses. Finally, the safety thickness of horizontal isolated pillar in this mine was determined to be 18 m. The results are concluded as follows. Firstly, with the increase of the thickness of the horizontal isolation pillar, the concentrated stress in the pillar decreases significantly, the distribution of the maximum principal stress tends to be uniform, and the distribution range of tensile stress decreases significantly, mainly in the stope part of the mining panel. Secondly, in the horizontal isolated pillar, the displacement presents an obvious nonlinear decreasing change law with the increase of the pillar thickness. The larger displacement occurs at the position where the pillar is close to the hanging wall of the orebody. When the pillar thickness is 18 m, the maximum displacement is 36.2 mm. Thirdly, the volume of the plastic zone in the pillar shows a nonlinear decreasing trend as the thickness of the horizontal isolation pillar increases. When the pillar thickness is 16 m, the plastic zone is no longer connected. In comparison, when the pillar thickness reaches 18 m, only a small amount of plastic failure occurs locally, and the isolated pillar is in a safe state. Finally, the deformation and settlement amount of the open pit surface gradually decreases with the increase of the thickness of the horizontal isolated pillar, and the position where the maximum displacement occurs is the same as the one where the maximum displacement occurs in the isolated pillar. When the pillar thickness is 18 m, the surface settlement amount of the open pit is 10.8 mm, indicating a good stability.
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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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