Numerical simulation of heat transfer of the crushed-rock interlayer embankment of Qinghai-Tibet Railway affected by aeolian sand clogging and climate change

The crushed-rock interlayer (CRI) has been used to cool the railway embankment subbase and subgrade of the Qinghai-Tibet Railway (QTR) in permafrost regions. However, in addition to the climate change, aeolian sand clogging has been affecting this mitigation techniques aimed to increase heat extraction and reduce subsurface heat penetration by air convection through the voids of the CAI. Its long-term performance is evaluated herein using a numerical modelling. Simulation results demonstrate an unclogged CRI can mitigate permafrost warming for the first 20 years with a simulated increase in average air temperature by 0.052 degrees C a(-1). But after sand clogging, including both filling of voids in the CRI and covering of embankment slopes, its cooling performance is weakened. In such conditions, permafrost table is increasing and the permafrost is warming up under different mean annual air temperature (MAAT) of -4.5, -5.5, and -6.5 degrees C. The water content of the aeolian sand can also affect the cooling effectiveness of CAI. A 1 m-thick dry sand cover can induce an increase in ground temperature. But wet sand layer can mitigate and delay the effect of climate change on the permafrost degradation. The sand-control measures and additional engineering techniques should be adopted to prevent the long-term thermal stability of the QTR in sandy permafrost zone of Qinghai-Tibet Plateau.