Research Article
New Construction Technology of a Shallow Tunnel in Boulder-Cobble Mixed Grounds
Table 1
∅25 ultimate pull-out strength of bolts.
| Number | Bolt condition | Actual penetration length (m) | Ultimate pull-out strength | Causes of termination | Gripping force corrected value (kN) |
| 3 | Including drill | 1.38 | 62.5 | When loaded to 62.5 kN, it suddenly fell back to 22.1 kN and could not continue to increase | 37.4 | 5 | Including drill | 1.24 | 74.3 | Loading to 74.3 kN reduces the drop to 28 kN | 47.6 | 7 | Including drill | 1.35 | 72.2 | Loading to 72.2 kN reduces the drop to 30.2 kN | 49.9 | 9 | Including drill | 1.50 | 82.5 | Achieves a predetermined value of 100 kN | ≥80.0 | 3 | Excluding drill | 1.71 | 92.2 | Loading to 92.2 kN reduces the drop to 42.0 kN | 70.1 | 4 | Excluding drill | 1.94 | 100 | Achieves a predetermined value of 100 kN | ≥80.0 | 5 | Excluding drill | 1.60 | 86.6 | Loading to 86.6 kN reduces the drop to 38 kN | 64.5 | 6 | Excluding drill | 1.78 | 100 | Achieves a predetermined value of 100 kN | ≥80.0 |
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