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

Table 3

Construction parameters of borehole detection.

Number	Elevation angle	Horizontal angle	Hole depth (m)	Aperture (mm)	Distance (m)	Distance from the roof (m)
1	29	0	45	93	1	0.72
2	35	0	40.5	93		0.1
3	40	0	50	93		0.1