Table 1 Hydraulic properties and seepage characteristics of high-pressure aquifers in overlying strata and their distance from the coal seam roof boundary.
| Â | Stratum | Water-richness | Distance to the coal seam roof | |
|---|---|---|---|---|
Cretaceous | K1h | Upper section | The aquifer is well-developed with weak water richness | 800m |
K1h | Lower section | Aquifer undeveloped, aquiclude | 550m | |
K1l | Upper section | The aquifer is moderately developed with medium water richness | 450m | |
Upper section of the middle | The aquifer is highly developed and has strong water-rich properties. | 350–400m | ||
Lower section of the middle | The aquifer is highly developed, with moderate to strong water-richness. | 200–250m | ||
Upper section of the lower | The aquifer is moderately developed with medium water richness. | 100–150m | ||
Lower section of the lower | The aquifer has a low level of development with weak water-rich properties. | 100m | ||
Jurassic | J2a | Complete section | Aquifer undeveloped, aquiclude. | 70m |
J2z | Upper section | Aquifer undeveloped, aquiclude. |  < 15m | |
Lower section | The aquifer is underdeveloped, resulting in slow groundwater runoff. |  < 15m | ||
J2y | Upper section | The aquifer is underdeveloped, resulting in slow groundwater runoff. | <10m | |
