Study on the Retention of Large Mining Height and Small Coal Pillar under Thick and Hard Roof of Bayangaole Coal

Table 2

Borehole parameters table at measuring point.

Dot	Location	Elevation (m)	Depth (m)	Hole depth (m)
1	3-1 high fructose 6 conduction point of coal return ventilation roadway	650	620	8
2	Guide point of S4 in the main channel 311103	651	620	8
3	Guide point J42 of the auxiliary channel on the 311102 working face	646	636	8