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Outline
In the process of hot dry rock mining in enhanced geothermal system, high temperature and cyclic cooling will lead to damage the thermal reservoir rock mass, change its physical and mechanical properties as well as microstructure, and affect the permeability of rock mass and mining efficiency. The granite samples after high temperature treatment at 400 ℃ were subjected to cyclic cooling treatment by different cooling methods. The shear permeability tests were carried out under different normal stresses. The shear fracture surface of granite was analyzed by three-dimensional morphology and scanning electron microscopy. The results show that the shear strength and shear displacement of granite increase with the increase of normal stress. The shear strength decreases with the increase of cyclic cooling times, and the shear strength of water-cooled samples decreases more obviously. The cohesive force decreases with the increase of cyclic cooling times, and the internal friction angle does not change significantly. The initial permeability decreases with the increase of normal stress, and the initial permeability of water-cooled samples is 1-2 orders of magnitude higher than that of natural cooling samples. The shear displacement corresponding to the minimum permeability increases firstly and then decreases with the increase of cyclic cooling times, and increases with the increase of normal stress. With the increase of cyclic cooling times, the intergranular cracks of the natural cooling sample increase, the width of the transgranular cracks increases. The secondary cracks of the water-cooled sample increase and crystal fracture occurs. The research results can provide theoretical basis and technical support for hot dry rock mining.
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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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