Research on Deformation Mechanism of Retracement Channel during Fully Mechanized Caving Mining in Superhigh Seam

Table 1

Rock mechanics parameters.

Lithology	Density d (kg·m^−3)	Bulk modulus K (GPa)	Shear modulus G (GPa)	Bond strength  (MPa)	Tensile strength  (MPa)	Internal friction angle f
Coarse mudstone and sandy mudstone (main roof)	2458	17.65	8.52	3.22	9.53	32.60
Mudstone and sandy mudstone (immediate roof)	2155	8.53	12.37	1.69	4.96	30.85
Coal	1298	2.39	1.68	1.42	0.46	23.88
Mudstone and sandy mudstone (direct bottom)	2155	4.98	8.56	1.83	6.35	30.66
Coarse sand rock (old bottom)	2655	13.29	11.04	8.30	9.26	31.55