地震作用下岩质边坡块体倾倒破坏分析

 基于传递系数法的概念，在建立地震作用下岩质边坡倾倒破坏地质力学模型的基础上，提出考虑地震作用边坡倾倒破坏的解析分析方法，并进一步分析地震作用对边坡倾倒稳定性的影响。该方法采用边坡几何力学参数以及潜在倾倒岩块编号来表征边坡倾倒稳定性分析中变量，从而使每个倾倒岩块的计算变量具有统一的表达式，因此很容易采用Microsoft Excel进行程序化分析。分析结果表明，地震作用下边坡的破坏模式取决于地震影响系数与其临界值的关系，地震影响系数临界值的大小取决于地震力方向以及缓倾结构面的倾角和内摩擦角，当地震影响系数小于该临界值时，按倾倒破坏分析边坡稳定性，否则边坡发生滑动破坏；边坡倾倒稳定性受地震力作用方向和地震影响系数的影响，地震作用方向对边坡倾倒稳定性影响较小，而边坡倾倒稳定性随地震影响系数的增加而显著降低。

ANALYSIS OF TOPPLING FAILURE OF ROCK SLOPES DUE TO EARTHQUAKES

Toppling is an important failure mode of rock slopes，which is dominantly controlled by the discontinuities existing in the slopes. Adopting the concept of the transfer coefficient，an analytical approach of toppling failure of rock slopes due to earthquakes is developed based on the corresponding geomechanical model，and influence of seismic actions on the toppling stability of rock slopes is analyzed. The variables of every rock block potential to toppling，used for stability analysis of a rock slope，are expressed by the geomechanical parameters of the slope and the serial number of the blocks，and hence have uniform expressions. Consequently，the method is easily implemented using a Microsoft Excel spreadsheet. An idealized example is analyzed adopting the Excel procedure. The results show that the failure mode of a rock slope，such as sliding or toppling，depends on the relationship between the seismic influence coefficient and its critical value which is determined by the direction of the seismic force，the dip angle and the friction angle of the slightly dipping discontinuities. The rock slope is potential to topple if the seismic influence coefficient is less than the critical value，or it will slide. It is also indicated that the toppling stability of rock slopes increases slightly with the angle of the seismic force with respect to the horizontal plane rising but descends markedly with the seismic coefficient increasing.