Overlying Strata Movement and Abutment Pressure Evolution Process of Fully Mechanized Top Coal Caving Mining in Extra Thick Coal Seam

Table 1

Lithology of the 8211 working face.

Lithology	Thickness (m)	Depth (m)	Lithology description
Aluminous mudstone and sandy mudstone interbedding	28.4	332.9	The upper part is purple patchy aluminum mudstone, and the lower part is yellow green sandy mudstone.
Medium coarse sandstone	9.2	342.1	It is grayish white coarse-grained massive structure, with gravel gradually increasing at the bottom.
Sandy mudstone and siltstone interbedding	39.4	381.5	It is mainly composed of light gray sandy mudstone and siltstone interbedded with thin layer of clay rock.
Medium coarse sandstone	13.5	395.0	Gray white coarse-grained massive structure intercalated with thin-layer siltstone.
Siltstone	3.2	398.2	The main mineral composition is quartz and calcareous cementation.
Carbonaceous mudstone	2.3	400.5	Black muddy structure, containing root plant fossils.
Coal seam	15.0	415.8	It is mainly black and semi dark coal with multilayer gangue and developed endogenous fractures.
Carbonaceous mudstone	5.3	421.1	Black muddy structure, containing root plant fossils.
Medium fine sandstone	14.5	435.6	Gray medium fine structure, containing a thin layer of silt and fine sandstone.