Failure Mechanism and Stability Control of Surrounding Rock of Docking Roadway under Multiple Dynamic Pressures in Extrathick Coal Seam

Table 2

Coefficients for the height of the caving zone.

Direct roof lithology	Compressive strength (MPa)
Hard	>40	2.1	16
Relatively hard	20~40	4.7	19
Soft	<20	6.2	32