Table 2 The roof and floor conditions of the three coal seams.
Top and bottom plate | Rock name | Thickness (m) | Average thickness (m) | Lithological characteristics |
|---|---|---|---|---|
Basic top | Siltstone and fine sandstone | 3.1–13.6 | 6.5 | Light gray, thickly layered, containing rock debris and mica, clayey cementation, wavy layering, semi-hard |
Direct top | Sandy mudstone | 3.5–14.7 | 7.3 | Dark grey, thick-layered, flat and uneven fracture, parallel bedding, containing a small number of incomplete plant fossils |
Coal seam | 3 Coal seam | 2.8–4.8 | 3.6 | Black in color, with a weak asphalt luster, mainly composed of dark coal, and the fracture surface is flat |
Direct bottom | Sandy mudstone and mudstone | 1.2–16.9 | 6.8 | Grey, thick-layered, flat and uneven fracture, parallel layering, semi-hard |
Basic bottom | Fine sandstone and siltstone | 4.9–14.4 | 8.1 | Light gray, extremely thick layered, containing rock debris and mica, clayey cementation, wavy layering, semi-hard |
