Full
Outline
The excavation construction of large underground cavern chambers is prone to induce the relaxation of the surrounding rock unloading. Generally, in-situ testing methods are used to determine the relaxation depth during the construction period, but there is a lack of effective means to estimate the relaxation depth during the survey and design stage. Firstly, the characteristics of surrounding rock unloading relaxation in cavern groups are analyzed, and it is pointed out that the adjustment of the stress field is the direct cause driving the macro-mesoscopic evolution of surrounding rock and the decline of bearing capacity. At present, borehole acoustic testing technology and acoustic change rate indicators are mostly used to identify the surrounding rock relaxation depth. The surrounding rock relaxation depth of underground powerhouse for the built hydropower station is generally within 5 m. Then, a quantitative analysis method for rock mass excavation unloading relaxation is established considering damage and deterioration effects, and quantitative indicators and criteria for the evolution of surrounding rock unloading relaxation are proposed. Finally, the assessment of surrounding rock unloading relaxation is carried out for actual projects. It is found that the proposed method and criteria can further quantitatively analyze the degree of surrounding rock disturbed by excavation on the basis of traditional plastic zone indicators, so as to realize more accurate and targeted cavern support design.
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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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