Abstract：In construction and maintenance of road engineering in cold regions，permafrost has been the mainly influencing factor in embankment stability. The cooling effect of the riprapped embankment on the soil beneath has been recognized. In this paper，the differences of the cooling effect and mechanism between the closed and open riprapped embankments have been compared through the laboratory test. It can be concluded that the cooling rate of the open model is faster than that of the closed one，but as far as a long-term effect is concerned，the closed one¢s cooling capability is larger under the condition of the experimental temperature. Furthermore，by analyzing the changing correlation between the top temperature and the temperature difference through the top and bottom of the riprapped layers，taking consideration of the temperature field in the riprapped layers，it is found that the cooling mechanisms of the two embankment models are quite different from each other. Namely，the cooling effect of the closed embankment model on the soil beneath mainly relies on the changing of the thermal conductivity of riprapped layer，which is caused by the changing of the inside nature convection，but that of the open model relies on the way of heat-transfer enhancement because of the inside forced convection induced by the low temperature wind outside. But the two ways of convection exist together because of the effect of many factors in actual engineering；therefore，both of the two models have good application perspective in permafrost regions where mean annual air temperature is subfreezing.
