Study on the Mechanism of Gas Ignition by Friction Effect of Hard Quartz Sandstone Instability

Table 1

Roof lithology of 1007 working face.

Lithology	Thickness (m)	Features
Sandstone and conglomerate	3.7	Gravel, quartz content is high, harder
Fine sandstone	2.9	Fine grain structure, calcium, clay cementing
Sandy mudstone	11.2	Sand and shale, high sand content partly, sandstone layer interbed
Quartz sandstone	13.9	High quartz composition, partly quartz stone, very hard
Fine sandstone	6.9	Glued calcium clay, hard, high quartz composition
No. 10 coal seam	5.5	Powdery or fragmented, brittle, vertical fissure development