反复微震作用下顺层及反倾岩质边坡的动力稳定性分析

水库蓄水后诱发的高频次微小地震在一定程度上会对区域地质体的稳定性产生重要影响。本文采用振动台试验、UDEC数值分析方法,对顺层、反倾两类典型岩质边坡在反复微小地震作用下的动力稳定性进行了深入研究。结果表明:两类边坡的加速度响应均表现出"高程效应"和"趋表效应",且随地震作用次数的增加,坡体损伤(表现为层面与次级节理的起裂、扩展、贯通)不断累积,造成两类边坡的动力响应均呈现减弱的趋势;在反复微震作用下,边坡自振频率减低和阻尼比增大是其动力特性变化的基本规律;边坡累积永久位移随着地震作用次数的增加而增加,而稳定性系数则呈现递减趋势;在反复微震作用下,顺层坡的后缘竖向拉裂缝逐渐向下扩展并与下卧层面连通,边坡主要发生沿层面的整体滑移失稳模式;反倾坡首先在坡肩及坡面出现块体崩落,随后上部岩层逐层剥落,最终形成圆弧形破坏面,边坡以坡肩处发生落石、中上部岩层发生崩塌为主要破坏特征。

Dynamic stability analysis of bedding and toppling rock slopes under repeated micro-seismic action

The high-frequency and micro earthquake induced by the Three Gorges Reservoir after impoundment will have an important influence on the stability of the regional geological body to a certain extent. The shaking table tests and UDEC numerical analysis method are used to analyze the dynamic stability of the typical bedding and toppling rock slopes under repeated micro earthquakes. The results show that the acceleration response of the two types of slopes exhibits the "elevation effect" and "surface effect", and with the increase of earthquake action frequency, the slope damage (manifested as the initiation, expansion and penetration of structural plane and secondary rock joint) accumulates continuously and the dynamic response of the two types of slopes decreases. Under the repeated micro earthquakes, the decrease of the natural frequency of the slopes and the increase of the damping ratio are the basic laws of the dynamic characteristics. The permanent displacement increases with the increase of earthquake action frequency, and the stability coefficient decreases. Under the repeated micro earthquakes, the vertical tension cracks at the trailing edge of the bedding slope gradually extend and connect with substratum, and the slope is mainly caused by the overall slip instability along the joint surface. Block caving firstly appears at the slope shoulder and the slope surface in the toppling slope, subsequently, the upper strata are peeled off layer by layer, and finally a circular failure surface is formed. The main characteristics of the slope are rock fall at the slope shoulder and collapse of the middle and upper strata.