Use of coarse aggregate materials to protect embankments located in permafrost regions

Abstract

This paper describes the physical principles, monitoring and application of porous filling materials used in embankments located in permafrost regions. The use of crushed rock and jackstones in slopes of roads and railways in the Tibetan plate an are studied. The mean diameter of crushed rocks and jackstones is a key parameter for the appropriate performance of an embankment, i.e. to prevent settlements due to permafrost thawing. Embankment settlements can sertoushy damage the performance of a road or railway. From experimental results, it as found that the thermal conductivity coefficient of a crushed rock layer during winter was around twelve times larger than that during summer. This can be explained by the presence of air convections in 1he porous crushed rock: layer which mainly occur with the change of air temperature and density only during winter. As a consequence, it 1s believed that the crushed rock layer plays an important heat shield role in the protection of the permafrost under a road. According to the embankment construction conditions and the air convection properties in the porous crushed rock materials, the best diameters for crushed rocks
are between 10 cm and 15 em and the thickness of the crushed rock layer is about three to four times that of the crushed rock diameters.