Full
Outline
In order to study the degradation law of mining height on the strength of overlying rock, taking the determination of reasonable initial mining height in the initial mining stage of Guojiawan 51208 working face as the background, the fracture density function was used to measure the degradation of mining height on the strength of overlying rock, and the theoretical model and numerical analysis model of the strength degradation of overlying rock under different mining heights were established. Combined with the parameters of the working face, the influence law of mining height on the stability of overlying rock was obtained. The results show that with the increase of mining height, the rotation angle gradually increases, the thickness of the rock layer loaded by the bearing layer gradually decreases, and the rock layer is more prone to rotary deformation and instability. When the advancing length of the working face is 40 m, the maximum displacement of the overlying rock and the plastic zone distribution of the basic roof are basically the same for the mining height of 2.5 m and 4.0 m. When the advancing length of the working face is 50 m and above, the maximum displacement of the overlying rock with a mining height of 4.0 m is more than10%higher than that with a mining height of 2.5 m, and the plastic zone of the basic roof is obviously increased. The peak value of advance support pressure increases with the increase of mining height, and the first weighting step decreases with the increase of mining height. The initial weighting step of 2.5 m mining height is 70 m. The initial mining height is 2.5 m, and the mining height is gradually adjusted to the actual coal thickness（4.0 m）after the first weighting of the main roof. The initial mining of the working face is more efficient and safe. The research results can provide reference for the initial mining roof control problem of the working face.
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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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