Fracture Development and Multifield Coupling Evolution Law of Soft Overburden Rock in a Medium-Thick Coal Seam Mine

Table 3

Relationships between fractal dimension and overburden deformation and damage.

Propulsion distance (m)	Double logistic regression equation	Fractal dimension	Correlation coefficient	Overburden destruction stage
20		1.096	0.9963	False top collapse
40		1.124	0.9969	Direct top collapse
50		1.139	0.9982	Key layer breakage
80		1.144	0.9990	Overlying rock bending
100		1.114	0.9992	Overall collapse
120		1.119	0.9993	Collapse compaction