Coal and Gas Comining in the High-Gas Detong Mine, China: Analytical and Numerical Parameter Optimization of Gas Extraction Boreholes

Table 3

Gas concentrations at nine different HLB locations.

HLB location		Gas concentration, % at the extraction port in the upper corner
Distance from the roof, m	Distance from the return airway, m
20	25	33.5	4
20	35	30.3	4.3
20	45	26.8	4.6
30	25	37.5	3.4
30	35	34.5	3.8
30	45	32.8	4.1
40	25	36.4	3.9
40	35	31.5	4.2
40	45	29.5	4.5