青藏高原三江并流区重大堵江滑坡孕育规律及其防灾挑战

青藏高原三江并流区剧烈的构造活动和强烈的河流侵蚀导致其高山峡谷中大型堵江滑坡频频发生，并且链生灾害剧烈，严重影响川藏铁路、滇藏铁路等国家重大工程的建设。青藏高原重大滑坡堵江具有独特的天然形成条件以及鲜明的内外动力特征，通过对典型堵江滑坡的考察，建立青藏高原三江并流区堵江滑坡数据库，对认识堵江滑坡地质孕育特征在区域上的普遍性规律及孕灾条件意义重大。本文基于2019年实施的三江并流区堵江滑坡野外地质调查和滑坡地质成因分析，阶段性揭示了堵江滑坡的一般孕育规律：（1）三江并流区的缝合带和活动断裂不仅易使斜坡岩体发生蚀变，从而降低坡体结构的完整性、提高对风化作用的敏感性，还会产生剧烈的地震内动力作用诱发堵江滑坡的启动；（2）堵江滑坡具有发生在倾倒变形的逆倾斜坡上以及岸坡凹岸处的空间分异特性，在河流下切作用下高势能、大方量的滑体往河谷运动形成堵江；（3）河谷中的背斜构造在河流侵蚀过程中为两岸的逆倾或近直立岩层创造了倾倒变形的临空条件，加上背斜核部邻近斜坡岩体的挤压破碎性质，使斜坡结构更易发生深层变形破坏，造成堵江滑坡事件；（4）软弱炭质岩层化学风化在内的外动力地质作用对坡体结构的变形、破坏亦有不可忽视的促进作用。基岩滑坡一旦发生堵江，其潜在的灾害链问题将十分严重，未来需要进一步优化、整合资源，借助高科技手段克服青藏高原滑坡灾害考察的诸多困难。本文通过揭示堵江滑坡孕育的一般规律，为堵江滑坡数据库的完善奠定了基础，有助于应对更严峻的青藏高原防灾减灾挑战。

Developing Law of Damming Landslide and Challenges for Disaster Prevention and Mitigation in the Three-river-parallel Territory in the Tibetan Plateau

Large-scale damming landslides frequently occur in high-relief mountainous regions in the Tibetan Plateau where is characterized by active tectonics and intense fluvial incision, which commonly result in flood, landslide reactivation, and some other secondary disasters. Such favorable conditions for geohazards will severely affect the construction safety of vital projects of China, i.e., Sichuan-Tibet and Yunnan-Tibet Railways. However, general developing laws of landslide damming and simulation of whole process of disaster chain have not been properly accounted for in the Tibetan Plateau. It is essential to establish a database of landslide dammings in the Three Rivers Region in the Tibetan Plateau for better obtaining the general laws. This study conducted detailed geological survey and mechanism analysis on landslides that have blocked valley river in the year of 2019, and periodically revealed the following conclusions: (1) suture and active fault not only alter the rock mass of hillslope and affect rock integrity and weathering extent, but also usually generate seismic events to trigger large landslides which slide rapidly and likely block rivers; (2) landslide dammings are prone to occur on the anaclinal hillslopes when river continuously erodes the concave bank, which would develop toppling deformations to a large-scale catastrophic landslide to block rivers; (3) anticline nucleus formed in the middle of a river valley commonly induces landslide damming by developing anaclinal hillslopes that would easily evolve into large landslide from toppling owing to the fragmented rock mass nearby the anticline; (4) chemical weathering of carbonaceous rock in the slope could facilitate the failure of large landslides. Large-scale rockslides will cause severe river blockage, flood and other disaster chain in mountainous region as long as the favorable geo-environment develops. An understanding of general developing laws of landslide damming in the Three Rivers Region could provide a conceptual model for our next work about the landslide database and is helpful to confront more challenges for disaster prevention and mitigation.