青藏高原多年冻土区两类低角度滑坡灾害形成机理探讨

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

青藏高原多年冻土区发育的两类低角度滑坡——融冻泥流和热融滑塌是冻融循环条件下特殊的斜坡失稳类型,在广大的非冻土地区一般很难见到这种低角度的滑坡类型。探讨了两类低角度滑坡灾害的形成机理,即质点迁移效应和滞水润滑效应。以摩尔-库仑强度准则为理论基础,应用所推导的沿坡面平行方向渗流条件下安全系数的统一形式,对青藏公路k3035里程热融滑塌体稳定性进行了分析评价,验证了活动层沿厚层地下冰面滑动的“滞水润滑效应”。从环境工程地质学的观点出发,针对热融滑塌这种可控的滑坡地质灾害,提出了基于保护冻土原则的具体的防治措施。

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.