甘肃积石山6.2级地震触发青海中川乡液化型滑坡-泥流特征与成因机理

Preliminary Study on the Characteristics and Initiation Mechanism of Zhongchuan Town Flowslide Triggered by Jishishan Ms 6.2 Earthquake in Gansu Province

  • 摘要: 2023年12月18日甘肃积石山县6.2级地震在青海省海东市民和县中川乡金田村和草滩村触发了一起典型地震液化型滑坡-泥流,致使大量房屋被厚达数米的淤泥包围掩埋,因其表现出显著的突发性和超强的流动性,曾被误认为“砂涌”。通过现场调查和遥感解译分析,确认该地质灾害为地震触发的液化型滑坡-泥流,并探讨了其成因机理。结果表明:(1)此次灾害是地震过程中的振动荷载导致台塬底部饱水粉砂层(黄土层)液化,形成滑坡并转化为泥流,泥流沿沟谷流动到达村庄后漫流成灾,并不是传统意义上的就地“砂涌”;(2)滑源区在液化过程中具体表现为溃散性破坏和侧向扩离两种失稳模式;( 3)地震触发土体液化多发生在具有明显应变软化特征的饱水颗粒材料(粉质黄土、细砂等)中。此类地质灾害发生具有突发性,失稳后往往呈流体状远程运动,易造成灾难性后果,应引起高度重视。

     

    Abstract: On 18th December 2023, the 6.2-magnitude earthquake centered in Jishishan County, Gansu Province triggered a prototypical earthquake-induced liquefaction flowslide in Jintian Village and Caotan Village, Zhongchuan Township, Minhe County, Haidong City, Qinghai Province. This hazard caused numerous buildings to be engulfed and interred by several meters of deposits. Owing to the abruptness of its occurrence and extremely high fluidity, it was mistakenly identified as a "sand surge". Through on-site investigation and remote sensing imagery analysis, we confirm this flowslide to be an earthquake-triggered liquefied flowslide event, and explore its causal mechanisms. The results show that: (1) This flowslide was induced by seismic vibratory loading causing liquefaction of the saturated silt layer (loess layer) underlying the plateau, forming a landslide that transformed into a mudflow moving along the valley, rather than an in-situ " sand surge " in the conventional sense; (2) This flowslide includes two failure modes: diffuse failure and lateral spreading; (3) Earthquake-induced soil liquefaction frequently occurs in saturated granular materials (silts, fine sands, etc.) exhibiting prominent strain softening characteristics. The occurrence of such geological hazard is abrupt. Post-instability, the landslide mass flows significant distances like a fluid, readily resulting in catastrophic consequences. This warrants heightened attention.

     

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