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In order to address the floor heave issue during the mining of fully mechanized top-coal caving faces in ultra-thick coal seams, the floor heave mechanism was investigated through field investigations, theoretical analysis, and numerical simulations. Corresponding control technologies were proposed. The ZF1409 working face in a coal mine in Shaanxi province was selected as the engineering case. Key findings include: Severe floor heave predominantly occurs during periodic weighting periods. Higher shield support resistance is observed, particularly in areas with mudstone-dominated floor strata or thin residual coal beneath the floor. The sliding surface of the floor stratum primarily consists of weak mudstone with low ultimate bearing capacity. Floor heave initiates when the applied load exceeds the ultimate bearing capacity. The frictional resistance and cohesion generated by the self-weight of the rock mass along the sliding surface are overcome. Numerical modeling of the ZF1409 face reveals that shield support resistance plays a critical role in floor heave evolution. Under fully mechanized top-coal caving conditions in ultra-thick coal seams, the sudden rupture of the near-field key stratum forms a cantilever beam structure, causing rapid escalation of shield resistance and subsequent floor heave. Implementing underground regional hydraulic fracturing technology to precondition the near-field key stratum effectively mitigates floor heave by optimizing stress redistribution.
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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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