Height of the Fractured Zone in Coal Mining under Extra-Thick Coal Seam Geological Conditions

Table 5

Comparison of overlying failure height determined by different methods.

Methods	Overlying failure height (m)
Key strata theory	174
EH4 electromagnetic imaging system	150–170
Borehole televiewer	171
《Code for coal pillar setting and coal mining under pressure in buildings, water bodies, railways and main roadways》	127.34