Table 3 Statistical table of the hollow grouted rock bolt free length for samples 4#, 5#, and 6#
Sample number | Wave velocity (m/s) | Propagation time (us) | Theoretical length (mm) | Calculated length (mm) | Error rate (%) |
|---|---|---|---|---|---|
4 | 4356 | 779 | 1740 | 1698 | 2.5 |
5 | 4356 | 813 | 1740 | 1770 | 1.7 |
6 | 4356 | 789 | 1740 | 1718 | 1.2 |