To study the mechanical properties of marble after damage caused by dynamic and static combined loads, the improved split Hopkinson pressure bar device was used to carry out dynamic and static combined load damage tests on marble at four axial compression levels (0, 18 MPa, 36 MPa, 54 MPa) and three impact velocity levels (8 m/s, 9 m/s, 10 m/s). The uniaxial compression acoustic emission tests on the damaged marble was carried out. The results show that under the action of static and dynamic combination, with the increase of axial static pressure, the dynamic peak stress, dynamic elastic modulus and wave velocity of marble increase firstly and then decrease. The absorption energy is closely related to the axial static pressure. When the axial static pressure is low, the energy required for the closure of microcracks in the rock is mainly obtained from the impact bar. With the increase of axial static pressure, the proportion of energy obtained from the impact bar gradually decreases. With the increase of axial static pressure, the uniaxial compressive strength and elastic modulus of rock after damage caused by dynamic and static combined load increase firstly and then decrease. When the axial static pressure is 18 MPa, the uniaxial compressive strength and elastic modulus of rock reach the maximum value. Appropriate axial static pressure can effectively improve the ability of rock to resist dynamic load and reduce rock damage. In the middle and later stages of the uniaxial loading failure process, the less the number of high-frequency acoustic emission signals (>400 kHz) of the rock with small damage degree, the more the number of medium and low-frequency acoustic emission signals (165 - 205 kHz). The proportion of acoustic emission signals at 165−205 kHz increases firstly and then decreases during the whole loading process, which can be used as a precursory feature of rock failure.
| 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 |