Abstract: In this study, the spontaneous combustion of a coal seam under the subgrade of the high fill highway embankment is taken as the background.  The coal seam spontaneous combustion and stratum lithology changes on both sides of the roadway embankment are investigated by the method of borehole temperature measurement. Based on borehole investigation on both sides of the roadbed, the monitoring data of formation temperature and the rock formation variations were obtained. After the statistical analysis, the burning area, the burning depth and the burning intensity of the coal seam at the lower part of the roadbed are determined. The coal seam combustion heat source in the unfilled abandoned mine gallery is located at a depth of approximately 50 meters below the ground. The temperature distribution along the vertical borehole is parabolic. The temperature can be divided into four areas from the surface downward: the normal temperature area of the surface subgrade; the abnormal temperature area of the general rock formation; the abnormal temperature area of the coal rock formation; and the deep normal temperature area. The thermal insulation and sealing performance of lime-loess mixture in the subgrade filling in the coal field fire area was verified. The detection results showed that there was no abnormally high temperature above 200 ℃ in the subgrade, which proved that the lime-loess mixture subgrade has a good sealing effect on the surface and thermal insulation.

Key words: Roadway Engineering, Underground Coal Fire Monitoring, Drilling Method, Numerical Analysis