Abstract: One of the measures of actively and forwardly protecting frozen soil is adjusting the temperature of embankment by ripped-rock layer, used in the railway design in permafrost regions. The effect of adjusting temperature consists of heat shield during summer-time and convective cooling during winter-time. In this study, a preliminary analysis was given to the thermal regime of ground temperature under the ripped-rock layer with both different grain diameters based on the in-situ measured data. The result showed that during summer-time, the ripped-rock layer with a grain diameter of 50－80 mm had better heat barrier than that one of 400－500 mm, but during winter-time, the latter had stronger convective cooling action. By a cyclic contrast, it was still found that the latter was excess to the former in the adjusting temperature. Moreover, the mostly part of 0℃ isotherm has closed to the natural ground surface when the foundation soil under the revetment reaches the maximum of thawed depth; this will be benefit to the thermal stability of embankment.

Key words: ripped-rock layer, grain diameter, permafrost table, heat shield, convective cooling, effect of adjusting temperature