多年冻土区缓倾角土层斜坡的地震反应

Seismic response of low-angle soil slope in permafrost regions

进行垂直和水平动荷载下的大型振动台模型试验,研究地震作用下多年冻土缓倾角土层斜坡的地震响应、诱发滑坡破坏的主要影响因素及滑坡破坏的演化过程。结果表明,在土层坡度为8°缓斜坡振动台模型试验条件下,斜坡模型破坏后其水平方向自振频率降低较明显,而垂直方向无明显变化;坡体滑动是整体沿着冰-土界面软弱层进行的失稳滑动,沿斜面滑下的斜坡土体内部没有发生破坏;模型斜坡的峰值加速度(PGA)放大系数随着坡体高程增加而增大,破坏前坡面PGA放大系数无明显变化,破坏时和破坏后变化较明显,斜坡土体对水平方向地震波的加速度动力放大响应大于垂直方向,冰-土界面软弱层的加速度放大系数明显小于上部土体和下部冰体,在加速度达到一定数值时,冰-土界面的孔隙水压力会升高。斜坡冰-土软弱界面和超孔隙水压力升高是地震荷载下多年冻土区缓倾角土层斜坡滑动的主要内因。

Large shaking table model tests were conducted to investigate the seismic response of low-angle soil slope in permafrost regions, main influencing factors and the evolution process of the landslide subjected to vertical and horizontal seismic loadings, respectively. When shaking table tests were conducted on the 8° low-angle slope, the horizontal natural frequency of vibration decreased sharply at the failure state, however there was no apparent change in the vertical direction. The failure of slope model was characterised by completely slipping along the interface between the unfrozen soil and ice layer, while the deformation of soil was not observed inside the sliding body. The amplification coefficients of peak ground acceleration（PGA） increased with the elevation of the slope. Compared with little change of amplification coefficients before sliding, more obvious changes occurred along the surface of the slope after sliding. The peak amplification coefficient subjected to the horizontal seismic loading was greater than that subjected to the vertical one. The peak amplification coefficient in the soil-ice interface was obviously lower than that in the upper soil and lower ice layer. The pore water pressure in the soil-ice interface of the slope increased when the input acceleration reached a specific value. The weak soil-ice interface and the increasing pore water pressure were the main internal factors inducing the permafrost landslide subjected to seismic loading.