The crushed rock layers (CRLs) with a satisfactory cooling effect has been widely used to mitigate permafrost thaw beneath road embankments in cold regions. However, whether the CRLs can still work as well for an expressway constructed with an integral embankment is still under discussion, it is generally accepted that the expressway with wide asphalt pavement should be constructed with two separated embankments rather than one integral embankment in permafrost zones. In that case, wind field around the two embankments would be of great importance as it would impact the work conditions of the CRLs considerably. Here, a coupled computational fluid dynamics and heat transfer model was developed to numerically investigate and quantify the characteristics of wind field and thermal performances of an expressway constructed with two separated crushed-rock embankments (SCREs) with different separating strip widths (SSWs). The model was validated by the field observed data of wind flows and ground temperatures around an experimental expressway. The simulated results indicated that the two SCREs can ensure the long-term thermal stability of permafrost subgrade in the projected climate warming scenario. However, due to different distribution of wind field around the two SCREs, permafrost thermal regimes beneath them differed considerably under different SSWs. The SSW exerted a significant impact on the cooling effect of the rear embankment, while less significant to that of the front embankment. To ensure that the two SCREs have close thermal performances, the SSW between them should be not less than 15 times of the embankment height. In addition, the local warming effect, which is caused by low wind speed, can result in severe permafrost degradation when the separating strips were narrow.

具有令人满意的冷却效果的碎石层（CRL）已被广泛用于缓解寒冷地区路堤下方的多年冻土融化。然而，对于具有整体式路堤的高速公路而言，CRL是否仍能正常工作仍在讨论中，人们普遍认为，宽阔的沥青路面的高速公路应在永久冻土区中由两个分开的路堤而不是一个整体式路堤来建造。在这种情况下，两个路堤周围的风场将非常重要，因为它将极大地影响CRL的工作条件。这里，建立了一个耦合的计算流体动力学和传热模型，以数值方式研究和量化了由两个具有不同分隔带宽度（SSW）的分离碎石路堤（SCRE）建造的高速公路的风场和热性能的特征。该模型已通过对实验高速公路周围的风流和地面温度的现场观测数据进行了验证。模拟结果表明，在预测的气候变暖情景中，这两个SCRE可以确保多年冻土路基的长期热稳定性。但是，由于两个SCRE周围的风场分布不同，因此在不同的SSW下，它们下面的多年冻土热力状态有很大不同。SSW对后路堤的冷却效果产生了重大影响，而对前路堤的重要性较小。为了确保两个SCRE具有接近的热性能，它们之间的SSW应不小于路堤高度的15倍。另外，由低风速引起的局部变暖效应在分隔条窄时会导致严重的永久冻土退化。