Discussion on landslides hazard mechanism of two kinds of low angle slope in permafrost region of Qinghai-Tibet plateau

Two kinds of low angle landslides, gelifluction and thaw slumping; in permafrost region of Qinghai-Tibet plateau are special slope instability patterns with freeze-thaw cycle. It is difficult to see in non-permafrost region. It is discussed in this paper that landslides mechanism of two kinds of low angle slope-soil particle transfer effect and lubrication effect with sluggish water. Based on Mohr-Coulomb strength criterion, stability analysis for thaw slumping of milepost K3035, Qinghai-Tibet highway has been carried out by applying unified safety factor formula derived with groundwater streamline parallel to slope surface to verify lubrication effect with sluggish water with active layer sliding along thick ice surface. From environmental engineering geology viewpoint, control measures based on permafrost protection principle for thaw slumping have been put forward.