金沙江“10·11”白格特大型滑坡形成机制及发展趋势初步分析

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

    • 摘要: 2018年10月11日,西藏昌都市江达县波罗乡白格村发生大规模滑坡,约有3165×104 m3的山体高速冲入金沙江形成堰塞坝,13日9时堰塞坝体被自然泄流冲开,堰塞湖威胁解除。11月3日,在时隔短短23 d后,该滑坡后缘约215×104 m3高位滑体再次发生滑动破坏,高速运动的滑体沿途铲刮坡体并冲入金沙江,再次形成堰塞坝。现场调查研究得出白格滑坡主要是受其后缘逆冲分支断层f2(不整合接触面)控制,并在长期重力卸荷、降雨和地下水的反复浸润作用影响下,最终整体失稳破坏。通过对滑坡演化过程分析得出,其变形破坏过程可分为5个阶段,即:后缘蠕滑和沉降下错阶段(Ⅰ)、坡体裂缝发展、贯通阶段(Ⅱ)、整体启动"锁固端"剪断阶段(Ⅲ)、高速凌空滑跃阶段(Ⅳ)、碰撞、破碎、堆积成坝阶段(Ⅴ)。一期变形破坏机制模式可归结为蠕滑-下错-剪断-滑跃式,破坏方式表现为推移式,后期临空条件较好,破坏将以牵引式为主。在此基础上,结合残留强变形区块(K1、K2、K3)及其周边影响区形貌特征和变形迹象,对其变形破坏特征和发展趋势进行了预测分析,认为后期强变形区总体将以渐进解体方式破坏为主。

       

      Abstract: 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.

       

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