Strata Caving and Gob Evolution Characteristic in Longwall Mining

Table 3

Coefficients for average height of caving zone [27, 28].

Strata lithology	Compressive strength (σc, MPa)	Coefficients
		c1	c2
Strong and hard	>40	2.1	16
Medium strong	20–40	4.7	19
Soft and weak	<20	6.2	32