Abstract: The secondary geological disasters induced by densely-developed landslides in the upstream of Jinsha River have severely threatened people’s livelihood and property security and the construction of reservoirs in the drainage basin. At present, however, river-blocking landslides in the Jinsha River basin, in particular, the mechanism of river blocking is rarely reported. In this paper, the development characteristics and river-blocking mechanism of a mega-landslide in the upstream of Jinsha River are investigated via drilling exploration and numerical simulation based on in-situ geological survey. Study results show that the bedrock landslide was developed on consequent and steep slope dominated by mica-quartz schist. With a total volume of 60 million m³, the landslide had blocked the Jinsha River severely, displaying an evident chair shape. The river-blocking mechanism is summarized as follows: high-speed sliding of bedding slope → collision and accumulation of front edge → pushing by the trailing edge → consolidation until damming → complete blocking of the river.

Key words: mega-landslide, landslide development, river-blocking characteristics, river-blocking mechanism, upper reach of Jinsha River