A PRELIMINARY ANALYSIS OF THE FORMATION MECHANISM AND DEVELOPMENT TENDENCY OF THE HUGE BAIGE LANDSLIDE IN JINSHA RIVER ON OCTOBER 11, 2018

On October 11, 2018, a massive landslide occurred in Baige Village, Boluo Town, Jiangdacounty, Changdu city, Tibet. About 3, 165×10⁴ cubic meter of a mountain mass rushed into the Jinsha River at a high speed, thus forming a barrier dam. At 9:00 on October 13, the body of the barrier dam was washed away by natural aerial drainage and the threat of forming a barrier lake was resolved. On November 3, only 23 days later, the high slip mass of 215×10⁴ cubic meter at the back edge of the landslide occurred sliding failure again. The high-speed slip mass scraped the slope along the way and then rushed into the Jinsha River, forming a barrier dam again. This paper held the view that the landslide happened in Baige Village was thought to be mainly controlled by the next branch margin thrust fault f₂, then finally generated buckling failure of the overall instability of the landslide with the influence of a long-term gravity unloading, rainfall and repeated infiltration of groundwater. The process of slip deformation and failure can be divided into five stages:trailing creep and settlement under the fault phase(Ⅰ), slope crack development, penetration stage(Ⅱ), overall launch of the "locking-fix end" cutting stage(Ⅲ), a stage with high moving speed(Ⅳ), collided, crushing and dam accumulation stage(Ⅴ). The failure mode of the first-stage deformation and failure mechanism can be summed up as creep-slip type-down fault type-shearing type-ski-jump type, and the failure mode is shown as the thrust type. In the later stage, the free surface condition of the slope is better, and the traction type can remain as the main failure mode. On this basis, combined with the residual strong deformation block(K1, K2, K3) and morphological characteristics and deformation signs of the surrounding influence zone, this paper predicted and analyzed the deformation and failure characteristics and development trend of the block, deeming that strong deformation areas can be destroyed by gradual disintegration. And these research findings can provide some reference for the monitoring, survey and governance of the future plan making and implementation.