Full
Outline
To address the problems of the determination of the safe thickness and stability of isolated pillars during open-pit to underground mining, taking a domestic metal mine with open-pit to underground mining as the engineering background, dynamic simulation and comparative analysis were carried out on the stopes under the conditions of different isolated pillar thicknesses and different stoping sequences based on the particle safety factor calculation method derived from the twin-shear unified strength theory and numerical simulation. The results are shown as follows. Firstly, when the mining room width is 20 m, the optimal safe thickness of the isolated pillar in the mining room is 39.37 m. At this time, the minimum value of the particle safety factor at the bottom surface of the isolated pillar is 1, which meets the engineering safety requirements. Considering the actual engineering conditions, the isolated pillar thickness is determined to be 40 m. Secondly, the particle safety factor at the bottom surface of the isolated pillar shows a nonlinear growth trend with the increase of thickness, with similar spatial distribution characteristics: the safety factor in the contact area with the hanging wall surrounding rock is lower than that of the footwall, the safety factor at the center of the bottom edge in the width direction of the roof is lower than that at both ends, and the safety factor shows an increasing trend from west to east in the length direction of the roof. Thirdly, mining disturbance leads to the deterioration of the stability of isolated pillars. As the exposed area of the goaf increases, the dangerous range expands accordingly. The closer the particles are to the goaf, the smaller their particle safety factor will be, and the dangerous area migrates from the center of the bottom surface to the midpoint of the long side with the advance of stoping. The proposed thickness optimization method for isolated pillars based on the critical safe thickness threshold and dynamic risk evolution can provide a reference for the problem of determining the safe thickness of isolated pillars in open-pit to underground mining mines.
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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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