Table 2 Peak displacement and frequency shift in compound key layer.
physical variable | Composite key stratum of working face 1 | Composite key stratum of working face 2 | ||||
|---|---|---|---|---|---|---|
fine sandstone | Lower conglomerate | Upper conglomerate | fine sandstone | Lower conglomerate | Upper conglomerate | |
Peak displacement / mm | 13.7 | 5.4 | 0.95 | 13.8 | 6.1 | 1.1 |
Frequency shift peak / MHz | 438.9 | 165.9 | 38.6 | 339.9 | 201.7 | 30.7 |
response relationship (MHz/mm) | 32.04 | 30.72 | 40.63 | 24.62 | 33.07 | 27.91 |
