Research Article
Construction Sequence Optimization and Settlement Control Countermeasures of Metro Tunnels Underpassing Expressway
Table 4
Parameters of the advanced small pipes.
| Small pipes | Length (mm) | Longitudinal spacing (mm) | Circumferential spacing (mm) | Extrapolation angle (°) | Grouting hole | Notes |
| Inner layer | 5 | 2.5 | 0.4 | 40 | Plum blossom arrangement with 0.5 m spacing | Chemical grouting | Outer layer | 3.5 | 2.0 | 0.3 | 10∼15 |
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