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2008年5.12汶川地震触发了大量滑坡灾害,牛眠沟滑坡是发生于震中的同震大型滑坡。经过现场调查,该滑坡启动后即与对岸山梁相撞并产生20m爬高,估算速度达19.8m/s,表现出高速启动特征。取滑带材料进行室内环剪试验,结果表明试样在不排水条件下具有很高的剪切液化能力,且动剪应力下容易液化,液化后材料视摩擦角仅为9.4°,从而得出地震滑带材料液化可能导致牛眠沟滑坡高速启动。通过能量方法,估算了不排水动剪试验材料的液化能量和地震过程通过滑带的地震能量。结果表明,滑带材料破坏所需峰值加速度为~192gal,液化所需能量为2.3×104 J/m2;汶川地震沿滑带方向提供最大地震加速度为799gal,从而满足滑带液化的能量条件,并推测滑坡可能在地震初期突然触发。
The 5.12 Wenchuan earthquake in 2008 triggered a large number of landslide disasters, and the Niuxiangou landslide was a large-scale coseismic landslide that occurred in the epicenter. After field investigation, the landslide collided with the other side of the mountain beam and caused a 20m climb, with an estimated speed of 19.8m / s, indicating a high-speed start-up characteristic. Taking the slip-ring material for indoor ring-shear test, the results show that the sample has high shear liquefaction ability under undrained conditions and liquefies easily under dynamic shear stress. The apparent friction angle of the liquefied material is only 9.4 °, Liquefaction of seismic belt material may lead to high-speed start-up of the Niuxiangou landslide. Through the energy method, the liquefaction energy of the undrained dynamic shear test material and the seismic energy of the seismic process passing through the sliding band are estimated. The results show that the peak acceleration required for the failure of the sliding strip material is ~ 192gal, and the energy required for liquefaction is 2.3 × 104 J / m2. The maximum seismic acceleration along the sliding direction of the Wenchuan earthquake is 799gal so as to satisfy the energy condition for the liquefaction of the sliding strip It is speculated that the landslide may trigger suddenly in the early stage of the earthquake.