To prevent coal spontaneous combustion disasters in the gob area and precisely delineate hazardous zones, the variation patterns of CO and O2 volume fractions along the gob length were statistically analyzed based on field measurements. Critical warning threshold ranges for spontaneous combustion were established and a gob hazard zoning method based on gas volume fraction kernel density was proposed. The results demonstrate that O2 volume fraction exhibits a linear variation with distinct stages, and the variation rate before the inflection point is lower than that after the point. The CO volume fraction follows a quadratic polynomial variation. The kernel densities of both CO and O2 volume fractions decrease with increasing gob length. Their highest kernel density distributions occur within 0-10m and 0-30m, respectively. O2 volume fraction is more stable before the inflection point but exhibits greater fluctuation afterward. The average upper and lower acceptable limits for O2 volume fraction before and after the inflection point are 3.3% and 6.3%, respectively. The critical CO and O2 volume fraction values for hazard zoning based on kernel density are 0.009% and 15.1%, which divides the gob area into four quadrants and three risk levels (safe, potentially hazardous, and hazardous).
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |