Stability Analysis and Fracture Patterns of Hard Main Roof in Longwall Top Coal Caving with Large Mining Height

Table 4

Ultimate fracture span of key stratum in No. 8100 longwall face.

Seam no.	Lithology of key stratum	Position of key stratum	Ultimate fracture span		Distance from the coal seam (m)
			Cantilever beam	Voussoir beam
17	Glutenite	Upper key strata	91.4	91.4–109.7	338.0
16	Fine-grained sandstone		90.0	90.0–108.0	258.0
12	Fine-grained sandstone		55.1	55.1–66.1	118.0
8	Fine-grained sandstone		37.2	37.2–44.6	58.0
4	Fine-grained sandstone	Lower key strata	33.1	33.1–39.7	18.0
2	Medium conglomerate		24.7	24.7–29.6	4.0