Based on field data, distribution characteristics and influential factors of embankment longitudinal cracks in permafrost regions were summarized. Moreover, according to the thermo-mechanical elastic-plastic element method, a 2D coupled thermal-mechanical model was set up to simulate how the sunny-shady slope has effected on the embankment longitudinal cracks in warm permafrost regions. The corresponding conclusion had a good agreement with the field results. (1) The high embankments with

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... s shady-sunny slope effect are more likely to develop longitudinal cracks at the beginning of roadbed service. When the height of embankment was less or equal to 2.0m, the probabilities to develop longitudinal cracks were very small in all conditions. (2) The "0 displacement line" is originally presented. The development of longitudinal cracks is due to strength failure of permafrost. Once the permafrost under sunny slope thaws into soft soil layer, there will be tensile stress in the embankment. When the most tensile stress in the embankment takes place, the longitudinal cracks depends on whether there appears "0 displacement line" or not on the embankment bottom. Where the "0 displacement line" is, where the longitudinal crack happens. (3) The uneven settlement between the sunny side and the shady side results in that the whole embankment slants to the sunny side. And the soil deformation of sunny slope is influenced by the thaw bowl (soft layer) under it, so the settlement of the sunny side is more than that of the shady one. The longitudinal crack was caused by both horizontal and vertical displacement. As a result, the longitudinal crack goes through the embankment in a slantwise direction.