Study on Fracture and Stress Evolution Characteristics of Ultra-Thick Hard Sandstone Roof in the Fully Mechanized Mining Face with Large Mining Height: A Case Study of Xiaojihan Coal Mine in Western China

Figure 13

Roof breaking and stress evolution: (a) 11213 working face excavation; (b) 11215 working face excavation; (c) stress distribution of the 11213 working face excavation; (d) stress distribution of the 11215 working face excavation.

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