Laboratory investigation on the cooling effect of crushed-rock interlayer embankment with ventilated ducts in permafrost regions

The engineering construction in permafrost regions would cause warming, even thaw of permafrost. This would bring thaw settlement damage and even failure to railway/highway embankments by exerting great influence on the embankment stability. Some traditional cooling measures have been proved to be effective on ensuring the thermal stability of embankment in the construction of the Qinghai–Tibet Railway. However, these cooling measures are applicable to the embankment of ordinary width, and would be unable to protect the underlying permafrost and ensure the stability of the high-grade highway embankment with multi-lane pavement. Due to the great heat intake caused by the asphalt-concrete pavement and a higher standard on settlement and uneven deformation, the permafrost problem is even more serious for high-grade highways of large-width than that for highway of ordinary width. To solve this new permafrost problem, traditional cooling measures should be either reinforced or combined. In this study, a new approach of a joint cooling measure consisting of crushed-rock interlayer and ventilated ducts was presented. A laboratory test was carried out to preliminarily investigate the effect of the new cooling measure. In the test, the temperature characteristics of two crushed-rock interlayer embankments with and without ventilated ducts are compared. The test results showed that the crushed-rock interlayer performed a more efficient cooling effect when the ventilated ducts are added than that when they are not added. The effect is direct: the performance of the ventilated ducts decreased the upper boundary temperature of the crushed-rock interlayer, and consequently enhanced its natural convection and cooling effect. Therefore, the crushed-rock interlayer embankment with ventilated ducts has a good cooling effect to the underlying permafrost, and should be recommended in the construction of large-width highways in permafrost regions.