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In order to analyze the dynamic response of the shield segments during the blasting excavation of a connecting channel, on-site vibration monitoring has been conducted based on the shield interval project of Qingdao Metro Line 8. The measured blasting vibration data show that the cut holes have the strongest impact on the shield segment vibrations. Then, based on the on-site charge of the cut holes, the MIDAS-GTS NX simulation software is used to establish a three-dimensional model to analyze the vibrations and stresses of the shield segments with 8 different blasting distances from the exit and entry of the connecting channel. Compared with the entry blasting, the impact of the exit blasting on the vibrations of the adjacent shield tunnel is more intense under the same blasting distance, and the peak vibration velocity is 2.9~3.4 times that of the entry blasting. On the other hand, the growing rate of the peak vibration velocity also increases with the decrease of the distance. When the allowable vibration velocity is 20 cm·s-1, the blasting distance should be greater than 5.0 m at the exit and greater than 1.25 m at the entry. The rocks that have not been excavated are excavated with non-blasting methods. The stress concentration is the most obvious in the opening segments, but the position where the maximum principal stress is generated shifts from the bottom of the rectangular opening through the intersection of transverse and longitudinal seams on the side of the rectangular opening to the top corners of both sides of the upper part of the rectangular opening with the decrease of spacing. Cutting the segments at the intersection of the connecting channel and the shield tunnel will form an incomplete opening structure, which will weaken the maximum principal stress on its inner side under the blasting load, but will cause a small range of stress concentration on its outer side, making it the weakest position of the shield tunnel lining structure.
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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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