MODELING THE THERMAL BEHAVIOR OF HIGHLY POROUS MEDIA EMBANKMENTS IN PERMAFROST REGIONS

Embankments for road and rail support in permafrost regions are typically made to be highly porous as part of efforts to ensure their long-term thermal stability. Examples include many important road and rail engineering projects, including the Qinghai-Tibet Railway and Highway in China, the Alaska Highway in the USA and the Baikal-Amur Railway in Russia. Typical construction methods include interlayer embankments, revetment embankments and U-shaped (interlayer and revetment) embankments. The cooling effects of highly porous media embankments made from crushed rocks or cinderblocks have been evaluated previously using numerical simulation, laboratory tests and in-situ observation. Thermal models have used a variety of approaches to characterize flow in highly porous media, including Darcy and non-Darcy porous media models as well as a block model based on fluid-solid coupled heat transfer theories.

Here we present the results of modeling work designed to evaluate the behavior of novel designs intended to increase the thermal stability of an expressway with a wide and high-temperature upper surface. This includes composite highly porous media embankment structures such as crushed-rock interlayer embankments with ventilated ducts, hollow concrete brick (cinderblock) embankments combined with ventilated ducts, and an embankment with an L-shaped thermosyphon and crushed-rock revetment. This work is designed to advance understanding of thermal interactions between built structures and permafrost, and to provide the basis for new road and rail embankment engineering in permafrost regions. Additional work focuses on simulating thermal behavior of embankment in permafrost regions under conditions likely to result from global warming.