Prediction and Analysis of Abnormal Gas Emission Law in Low-Gas Tunnel Based on K-Line Diagram

Table 2

Gas concentration in different construction processes at the tunnel face.

Construction process	Time (h)	Gas concentration (%)	Construction process	Time (h)	Gas concentration (%)
Drilling and blasting	0	0.02	Frame erecting	8	0.06
	1	0.02		9	0.05
	2	0.47		10	0.04
	3	0.35		11	0.04
Mucking	4	0.26	Shotcreting	12	0.06
	5	0.04		13	0.02
	6	0.02		14	0.01
	7	0.03		15	0.04