Prevention and Control Technology for Harmful Toxic Gas Intrusion in High-Fire-Hazard-Risk Areas of Close-Distance Coal Seams

Table 1

Actual measured ground stress.

Measured location	Stress category	Principal stress value (MPa)	Azimuth (°)	Dip angle (°)
31201 air-return laneway	Maximum principal stress σ1	6.57	264.7	2.9
	Intermediate principal stress σ2	5.76	37.0	85.7
	Minimum principal stress σ3	5.15	174.5	3.1