Table 6 Duration of fracture development under each key stratum.
Key stratum number | Rock lithology | Failure step distance (m) | Separated strata type | Duration (days) |
|---|---|---|---|---|
Key stratum 4 | Limestone | 869.21 | Cavity-type | after the fracture of key stratum 3 |
Primary key stratum 3 | Limestone | 87.125 | Cavity-type | 11.47 |
Key stratum 2 | Fine sandstone | 25.19 | Fracture-type | 0.59 |
Sub-key stratum 1 | Siltstone | 22 | – | – |
