Abstract:The adjustable ventilated embankment,which is adopted in Qinghai―Tibet Railway,is an ideal engineering measure to protect warm frozen soil. Aiming at the freezing-thawing problems of warm frozen soil where Qinghai―Tibet Railway has been constructed,this paper has considered the influence of solar radiation and the adherent layer on the boundary conditions and has performed detailed numerical simulation analysis and comparison between the traditional ventilated embankment,in which both ends of the ducts are open,and the adjustable ventilated embankment,in which both ends of the ducts are closed. The numerical results show that the location of 0 ℃ isotherm of the adjustable ventilated embankments is higher than that of the traditional ventilated embankment in summer season. It shows that the permafrost table is lifted more under the adjustable ventilated embankment and the permafrost underlying is protected better. And it does not occur the thawing bulb in summer. On the other hand the propagation depth of its -4 ℃ isotherm is larger than that of the traditional ventilated embankment in winter season. These indicate that the cooling effect of the adjustable ventilated embankments on permafrost is quite better than that of the traditional ventilated embankments.