双面高陡岩质边坡地震滑坡机制的研究

Analysis of landslide mechanisms of a high steep rock hill with two-side slopes under ground shaking

以国道G213左侧双面高陡岩质边坡为原型,采用新型连续介质离散元计算方法(CDEM),结合振动台试验结果,对高烈度地震作用下双面高陡岩质边坡的地震滑坡机制进行了研究。结果表明:在地震力和重力作用下,滑体顶部先出现拉应力集中,造成滑体沿滑体结构面后缘产生变形,进而造成该处出现拉伸、剪切破坏点;之后随着地震动的持续,滑体结构面上的剪切破坏点逐渐向滑体中前部的锁固段扩展,同时伴随着滑体表面拉伸破坏点的增加;最终造成锁固段发生渐进性破坏,滑体从剪出口滑出形成滑坡。滑床、滑体间运动的不一致性、地震动能量分布和耗散的差异性以及随地震烈度增大结构面强度的降低是诱发滑坡的3项主控影响因素。在地震动加速度较小时,滑床、滑体内加速度的瞬时频率基本一致,滑体结构面的能量透射系数及滑体内地震动能量的控制性频带均稳定在一定范围内;随着地震烈度的增加,滑体内加速度的瞬时频率逐渐下降,滑体结构面的能量透射系数逐渐减小,最后两者均趋于稳定,同时滑体内地震动能量的控制性频带也逐渐由高频带向低频带转移。

A high steep rock hill with two-side slopes near National Road 213 is used as a prototype. Combining with the results of shaking table test, the landslide mechanisms of the high steep rock hill with two-side slopes are researched by a new continuum-discrete element method （CDEM）. The research results show： The stress concentration phenomenon appears at the top of the sliding mass firstly; and then some tension failure points and some shear failure points appear there, which expands toward the toe of the sliding mass from the top of that along the structural plane. At the same time, the number of tension failure points gradually increases. At last, the toe of the sliding mass breaks; and then the sliding mass shears but from the toe. The non-consistent movement, the reduce of strength of the structural plane and the difference of distribution and dissipation of the earthquake energy in the sliding body and the sliding bed are three of the major influence factors which induce the landslide. When the accelerations are small, the instantaneous frequency of the accelerations between sliding bed and sliding body are generally consistent; the energy transmittance coefficients of the sliding structural plane and the regulatory frequency band all range in a limitation. With the increase of the seismic intensity, the instantaneous frequency and the energy transmittance coefficients gradually decrease; and then they are steady within the lower limitation. At the same time, the regulatory frequency band also gradually shifts from high frequency band to the lower one.